background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

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D

Maximum Throughput 400 KSPS

D

Built-In Reference and 8

×

 FIFO

D

Differential/Integral Nonlinearity Error: 

±

1 LSB

D

Signal-to-Noise and Distortion Ratio:

69 dB,  f

i

 = 12 kHz

D

Spurious Free Dynamic Range: 75 dB,

f

i

 = 12 kHz

D

SPI/DSP-Compatible Serial Interfaces With

SCLK up to 20 MHz

D

Single Supply 5 Vdc

D

Analog Input Range 0 V to Supply Voltage

With 500 kHz BW

D

Hardware Controlled and Programmable

Sampling Period

D

Low Operating Current (4 mA at 5.5 V

External Ref,

 

6 mA at 5.5 V, Internal Ref)

D

Power Down: Software/Hardware

Power-Down Mode (1

 µ

A Max, Ext Ref),

Auto Power-Down Mode (1 

µ

A, Ext Ref)

D

Programmable Auto-Channel Sweep

     

1

2

3

5

6

7

8

9

10

20

19

18

17

16

15

14

13

12

11

SDO

SDI

SCLK

EOC/(INT)

V

CC

A0

A1

A2

A3

A4

CS

REFP

REFM

FS

PWDN

GND

CSTART

A7

A6

A5

DW OR PW PACKAGE

1

2

3

5

6

7

8

16

15

14

13

12

11

10

9

SDO

SDI

SCLK

EOC/(INT)

V

CC

A0

A1

A2

CS

REFP

REFM

FS

PWDN

GND

CSTART

A3

D OR PW PACKAGE

(TOP VIEW)

(TOP VIEW)

description

The TLC2558 and TLC2554 are a family of high-performance, 12-bit low power, 1.6 

µ

s, CMOS analog-to-digital

converters (ADC) which operate from a single 5 V power supply. These devices have three digital inputs and

a 3-state output [chip select (CS), serial input-output clock (SCLK), serial data input (SDI), and serial data output

(SDO)] that provide a direct 4-wire interface to the serial port of most popular host microprocessors (SPI

interface). When interfaced with a DSP, a frame sync (FS) signal is used to indicate the start of a serial data

frame.

In addition to a high-speed A/D converter and versatile control capability, these devices have an on-chip analog

multiplexer that can select any analog inputs or one of three internal self-test voltages. The sample-and-hold

function is automatically started after the fourth SCLK edge (normal sampling) or can be controlled by a special

pin, CSTART, to extend the sampling period (extended sampling). The normal sampling period can also be

programmed as short (12 SCLKs) or as long (24 SCLKs) to accommodate faster SCLK operation popular

among high-performance signal processors. The TLC2558 and TLC2554 are designed to operate with very low

power consumption. The power-saving feature is further enhanced with software/hardware/auto power down

modes and programmable conversion speeds. The converter uses the external SCLK as the source of the

conversion clock to achieve higher (up to 1.6 

µ

s when a 20 MHz SCLK is used) conversion speed. There is a

4-V internal reference available. An optional external reference can also be used to achieve maximum flexibility.

Copyright 

©

 1999, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

 

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

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TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

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functional block diagram

Command

Decode

SDI

CS

FS

EOC/(INT)

Low Power

12-BIT

SAR ADC

Control Logic

CSTART

PWDN

VCC

GND

REFP

Analog

MUX

4 V

Reference

S/H

Conversion

Clock

M

U

X

FIFO

12 Bit 

×

 8

CFR

SCLK

SDO

2558

A0

A1

A2

A3

A4

A5

A6

A7

REFM

2554

A0

X

A1

X

A2

X

A3

X

CMR (4 MSBs)

AVAILABLE OPTIONS

PACKAGED DEVICES

TA

20-TSSOP

(PW)

20-SOIC

(DW)

16-SOIC

(D)

16-TSSOP

(PW)

0

°

C to 70

°

C

TLC2558CPW

TLC2558CDW

TLC2554CD

TLC2554CPW

– 40

°

C to 85

°

C

TLC2558IPW

TLC2558IDW

TLC2554ID

TLC2554IPW

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TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

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Terminal Functions

TERMINAL

NAME

NO.

I/O

DESCRIPTION

NAME

TLC2554

TLC2558

A0

A0

A1

A1

A2

A2

A3

A3

A4

A5

A6

A7

6

7

8

9

6

7

8

9

10

11

12

13

I

Analog signal inputs. The analog inputs are applied to these terminals and are internally

multiplexed. The driving source impedance should be less than or equal to 1 k

.

For a source impedance greater than 1 k

, use the asynchronous conversion start signal CSTART

(CSTART low time controls the sampling period) or program long sampling period to increase the

sampling time.

CS

16

20

I

Chip select. A high-to-low transition on the CS input resets the internal 4-bit counter, enables SDI,

and removes SDO from 3-state within a maximum setup time. SDI is disabled within a setup time

after the 4-bit counter counts to 16 (clock edges) or a low-to-high transition of CS whichever

happens first. SDO is 3-stated after the rising edge of CS.

CS can be used as the FS pin when a dedicated serial port is used.

CSTART

10

14

I

This terminal controls the start of sampling of the analog input from a selected multiplex channel.

A high-to-low transition starts sampling of the analog input signal. A low-to-high transition puts the

S/H in hold mode and starts the conversion. This input is independent from SCLK and works when

CS is high (inactive). The low time of CSTART controls the duration of the sampling period of the

converter (extended sampling).

Tie this terminal to VCC if not used.

EOC/(INT)

4

4

O

End of conversion or interrupt to host processor.

[PROGRAMMED AS EOC]: This output goes from a high-to-low logic level at the end of the

sampling period and remains low until the conversion is complete and data are ready for transfer.

EOC is used in conversion mode 00 only.

[PROGRAMMED AS INT]: This pin can also be programmed as an interrupt output signal to the

host processor. The falling edge of INT indicates data are ready for output. The following CS

 or

FS

 clears INT. The falling edge of INT puts SDO back to 3-state even if CS is still active.

FS

13

17

I

DSP frame sync input. Indication of the start of a serial data frame in or out of the device. If FS

remains low at the falling edge of CS, SDI is not enabled. A high-to-low transition on the FS input

resets the internal 4-bit counter and enables SDI within a maximum setup time. SDI is disabled

within a setup time after the 4-bit counter counts to 16 (clock edges) or a low-to-high transition of

CS whichever happens first. SDO is 3-stated after the 16th bit is presented.

Tie this terminal to VCC if not used.

GND

11

15

I

Ground return for the internal circuitry. Unless otherwise noted, all voltage measurements are with

respect to GND.

PWDN

12

16

I

Both analog and reference circuits are powered down when this pin is at logic zero. The device can

be restarted by active CS or CSTART after this pin is pulled back to logic one.

SCLK

3

3

I

Input serial clock. This terminal receives the serial SCLK from the host processor. SCLK is used

to clock the input SDI to the input register. It is also used as the source of the conversion clock.

SDI

2

2

I

Serial data input. The input data is presented with the MSB (D15) first. The first 4-bit MSBs,

D(15–12) are decoded as one of the 16 commands (12 only for the TLC2554). All trailing blanks

are filled with zeros. The configure write commands require an additional 12 bits of data. 

When FS is not used (FS =1), the first MSB (D15) is expected after the falling edge of CS and is

shifted in on the rising edges of SCLK (after CS

).

When FS is used (typical with an active FS from a DSP) the first MSB (D15) is expected after the

falling edge of FS and is shifted in on the falling edges of SCLK.

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TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

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Terminal Functions (Continued)

TERMINAL

NAME

NO.

I/O

DESCRIPTION

NAME

TLC2554

TLC2558

SDO

1

1

O

The 3-state serial output for the A/D conversion result. SDO is kept in the high-impedance state

when CS is high and after the CS falling edge and until the MSB (D15) is presented. The output

format is MSB (D15) first.

When FS is not used (FS = 1 at the falling edge of CS), the MSB (D15) is presented to the SDO

pin after the CS falling edge, and successive data are available at the rising edge of SCLK.

When FS is used (FS = 0 at the falling edge of CS), the MSB (D15) is presented to SDO after the

falling edge of CS and FS = 0 is detected. Successive data are available at the falling edge of SCLK.

(This is typically used with an active FS from a DSP.)

For conversion and FIFO read cycles, the first 12 bits are the result from the previous conversion

(data) followed by 4 trailing zeros. The first four bits from SDO for CFR read cycles should be

ignored. The register content is in the last 12 bits. SDO is 3 stated after the 16th bit.

REFM

14

18

I

External reference input or internal reference decoupling.

REFP

15

19

I

External reference input or internal reference decoupling. (Shunt capacitors of 10 

µ

F and 0.1 

µ

F

between REFP and REFM.) The maximum input voltage range is determined by the difference

between the voltage applied to this terminal and the REFM terminal when an external reference

is used.

VCC

5

5

I

Positive supply voltage

detailed description

analog inputs and internal test voltages

The 4/8 analog inputs and three internal test inputs are selected by the analog multiplexer depending on the

command entered. The input multiplexer is a break-before-make type to reduce input-to-input noise injection

resulting from channel switching.

pseudo-differential/single-ended input

All analog inputs can be programmed as single-ended or pseudo-differential mode. Pseudo-differential mode

is enabled by setting CFR.D7 – 1. Only three analog input channels (or seven channels for TLC2558) are

available for TLV2554 since one input (A1 for TLC2554 or A2 for TLC2558) is used as the MINUS input when

pseudo-differential mode is used. The minus input pin can have a maximum 

±

0.2 V ripple. This is normally used

for ground noise rejection.

converter

The TLC2554/58 uses a 12-bit successive approximation ADC and 2-bit resistor string. The CMOS threshold

detector in the successive-approximation conversion system determines each bit by examining the charge on

a series of binary-weighted capacitors (see Figure 1). In the first phase of the conversion process, the analog

input is sampled by closing the SC switch and all ST switches simultaneously. This action charges all the

capacitors to the input voltage.

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TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

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converter (continued)

SC

Threshold

Detector

Node

512

VI

To Output

Latch

ST

ST

ST

ST

ST

ST

ST

1

1

2

4

8

256

512

REF–

REF–

REF–

REF–

REF–

REF–

REF+

REF+

REF+

REF+

REF+

REF+

2-Bit

R-String

DAC

Figure 1. Simplified Model of the Successive-Approximation System

In the next phase of the conversion process the threshold detector begins identifying bits by identifying the

charge (voltage) on each capacitor relative to the reference (REFM) voltage. In the switching sequence, ten

capacitors are examined separately until all ten bits are identified and the charge-convert sequence is repeated.

In the first step of the conversion phase, the threshold detector looks at the first capacitor (weight = 512). Node

512 of this capacitor is switched to the REFP voltage, and the equivalent nodes of all the other capacitors on

the ladder are switched to REFM. If the voltage at the summing node is greater than the trip point of the threshold

detector (approximately one-half the V

CC

 voltage), a bit 0 is placed in the output register and the 512-weight

capacitor is switched to REFM. If the voltage at the summing node is less than the trip point of the threshold

detector, a bit 1 is placed in the register. The 512-weight capacitor remains connected to REFP through the

remainder of the successive-approximation process. The process is repeated for the 1024-weight capacitor,

the 128-weight capacitor, and so forth down the line until all bits are counted.

With each step of the successive-approximation process, the initial charge is redistributed among the

capacitors. The conversion process relies on charge redistribution to count and weigh the bits from MSB to LSB.

serial interface

INPUT DATA FORMAT

MSB

LSB

D15–D12

D11–D0

Command

Configuration data field

Input data is binary. All trailing blanks can be filled with zeros.

OUTPUT DATA FORMAT READ CFR

MSB

LSB

D15–D12

D11–D0

Don’t care

Register content

OUTPUT DATA FORMAT CONVERSION/READ FIFO

MSB

LSB

D15–D4

D3–D0

Conversion result

All zeros

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5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

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serial interface (continued)

The output data format is either binary (unipolar straight binary) or 2s complement.

binary

Zero scale code = 000h, Vcode = VREFM

Full scale code = FFFh, Vcode = VREFP – 1 LSB

2’s complement

Minus full scale code = 800h, Vcode = VREFM

Full scale code = 7FFh, Vcode = VREFP – 1 LSB

control and timing

start of the cycle:

D

When FS is not used ( FS = 1 at the falling edge of CS), the falling edge of CS is the start of the cycle. Input

data is shifted in on the rising edge, and output data changes on the falling edge of SCLK. This is typically

used for a SPI microcontroller, although it can also be used for a DSP.

D

When FS is used ( FS is an active signal from a DSP), the falling edge of FS is the start of the cycle. Input

data is shifted in on the falling edge, and output data changes on the rising edge of SCLK. This is typically

used for a TMS320 DSP.

first 4-MSBs: the command register (CMR)

The TLC2554/TLC2558 have a 4-bit command set (see Table 1) plus a 12-bit configuration data field. Most of

the commands require only the first 4 MSBs, i.e. without the 12-bit data field.

NOTE:

The device requires a write CFR (configuration register) with 000h data (write A000h to the serial

input) at power up to initialize host select mode.

The valid commands are listed in Table 1.

Table 1. TLC2554/TLC2558 Command Set

SDI D(15–12) BINARY, HEX

TLC2558 COMMAND

TLC2554 COMMAND

0000b

0000h

Select analog input channel 0

Select analog input channel 0

0001b

1000h

Select analog input channel 1

N/A

0010b

2000h

Select analog input channel 2

Select analog input channel 1

0011b

3000h

Select analog input channel 3

N/A

0100b

4000h

Select analog input channel 4

Select analog input channel 2

0101b

5000h

Select analog input channel 5

N/A

0110b

6000h

Select analog input channel 6

Select analog input channel 3

0111b

7000h

Select analog input channel 7

N/A

1000b

8000h

SW power down (analog + reference)

1001b

9000h

Read CFR register data shown as SDO D(11–0)

1010b

A000h plus data

Write CFR followed by 12-bit data

1011b

B000h

Select test, voltage = (REFP+REFM)/2

1100b

C000h

Select test, voltage = REFM

1101b

D000h

Select test, voltage = REFP

1110b

E000h

FIFO read, FIFO contents shown as SDO D(15–4), D(3–0) = 0000

1111b

F000h plus data

Reserved

1111b

F000h plus data

Reserved

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5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

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control and timing (continued)

configuration

Configuration data is stored in one 12-bit configuration register (CFR) (see Table 2 for CFR bit definitions). Once

configured after first power up, the information is retained in the H/W or S/W power-down state. When the device

is being configured, a write CFR cycle is issued by the host processor. This is a 16-bit write. If the SCLK stops

after the first 8 bits are entered, then the next eight bits can be taken after the SCLK is resumed. The status of

the CFR can be read with a read CFR command.

Table 2. TLC2554/TLC2558 Configuration Register (CFR) Bit Definitions

BIT

DEFINITION

D(15–12)

All zeros, nonprogrammable

D11

Reference select

0: External

1: Internal

D10

Output select

0: Unipolar straight binary

1: 2’s complement

D9

Sample period select

0: Short sampling 12 SCLKs (1x sampling time)

1: Long sampling 24 SCLKs (2x sampling time)

D8

Conversion clock source select

0: Conversion clock = SCLK

1: Conversion clock = SCLK/2

D7

Input select

0: Normal

1: Pseudo differential CH A2(2558) or CH A1 (2554) is the differential input

D(6,5)

Conversion mode select

00: Single shot mode

01: Repeat mode

10: Sweep mode

11: Repeat sweep mode

D(4,3)†

TLC2558

TLC2554

Sweep auto sequence select

00: 0–1–2–3–4–5–6–7

01: 0–2–4–6–0–2–4–6

10: 0–0–2–2–4–4–6–6

11: 0–2–0–2–0–2–0–2

Sweep auto sequence select

00: N/A

01: 0–1–2–3–0–1–2–3

10: 0–0–1–1–2–2–3–3

11: 0–1–0–1–0–1–0–1

D2

EOC/INT – pin function select

0: Pin used as INT

1: Pin used as EOC

D(1,0)

FIFO trigger level (sweep sequence length)

00: Full (INT generated after FIFO level 7 filled)

01: 3/4 (INT generated after FIFO level 5 filled)

10: 1/2 (INT generated after FIFO level 3 filled)

11: 1/4 (INT generated after FIFO level 1 filled)

† These bits only take effect in conversion modes 10 and 11.

sampling

The sampling period starts after the first 4 input data are shifted in if they are decoded as one of the conversion

commands. These are select analog input (channel 0 through 7) and select test (channel 1 through 3).

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normal sampling

When the converter is using normal sampling, the sampling period is programmable. It can be 12 SCLKs (short

sampling) or 24 SCLKs (long sampling). Long sampling helps the input analog signal sampled to settle to 0.5

LSB accuracy when input source resistance is high.

extended sampling

An asynchronous (to the SCLK) signal, via dedicated hardware pin CSTART, can be used in order to have total

control of the sampling period and the start of a conversion. This is extended sampling. The falling edge of

CSTART is the start of the sampling period. The rising edge of CSTART is the end of the sampling period and

the start of the conversion. This function is useful for an application that requires:

D

The use of an extended sampling period to accommodate different input source impedance.

D

The use of a faster I/O clock on the serial port but not enough sampling time is available due to the fixed

number of SCLKs. This could be due to a high input source impedance or due to higher MUX ON resistance

at lower supply voltage (refer to application information).

Once the conversion is complete, the processor can initiate a read cycle using either the read FIFO command

to read the conversion result or simply select the next channel number for conversion. Since the device has a

valid conversion result in the output buffer, the conversion result is simply presented at the serial data output.

TLC2554/TLC2558 conversion modes

The TLC2554 and TLC2558 have four different conversion modes (mode 00, 01, 10, 11).  The operation of each

mode is slightly different, depending on how the converter performs the sampling and which host interface is

used. The trigger for a conversion can be an active CSTART (extended sampling), CS (normal sampling, SPI

interface), or FS (normal sampling, TMS320 DSP interface). When FS is used as the trigger, CS can be held

active, i.e. CS does not need to be toggled through the trigger sequence. Different types of triggers should not

be mixed throughout the repeat and sweep operations. When CSTART is used as the trigger, the conversion

starts on the rising edge of CSTART. The minimum low time for CSTART is 800 ns. If an active CS or FS is used

as the trigger, the conversion is started after the 16th or 28th SCLK edge. Enough time (for conversion) should

be allowed between consecutive triggers so that no conversion is terminated prematurely.

one shot mode (mode 00)

One shot mode (mode 00) does not use the FIFO, and the EOC is generated as the conversion is in progress

(or INT is generated after the conversion is done).

repeat mode (mode 01)

Repeat mode (mode 01) uses the FIFO. Once the programmed FIFO threshold is reached, the FIFO must be

read, or the data is lost and the sequence starts over again. This allows the host to set up the converter and

continue monitoring a fixed input and come back to get a set of samples when preferred. The first conversion

must start with a select command so an analog input channel can be selected.

sweep mode (mode 10)

Sweep mode (mode 10) also uses the FIFO. Once it is programmed in this mode, all of the channels listed in

the selected sweep sequence are visited in sequence. The results are converted and stored in the FIFO. This

sweep sequence may not be completed if the FIFO threshold is reached before the list is completed. This allows

the system designer to change the sweep sequence length. Once the FIFO has reached its programmed

threshold, an interrupt (INT) is generated. The host must issue a read FIFO command to read and clear the FIFO

before the next sweep can start.

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TLC2554/TLC2558 conversion modes (continued)

repeat sweep mode (mode 11)

Repeat sweep mode (mode 11) works the same way as mode 10 except the operation has an option to continue

even if the FIFO threshold is reached. Once the FIFO has reached its programmed threshold, an interrupt (INT)

is generated. Then two things may happen:

1.

The host may choose to act on it (read the FIFO) or ignore it. If the next cycle is a read FIFO cycle, all of

the data stored in the FIFO is retained until it has been read in order.

2.

If the next cycle is not a read FIFO cycle, or another CSTART is generated, all of the content stored in the

FIFO is cleared before the next conversion result is stored in the FIFO, and the sweep is continued.

Table 3. TLC2554/TLC2558 Conversion Mode

CONVERSION

MODE

CFR

D(6,5)

SAMPLING

TYPE

OPERATION

One shot

00

Normal

Single conversion from a selected channel

CS or FS to start select/sampling/conversion/read

One INT or EOC generated after each conversion

Host must serve INT by selecting channel, and converting and reading the previous output.

Extended

Single conversion from a selected channel

CS to select/read

CSTART to start sampling and conversion

One INT or EOC generated after each conversion

Host must serve INT by selecting next channel and reading the previous output.

Repeat

01

Normal

Repeated conversions from a selected channel

CS or FS to start sampling/conversion

One INT generated after FIFO is filled up to the threshold

Host must serve INT by either 1) (FIFO read) reading out all of the FIFO contents up to the

threshold, then repeat conversions from the same selected channel or 2) writing another

command(s) to change the conversion mode. If the FIFO is not read when INT is served, it

is cleared.

Extended

Same as normal sampling except CSTART starts each sampling and conversion when CS is

high.

Sweep

10

Normal

One conversion per channel from a sequence of channels

CS or FS to start sampling/conversion

One INT generated after FIFO is filled up to the threshold

Host must serve INT by (FIFO read) reading out all of the FIFO contents up to the threshold,

then write another command(s) to change the conversion mode.

Extended

Same as normal sampling except CSTART starts each sampling and conversion when CS is

high.

Repeat sweep

11

Normal

Repeated conversions from a sequence of channels

CS or FS to start sampling/conversion

One INT generated after FIFO is filled up to the threshold

Host must serve INT by either 1) (FIFO read) reading out all of the FIFO contents up to the

threshold, then repeat conversions from the same selected channel or 2) writing another

command(s) to change the conversion mode. If the FIFO is not read when INT is served it is

cleared.

Extended

Same as normal sampling except CSTART starts each sampling and conversion when CS is

high.

NOTE: Programming the EOC/INT pin as the EOC signal works for mode 00 only. The other three modes automatically generate an INT signal

irrespective of whether EOC/INT is programmed.

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timing diagrams

The timing diagrams can be categorized into two major groups: nonconversion and conversion. The

nonconversion cycles are read and write (configuration). None of these cycles carry a conversion. Conversion

cycles are those four modes of conversion.

read cycle (read FIFO or read CFR)

read CFR cycle:

The read command is decoded in the first 4 clocks. SDO outputs the contents of the CFR after the 4th SCLK.

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎ

ÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

SCLK

CS

FS

SDI

INT

EOC

SDO

ID14

ID13

ID12

ID15

OD11 OD10

OD9

OD4

OD3

OD2

OD1

OD0

1

2

3

4

5

6

7

13

14

15

16

1

12

ID15

Figure 2. TLC2554/TLC2558 Read CFR Cycle (FS active)

ÎÎÎ

ÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

SCLK

CS

FS

SDI

INT

EOC

SDO

ID15

ID14

ID13

ID12

ID14

OD4

OD3

OD2

OD1

OD0

1

2

3

4

5

6

7

13

14

15

16

1

12

ÎÎÎÎ

ÎÎÎÎÎÎ

OD11 OD10

OD9

ID15

Figure 3. TLC2554/TLC2558 Read CFR Cycle (FS = 1)

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read cycle (read FIFO or read CFR) (continued)

FIFO read cycle

The first command in the active cycle after INT is generated, if the FIFO is used, is assumed as the FIFO read

command. The first FIFO content is output immediately before the command is decoded. If this command is

not a FIFO read, then the output is terminated but the first data in the FIFO is retained until a valid FIFO read

command is decoded. Use of more layers of the FIFO reduces the time taken to read multiple data. This is

because the read cycle does not generate EOC or INT nor does it carry out any conversion.

ÎÎÎ

ÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

SCLK

CS

FS

SDI

INT

EOC

SDO

ID15

ID14

ID13

ID12

ID14

OD8

OD7

OD5

OD0

1

2

3

4

5

6

7

13

14

15

16

1

12

ÎÎÎ

ÎÎÎ

OD11 OD10

OD9

ID15

OD6

Figure 4. TLC2554/TLC2558 Continuous FIFO Read Cycle (FS = 1)

(controlled by SCLK, SCLK can stop between each 16 SCLKs)

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write cycle (write CFR)

The write cycle is used to write to the configuration register CFR (with 12-bit register content). The write cycle

does not generate an EOC or INT nor does it carry out any conversion.

ÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

ÎÎÎÎ

ÎÎÎÎ

ÎÎÎÎÎ

ÎÎÎÎÎ

SCLK

CS

FS

SDI

INT

EOC

SDO

ID14

ID13

ID12

ID15

ID11

ID10

ID9

ID4

ID3

ID2

ID1

ID0

1

2

3

4

5

6

7

13

14

15

16

1

12

ÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎ

ID15

Figure 5. TLC2554/TLC2558 Write Cycle (FS active)

ÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

ÎÎÎ

ÎÎÎ

ÎÎÎÎ

SCLK

CS

FS

SDI

INT

EOC

SDO

ID15

ID14

ID13

ID12

ID15

ID11

ID10

ID9

ID4

ID3

ID2

ID1

ID0

1

2

3

4

5

6

7

13

14

15

16

1

12

ÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

ID14

Figure 6. TLC2554/TLC2558 Write Cycle (FS = 1)

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conversion cycles

DSP/normal sampling

ÎÎÎ

ÎÎÎ

SCLK

CS

FS

SDI

INT

EOC

SDO

ID15

ID14

ID13

ID12

OD11

OD10

OD8

OD7

OD6

OD5

1

2

3

4

5

7

13

14

15

16

1

12

28

OD9

tsample (Long)

tsample (Short)

6

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎ

ID15

OD0

ÎÎÎÎÎ

ÎÎÎÎÎ

tconv

t conv

Figure 7. Mode 00 Single Shot/Normal Sampling (FS signal used)

ÎÎÎ

ÎÎÎ

SCLK

CS

FS

SDI

INT

EOC

SDO

ID15

ID14

ID13

ID12

OD10

OD8

OD7

OD6

OD5

1

2

3

4

5

7

13

14

15

16

1

12

28

OD9

tsample (Long)

tsample (Short)

6

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

ID15

OD0

ÎÎÎÎ

ÎÎÎÎ

tconv

t conv

OD11

ID14

Figure 8. Mode 00 Single Shot/Normal Sampling (FS = 1, FS signal not used)

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conversion cycles (continued)

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎ

ÎÎÎÎ

CS

CSTART

SDI

INT

EOC

SDO

Hi-Z

Select/Read

Cycle

Select/Read

Cycle

tsample

tconvert

Previous Conversion

Result

Previous Conversion

Result

FS

Hi-Z

Hi-Z

† This is one of the single shot commands. Conversion starts on next rising edge of CSTART.

Figure 9. Mode 00 Single Shot/Extended Sampling (FS signal used, FS pin connected to TMS320 DSP)

CS used as FS input

When interfacing with the TMS320 DSP using conversion mode 00, the FSR signal from the DSP may be

connected to the CS input if this is the only device on the serial port. This will save one output pin from the DSP.

Output data is made available on the rising edge of SCLK and input data is latched on the rising edge of SCLK

in this case.

modes using the FIFO: modes 01, 10, 11 timing

Modes 01, 10, and 11 timing are very similar except for how and when the FIFO is read, how the device is

configured, and how channel(s) are selected.

Mode 01 (repeat mode) requires a two-cycle configuration where the first one sets the mode and the second

one selects the channel. Once the FIFO is filled up to the threshold programmed, it has the option to either read

the FIFO or configure for other modes. Therefore, the sequence is either configure: select : triggered

conversions : FIFO read : select : triggered conversions : FIFO read or configure : select : triggered conversions

: configure : .... Each configure clears the FIFO and the action that follows the configure command depends on

the mode setting of the device.

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modes using the FIFO: modes 01, 10, 11 timing (continued)

CS

CSTART

SDI

INT

SDO

Hi-Z

From Channel 2

tconvert

FS

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

§

§

Hi-Z

tsample

tsample

tsample

tconvert

Configure

Select

Conversion #1

Select

Conversion #4

Read FIFO

#1

#2

#3

#4

Next #1

Top of FIFO

From Channel 2

tconvert

† Command = Configure write for mode 01, FIFO threshold = 1/2

‡ Command = Read FIFO, 1st FIFO read

§ Command = Select ch2.

Figure 10. TLC2554/TLC2558 Mode 01 DSP Serial Interface (conversions triggered by FS)

CS

CSTART

SDI

INT

SDO

Hi-Z

From Channel 2

FS

(DSP)

From Channel 2

Configure

Select

Conversion #1

Select

Conversion #4

Read FIFO

First FIFO Read

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎÎ

ÎÎÎ

ÎÎÎ

ÎÎÎ

ÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎ

§

#1

#2

#3

#4

Next #1

ÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

tsample(1)

tconvert(1)

§

tsample(2)

tsample(3)

tsample(4)

tconvert(2)

tconvert(3)

tconvert(4)

Hi-Z

tSample(i) > = MIN(tSample)

† Command = Configure write for mode 01, FIFO threshold = 1/2

‡ Command = Read FIFO, 1st FIFO read

§ Command = Select ch2.

Figure 11. TLC2554/TLC2558 Mode 01 

µ

p/DSP Serial Interface (conversions triggered by CSTART)

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modes using the FIFO: modes 01, 10, 11 timing (continued)

Mode 10 (sweep mode) requires reconfiguration at the start of each new sweep sequence. Once the FIFO is

filled up to the programmed threshold, the host has the option to either read the FIFO or configure for other

modes. Once the FIFO is read, the host must reconfigure the device before the next sweep sequence can be

started. So the sequence is either configure : triggered conversions : FIFO read : configure. or configure :

triggered conversions : configure : .... Each configure clears the FIFO and the action that follows the configure

command depends on the mode setting of the device.

Mode 11 (repeat sweep mode) requires one cycle configuration. This sweep sequence can be repeated without

reconfiguration. Once the FIFO is filled up to the programmed threshold, the host has the option to either read

the FIFO or configure for other modes. So the sequence is either configure : triggered conversions : FIFO read

: triggered conversions : FIFO read ... or configure : triggered conversions : configure : .... Each configure clears

the FIFO and the action that follows the configure command depends on the mode setting of the device.

CS

CSTART

SDI

INT

SDO

From Channel 0

FS

(DSP)

From Channel 3

Configure

Conversion

Conversion

Read FIFO

#1

#2

#3

#4

Top of FIFO

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎ

ÎÎ

ÎÎ

tsample(1)

Read FIFO

#1

From Channel 0

Conversion

From Channel 3

Conversion

Repeat

Second FIFO Read

Repeat

ÎÎ

ÎÎ

tsample(2)

tsample(3)

tsample(4)

First FIFO Read

tconvert

tconvert

tSample(i) > = MIN(tSample)

† Command = Configure write for mode 10 or 11, FIFO threshold = 1/2, sweep seq = 0–1–2–3.

‡ Command = Read FIFO

Figure 12. TLC2554/TLC2558 Mode 10/11 DSP Serial Interface (conversions triggered by FS)

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modes using the FIFO: modes 01, 10, 11 timing (continued)

tsample (3)

CS

CSTART

SDI

INT

SDO

From Channel 0

FS

(DSP)

Configure

Conversion

Read FIFO

#1

#2

#3

#4

Top of FIFO

Read FIFO

#1

From Channel 0

Conversion

Repeat

First FIFO Read

Second FIFO Read

Repeat

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

tsample(i) >= MIN (tsample)

ÎÎ

ÎÎ

tsample (2)

tsample (4)

tconvert

From Channel 3

Conversion

Conversion

From Channel 3

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎ

tconvert

tsample (1)

ÎÎ

ÎÎ

† Command = Configure write for mode 10 or 11, FIFO threshold = 1/2, sweep seq = 0–1–2–3.

‡ Command = Read FIFO

Figure 13. TLC2554/TLC2558 Mode 10/11 DSP Serial Interface (conversions triggered by CSTART)

CS

CSTART

SDI

INT

SDO

From Channel 0

tconvert

Configure

Conversion

Conversion

Read FIFO

#1

#2

#3

#4

Top of FIFO

Read FIFO

#1

Conversion

Conversion

Repeat

First FIFO Read

Second FIFO Read

Repeat

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

ÎÎ

tSample (i) > = MIN(tSample)

From Channel 3

From Channel 0

From Channel 3

Î

Î

ÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎ

tsample(1)

tsample(2)

tsample(3)

tsample(4)

tconvert

† Command = Configure write for mode 10 or 11, FIFO threshold = 1/2, sweep seq = 0–1–2–3.

‡ Command = Read FIFO

Figure 14. TLC2554/TLC2558 Mode 00/11 

µ

p Serial Interface (conversions triggered by CS)

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FIFO operation

7

6

5

4

3

2

1

0

ADC

12-BIT

×

8

FIFO

OD

Serial

FIFO Full

FIFO 3/4 Full

FIFO 1/2 Full

FIFO 1/4 Full

FIFO Threshold Pointer

Figure 15. TLC2554/TLC2558 FIFO

The device has an 8 layer FIFO that can be programmed for different thresholds. An interrupt is sent to the host

after the preprogrammed threshold is reached. The FIFO can be used to store data from either a fixed channel

or a series of channels based on a preprogrammed sweep sequence. For example, an application may require

eight measurements from channel 3. In this case, the FIFO is filled with 8 data sequentially taken from channel

3. Another application may require data from channel 0, channel 2, channel 4, and channel 6 in an orderly

manner. Therefore, the threshold is set for 1/2 and the sweep sequence 0–2–4–6–0–2–4–6 is chosen. An

interrupt is sent to the host as soon as all four data are in the FIFO.

SCLK and conversion speed

There are multiple ways to adjust the conversion speed. The maximum equivalent conversion clock (f

SCLK

/DIV)

should not exceed 10 MHz.

D

The SCLK is used as the source of the conversion clock and 14 conversion clocks are required to complete

a conversion plus 4 SCLKs overhead.

The devices can operate with an SCLK up to 20 MHz for the supply voltage range specified. The clock

divider provides speed options appropriate for an application where a high speed SCLK is used for faster

I/O. The total conversion time is 14 

×

(DIV/f

SCLK

) where DIV is 1 or 2. For example a 20-MHz SCLK with the

divide by 2 option produces a {14 

×

 (2/20 M) + 4

×

 (1/20 MHz)} = 1.6 

µ

s conversion time.

D

Auto power down can be used. This mode is always on. If the device is not accessed (by CS or CSTART),

the converter is powered down to save power. The built-in reference is left on in order to quickly resume

operation within one half SCLK period. This provides unlimited choices to trade speed with power savings.

reference voltage

The device has a built-in reference with a level of 4 V. If the internal reference is used, REFP is set to 4 V and

REFM is set to 0 V. An external reference can also be used through two reference input pins, REFP and REFM,

if the reference source is programmed as external. The voltage levels applied to these pins establish the upper

and lower limits of the analog inputs to produce a full-scale and zero-scale reading respectively. The values of

REFP, REFM, and the analog input should not exceed the positive supply or be lower than GND consistent with

the specified absolute maximum ratings. The digital output is at full scale when the input signal is equal to or

higher than REFP and at zero when the input signal is equal to or lower than REFM.

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FIFO operation (continued)

power down

Writing 8000h to the device puts the device into a software power-down state. For a hardware power down, the

dedicated PWDN pin provides another way to power down the device asynchronously. These two power-down

modes power down the entire device including the built-in reference to save power. It requires 20 ms to resume

from either a software or hardware power down.

Auto power down mode is always enabled. This mode maintains the built-in reference if an internal reference

is used, so resumption is fast enough to be used between cycles.

The  configuration register is not affected by any of the power down modes but the sweep operation sequence

has to be started over again. All FIFO contents are cleared by the power-down modes.

power up and initialization

Initialization requires:

1.

Determine processor type by writing A000h to the TLC2554/58

2.

Configure the device

The first conversion after power up or resuming from power down is not valid.

absolute maximum ratings over operating free-air temperature (unless otherwise noted)

Supply voltage range, GND to V

CC

  

–0.3 V to 6.5 V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Analog input voltage range 

–0.3 V to V

CC 

+ 0.3 V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Reference input voltage  

V

CC 

+ 0.3 V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Digital input voltage range 

–0.3 V to V

CC 

+ 0.3 V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Operating

 

virtual junction temperature range, T

J

  – 40

°

C to 150

°

C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Operating free-air temperature range, T

A

: TLC2554/58C 0

°

C to 70

°

C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

TLC2554/58I –40

°

C to 85

°

C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Storage temperature range, T

stg 

  – 65

°

C to 150

°

C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 

260

°

C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and

functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not

implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

recommended operating conditions

MIN

NOM

MAX

UNIT

Supply voltage, VCC

4.5

5

5.5

V

Positive external reference voltage input,  VREFP (see Note 1)

2

VCC

V

Negative external reference voltage input, VREFM (note Note 1)

0

2

V

Differential reference voltage input, VREFP – VREFM (see Note 1)

2

VCC VCC+0.2

V

Analog input voltage (see Note 1)

0

VCC

V

High level control input voltage, VIH

2.1

V

Low-level control input voltage, VIL

0.6

V

Rise time, for CS, CSTART SDI at 0.5 pF, tr(I/O)

 

4.76

ns

Fall time, for CS, CSTART SDI at 0.5 pF, tf(I/O)

 

2.91

ns

Rise time, for INT, EOC, SDO at 30 pF, tr(Output)

 

2.43

ns

Fall time, for INT, EOC, SDO at 30 pF, tf(Output)

 

2.3

ns

NOTE 1: When binary output format is used, analog input voltages greater than that applied to REFP convert as all ones (111111111111), while

input voltages less than that applied to REFM convert as all zeros (000000000000). The device is functional with reference down to

2 V (VREFP – VREFM –1); however, the electrical specifications are no longer applicable.

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recommended operating conditions (continued)

MIN

NOM

MAX

UNIT

Transition time, for FS, SCLK, SDI, tt(CLK)

0.5

SCLK

Setup time, CS falling edge before SCLK rising edge (FS=1) or before SCLK falling edge (when FS is active),

tsu(CS-SCLK)

0.5

SCLK

Hold time, CS rising edge after SCLK rising edge (FS=1) or after SCLK falling edge (when FS is active),

th(SCLK-CS)

5

ns

Delay time, delay from CS falling edge to FS rising edge, td(CSL-FSH)

0.5

7

SCLKs

Delay time, delay time from 16th SCLK falling edge to CS rising edge (FS is active), td(SCLK16F-CSH)

0.5

SCLKs

Setup time, FS rising edge before SCLK falling edge, tsu(FSH-SCLKF)

0.5

SCLKs

Hold time, FS hold high after SCLK falling edge, th(FSH-SCLKF)

0.5

SCLKs

Pulse width, CS high time, twH(CS)

100

ns

SCLK cycle time, VCC = 2.7 V to 3.6V, tc(SCLK)

67

ns

SCLK cycle time, VCC = 4.5 V to 5.5V,  tc(SCLK)

50

ns

Pulse width, SCLK low time, twL(SCLK)

20

30

ns

Pulse width, SCLK high time, twH(SCLK)

20

30

ns

Setup time, SDI valid before falling edge of SCLK (FS is active) or the rising edge of SCLK (FS=1),

tsu(DI-SCLK)

25

ns

Hold time, SDI hold valid after falling edge of SCLK (FS is active) or the rising edge of SCLK (FS=1),

th(DI-SCLK)

5

 

ns

Delay time, delay from CS falling edge to SDO valid, td(CSL-DOV)

1

 25

ns

Delay time, delay from FS falling edge to SDO valid, td(FSL-DOV)

1

 25

ns

Delay time, delay from SCLK rising edge (FS is active) or SCLK falling edge (FS=1) SDO valid, td(CLK-DOV)

1

25

ns

Delay time, delay from CS rising edge to SDO 3-stated, td(CSH-DOZ)

1

 25

ns

Delay time, delay from 16th SCLK falling edge (FS is active) or the 16th rising edge (FS=1) to EOC falling

edge, td(CLK-EOCL)

1

 25

ns

Delay time, delay from EOC rising edge to SDO 3-stated if CS is low, td(EOCH-DOZ)

 1

50

ns

Delay time, delay from 16th SCLK rising edge to INT falling edge (FS =1) or from the 16th falling edge SCLK

to INT falling edge (when FS active), td(SCLK-INTL)

 

3.5

µ

s

Delay time, delay from CS falling edge to INT rising edge, td(CSL-INTH)

1

 50

ns

Delay time, delay from CS rising edge to CSTART falling edge, td(CSH-CSTARTL)

100

 

ns

Delay time, delay from CSTART rising edge to EOC falling edge, td(CSTARTH-EOCL)

1

50

ns

Pulse width, CSTART low time, twL(CSTART)

0.8

µ

s

Delay time, delay from CS rising edge to EOC rising edge, td(CSH-EOCH)

1

50

ns

Delay time, delay from CSTART rising edge to CSTART falling edge, td(CSTARTH-CSTARTL)

3.6

 

µ

s

Delay time, delay from CSTART rising edge to INT falling edge, td(CSTARTH-INTL)

3.5

 

µ

s

Operating free air temperature TA

TLC2554C/TLC2558C

0

70

_

C

Operating free-air temperature, TA

TLC2554I/TLC2558I

–40

85

_

C

NOTE 2: This is the time required for the clock input signal to fall from VIH max or  to rise from VILmax to VIHmin. In the vicinity of normal room

temperature, the devices function with input clock transition time as slow as 1 

µ

s for remote data-acquisition applications where the

sensor and A/D converter are placed several feet away from the controlling microprocessor.

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

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electrical characteristics 

over recommended operating free-air temperature range, V

CC

 = V

REFP

 = 4.5 V to

5.5 V, SCLK frequency = 20 MHz at 5 V, (unless otherwise noted)

PARAMETER

TEST CONDITIONS

MIN

TYP†

MAX

UNIT

V

OH

High-level output voltage

V

CC 

= 5.5 V, I

OH

 = –20 

µ

A at 30 pF load

2.4

V

V

OL

Low-level output voltage

V

CC 

= 5.5 V, I

OL

 = 20 

µ

A at 30 pF load

0.4

V

I

OZ

Off-state output current

V

O

 = V

CC

CS

V

1

2.5

µ

A

I

OZ

O s a e ou u cu e

(high-impedance-state)

V

= 0

CS = V

CC

–1

-2.5

µ

A

I

IH

High-level input current

V

= V

CC

0.005

2.5

µ

A

I

IL

Low-level input current

V

= 0 V

–0.005

2.5

µ

A

I

CC

Operating supply current, normal sampling

CS at 0 V, Ext ref

V

CC

 = 4.5 V to 5.5 V

4

mA

I

CC

O e a

g su

y cu e , o

a sa

g

(short)

CS at 0 V, Int ref

V

CC

 = 4.5 V to 5.5 V

6

mA

I

CC

Operating supply current extended sampling

CS at 0 V, Ext ref

V

CC

 = 4.5 V to 5.5 V

1.9

mA

I

CC

Operating supply current, extended sampling

CS at 0 V, Int ref

V

CC

 = 4.5 V to 5.5 V

2

mA

Internal reference supply current

CS at 0 V, V

CC

 = 4.5 V to 5.5 V

2

mA

I

CC(PD)

Power-down supply current

For all digital inputs, 

0

 V

I

 

 0.3 V or V

 V

CC

– 0.3 V,

SCLK = 0, V

CC

 = 4.5 V to 5.5 V, 

Ext clock

0.1

1

µ

A

I

CC(AUTOPWDN)

Auto power-down current

For all digital inputs,

0

 V

I

 

 0.3 V or V

 V

CC

– 0.3 V,

SCLK = 0, V

CC

 = 4.5 V to 5.5 V,

Ext clock, Ext ref

5

µ

A

Selected channel leakage current

Selected channel at V

CC

1

µ

A

Selected channel leakage current

Selected channel at 0 V

–1

µ

A

Maximum static analog reference current into

REFP (use external reference)

V

REFP

 = V

CC

 = 5.5 V, V

REFM

 = GND

1

µ

A

C

i

Input capacitance

Analog inputs

45

50

pF

C

i

Input capacitance

Control Inputs

5

25

pF

Z

i

Input MUX ON resistance

V

CC

 = 5.5 V

500

† All typical values are at VCC = 5 V, TA = 25

°

C.

‡ 800 

µ

A if internal reference is used.

ac specifications

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

SINAD

Signal-to-noise ratio +distortion

fI = 12 kHz at 400 KSPS

69

71

dB

THD

Total harmonic distortion

fI = 12 kHz at 400 KSPS

–82

–76

dB

ENOB

Effective number of bits

fI = 12 kHz at 400 KSPS

11.6

Bits

SFDR

Spurious free dynamic range

fI = 12 kHz at 400 KSPS

–84

–75

dB

Analog input

Full power bandwidth, –3 dB

1

MHz

Full power bandwidth, –1 dB

500

kHz

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

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reference specifications (0.1 

µ

F and 10 

µ

F between REFP and REFM pins)

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Reference input voltage, REFP

VCC = 4.5 V

VCC

V

Input impedance

VCC = 5 5 V

CS = 1,

SCLK = 0, (off)

100

M

Input impedance

VCC = 5.5 V

CS = 0,

SCLK = 20 MHz (on)

20

25

k

Input voltage difference, REFP – REFM

VCC = 4.5 V

2

VCC

V

Internal reference voltage,REFP – REFM

VCC = 5.5 V Reference select = internal

3.85

4

4.15

V

Internal reference start up time

VCC = 5.5 V 10 

µ

F

20

ms

Reference temperature coefficient

VCC = 4.5 V

16

40

PPM/

°

C

operating characteristics over recommended operating free-air  temperature range, V

CC

 = V

REFP

 = 4.5 V,

SCLK frequency = 20 MHz (unless otherwise noted)

PARAMETER

TEST CONDITIONS

MIN

TYP†

MAX

UNIT

Integral linearity error (INL) (see Note 4)

±

1

LSB

Differential linearity error (DNL)

See Note 3

±

1

LSB

EO

Offset error (see Note 5)

See Note 3

±

2.5

LSB

EG

Gain  error (see Note 5)

See Note 3

±

1

±

2

LSB

ET

Total unadjusted error (see Note 6)

±

2

LSB

SDI = B000h

800h

(2048D)

Self-test output code (see Table 1 and Note 7)

SDI = C000h

000h

(0D)

SDI = D000h

FFFh

(4095D)

tconv

Conversion time

External SCLK

(14XDIV)

fSCLK

tsample

Sampling time

At 1 k

600

ns

tt(I/O)

Transition time for EOC, INT

50

ns

tt(CLK)

Transition time for SDI, SDO

25

ns

† All  typical values are at TA = 25

°

C.

NOTES:

3. Analog input voltages greater than that applied to REFP convert as all ones (111111111111), while input voltages less than that

applied to REFM convert as all zeros (0000000000). The device is functional with reference down to 2 V (VREFP – VREFM);

however, the electrical specifications are no longer applicable.

4. Linear error is the maximum deviation from the best straight line through the A/D transfer characteristics.

5. Zero error is the difference between 000000000000 and the converted output for zero input voltage: full-scale error is the difference

between 111111111111 and the converted output for full-scale input voltage.

6. Total unadjusted error comprises linearity, zero, and full-scale errors.

7. Both the input data and the output codes are expressed in positive logic.

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

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PARAMETER MEASUREMENT INFORMATION

ÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

VIH

VIL

VIH

VIL

VIH

VIL

VIH

VIL

VOH

VOL

VOH

VOL

VOH

VOL

CS

FS

SCLK

SDI

SDO

EOC

INT

tt(I/O)

tt(I/O)

twH(CS)

td(SCLK16F-CSH)

th(FSH-SCLKF)

tsu(FSH-SCLKF)

twH(SCLK)

twL(SCLK)

tsu(CS-SCLK)

td(CSL-FSH)

tc(SCLK)

tsu(DI-CLK)

th(DI-CLK)

td(FSL-DOV)

td(CLK-DOV)

th(SCLK-CS)

ID15

ID1

Hi-Z

td(EOCH–DOZ)

td(CLK-EOCL)

td(SCLK-INTL)

td(CSL-INTH)

90%

50%

10%

1

16

td(CSL-DOV)

Figure 16. Critical Timing (normal sampling, FS is active)

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

24

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PARAMETER MEASUREMENT INFORMATION

CS

CSTART

EOC

INT

VOH

VOL

VIH

VIL

VOH

VOL

VIH

VIL

td(CSH-CSTARTL)

twL(CSTART)

td(CSH-EOCH)

tt(I/O)

tt(I/O)

tconvert

td(EOCH-INTL)

td(CSTARTH-EOCL)

td(CSL-INTH)

Figure 17. Critical Timing (extended sampling, single shot)

VIH

VIL

VOH

VOL

VOH

VOL

VIH

VIL

CS

CSTART

EOC

INT

td(CSL-CSTARTL)

twL(CSTART)

td(CSTARTH–CSTARTL)

td(CSH-EOCH)

tt(I/O)

tt(I/O)

td(CSTARTH-EOCL)

td(CSTARTH-INTL)

td(CSL-INTH)

90%

50%

10%

Figure 18. Critical Timing (extended sampling, repeat/sweep/repeat sweep)

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

25

POST OFFICE BOX 655303 

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PARAMETER MEASUREMENT INFORMATION

ÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ

Hi-Z

Hi-Z

VOH

VOL

VIH

VIL

VIH

VIL

VIH

VIL

VOH

VOL

VOH

VOL

CS

SCLK

SDI

SDO

ECO

INT

ID15

ID1

OD15

OD1

OD0

tt(I/O)

tt(I/O)

twH(CS)

td(SCLK16F-CSH)

tsu(CS-SCLK)

twL(SCLK)

twH(SCLK)

tc(SCLK)

tsu(DI-CLK)

th(DI-CLK)

td(CSL-DOV)

td(CLK-DOV)

td(CLK-EOCL)

td(EOCH-DOZ)

td(SCLK-INTL)

td(CSL-INTH)

1

16

tt(CLK)

Figure 19. Critical Timing (normal sampling, FS = 1)

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

26

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TYPICAL CHARACTERISTICS

Figure 20

TA – Temperature – 

°

C

0.49

0.47

0.45

–40

INL

 – Integral Nonlinearity – LSB

0.51

0.53

INTEGRAL NONLINEARITY

vs

TEMPERATURE

0.55

25

85

VCC = 5 V,

Internal Reference = 4 V,

SCLK = 20 MHz,

Single Shot,

Short Sample,

Mode 00 

µ

P mode

Figure 21

TA – Temperature – 

°

C

0.3

0.25

0.2

0.1

–40

25

DNL

 – Differential Nonlinearity – LSB

0.4

0.45

DIFFERENTIAL NONLINEARITY

vs

TEMPERATURE

0.5

85

0.35

0.15

VCC = 5 V,

Internal Reference = 4 V,

SCLK = 20 MHz,

Single Shot,

Short Sample,

Mode 00 

µ

P mode

Figure 22

0.9

0.7

0.3

0

–40

25

Offset Error – LSB

1.5

1.6

OFFSET ERROR

vs

TEMPERATURE

1.7

85

1.4

1.3

1.2

1.1

1

0.8

0.6

0.5

0.4

0.2

0.1

TA – Temperature – 

°

C

VCC = 5 V,

External Reference = 4 V,

SCLK = 20 MHz,

Single Shot,

Short Sample,

Mode 00 

µ

P mode

Figure 23

–2.5

–3

–3.5

–5

–40

25

Gain Error – LSB

–1

–0.5

GAIN ERROR

vs

TEMPERATURE

0

85

–1.5

–2

–4

–4.5

TA – Temperature – 

°

C

VCC = 5 V,

External Reference = 4 V,

SCLK = 20 MHz,

Single Shot,

Short Sample,

Mode 00 

µ

P mode

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

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TYPICAL CHARACTERISTICS

Figure 24

3.7

3.4

3.3

3

–40

25

Supply Current – mA

3.8

3.9

SUPPLY CURRENT

vs

TEMPERATURE

4

85

3.6

3.5

3.2

3.1

TA – Temperature – 

°

C

VCC = 5.5 V,

External Reference = 4 V,

SCLK = 20 MHz,

Single Shot,

Short Sample,

Mode 00 

µ

P mode

Figure 25

0.2

–0.1

–0.2

–0.5

–40

25

Power Down – 

0.3

0.4

POWER DOWN CURRENT

vs

TEMPERATURE

0.5

85

0.1

0

–0.3

–0.4

A

µ

TA – Temperature – 

°

C

VCC = 5.5 V,

External Reference = 4 V,

SCLK = 20 MHz,

Single Shot,

Short Sample,

Mode 00 

µ

P mode

–1.0

–0.8

–0.6

–0.4

–0.2

–0.0

0.2

0.4

0.6

0.8

1.0

0

2048

4096

INL

 – Integral Nonlinearity – LSB

Samples

INTEGRAL NONLINEARITY

vs

SAMPLES

VCC = 5 V, External Reference = 5 V, SCLK = 20 MHz,

Single Shot, Short Sample, Mode 00 DSP Mode

Figure 26

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

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TYPICAL CHARACTERISTICS

–1.0

–0.8

–0.6

–0.4

–0.2

–0.0

0.2

0.4

0.6

0.8

1.0

0

2048

4096

DNL

 – Differential Nonlinearity – LSB

Samples

DIFFERENTIAL NONLINEARITY

vs

SAMPLES

VCC = 5 V, External Reference = 5 V, SCLK = 20 MHz,

Single Shot, Short Sample, Mode 00 DSP Mode

Figure 27

–1.0

–0.8

–0.6

–0.4

–0.2

–0.0

0.2

0.4

0.6

0.8

1.0

0

2048

4096

INL

 – Integral Nonlinearity – LSB

Samples

INTEGRAL NONLINEARITY

vs

SAMPLES

VCC = 5 V, Internal Reference = 4 V, SCLK = 20 MHz,

Single Shot, Short Sample, Mode 00 DSP Mode

Figure 28

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

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TYPICAL CHARACTERISTICS

–1.0

–0.8

–0.6

–0.4

–0.2

–0.0

0.2

0.4

0.6

0.8

1.0

0

2048

4096

DNL

 – Differential Nonlinearity – LSB

Samples

DIFFERENTIAL NONLINEARITY

vs

SAMPLES

VCC = 5 V, Internal Reference = 4 V, SCLK = 20 MHz,

Single Shot, Short Sample, Mode 00 DSP Mode

Figure 29

–100

–140

0

50

100

Magnitude – dB

–40

–20

f – Frequency – kHz

FAST POURIER TRANSFORM

vs

FREQUENCY

0

150

200

–60

–80

–120

AIN = 50 kHz

VCC = 5 V,  Channel 0

External Reference = 4 V

SCLK = 20 MHz

Single Shot, Short Sample

Mode 00 DSP Mode

Figure 30

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

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TYPICAL CHARACTERISTICS

40

45

50

55

60

65

70

75

80

0

100

200

Figure 31

SINAD – Signal-to-Noise + Distortion – dB

f – Frequency – kHz

SIGNAL-TO-NOISE + DISTORTION

vs

INPUT FREQUENCY

VCC = 5 V, External Reference = 4 V,

SCLK = 20 MHz, Single Shot, Short

Sample, Mode 00 DSP Mode

9.00

9.20

9.40

9.60

9.80

10.00

10.20

10.40

10.60

10.80

11.00

11.20

11.40

11.60

11.80

12.00

0

100

200

Figure 32

ENOB – Effective Number of Bits – BITS

f – Frequency – kHz

EFFECTIVE NUMBER OF BITS

vs

INPUT FREQUENCY

VCC = 5 V, External Reference = 4 V,

SCLK = 20 MHz, Single Shot,

Short Sample, Mode 00 DSP Mode

–80

–75

–70

–65

–60

–55

–50

0

25

50

75

100

125

150

175

200

Figure 33

THD 

– 

T

otal Harmonic Distortion – dB

TOTAL HARMONIC DISTORTION

vs

INPUT FREQUENCY

f – Frequency – kHz

VCC = 5 V, External Reference = 4 V,

SCLK = 20 MHz, Single Shot,

Short Sample, Mode 00 DSP Mode

–100

–80

–60

–40

–20

0

0

25

50

75

100

125

150

175

200

Figure 34

Spurious Free Dynamic Range – dB

f – Frequency – kHz

SPURIOUS FREE DYNAMIC RANGE

vs

INPUT FREQUENCY

VCC = 5 V, External Reference = 4 V,

SCLK = 20 MHz, Single Shot,

Short Sample, Mode 00 DSP Mode

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

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PRINCIPLES OF OPERATION

1000000000

0111111111

0000000010

0000000001

0000000000

1111111110

0

0.0024

2.4564

2.4576

2.4588

Digital Output Code

1000000001

1111111101

1111111111

4.9056

4.9104

4.9152

2048

2047

2

1

0

4094

Step

2049

4093

4095

0.0006

VI – Analog Input Voltage – V

VZT =VZS + 1/2 LSB

VZS

See Notes A and B

4.9134

0.0012

VFT = VFS – 1/2 LSB

VFS

VFS Nom

NOTES: A. This curve is based on the assumption that Vref+ and Vref– have been adjusted so that the voltage at the transition from digital 0 to

1 (VZT) is 0.0006 V, and the transition to full scale (VFT) is 4.9134 V, 1 LSB = 1.2 mV.

B. The full scale value (VFS) is the step whose nominal midstep value has the highest absolute value. The zero-scale value (VZS) is

the step whose nominal midstep value equals zero.

Figure 35. Ideal 12-Bit ADC Conversion Characteristics

GND

CS

XF

TMS320 DSP

TLC2554/

TLC2558

SDI

SDO

SCLK

INT

TXD

RXD

CLKR

BIO

10 k

vcc

AIN

VDD

FSR

FS

CLKX

FSX

Figure 36. Typical Interface to a TMS320 DSP

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

32

POST OFFICE BOX 655303 

 DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

simplified analog input analysis

Using the equivalent circuit in Figure 39, the time required to charge the analog input capacitance from 0 to VS

within 1/2 LSB can be derived as follows.

The capacitance charging voltage is given by:

Vc

+

Vs

ǒ

1

–EXP

ǒ

–tc

Rt

 

Ci

Ǔ

Ǔ

Where

Rt = Rs + Zi

tc = Cycle time

(1)

The input impedance Zi is 0.5 k

 at 5 V. The final voltage to 1/2 LSB is given by:

VC (1

ń

2

LSB)

+

VS–

ǒ

VS

8192

Ǔ

(2)

Equating equation 1 to equation 2 and solving for cycle time tc gives:

Vs–

ǒ

VS

8192

Ǔ

+

Vs

ǒ

1

–EXP

ǒ

–tc

Rt

 

Ci

Ǔ

Ǔ

(3)

and time to change to 1/2 LSB (minimum sampling time) is:

tch (1

ń

2

LSB)

+

Rt

 

Ci

 

In(8192)

Where

In(8192) = 9.011

Therefore, with the values given, the time for the analog input signal to settle is:

tch (1

ń

2

LSB)

+

(Rs

)

0.5

k

W

)

 

Ci

 

In(8192)

(4)

This time must be less than the converter sample time shown in the timing diagrams. This is 12

×

 SCLKs (if the

sampling mode is short normal sampling mode).

tch (1

ń

2

LSB)

v

12

 

1

f (SCLK)

(5)

Therefore the maximum SCLK frequency is:

max

ƪ

f (SCLK)

ƫ

+

12

tch

ǒ

1

ń

2

LSB

Ǔ +

12

[In(8192)

 

Rt

 

Ci]

(6)

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

33

POST OFFICE BOX 655303 

 DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

Rs

ri

VS

VC

Driving Source†

TLC2554/58

Ci

VI

VI = Input Voltage at AIN

VS = External Driving Source Voltage

Rs = Source Resistance

ri = Input Resistance (MUX on Resistance)

Ci = Input Capacitance

VC= Capacitance Charging Voltage

† Driving source requirements:

Noise and distortion for the source must be equivalent to the resolution of the converter.

Rs must be real at the input frequency.

Figure 37. Equivalent Input Circuit Including the Driving Source

maximum conversion throughput

For a supply voltage of 5 V, if the source impedance is less than 1 k

, and the ADC analog input capacitance

Ci is less than 50 pF, this equates to a minimum sampling time tch(0.5 LSB) of 0.676 

µ

s. Since the sampling

time requires 12 SCLKs, the fastest SCLK frequency is 12/tch = 18 MHz.

The minimal total cycle time is given as:

tc

+

tcommand

)

tch

)

tconv

)

td(EOCH–CSL)

+

4

 

1

f (SCLK)

)

12

 

1

f (SCLK)

)

1.6

m

s

)

0.1

m

s

+

16

 

1

18

MHz

)

1.7

m

s

+

2.59

m

s

This is equivalent to a maximum throughput of 386 KSPS. The throughput can be even higher with a smaller

source impedance.

When source impedance is 100 

, the minimum sampling time becomes:

tch (1

ń

2

LSB)

+

Rt

 

Ci

 

In(8192)

+

0.27

m

s

The maximum SCLK frequency possible is 12/tch = 44 MHz. Then a 20 MHz clock (maximum SCLK frequency

for the TLC2554/2548 ) can be used. The minimal total cycle time is then reduced to:

tc

+

tcommand

)

tch

)

tconv

)

td(EOCH–CSL)

+

4

 

1

f (SCLK)

)

12

 

1

f (SCLK)

)

1.6

m

s

)

0.1

m

s

+

0.8

m

s

)

1.6

m

s

)

0.1

m

s

+

2.5

m

s

The maximum throughput is 1/2.5 

µ

s = 400 KSPS for this case.

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

34

POST OFFICE BOX 655303 

 DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

power down calculations

i(AVERAGE) = (f

S

/f

SMAX

×

 i(ON) + (1–f

S

/f

SMAX

×

 i(OFF)

CASE 1: If V

DD

 = 3.3 V, auto power down, and an external reference is used:

f

S

+

10

kHz

f

SMAX

+

200

kHz

i (ON)

+X

1

mA operating current and i (OFF)

+X

1

m

A auto power-down current

so

i (AVERAGE)

+

0.05

 

1000

m

A

)

0.95

 

1

m

A

+

51

m

A

CASE 2: Now if software power down is used, another cycle is needed to shut it down.

f

S

+

20

kHz

f

SMAX

+

200

kHz

i (ON)

+X

1

mA operating current and i (OFF)

+X

1

m

A power-down current

so

i (AVERAGE)

+

0.1

 

1000

m

A

)

0.9

 

1

m

A

+

101

m

A

In reality this will be less since the second conversion never happened. It is only the additional cycle to shut down

the ADC.

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

35

POST OFFICE BOX 655303 

 DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

CASE 3: Now if the hardware power down is used.

f

S

+

10

kHz

f

SMAX

+

200

kHz

i (ON)

+X

1

mA operating current and i (OFF)

+X

1

m

A power-down current

so

i (AVERAGE)

+

0.05

 

1000

m

A

)

0.95

 

1

m

A

+

51

m

A

difference between modes of conversion

The major difference between sweep mode (mode 10) and repeat sweep mode (mode 11) is that the sweep

sequence ends after the FIFO is filled up to the programmed threshold. The repeat sweep can either dump the

FIFO (by ignoring the FIFO content but simply reconfiguring the device) or read the FIFO and then repeat the

conversions on the the same sequence of the channel as before.

FIFO reads are expected after the FIFO is filled up to the threshold in each case. Mode 10 – the device allows

only FIFO read or CFR read or CFR write to be executed. Any conversion command is ignored. In the case of

mode 11, in addition to the above commands, conversion commands are also executed , i.e. the FIFO is cleared

and the sweep sequence is restarted.

Both single shot and repeat modes require selection of a channel after the device is configured for these modes.

Single shot mode does not use the FIFO, but repeat mode does. When the device is operating in repeat mode,

the FIFO can be dumped (by ignoring the FIFO content and simply reconfiguring the device) or the FIFO can

be read and then the conversions repeated on the same channel as before. However, the channel has to be

selected first before any conversion can be carried out. The devices can be programmed with the following

sequences for operating in the different modes that  use a FIFO:

background image

TLC2554, TLC2558

5-V, 12-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

 

SLAS220A –JUNE 1999

36

POST OFFICE BOX 655303 

 DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

difference between modes of conversion (continued)

REPEAT:

Configure FIFO Depth=4 /CONV Mode 01

Select Channel/

1st Conv (CS or CSTART)

2nd Conv (CS or CSTART)

3rd Conv (CS or CSTART)

4th Conv (CS or CSTART

FIFO READ 1

FIFO READ 2

FIFO READ 3

FIFO READ 4

Select Channel

1st Conv (CS or CSTART)

2nd Conv (CS or CSTART)

3rd Conv (CS or CSTART)

4th Conv (CS or CSTART

SWEEP:

Configure FIFO Depth=4 SEQ=1–2–3–4/CONV Mode 10

conv ch 1 (CS/CSTART)

conv ch 2 (CS/CSTART)

conv ch 3 (CS/CSTART)

conv ch 4 (CS/CSTART

FIFO READ ch 1 result

FIFO READ ch 2 result

FIFO READ ch 3 result

FIFO READ ch 4 result

Configure (not required if same sweep sequence is to be used again)

REPEAT SWEEP:

Configure FIFO Depth=4 SWEEP SEQ=1-2-3-4/CONV Mode 11

conv ch 1 (CS/CSTART)

conv ch 2 (CS/CSTART)

conv ch 3 (CS/CSTART)

conv ch 4 (CS/CSTART

FIFO READ ch 1 result

FIFO READ ch 2 result

FIFO READ ch 3 result

FIFO READ ch 4 result

conv ch 1 (CS/CSTART)

conv ch 2 (CS/CSTART)

conv ch 3 (CS/CSTART)

conv ch 4 (CS/CSTART

background image

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©

 1999, Texas Instruments Incorporated