Am27C256

FINAL

Publication# 08007

Rev: I

Amendment/0

Issue Date: May 1998

Am27C256

256 Kilobit (32 K x 8-Bit) CMOS EPROM

DISTINCTIVE CHARACTERISTICS

■

Fast access time

— Speed options as fast as 45 ns

■

Low power consumption

— 20 µA typical CMOS standby current

■

JEDEC-approved pinout

■

Single +5 V power supply

■

10% power supply tolerance standard

■

100% Flashrite™ programming

— Typical programming time of 4 seconds

■

Latch-up protected to 100 mA from –1 V to

+ 1 V

■

High noise immunity

■

Versatile features for simple interfacing

— Both CMOS and TTL input/output compatibility

— Two line control functions

■

Standard 28-pin DIP, PDIP, and 32-pin PLCC

packages

GENERAL DESCRIPTION

The Am27C256 is a 256-Kbit, ultraviolet erasable pro-

grammable read-only memory. It is organized as 32K

words by 8 bits per word, operates from a single +5 V

supply, has a static standby mode, and features fast

single address location programming. Products are

available in windowed ceramic DIP packages, as well

as plastic one time programmable (OTP) PDIP and

PLCC packages.

Data can be typically accessed in less than 55 ns, al-

lowing high-performance microprocessors to operate

without any WAIT states. The device offers separate

Output Enable (OE#) and Chip Enable (CE#) controls,

thus eliminating bus contention in a multiple bus micro-

processor system.

AMD’s CMOS process technology provides high

speed, low power, and high noise immunity. Typical

power consumption is only 80 mW in active mode, and

100 µW in standby mode.

All signals are TTL levels, including programming sig-

nals. Bit locations may be programmed singly, in

blocks, or at random. The device supports AMD’s

Flashrite programming algorithm (100 µs pulses), re-

sulting in a typical programming time of 4 seconds.

BLOCK DIAGRAM

08007I-1

A0–A14

Address

Inputs

CE#

OE#

Data Outputs

DQ0–DQ7

Output

Buffers

Gating

262,144

Bit Cell

Matrix

Decoder

Output Enable

Chip Enable

and

Prog Logic

Am27C256

PRODUCT SELECTOR GUIDE

CONNECTION DIAGRAMS

Top View

DIP

PLCC

Notes:

1. JEDEC nomenclature is in parenthesis.

2. Don’t use (DU) for PLCC.

PIN DESIGNATIONS

A0–A14

= Address Inputs

CE# (E#)

= Chip Enable Input

DQ0–DQ7

= Data Input/Outputs

OE# (G#)

= Output Enable Input

= V

Supply Voltage

= Program Voltage Input

= Ground

= No Internal Connection

LOGIC SYMBOL

Family Part Number

Am27C256

Speed Options

= 5.0 V

-255

= 5.0 V

10%

-45

-55

-70

-90

-120

-150

-200

Max Access Time (ns)

120

150

200

250

CE# (E#) Access (ns)

120

150

200

250

OE# (G#) Access (ns)

DQ0

DQ1

DQ2

A11

OE# (G#)

A10

CE# (E#)

DQ7

A14

DQ6

A13

DQ5

DQ4

DQ3

A12

08007I-2

DQ5

DQ4

DQ3

31 30

17 18 19 20

DQ0

A11

OE# (G#)

A10

CE# (E#)

DQ7

DQ6

A12

A14

A13

DQ1

DQ2

08007I-3

DQ0–DQ7

A0–A14

CE# (E#)

OE# (G#)

08007I-4

Am27C256

ORDERING INFORMATION

UV EPROM Products

AMD standard products are available in several packages and operating ranges. The order number (Valid Combination) is formed

by a combination of the following:

Valid Combinations

Valid Combinations list configurations planned to be sup-

ported in volume for this device. Consult the local AMD sales

office to confirm availability of specific valid combinations and

to check on newly released combinations.

DEVICE NUMBER/DESCRIPTION

Am27C256

256 Kilobit (32 K x 8-Bit) CMOS UV EPROM

AM27C256

-45

OPTIONAL PROCESSING

Blank = Standard Processing

= Burn-In

TEMPERATURE RANGE

C = Commercial (0

C to +70

= Industrial (–40

C to +85

= Extended (–55

C to +125

PACKAGE TYPE

D = 28-Pin Ceramic DIP (CDV028)

SPEED OPTION

See Product Selector Guide and Valid Combinations

Valid Combinations

AM27C256-45

DC, DCB, DI, DIB

AM27C256-55

AM27C256-70

DC, DCB, DI, DIB, DE, DEB

AM27C256-90

AM27C256-120

AM27C256-150

AM27C256-200

AM27C256-255

= 5.0 V

DC, DCB, DI, DIB

Am27C256

ORDERING INFORMATION

OTP EPROM Products

AMD standard products are available in several packages and operating ranges. The order number (Valid Combination) is formed

by a combination of the following:

Valid Combinations

Valid Combinations list configurations planned to be sup-

ported in volume for this device. Consult the local AMD sales

office to confirm availability of specific valid combinations and

to check on newly released combinations.

DEVICE NUMBER/DESCRIPTION

Am27C256

256 Kilobit (32 K x 8-Bit) CMOS OTP EPROM

AM27C256

-55

OPTIONAL PROCESSING

Blank = Standard Processing

TEMPERATURE RANGE

C = Commercial (0

C to +70

= Industrial (–40

C to +85

PACKAGE TYPE

= 28-Pin Plastic DIP (PD 028)

= 32-Pin Square Plastic Leaded Chip Carrier (PL 032)

SPEED OPTION

See Product Selector Guide and Valid Combinations

Valid Combinations

AM27C256-55

JC, PC

AM27C256-70

JC, PC, JI, PI

AM27C256-90

AM27C256-120

AM27C256-150

AM27C256-200

AM27C256-255

Am27C256

FUNCTIONAL DESCRIPTION

Device Erasure

In order to clear all locations of their programmed con-

tents, the device must be exposed to an ultraviolet light

source. A dosage of 15 W seconds/cm

is required to

completely erase the device. This dosage can be ob-

tained by exposure to an ultraviolet lamp—wavelength

of 2537 Å—with intensity of 12,000 µW/cm

for 15 to 20

minutes. The device should be directly under and about

one inch from the source, and all filters should be re-

moved from the UV light source prior to erasure.

Note that all UV erasable devices will erase with light

sources having wavelengths shorter than 4000 Å, such

as fluorescent light and sunlight. Although the erasure

process happens over a much longer time period, ex-

posure to any light source should be prevented for

maximum system reliability. Simply cover the package

window with an opaque label or substance.

Device Programming

Upon delivery, or after each erasure, the device has

all of its bits in the “ONE”, or HIGH state. “ZEROs” are

loaded into the device through the programming pro-

cedure.

The device enters the programming mode when 12.75

0.25 V is applied to the V

pin, OE# is at V

and

CE# is at V

For programming, the data to be programmed is ap-

plied 8 bits in parallel to the data pins.

The flowchar t in the Programming section of the

EPROM Products Data Book (Section 5, Figure 5-1)

shows AMD’s Flashrite algorithm. The Flashrite algo-

rithm reduces programming time by using a 100 µs pro-

gramming pulse and by giving each address only as

many pulses to reliably program the data. After each

pulse is applied to a given address, the data in that ad-

dress is verified. If the data does not verify, additional

pulses are given until it verifies or the maximum pulses

allowed is reached. This process is repeated while se-

quencing through each address of the device. This part

of the algorithm is done at V

= 6.25 V to assure that

each EPROM bit is programmed to a sufficiently high

threshold voltage. After the final address is completed,

the entire EPROM memory is verified at V

= V

5.25 V.

Please refer to Section 5 of the EPROM Products Data

Book for additional programming information and spec-

ifications.

Program Inhibit

Programming different data to multiple devices in par-

allel is easily accomplished. Except for CE#, all like in-

puts of the devices may be common. A TTL low-level

program pulse applied to one device’s CE# input with

= 12.75 V

0.25 V and OE# HIGH will program

that particular device. A high-level CE# input inhibits

the other devices from being programmed.

Program Verify

A verification should be performed on the programmed

bits to determine that they were correctly programmed.

The verify should be performed with OE# at V

, CE# at

, and V

between 12.5 V and 13.0 V.

Autoselect Mode

The autoselect mode provides manufacturer and de-

vice identification through identifier codes on DQ0–

DQ7. This mode is primarily intended for programming

equipment to automatically match a device to be pro-

grammed with its corresponding programming algo-

rithm. This mode is functional in the 25

ambient temperature range that is required when pro-

gramming the device.

To activate this mode, the programming equipment

must force V

on address line A9. Two identifier bytes

may then be sequenced from the device outputs by tog-

gling address line A0 from V

to V

(that is, changing

the address from 00h to 01h). All other address lines

must be held at V

during the autoselect mode.

Byte 0 (A0 = V

) represents the manufacturer code,

and Byte 1 (A0 = V

), the device identifier code. Both

codes have odd parity, with DQ7 as the parity bit.

Read Mode

To obtain data at the device outputs, Chip Enable (CE#)

and Output Enable (OE#) must be driven low. CE# con-

trols the power to the device and is typically used to se-

lect the device. OE# enables the device to output data,

independent of device selection. Addresses must be

stable for at least t

ACC

–t

Refer to the Switching

Waveforms section for the timing diagram.

Standby Mode

The device enters the CMOS standby mode when CE#

is at V

0.3 V. Maximum V

current is reduced to

100 µA. The device enters the TTL-standby mode

when CE# is at V

. Maximum V

current is reduced

to 1.0 mA. When in either standby mode, the device

places its outputs in a high-impedance state, indepen-

dent of the OE# input.

Output OR-Tieing

To accommodate multiple memory connections, a

two-line control function provides:

■

Low memory power dissipation, and

■

Assurance that output bus contention will not occur.

CE# should be decoded and used as the primary de-

vice-selecting function, while OE# be made a common

Am27C256

connection to all devices in the array and connected to

the READ line from the system control bus. This as-

sures that all deselected memory devices are in their

low-power standby mode and that the output pins are

only active when data is desired from a particular mem-

ory device.

System Applications

During the switch between active and standby condi-

tions, transient current peaks are produced on the ris-

ing and falling edges of Chip Enable. The magnitude of

these transient current peaks is dependent on the out-

put capacitance loading of the device. At a minimum, a

0.1 µF ceramic capacitor (high frequency, low inherent

inductance) should be used on each device between

and V

to minimize transient effects. In addition,

to overcome the voltage drop caused by the inductive

effects of the printed circuit board traces on EPROM ar-

rays, a 4.7 µF bulk electrolytic capacitor should be used

between V

and V

for each eight devices. The loca-

tion of the capacitor should be close to where the

power supply is connected to the array.

MODE SELECT TABLE

Notes:

1. V

= 12.0 V

0.5 V.

2. X = Either V

or V

3. A1–A8 and A10–14 = V

4. See DC Programming Characteristics for V

voltage during programming.

Mode

CE#

OE#

Outputs

Read

OUT

Output Disable

High Z

Standby (TTL)

High Z

Standby (CMOS)

0.3 V

High Z

Program

Program Verify

OUT

Program Inhibit

High Z

Autoselect

(Note 3)

Manufacturer Code

01h

Device Code

10h

Am27C256

ABSOLUTE MAXIMUM RATINGS

Storage Temperature

OTP Products. . . . . . . . . . . . . . . . . . –65

C to +125

All Other Products . . . . . . . . . . . . . . –65

C to +150

Ambient Temperature

with Power Applied. . . . . . . . . . . . . . –55

C to +125

Voltage with Respect to V

All pins except A9, V

, V

. . –0.6 V to V

+ 0.6 V

A9 and V

(Note 2) . . . . . . . . . . . . . –0.6 V to 13.5 V

(Note 1). . . . . . . . . . . . . . . . . . . . . –0.6 V to 7.0 V

Notes:

1. Minimum DC voltage on input or I/O pins –0.5 V. During

voltage transitions, the input may overshoot V

to –2.0 V

for periods of up to 20 ns. Maximum DC voltage on input

and I/O pins is V

+ 5 V. During voltage transitions, input

and I/O pins may overshoot to V

+ 2.0 V for periods up

to 20 ns.

2. Minimum DC input voltage on A9 is –0.5 V. During voltage

transitions, A9 and V

may overshoot V

to –2.0 V for

periods of up to 20 ns. A9 and V

must not exceed +13.5

V at any time.

Stresses above those listed under “Absolute Maximum Rat-

ings” may cause permanent damage to the device. This is a

stress rating only; functional operation of the device at these

or any other conditions above those indicated in the opera-

tional sections of this specification is not implied. Exposure of

the device to absolute maximum ratings for extended periods

may affect device reliability.

OPERATING RANGES

Commercial (C) Devices

Ambient Temperature (T

) . . . . . . . . . . .0

C to +70

Industrial (I) Devices

Ambient Temperature (T

) . . . . . . . . .–40

C to +85

Extended (E) Devices

Ambient Temperature (T

) . . . . . . . .–55

C to +125

Supply Read Voltages

for ± 5% devices . . . . . . . . . . +4.75 V to +5.25 V

for ± 10% devices . . . . . . . . . +4.50 V to +5.50 V

Operating ranges define those limits between which the func-

tionality of the device is guaranteed.

Am27C256

DC CHARACTERISTICS over operating range (unless otherwise specified)

Caution: The device must not be removed from (or inserted into) a socket when V

or V

is applied.

Notes:

1. V

must be applied simultaneously or before V

, and removed simultaneously or after V

2. I

CC1

is tested with OE# = V

to simulate open outputs.

3. Minimum DC Input Voltage is –0.5 V. During transitions, the inputs may overshoot to –2.0 V for periods less than 20 ns.

Maximum DC Voltage on output pins is V

+ 0.5 V, which may overshoot to V

+ 2.0 V for periods less than 20 ns.

Figure 1.

Typical Supply Current vs. Frequency

= 5.5 V, T = 25

Figure 2.

Typical Supply Current vs. Temperature

= 5.5 V, f = 10 MHz

Parameter

Symbol

Parameter Description

Test Conditions

Min

Max

Unit

Output HIGH Voltage

= –400 µA

2.4

Output LOW Voltage

= 2.1 mA

0.45

Input HIGH Voltage

2.0

+ 0.5

Input LOW Voltage

–0.5

+0.8

Input Load Current

= 0 V to V

1.0

µA

Output Leakage Current

OUT

= 0 V to V

C/I Devices

1.0

µA

E Devices

5.0

CC1

Active Current (Note 2)

CE# = V

, f = 10 MHz,

OUT

= 0 mA

CC2

TTL Standby Current

CE# = V

1.0

CC3

CMOS Standby Current

CE# = V

0.3 V

100

µA

PP1

Supply Current (Read)

CE# = OE# = V

, V

= V

100

µA

08007I-5

Frequency in MHz

ppl

y C

urre

08007I-6

–75 –50 –55

75 100 125 150

Temperature in

pply

rre

Am27C256

TEST CONDITIONS

Table 1.

Test Specifications

SWITCHING TEST WAVEFORM

KEY TO SWITCHING WAVEFORMS

2.7 k

Ω

6.2 k

Ω

5.0 V

Device

Under

Test

08007I-7

Figure 3.

Test Setup

Note:

Diodes are IN3064 or equivalents.

Test Condition

-45, -55

and -70

All

others

Unit

Output Load

1 TTL gate

Output Load Capacitance, C

(including jig capacitance)

100

Input Rise and Fall Times

≤

Input Pulse Levels

0.0–3.0

0.45–2.4

Input timing measurement

reference levels

1.5 0.8,

2.0

Output timing measurement

reference levels

1.5

0.8, 2.0

2.4 V

0.45 V

Input

Output

Test Points

2.0 V

0.8 V

08007I-8

3 V

0 V

Input

Output

1.5 V

Test Points

Note: For C

= 100 pF.

Note: For C

= 30 pF.

KS000010-PAL

WAVEFORM

INPUTS

OUTPUTS

Steady

Changing from H to L

Changing from L to H

Don’t Care, Any Change Permitted

Changing, State Unknown

Does Not Apply

Center Line is High Impedance State (High Z)

Am27C256

AC CHARACTERISTICS

Caution: Do not remove the device from (or insert it into) a socket or board that has V

or V

applied.

Notes:

1. V

must be applied simultaneously or before V

, and removed simultaneously or after V

2. This parameter is sampled and not 100% tested.

3. Switching characteristics are over operating range, unless otherwise specified.

4. See Figure 3 and Table 1 for test specifications.

SWITCHING WAVEFORMS

Notes:

1. OE# may be delayed up to t

ACC

– t

after the falling edge of the addresses without impact on t

ACC

2. t

is specified from OE# or ‘CE#, whichever occurs first.

PACKAGE CAPACITANCE

Notes:

1. This parameter is only sampled and not 100% tested.

2. T

= +25

C, f = 1 MHz.

Parameter Symbols

Description

Test Setup

Am27C256

Unit

JEDEC

Standard

-45

-55

-70

-90

-120 -150 -200 -255

AVQV

ACC

Address to Output Delay

CE#,

OE# = V

Max

120

150

200

250

ELQV

Chip Enable to Output Delay

OE# = V

Max

120

150

200

250

GLQV

Output Enable to Output

Delay

CE# = V

Max

EHQZ

GHQZ

(Note 2)

Chip Enable High or Output

Enable High to Output High Z,

Whichever Occurs First

Max

AXQX

Output Hold Time from

Addresses, CE# or OE#,

Whichever Occurs First

Min

Addresses

CE#

OE#

Output

08007I-9

Addresses Valid

High Z

Valid Output

2.4

0.45

2.0

0.8

2.0

0.8

ACC

(Note 1)

(Note 2)

Parameter Symbol

Parameter

Description

Test Conditions

CDV028

PL 032

PD 028

Unit

Typ

Max

Typ

Max

Typ

Max

Input Capacitance

= 0

OUT

Output Capacitance

OUT

= 0

Am27C256

PHYSICAL DIMENSIONS*

CDV028—28-Pin Ceramic Dual In-Line Package, UV Lens (measured in inches)

* For reference only. BSC is an ANSI standard for Basic Space Centering.

PD 028—28-Pin Plastic Dual In-Line Package (measured in inches)

TOP VIEW

SIDE VIEW

END VIEW

INDEX AND

TERMINAL NO. 1

I.D. AREA

.565

.605

1.435

1.490

.005 MIN

.045

.065

.014

.026

.100 BSC

.015

.060

.160

.220

.125

.200

BASE PLANE

SEATING PLANE

.300 BSC

.600

BSC

.008

.018

105

.700

MAX

16-000038H-3

CDV028

DF10

3-30-95 ae

DATUM D

CENTER PLANE

DATUM D

CENTER PLANE

UV Lens

Pin 1 I.D.

1.440

1.480

.530

.580

.005 MIN

.045

.065

.090

.110

.140

.225

.120

.160

.014

.022

SEATING PLANE

.015

.060

.630

.700

.600

.625

16-038-SB-AG

PD 028

DG75

7-13-95 ae

.008

.015

Am27C256

PHYSICAL DIMENSIONS

PL 032—32-Pin Plastic Leaded Chip Carrier (measured in inches)

REVISION SUMMARY FOR AM27C256

Revision I

Global

Changed formatting to match current data sheets.

Distinctive Characteristics

Fast access time: Changed “Speed options as fast as

55 ns” to “Speed options as fast as 45 ns”.

Product Selector Guide

Added the -45 speed option.

Ordering Information

UV EPROM Products: Added the AM27C256-45 Valid

Combination.

Test Conditions

Table 1. Test Specifications: Added the -45 speed op-

tion.

AC Characteristics

Added the -45 speed option.

Trademarks

AMD, the AMD logo, and combinations thereof are trademarks of Advanced Micro Devices, Inc.

Flashrite is a trademark of Advanced Micro Devices, Inc.

Product names used in this publication are for identification purposes only and may be trademarks of their respective companies.

.050 REF.

.026

.032

TOP VIEW

Pin 1 I.D.

.485

.495

.447

.453

.585

.595

.547

.553

16-038FPO-5

PL 032

DA79

6-28-94 ae

SIDE VIEW

SEATING

PLANE

.125

.140

.009

.015

.080

.095

.042

.056

.013

.021

.400

REF.

.490

.530

Document Outline