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UC1838A

UC2838A

UC3838A

Magnetic Amplifier Controller

FEATURES

Independent 1% Reference

Two Uncommitted, Identical

Operational Amplifiers

100mA Reset Current Source

with –120V Capability

5V to 40V Analog Operation

5W DIL Package

10

VCC

VREF

9

2.5V

REFERENCE

INV. IN

8

E/A OUT

3

INV. IN

6

7

N.I. IN

2

1

N.I. IN

C/L OUT

C/L

E/A

3.5V

15 DR 1

16 DR 2

RESET

14

VM

11

5

12

13

4

GND GND GND GND

20

1k

5k

BLOCK DIAGRAM

04/99

UDG-97174

DESCRIPTION

The UC1838A family of magnetic amplifier controllers contains the circuitry to gen-

erate and amplify a low-level analog error signal along with a high volt-

age-compliant current source. This source will provide the reset current necessary

to enable a magnetic amplifier to regulate and control a power supply output in the

range of 2A to 20A.

By controlling the reset current to a magnetic amplifier, this device will define the

amount of volt-seconds the magnetic amplifier will block before switching to the

conducting state. Magnetic amplifiers are ideal for post-regulators for multi-

ple-output power supplies where each output can be independently controlled with

efficiencies up to 99%. With a square or pulse-width-modulated input voltage, a

magnetic amplifier will block a portion of this input waveform, allowing just enough

to pass to provide a regulated output. With the UC1838A, only the magnetic ampli-

fier coil, three diodes, and an output L-C filter are necessary to implement a com-

plete closed-loop regulator.

The UC1838A contains a precision 2.5V reference, two uncommitted high-gain op

amps and a high-gain PNP-equivalent current source which can deliver up to

100mA of magnetic amplifier reset current and with –120 volt capability.

These devices are available in a plastic “bat-wing” DIP for operation over a –20°C

to +85°C temperature range and, with reduced power, in a hermetically sealed

cerdip for –55°C to +125°C operation. Surface mount versions are also available.

This improved “A” version replaced the non “A” version formerly introduced.

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2

UC1838A

UC2838A

UC3838A

ABSOLUTE MAXIMUM RATINGS

Supply Voltage, V

CC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

40V

Magnetic Amp. Source Voltage, V

M . . . . . . . . . . . . . . . . . . . . . . . .

40V

Reset Output Voltage, V

R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

–120V

Total Current Source Voltage, V

M

- V

R . . . . . . . . . . . . . . . . . .

–140V

Amplifier Input Range . . . . . . . . . . . . . . . . . . . . . . –0.3V to V

CC

Reset Input Current, I

DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

–10mA

Power Dissipation at T

A

= 25°C

Q, N, DP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2W

J, L Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1W

Power Dissipation at T (leads/case) = 25°C

Q, N, DP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5W

J, L Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2W

Operating Temperature Range . . . . . . . . . . . . –55°C to +125°C

Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C

Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . . . 300°C

Note: All voltages are with respect to ground pins. All currents

are positive into the specified terminal. Consult Packaging

section of Databook for thermal limitations and considerations

of package.

DR 2

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

DR 1

Reset

Gnd

Gnd

V

M

V

CC

V

REF

C/L Out

C/L N.I. In

C/L INV. In

Gnd

Gnd

E/A Inv. In

E/A N.I. In

E/A Out

CONNECTION DIAGRAMS

DIL-16, SOIC-16 (TOP VIEW)

J or N Package, DP Package

3

18

17

16

N/C

1

2

20 19

15

14

4

5

6

7

8

9

11

10

12 13

C/L Out

C/L N.I. In

DR2

DR1

Reset

N/C

N/C

GND

V

M

C/L Inv. In

GND

N/C

N/C

E/A Inv. In

V

CC

V

REF

N/C

E/A N.I. In

E/A Out

PLCC-20, LCC-20 (TOP VIEW)

Q, L Packages

Note: All four ground pins must be connected to a common

ground

TEMPERATURE RANGE

PACKAGE

UC1838AJ

–55

°

C to +125

°

C

Ceramic Dip

UC1838AL

CLCC

UC2838ADP

–20

°

C to +85

°

C

Power SOIC

UC2838AN

Plastic Dip

UC2838AQ

PLCC

UC3838ADP

0

°

C to +70

°

C

Power SOIC

UC3838AN

Plastic Dip

UC3838AQ

PLCC

ORDERING INFORMATION

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UC1838A

UC2838A

UC3838A

ELECTRICAL CHARACTERISTICS:

Unless otherwise stated, these specifications apply for T

A

= –55°C to +125°C for the

UC1838A, –20°C to +85°C for the UC2838A, and 0°C to +70°C for the UC3838A, V

CC

= 20V, V

M

= 5V, T

A

= T

J.

PARAMETER

TEST CONDITIONS

UC1838A / UC2838A

UC3838A

UNITS

MIN

TYP

MAX

MIN

TYP

MAX

Reference Section

Supply Current

V

CC

= V

M

= 40V

4

8

4

8

mA

Reference Output

T

A

= 25°C

2.47

2.5

2.53

2.45

2.5

2.55

V

Line Regulation

V

CC

= 5 to 30V

1

5

1

10

mV

Load Regulation

I

O

= 0 to –2mA

5

20

5

20

mV

Short Circuit Current

V

REF

= 0V

–30

–60

–30

–60

mA

Temperature Stability*

Over Operating Temp. Range

15

25

10

25

mV

Amplifier Section (Each Amplifier)

Offset Voltage

V

CM

= 2.5V

5

10

mV

Input Bias Current

V

IN

= 0V

–1

–1

µ

A

Input Offset Current

100

100

nA

Minimum Output Swing

0.4

18

0.4

18

V

Output Sink Current

V

O

=  5V

1

10

30

1

10

30

mA

Output Source Current

V

O

= 0V

–1

–10

–20

–1

–10

–20

mA

A

VOL

V

O

= 1 to 11V

100

120

100

120

dB

C

MRR

V

IN

= 1 to 11V

70

80

70

80

dB

P

SRR

V

CC

= 10 to 20V

70

100

70

100

dB

Gain Bandwidth*

0.6

0.8

0.6

0.8

MHz

Reset Drive Section

Input Leakage

V

DR

= 40V

10

10

µ

A

Output Leakage

V

R

= –120V

–100

–100

µ

A

Input Current

I

R

= –50mA

–1

–2

–1

–2

mA

Maximum Reset Current

I

DR

= –3mA

–100

–120

–200

–100

–120

–200

mA

Transconductance

I

R

= –10 to –50mA

.03

.042

.055

.03

.042

.055

A/V

* These parameters are guaranteed by design but not 100% tested in production.

TYPICAL APPLICATION

+12V, 4A output with switching frequency = 50 kHz.

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UC1838A

UC2838A

UC3838A

APPLICATION INFORMATION

Figure 1. Amplifier open loop response.

Figure 2. Reset driver-input current.

Figure 5. Reset driver-input voltage.

Figure 3. Reset driver-output impedance.

Figure 6. Reference temperature coefficient.

UNITRODE CORPORATION

7 CONTINENTAL BLVD. • MERRIMACK, NH  03054

TEL. (603) 424-2410 • FAX (603) 424-3460

Figure 4. Reset driver response.

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accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent

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Copyright 

©

 1999, Texas Instruments Incorporated