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UCC381-5 Datasheet Preview

UCC381-5 Datasheet

Low Dropout 1 Ampere Linear Regulator

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UCC281-3/-5/-ADJ

UCC381-3/-5/-ADJ

Low Dropout 1 Ampere Linear Regulator Family

FEATURES

• Precision Positive Linear Voltage

Regulation

• 0.5V Dropout at 1A

• Guaranteed Reverse Input/ Output

Voltage Isolation with Low Leakage

• Low Quiescent Current Irrespective of

Load

• Adjustable Output Voltage Version

• Fixed Versions for 3.3V and 5V

Outputs

• Logic Shutdown Capability

• Short Circuit Power Limit of

3% • VIN • Current Limit

• Remote Load Voltage for Accurate

Load Regulation

DESCRIPTION

The UCC381-3/-5/-ADJ family of positive linear series pass regulators is

tailored for low drop out applications where low quiescent power is impor-

tant. Fabricated with a BiCMOS technology ideally suited for low input to

output differential applications, the UCC381 will pass 1A while requiring

only 0.5V of input voltage headroom. Dropout voltage decreases linearly

with output current, so that dropout at 200mA is less than 100mV. Quies-

cent current is always less than 650µA. To prevent reverse current conduc-

tion, on-chip circuitry limits the minimum forward voltage to typically 50mV.

Once the forward voltage limit is reached, the input-output differential volt-

age is maintained as the input voltage drops until undervoltage lockout dis-

ables the regulator.

UCC381-3 and UCC381-5 versions have on-chip resistor networks preset

to regulate either 3.3V or 5.0V, respectively. Furthermore, remote sensing

of the load voltage is possible by connecting the VOUTS pin directly at the

load. The output voltage is then regulated to 1.5% at room temperature and

better than 2.5% over temperature. The UCC381-ADJ version has a regu-

lated output voltage programmed by an external user-definable resistor ra-

tio.

(continued)

BLOCK DIAGRAM

VIN 8

1.3/2.1A

CURRENT

REFERENCE

CURRENT

LIMIT

–

SHUTDOWN FOR FIXED VERSIONS

CT* 5

0.65V

*ADJ

VERSION

ONLY

3% DUTY CYCLE

CURRENT LIMIT TIMER

REVERSE VOLTAGE

SENSE

THERMAL

SHUTDOWN

SLUS214B -JANUARY 2001

VPUMP

UVLO

VOLTAGE

AMPLIFIER

–

1.25V

1 VOUT

4 VOUTS

2 GND

3 GND

6 GND

7 GND

UCC381-ADJ

UCC381-3

UCC381-5

R2 R1

0 OPEN

82k 50k

150k 50k

UDG-98112

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UCC381-5 Datasheet Preview

UCC381-5 Datasheet

Low Dropout 1 Ampere Linear Regulator

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UCC281-3/-5/-ADJ

UCC381-3/-5/-ADJ

ABSOLUTE MAXIMUM RATINGS

VIN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9V

CT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −0.3 to 3V

Storage Temperature . . . . . . . . . . . . . . . . . . . −65°C to +150°C

Junction Temperature . . . . . . . . . . . . . . . . . . . −55°C to +150°C

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

CONNECTION DIAGRAMS

SOIC-8 (Top View)

DP Package

VOUT 1

Currents are positive into, negative out of the specified terminal.

Consult Packaging Section of Databook for thermal limitations

and considerations of packages. All voltages are referenced to

GND.

GND 2

GND 3

VOUTS 4

8 VIN

7 GND

6 GND

5 CT*

DESCRIPTION (cont.)

Short circuit current is internally limited. The device re-

sponds to a sustained overcurrent condition by turning

off after a TON delay. The device then stays off for a pe-

riod, TOFF, that is 32 times the TON delay. The device

then begins pulsing on and off at the TON /(TON+TOFF)

duty cycle of 3%. This drastically reduces the power dis-

sipation during short circuit such that heat sinking, if at all

required, must only accommodate normal operation. On

the fixed output versions of the device TON is fixed at

400µs − a guaranteed minimum. On the adjustable ver-

sion an external capacitor sets the on time. The off time

is always 32 times TON.

* ADJ version only

The UCC381 can be shutdown to 25µA (max) by pulling

the CT pin low.

Internal power dissipation is further controlled with ther-

mal overload protection circuitry. Thermal shutdown oc-

curs if the junction temperature exceeds 165°C. The chip

will remain off until the temperature has dropped 20°C.

The UCC281 series is specified for operation over the in-

dustrial range of −40°C to +85°C, and the UCC381 se-

ries is specified from 0°C to +70°C. These devices are

available in the 8 pin DP surface mount power package.

For other packaging options consult the factory.

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications hold for TA = 0°C to 70°C for the

UCC381-X series and −40°C to +85°C for the UCC283-X series, VIN = VOUT + 1.5V, IOUT = 0mA, COUT = 2.2µF. CT = 1500pF for

the UCC381-ADJ version and VOUT set to 5V. TJ = TA.

PARAMETER

TEST CONDITIONS

MIN TYP MAX UNITS

UCC381-5 Fixed 5V, 1A Family

Output Voltage

TJ = 25°C

4.925 5 5.075 V

Over Temperature

4.875

5.125 V

Line Regulation

Load Regulation

VIN = 5.15V to 9V

IOUT = 0mA to 1A

1 3 mV

2 5 mV

Drop Out Voltage, VIN – VOUT

Peak Current Limit

IOUT = 1A, VOUT = 4.85V, TA < 85°C

IOUT = 200mA, VOUT = 4.85V, TA < 85°C

VOUT = 0V

0.5 0.6

100 200 mV

2 3.5 A

Overcurrent Threshold

1 1.8 A

Current Limit Duty Cycle

Overcurrent Time Out, TON

Quiescent Current

VOUT = 0V

3 5%

400 750 1600 µs

400 650 µA

Quiescent Current in Shutdown

Shutdown Threshold

Reverse Leakage Current

VIN = 9V

At CT Input

1V < VIN < VOUT, VOUT < 5.1V, at VOUT

0.25 0.65

µA

UVLO Threshold

VIN where VOUT passes current

2.5 2.8 3.0

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UCC381-5 Datasheet

Low Dropout 1 Ampere Linear Regulator

UCC381-5 Datasheet

Low Dropout 1 Ampere Linear Regulator

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