4

UC182-1,-2,-3,-ADJ

UC282-1,-2,-3,-ADJ

UC382-1,-2,-3,-ADJ

1.6

1.7

1.8

1.9

01

23

100

200

300

400

100mA

1A

2A

3A

PIN DESCRIPTIONS

ADJ: In the adjustable version, the user programs the

output voltage with two external resistors. The resistors

should be 0.1% for high accuracy. The output amplifier is

configured as a non-inverting operational amplifier. The

resistors should meet the criteria of R3 || R4 < 100

Ω.

Connect ADJ to VOUT for an output voltage of 1.2V. Note

that the point at which the feedback network is

connected to the output is the Kelvin sense point.

GND: For accurate results, the GND pin should be

referenced to the load ground.

VB: Supplies power to all circuits of the regulator except

the collector of the output power transistor. The 2V

headroom from VB to VOUT allows the use of a

Darlington

output

stage

for

inherently

low

output

impedance and fast response. (Dropout is derated for

junction temperatures below 0°C.)

VIN: Supplies the current to the collector of the output

power transistor only. The dropout (VIN-VOUT) is under

100mV for light loads; maximum dropout is 450mV at 3A

temperatures over 110°C.) At full load, the majority of the

VB current is going to the load.

VOUT: This pin should be connected to the load via a

low impedance path. Avoid connectors which add

significant inductance and resistance. Note that even

though a Kelvin sense is available througha5pin

package, care must be taken since voltage drops along

wire traces add to the dropout voltage.

The UC382 is easy to use. The adjustable version re-

quires two 0.1% resistors to set the output voltage. The

fixed versions of the UC382 require no external resistors.

All versions of the UC382 require decoupling capacitors

on the input and output. In a typical application, VB and

VIN are driven from switching power supplies which may

have large filter capacitors at their outputs. If the UC382

is further than 12 inches from the power supply, it is rec-

ommended to add local decoupling as close as possible

to the linear regulator.

Decouple the output of the UC382 with at least 100

µFof

high quality tantalum or Sanyo OSCON capacitors close

to the VOUT pin for maximum stability. Many applications

involving ultra fast GTL or BTL applications require addi-

tional capacitance close to the load. The exact amount

will vary according to speed and magnitude of the load

transients and the tolerance allowed for transients on

VOUT. When specifying the decoupling capacitors, the

series resistance of the capacitor bank is an important

factor in its ability to filter load transients.

The UC382 allows for Kelvin sensing the voltage at the

load. This improves regulation performance and elimi-

nates the voltage drops due to wire trace resistance. This

voltage drop must be added to the headroom (VIN to

VOUT and VB to VOUT). The dropout of 450mV is mea-

sured at the pins and does not include additional drops

due to trace resistance. The minimum load current is

10mA.

Two or more UC382’s may be used in parallel. While sta-

ble, this arrangement does degrade the transient re-

sponse.

APPLICATION INFORMATION