UCC283-3, UCC283-5, UCC283-ADJ, UCC383-3, UCC383-5, UCC383-ADJ

LOW DROPOUT 3A LINEAR REGULATOR FAMILY

SLUS215B − OCTOBER 1998 − REVISED FEBRUARY 2004

5

POST OFFICE BOX 655303

pin descriptions

ADJ: Adjust pin for the UCC283−ADJ version only. Feedback pin for the linear regulator. Program the output

voltage with R1 connected from ADJ to GND and R2 connected from VOUT to ADJ. Output voltage is given

by:

V

OUT +

1.25 V

(R1

) R2)

R1

CT: Short-circuit timing capacitor and shutdown input for the UCC283−ADJ version. Pulling CT below 0.25 V

turns off the regulator and places it in a low quiescent-current mode. A timing capacitor, C, from CT to GND

t

ON +

750 k

C

GND: Reference ground.

VIN: Input voltage, This pin must be bypassed with a low ESL/ESR 1-

µF or larger capacitor to GND. VIN can

from VOUT to VIN is less than 75

µA.

VOUT: Regulated output voltage. A bypass capacitor is not required at VOUT, but may be desired for good

transient response. The bypass capacitor must not exceed a maximum value in order to insure the regulator

can start.

APPLICATION INFORMATION

overview

The UCC383 family of low dropout linear (LDO) regulators provide a regulated output voltage for applications

with up to 3 A of load current. The regulators feature a low dropout voltage and short-circuit protection, making

their use ideal for demanding high-current applications requiring fault protection.

short-circuit-protection

The UCC383 provides unique short-circuit protection circuitry that reduces power dissipation during a fault.

When an overload situation is detected, the device enters a pulsed mode of operation at 3% duty cycle reducing

the heat sink requirements during a fault. The UCC383 has two current thresholds that determine its behavior

during a fault as shown in Figure 1. When the regulator current exceeds the overcurrent threshold for a period

actively limits the maximum current to the peak current limit value. The peak current limit is nominally 3 A

greater than the overcurrent threshold. The regulator continues in pulsed mode until the fault is cleared as

illustrated in Figure 1.