SC4212LM

9

Introduction

The SC4212LM is intended for applications where high

current capability and very low dropout voltage are

required. It provides a very simple, low cost solution that

uses very little PCB area. Additional features include an

enable pin to allow for a very low power consumption in

standby mode, and a fully adjustable output.

V

By connecting the FB pin directly to the VO pin, the output

voltage will be regulated to the 0.5V internal reference. In

this configuration, R2 should be 10kΩ.

V

The use of 1% resistors, and designing for a current flow ≥

50µA is recommended to ensure a well regulated output

(thus R

R

Enable

Pulling this pin below 0.4V turns the regulator off, reduc-

ing the quiescent current to a fraction of its operating

value. Driving this pin high enables the regulator. A pull

up resistor ≤ 400kΩ should be connected from this pin to

the VIN pin in applications where the Enable pin is not

driven from a control circuit.

Input Capacitor

decoupling capacitor is recommended to be placed

directly next to the VIN pin. This allows for the device

being some distance from the input source, reducing the

input droop due to load transients and improving load

transient response. Additional capacitance may be needed

if large step, fast di/dt load transients are required or the

LDO is located far away from the input source.

Output Capacitor

decoupling capacitor is recommended.

Applications Information

Soft-Start

Soft-start is achieved by using a voltage ramp as the

voltage reference for the internal error amplifier during

current source charging an external soft-start capacitor.

When the voltage ramp reaches 500mV, the voltage refer-

ence for the internal error amplifier switches to the fixed

500mV V

internal voltage ramp, which limits the input inrush

current and provides a programmed soft-start profile for a

wide range of applications. The soft-start time t

calculated with the below equation:

t

6

C

SS

Power Good

The power good output is an open-drain output which

requires a pull-up resistor. The SC4212LM features an

active-high power good. During startup, the power good

pin will not be pulled high until the soft-start is completed.

In any case, the power good output will be low when the

FB pin voltage is not within 10% of V

Over-Current and Thermal Shutdown

The over-current protection and thermal shutdown func-

tions protect the regulator against damage due to exces-

current limit when the output current reaches 1.6A

(typical). When the load exceeds 1.6A, the output voltage

The thermal shutdown function limits the junction tem-

down turns off the regulator as the junction temperature

turned on once again.

Thermal Considerations

The power dissipation in the SC4212LM is roughly given

by the following equation:

P