1

Features

s

5V ± 4% Output Voltage

s

Low Dropout Voltage

(1.2V @ 1A)

s

Low Quiescent Current

s

µP Compatible Control

Functions

s

Low Current Sleep Mode

s

Fault Protection

Thermal Shutdown

Short Circuit

60V Peak Transient

Voltage

ENABLE

RESET

Package Options

5 Lead TO-220

1

5V, 1A Linear Regulator

with

and ENABLE

RESET

CS8121

Description

Block Diagram

2

3 Gnd

4

RESET

ENABLE

1

1NC

3

4 Gnd

5

RESET

ENABLE

December, 2001 - Rev. 7

ON Semiconductor

2000 South County Trail, East Greenwich, RI 02818

Tel: (401)885–3600 Fax: (401)885–5786

N. American Technical Support: 800-282-9855

Web Site: www.cherry–semi.com

The CS8121 is a 5V, 1A precision linear

regulator with two microprocessor

compatible control functions and pro-

tection circuitry included on chip. The

composite NPN-PNP output pass tran-

sistor assures a lower dropout voltage

(1.2V @ 1A) without requiring exces-

sive supply current (4mA).

The CS8121’s two logic control func-

tions make this regulator well suited to

applications requiring microprocessor-

based control at the board or module

level.

controls the output

stage. A high voltage (>2.9V) on

the

lead turns off the regula-

tor’s pass transistor and sends the IC

into Sleep mode where it draws only

250µA.

sends a

signal

when the IC is powering up or when-

ever the output voltage falls out of reg-

ulation. The

signal is valid

The CS8121 design optimizes supply

rejection by switching the internal

bandgap reference from the supply

input to the regulator output as soon as

the nominal output voltage is achieved.

Additional on chip filtering enhances

rejection of high frequency transients

on all external leads.

The CS8121 is fault protected against

short circuit, over voltage and thermal

runaway conditions.

RESET

RESET

RESET

ENABLE

ENABLE

Over

Voltage

Shutdown

RESET

Comparator

Error

Amplifier

+

+

-

VREF

ENABLE

Comparator

Bandgap

Supply

Output

Current

Limit

Bandgap

Reference

Thermal

Shutdown

-

ENABLE

RESET

Gnd

5 Lead

TO-220