1

Features

s

Externally Set Delay for

Reset

s

60V Load Dump

Protection

s

Internal Thermal

Overload Protection

s

3% Output Accuracy

s

Active RESET

s

Noise Immunity

s

On Chip EMC Hardening

Protection Incorporated

s

Externally Set Current

Limit

s

Externally Set

Overvoltage Shutdown

Package Options

8 Lead SO Narrow

5V Linear Controller/Driver

1

2

3

4

Sense

Delay

Pwr Gnd

SHUTDOWN

Ref Gnd

8

7

6

5

RESET

CS8128

Description

Block Diagram

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 CS8128 contains all the necessary

control circuitry to implement a 5V lin-

ear regulator. An external pass device is

used to produce superior performance

compared to conventional monolithic

regulators. The CS8128 with a TIP42

PNP transistor typically provides a

100mV dropout voltage at 500mA,

increasing to 350mV at 3A. Quiescent

current at 500mA is only 5mA.

Monolithic regulators cannot approach

these figures because their power tran-

sistors do not provide the high beta and

excellent saturation characteristics at

high currents. The CS8128 is compatible

with a wide variety of external transis-

tors, allowing flexibility for thermal,

space, and cost management.

The CS8128 includes thermal shutdown

and externally programmable current

limit and over-voltage shutdown, mak-

ing it suitable for use in automotive and

switching regulator post regulator appli-

cations. An optional external RC filter

added to the CS8128 supply lead pro-

vides EMC hardening in addition to the

on-chip EMC hardening. The SENSE

lead allows remote sensing of the output

voltage for improved regulation.

An active microprocessor RESET func-

tion is included on-chip with externally

programmable delay time. During

power-up, or after detection of any error

in the regulated output, the RESET lead

will remain in the low state for the dura-

tion of the delay. Types of errors include

short circuit, low input voltage, over-

voltage shutdown, thermal shutdown,

or others that cause the output to

become unregulated. This function is

independent of the input voltage and

will function correctly with an output

voltage as low as 1V. Hysteresis is

included in both the reset and delay

comparators for noise immunity and to

prevent oscillations. A latching dis-

charge circuit is used to discharge the

delay capacitor, even when triggered by

a relatively short fault condition. This

circuit improves upon the commonly

used SCR structure by providing

improved noise immunity and full

capacitor discharge (0.2V typ).

+

-

-

+

IC

Reference

Gnd

PRE-

REGULATOR

IC

Power

Gnd

Regulated Supply

for Circuit Bias

10

µA

Delay

Current

Delay

Ref Gnd

Pwr Gnd

Thermal

Shutdown

Bandgap

Reference

Reset

Comparator

Latching

Discharge

Q S

R

Delay

Comparator

1.25V

Error

Amp

SHUTDOWN

Sense

-

Over

Voltage

Shutdown

-

+

RESET