CS8321 datasheet(2/6 Pages) CHERRY

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Electrical Characteristics: 6V < VIN < 26V, IOUT=1mA, -40¡C ² TA ² 125¡C, -40¡C ² TJ ² 150¡C unless otherwise specified.

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

PACKAGE LEAD #

LEAD SYMBOL

FUNCTION

Circuit Description and Application Notes

The CS8321 is a series pass voltage regulator. It consists of

an error amplifier, bandgap voltage reference, PNP pass

transistor with antisaturation control, and current limit.

As the voltage at the input, VIN, is increased, QN is for-

ward biased via R. QN provides base drive for QP. As QP

becomes forward biased, the output voltage, VOUT, begins

to rise as QPÕs output current charges the output capacitor.

Once VOUT rises to a certain level, the error amplifier

becomes biased and provides the appropriate amount of

base current to QP. The error amplifier monitors the scaled

output voltage via an internal voltage divider, R1 and R2,

and compares it to the bandgap voltage reference. The

error amplifierÕs output is a current which is equal to the

error amplifierÕs differential input voltage times its

transconductance. Therefore, the error amplifier varies the

base drive current to QN, which provides bias to QP, based

on the difference between the reference voltage and the

scaled output voltage, VOUT.

Antisaturation Protection

An antisaturation control circuit has also been added to

prevent the pass transistor from going into deep satura-

tion, which would cause excessive power dissipation due

to large bias currents lost to the substrate via a parasitic

PNP transistor, as shown in Figure 1.

Figure 1. The parasitic PNP transistor which is part of the pass transis-

tor (QP) structure.

VOUT

VIN

QParasitic

Substrate

Voltage Reference and Output Circuitry

Package Lead Description

s Output Stage

Output Voltage, VOUT

9V < VIN < 16V,

4.90

5.00

5.10

100µA ² IOUT ² 150mA

Dropout Voltage (VIN-VOUT)IOUT = 150mA, -40¡C ² TA ² 85¡C

0.3

0.5

IOUT = 150mA, TA = 125¡C

0.6

Quiescent Current, (IQ)IOUT = 1mA @ VIN = 13V

200

µA

IOUT < 50mA @ VIN = 13V

IOUT < 150mA @ VIN = 13V

Load Regulation

VIN = 14V, 100µA < IOUT < 150mA

Line Regulation

6V < V < 26V, IOUT = 1mA

Ripple Rejection

7 Ð VIN Ð 17V, IOUT = 150mA,

f = 120Hz

Current Limit

175

250

Short Circuit Output Current

VOUT = 0V

200

Reverse Current

VOUT = 5V, VIN = 0V

140

200

µA

3L D2PAK

3L TO-220

VIN

Input Voltage

Gnd

Ground. All Gnd leads must be connected to Ground.

VOUT

5V, ±2%, 150mA Output.

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