CS8321 Ver la hoja de datos (PDF) - Cherry semiconductor

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CS8321

Micropower 5V, 150mA Low Dropout Linear Regulator

Cherry semiconductor 

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

s Output Stage

Output Voltage, VOUT

9V < VIN < 16V,

100µA ² IOUT ² 150mA

4.90

5.00

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

0.3

IOUT = 150mA, TA = 125¡C

Quiescent Current, (IQ)

IOUT = 1mA @ VIN = 13V

IOUT < 50mA @ VIN = 13V

4

IOUT < 150mA @ VIN = 13V

15

Load Regulation

VIN = 14V, 100µA < IOUT < 150mA

5

Line Regulation

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

5

Ripple Rejection

7 Ð VIN Ð 17V, IOUT = 150mA,

f = 120Hz

60

75

Current Limit

175

250

Short Circuit Output Current VOUT = 0V

Reverse Current

VOUT = 5V, VIN = 0V

60

200

140

5.10

V

0.5

V

0.6

V

200

µA

6

mA

25

mA

50

mV

50

mV

dB

mA

mA

200

µA

PACKAGE LEAD #

3L D2PAK

3L TO-220

1

1

2

2

3

3

Package Lead Description

LEAD SYMBOL

FUNCTION

VIN

Gnd

VOUT

Input Voltage

Ground. All Gnd leads must be connected to Ground.

5V, ±2%, 150mA Output.

Circuit Description and Application Notes

Voltage Reference and Output Circuitry

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.

VIN

QP

QParasitic

Substrate

VOUT

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

tor (QP) structure.

2

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