4

Typical Performance Characteristics: continued

Precision Voltage Reference

The regulated output voltage depends on the precision

band gap voltage reference in the IC. By adding an error

amplifier into the feedback loop, the output voltage is

maintained within ±4% over temperature and supply vari-

ation.

Output Stage

The composite PNP-

NPN output structure

(Figure 1) provides 1A

(typ) of output current

while maintaining a

low drop out voltage

(1.2V) and drawing lit-

tle quiescent current

(4mA).

The NPN pass device prevents deep saturation of the output

stage which in turn improves the IC’s efficiency by prevent-

ing excess current from being used and dissipated by the IC.

Output Stage Protection

The output stage is protected against overvoltage, short

circuit and thermal runaway conditions (Figure 2).

Voltage Reference and Output Circuitry

Load

Dump

Short

Circuit

Thermal

Shutdown

> 30V

Figure 1. Composite Output Stage of the CS8121

Circuit Description

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

0

0.1

-40

°C

25

°C

125

°C

VIN = 14V

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Quiescent Current vs. Output Current Over Temperature

22.0

20.0

16.0

12.0

8.0

4.0

0.0

10.0

8.0

6.0

4.0

2.0

0.0

0.0

1.0

2.0

3.0

4.0

5.0

5.5

Supply Voltage

Output Voltage and Supply Current vs. Input Voltage

2000

1800

1600

1400

1200

1000

800

600

400

200

0

1

5

10

15

20

25

30

35

40

Reset Output Current (mA)

RESET Output Voltage vs. Output Current

Figure 2. Typical Circuit Waveforms for Output Stage Protection.