SG29125/125A

12/90 Rev 1.1 2/94

Copyright

© 1994

11861 Western Avenue

∞

∞

∞

∞

∞ Garden Grove, CA 92841

3

(714) 898-8121

∞

∞

∞

∞

∞ FAX: (714) 893-2570

Test Conditions

Parameter

Standby Output (V

Units

6V

≤ V

6V

≤ V

1mA

≤ I

1mA

≤ I

1mA

I

10Hz - 100kHz

F

I

4.75V

≤ V

SG29125/125A

Min.

Max.

4.75

50

60

5.0

4

10

25

1

1.2

300

20

66

0.55

100

70

5.25

50

25

50

3

0.7

Typ.

V

mV

mV

mV

Ω

mA

µV

RMS

mV/1000hr

dB

V

mA

V

Line Regulation

Load Regulation

Output Impedance

Quiescent Current

Output Noise Voltage

Long Term Stability

Ripple Rejection

Dropout Voltage

Current Limit

Maximum Operational Input Voltage

TYPICAL CIRCUIT WAVEFORM

14V

0V

2V

0.8V

5V

0V

5V

INPUT

VOLTAGE

PIN 1 (V)

ON/OFF

SWITCH

OUTPUT

VOLTAGE

PIN 2 (V)

STANDBY

VOLTAGE

PIN 5 (V)

TURN

ON

SYSTEM

CONDITION

LOAD

DUMP

LOW V

IN

3.7V

3.5V

12V

12V

12V

60V

33V

4V

26V

14V

0.8V

0V

12V

12V

5.0V

TURN

OFF

THERMAL

SHUTDOWN

V

OUT

SHORT

CIRCUIT

LINE NOISE,

ETC.

Note 4. The temperature extremes are guaranteed but not 100% production tested.

APPLICATION NOTES

regulator enters a micropower mode.

Here all but the most

essential circuitry to power the standby output is deactivated.

This allows the lowest possible quiescent current (typical around

1.2mA), a vital factor when used in a battery powered system.

In some applications the regulator output voltage is used not only

as a power supply but also as a voltage reference for control

systems. In such cases not just the temperature stability of the

output is important but also the initial accuracy. The SG29125/

125A fills this need as the internal bandgap reference is trimmed

allowing a typical output voltage tolerance of ±1%.

The advantages of using a low-dropout regulator such as the

SG29125/125A are the need for less “headroom” for full regula-

tion, and the inherent reverse polarity protection provided by the

PNP output device. A typical NPN regulator design requires an

input to output differential of approximately two volts minimum.

This is due to the 2Vbe + Vcesat of the NPN Darlington used in

the output, coupled with the voltage drop across the current limit

resistor. In contrast, the “PNP Regulator” uses a single series

pass transistor with its single Vcesat, thus the lower input to

output voltage differential or dropout voltage.

In addition to a low dropout voltage, an important advantage of

the SG29125/125A series is low quiescent current in the standby

mode. When the high current or primary regulator is shut off, the