SG29055/55A
12/90 Rev 1.1 2/94
Copyright
1994
L
IN
F
IN
ITY
Microelectronics Inc.
11861 Western Avenue
∞
∞
Garden Grove, CA 92841
(714) 898-8121
∞
FAX: (714) 893-2570
3
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 SG29055/
55A 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
SG29055/55A 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 SG29055/55A series is low quiescent current in the standby
mode. When the high current or primary regulator is shut off, the
ELECTRICAL CHARACTERISTICS
(continued)
Test Conditions
Parameter
Standby Output (V
SB
) Section
Output Voltage
(Note 4)
Tracking
Line Regulation
Load Regulation
Units
SG29055/55A
Min.
Typ.
Max.
4.75
50
60
5.0
50
4
10
25
1
1.2
300
20
66
0.55
100
70
5.25
200
50
25
50
3
0.7
V
mV
mV
mV
mV
mA
μ
V
mV/1000hr
dB
V
mA
V
Output Impedance
Quiescent Current
Output Noise Voltage
Long Term Stability
Ripple Rejection
Dropout Voltage
Current Limit
Maximum Operational Input Voltage
Note 4. The temperature extremes are guaranteed but not 100% production tested.
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
5.0V
5.0V
5.0V
60V
33V
4V
26V
14V
0.8V
0V
5.0V
5.0V
5.0V
TURN
OFF
THERMAL
SHUTDOWN
V
SHORT
CIRCUIT
LINE NOISE,
ETC.
6V
≤
V
≤
26V, I
≤
50mA, -40
°
C
≤
T
A
≤
85
°
C
V
- Standby Output Voltage
6V
≤
V
IN
≤
26V
1mA
≤
I
O
≤
35mA
1mA
≤
I
≤
50mA
1mA
and 1mA
, 100Hz - 10kHz
I
≤
10mA, V
OFF
10Hz - 100kHz
F
O
= 120Hz
I
O
≤
50mA
4.75V
≤
V
O
≤
6V