LP2950 Datasheet, PDF (11/16 Pages) National Semiconductor (TI) – Series of Adjustable Micropower Voltage Regulators

LP2950
Figure 22. Regulator with Early Warning and Auxiliary Output
+Vin
8
5
Error
Vin
Vout
1
D1
SNS ²
LP2951CN
NC ³ SD ^#1 _{VO T} ⁶
Gnd FB
4
7
D2
1.0 µF
Memory
V+
20
3.6 V
NiCad
27 k
D3
2.7 M
Q1
D4
2N3906
330 k
8
5 _Error
Vin
Vout
1
SNS ²
LP2951CN
3 _SD #2 _{VO T} 6
Gnd FB
4
7
Early Warning
Reset
µP
VDD
Main
Output
1.0 µF
All diodes are 1N4148.
Early Warning flag on low input voltage.
Main output latches off at lower input
voltages.
Battery backup on auxiliary output.
Operation: Regulator #1’s Vout is
programmed one diode drop above 5.0 V.
Its error flag becomes active when Vin < 5.7
V. When Vin drops below 5.3 V, the error
flag of regulator #2 becomes active and via
Q1 latches the main output “off”. When Vin
again exceeds 5.7 V, regulator #1 is back in
regulation and the early warning signal
rises, unlatching regulator #2 via D3.
Figure 23. 2.0 A Low Dropout Regulator
Current Limit
+Vin
Section
680
2N3906
470
0.05
1000 µF
2N3906
4.7 M
Error
Flag
220
20 k
MJE2955
10 k .33 µF
8
5 _Error
Vin
Vout
1
SNS ² NC
LP2951CN
3 _SD
VO T ^{6 NC}
Gnd FB .01 µF
4
7
47
4.7 µF
Tant
R1
Vout @ 2.0 A
100 µF
R2
0.033 µF
Vout = 1.25V (1.0 + R1/R2)
For 5.0 V output, use internal resistors. Wire Pin 6 to 7,
and wire Pin 2 to +Vout Bus.
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