AMS2954
TYPICAL APPLICATIONS (Continued)
2 Ampere Low Dropout Regulator
Regulator with Early Warning and Auxiliary Output
CURRENT
LIMIT
SECTION
+VIN
+VIN = VOUT +.5V
D1
8
2
+VIN
0.05
SENSE
5V MEMORY
SUPPLY
680
D2
6
7
1
VTAP
AMS2954
#1
VOUT
20
5
470
+
FB
ERROR
1
F
m
3.6V
NICAD
GND
4
MJE2955
2N3906
4.7M
+VOUT @ 2A
10k
W
W
8
+VIN
27 k
W
ERROR
FLAG
5
ERROR
+
+
100mF
EARLY WARNING
R1
D3
4.7
2.7M
Q1
W
AMS2954
TANT.
7
3
D4
SD
GND
FB
VOUT
1%
R2
220
8
2
SENSE
VOUT
AMS2954
4
1
RESET
330 k
W
+VIN
20k
W
P
m
6
MAIN 5V OUTPUT
.033
VDD
VTAP
7
3
FB
SD
#2
5
+
ERROR
1mF
GND
4
VOUT = 1.23V(1+R1/R2)
·
·
·
Early warning flag on low input voltage
Main output latches off at lower input voltages
Battery backup on auxiliary output
For 5V VOUT, use internal resistors. Wire pin 6 to 7 and pin 2 to +VOUTBuss.
Operation: Reg.#1’s VOUT is programmed one diode drop above 5V. It’s error flag
becomes active when VIN£ 5.7V. When VIN drops below 5.3V, the error flag of
Reg.#2 becomes active and via Q1 latches the main output off. When VIN again
exceeds 5.7V Reg.#1 is back in regulation and the early warning signal rises,
unlatching Reg.#2 via D3.
1A Regulator with 1.2V Dropout
Latch Off When Error Flag Occurs
+VIN
UNREGULATE
D INPUT
k
F
0.01m
10 W
F
1m
SUPERTEX
VP12C
470k
W
8
VOUT
+VIN
8
5
3
1
7
VOUT
ERROR
IN
OUTPUT
5V ± 1% @
0 TO 1A
470k
W
2
1
6
7
VTAP
SENSE
AMS2954
R1
R2
+
220mF
AMS2954
+
SD
FB
1mF
RESET
GND
4
FB
OUT
GND
4
k
2 W
1MW
0.002mF
IQ @ 400mA
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
ADMOS [ ADVANCED MONOLITHIC SYSTEMS ]
