LP2950 Datasheet, PDF (11/14 Pages) National Semiconductor (TI) – Series of Adjustable Micropower Voltage Regulators

LP2950/2951
+V = 2 ^→ 30V
IL↓
LOAD
1.23
IL= _R
8
VIN
VOUT ¹
LP2951
SHUTDOWN 3
SD
INPUT
GND FB
4
7
R
1%
1µF
0.1µF
Low Drift Current Source
+V _IN
Micrel
+V _IN
VOUT
LP2950Z
GND
*VOUT = 5V
+
1µF
5 Volt Current Limiter
* MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT.
+V _IN
D1
3
8
+V _IN
2
SENSE
VOUT ¹
LP2951
#1
5
ERROR
GND
4
27kΩ
2.7MΩ
D4
D3
D2
MEMORY
V+
20
1µF
3.6V
NICAD
EARLY WARNING
Q1
8
2
+VIN SENSE
VOUT ¹
LP2951
3 _SD
#2 _{ERROR 5}
GND
4
330kΩ
MAIN
OUTPUT
RESET
µP
VDO
+
1µf
Regulator with Early Warning and Auxiliary Output
• EARLY WARNING FLAG ON LOW INPUT VOLTAGE
• MAIN OUTPUT LATCHES OFF AT LOWER INPUT VOLTAGES
• BATTERY BACKUP ON AUXILIARY OUTPUT
OPERATION: REG. #1’S V_OUT IS PROGRAMMED ONE DIODE DROP ABOVE 5 V.
ITS ERROR FLAG BECOMES ACTIVE WHEN V_IN ≤ 5.7 V. WHEN V_IN DROPS
BELOW 5.3 V, THE ERROR FLAG OF REG. #2 BECOMES ACTIVE AND VIA Q1
LATCHES THE MAIN OUTPUT OFF. WHEN V_IN AGAIN EXCEEDS 5.7 V REG. #1
IS BACK IN REGULATION AND THE EARLY WARNING SIGNAL RISES,
UNLATCHING REG. #2 VIA D3.
February 1999
3-45