AP431/AP431A
ADJUSTABLE PRECISION SHUNT REGULATOR
Application Examples
VIN
VIN
IOUT
RCL
R
VIN
R1B
R1A
O
N
+
R2A
R2B
OFF
VIN
Delay =
RC x ln (
)
IOUT = VREF / RCL
<
<
LED on when Low Limit VIN High Limit
V
IN -V
REF
≈
≈
Low Limit
High Limit
VREF (1+R1B/R2B)
REF (1+R1A/R2A)
V
Fig. 5 Delay
Timer
Fig. 4 Voltage
Monitor
Fig. 6 Current Limiter or Current
Source
VIN
IOUT
VIN
VOUT
VIN
VOUT
PULSE
R
1
R
1
R
2
R
2
RS
LIMIT
(1 + R1/R2) x VREF
VOUT
= (1 + R1/R2) x VREF
IOUT = VREF / RS
Fig. 7 Constant-Current
Sink
Fig. 8 Higher-Current Shunt
Regulator
Fig. 9 Crow Bar
VIN
R1A
R2A
R1B
Output ON when
Low Limit <
VIN < High Limit
+
VBE
R2B
(1 + R1B/R2B) +VBE
(1 + R1A/R2A)
Low Limit
High Limit
VREF
VREF
Fig.10 Over-Voltage / Under-Voltage Protection Circuit
AP431/AP431A Rev. 5
10 of 14
MARCH 2007
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