TL431A_13 Datasheet, PDF (31/79 Pages) Texas Instruments – PRECISION PROGRAMMABLE REFERENCE

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V_I(BATT)
R1A
TL431
R3
(see Note A)
R1B
R4
(see Note A)
R2A
R2B
TL431, TL431A, TL431B
TL432, TL432A, TL432B
SLVS543M – AUGUST 2004 – REVISED JULY 2012
Low Limit =
1+
R1B
R2B
V_ref
High Limit =
1+
R1A
R2A
V_ref
LED on When Low Limit < V_I(BATT) < High Limit
A. Select R3 and R4 to provide the desired LED intensity and cathode current ≥1 mA to the TL431 at the available
V_I(BATT).
Figure 29. Voltage Monitor
12 V
650 Ω
R
2 kΩ
TL431
Off
On
C
Delay
=
R
×
C
×
I_n
æ
ççè ₁₂
12 V
V – V_ref
ö
÷÷ø
Figure 30. Delay Timer
V_I(BATT)
R1
R_CL
I_O
0.1%
TL431
I_out
=
V_ref
R_CL
+
I_KA
R1
=
V_I(BATT)
IO
h _FE
+ I_KA
Figure 31. Precision Current Limiter
V_I(BATT)
I_O
TL431
R_S
0.1%
IO =
V_ref
R_S
Figure 32. Precision Constant-Current Sink
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