Datasheet

TLV431, TLV431A, TLV431B
LOW-VOLTAGE ADJUSTABLE PRECISION SHUNT REGULATOR
SLVS139T − JULY 1996 − REVISED JUNE 2007
18
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
~
~
P
−
+
P
P
V
CC
V
FB
Current
Sense
Gate Drive
GND
Controller
P
P
PP
TLV431
or
TLV431A
or
TLV431B
V
O
3.3 V
V
I
120 V
Figure 18. Flyback With Isolation Using TLV431, TLV431A, or TLV431B
as Voltage Reference and Error Amplifier
Figure 18 shows the TLV431, TLV431A, or TLV431B used in a 3.3-V isolated flyback supply. Output voltage V
O
can be as low as reference voltage V
REF
(1.24 V ± 1%). The output of the regulator, plus the forward voltage
drop of the optocoupler LED (1.24 + 1.4 = 2.64 V), determine the minimum voltage that can be regulated in an
isolated supply configuration. Regulated voltage as low as 2.7 Vdc is possible in the topology shown in
Figure 18.