NCP100 ON Semiconductor, NCP100 Datasheet - Page 9

• Manufacturer Part Number: NCP100
• Description: Sub 1v Precision Adjustable Shunt Regulator
• Manufacturer: ON Semiconductor

compensated amplifier for controlling the feedback loop of
an isolated output line powered converter. This device
allows the converter to directly regulate the output voltage
at a significantly lower level than obtainable with the
The circuit in Figure 28 uses the NCP100 as a
Opto
Figure 26. High Current Shunt Regulator
1/2
V
in
AC Line
Input
R
in
V out +
V out min + 0.9 V ) V be
+
−
UC3842
1 ) R1
+
R2
Figure 28. Offline Converter with Isolated DC Output
V
REF
R1
R2
V
out
+
−
+
−
http://onsemi.com
S
R
Q
NCP100
+
−
9
common TL431 device family. The output voltage is
programmed by the resistors R1 and R2. The minimum
regulated DC output is limited to the sum of the lowest
allowable cathode to anode voltage (0.9 V) and the forward
drop of the optocoupler light emitting diode (1.4 V).
Figure 27. Low Dropout Series Pass Regulator
V
in
V out min + V REF
V out +
Minimum V
1 ) R1
R2
Opto
NCP
out
1/2
100
V
= (0.9 + 1.4) = 2.3 V
REF
R1
R2
V
out
R1
R2
Isolated
DC
Output
−