CAT102 Catalyst Semiconductor, CAT102 Datasheet - Page 6

• Manufacturer Part Number: CAT102
• Description: Precision/ Adjustable Shunt Regulator (600mV Reference)
• Manufacturer: Catalyst Semiconductor

Doc. No. 4007, Rev. L
The CAT102 adjustable shunt regulator features
isolated supply inputs and outputs, ideal for isolated
power-supply applications using an optocoupler in
the feedback path. The CAT102 sinks 20mA with V
at 0.3V. The wide input supply range allows the
device to operate from 2.2V to 18V. The CAT102
compares the FB input to a precision 600mv reference.
If the FB input is low, the OUT pin sinks no current. If
FB rises above 600mV, the OUT pin sinks up to
20mA.
Figure 1 shows the CAT102 configured as a shunt
regulator. To generate an output voltage of 0.6V, the
FB pin has to be directly connected to the OUT pin. A
1.0 F capacitor from OUT to GND is recommended
when the output voltage is 0.6V. A resistor-divider
connected from OUT to GND is used to produce a
higher output voltage as set by the following equation:
APPLICATIONS INFORMATION
V
OUT
= (1 + R1/R2) x 0.6V
Figure 1. Application circuits for 0.6V output and 1.2V output voltages
3.3V
3.3V
V IN
V IN
5
5
2
2
IN
GND
IN
GND
CAT102
CAT102
R3
R3
OUT
6
OUT
OUT
FB
FB
The current limit can be adjusted by using a resistor
R3 connected between the IN and OUT pins. For
example, a 3.3V supply V
135 , and a 10V supply works best with R3 = 470 .
The CAT102 shunt regulator is limited to low-current
applications with the OUT pin capable of sinking up to
20mA max.
3
1
3
1
R2
10k
R1
10k
V OUT
0.6V/20mA
V OUT = (1+R1/R2) x 0.6V
IN
1.2V/20mA
is associated with R3 =