CAT102
Precision, Adjustable Shunt Regulator
(600 mV Reference)
FEATURES
600 mV low voltage reference
±6 mV initial accuracy
High PSRR: 45 dB at 300 kHz
Better line regulation: 1 mV (V
IN
from 2.2 V to 18 V)
Low supply current: 90 µA
Open drain output
Directly drives optocouplers
Industrial temperature range of -40ºC to 85ºC
RoHS-compliant 5-lead TSOT23 package
DESCRIPTION
The CAT102 is a low-voltage reference and amplifier.
Designed for the control loop of low-voltage power
supplies, the reference voltage has been designed for
600 mV. Over a temperature from -40°C to 85°C, the
reference voltage is within 8 mV of the nominal
600mV. In addition, the error amplifier output and the
supply voltage pin (IN) are on separate pins.
Power supply rejection is a high 45 dB at 300 kHz.
The output, OUT, can sink 20 mA at a maximum
saturation voltage of 250 mV.
When combined with an optocoupler, the CAT102 can
be used as an error amplifier that controls the
feedback loop in isolated low-output voltage switching
power supplies.
APPLICATION
SMPS control loop
Low temperature coefficient voltage reference
Power management
Replaces zener diodes
Isolated DC-to-DC converters
Network, telecom and cellular base station
Adjustable voltage reference
For Ordering Information details, see page 7.
FUNCTIONAL DIAGRAM
IN
Error
Amplifier
+
PIN CONFIGURATION
OUT
3
TSOT-23 5L
Top View
FB
GND
OUT
1
1
2
2
4
3
4
5
NC
5
8
IN
5
FB
1
V
REF
600mV
–
+
–
PIN DESCRIPTION
Pin Name
2
GND
Function
Inverting input to error amplifier
Ground
Output of error amplifier. Source & sink
current capability is 20 mA.
No connection
Positive supply
FB
GND
OUT
NC
IN
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
1
Doc. No. MD-4007 Rev. P
CAT102
ABSOLUTE MAXIMUM RATINGS
Parameters
V
IN
Voltage
OUT Voltage
FB Voltage
V
IN
, OUT, FB Current
Operating Junction Temperature (10 seconds)
Lead Soldering Temperature (10 seconds)
Storage Temperature Range
(1)
Ratings
20
20
20
50
150
260
-65 to +150
Units
V
V
V
mA
ºC
ºC
ºC
ELECTRICAL CHARACTERISTICS
Electrical characteristics are guaranteed over the full operating temperature range of -40°C to +85°C unless
otherwise specified. Ambient temperature must be de-rated based upon power dissipation and package thermal
characteristics.
1
Unless otherwise stated, test conditions are V
IN
= 3 V, FB = OUT, I
OUT
= 1 mA.
Symbol
V
IN
I
IN
V
FB
Parameter
Supply Voltage Range
Quiescent Supply Current
FB Threshold Reference Voltage
Line Regulation
Load Regulation
I
FB
PSRR
(3)
A
V
BW
(3)
V
OUT
I
LEAK
I
OUT(MAX)
FB Input Current
Reference Power Supply
Rejection
Error Amplifier Open Loop Gain
Unity Gain Frequency
Output Saturation voltage
Output Leakage Current
Maximum Output Current
V
OUT
=1 V
T
J
= 25ºC
-40ºC < T
J
< 85ºC
V
IN
= 2.2 V to V
IN
=18 V
V
OUT
= 0.6 V
I
OUT
= 1 mA to 10 mA
V
OUT
= 0.6 V
Frequency = 300 kHz
I
OUT
= 2 mA, V
OUT
= 1 V
I
OUT
= 2 mA, V
OUT
= 1 V
I
OUT
= 20 mA, V
FB
= HIGH
I
OUT
= 1 mA to 20 mA
V
OUT
= 16 V, V
FB
= 0
V
OUT
= 0.3 V
20
594
592
0.5
3
-500
35
60
1
65
80
2
130
2.5
0.5
2
250
Conditions
Min
2.2
90
600
Typ
Max
18
500
606
608
1
8
500
Units
V
µA
mV
mV
mV
nA
dB
dB
MHz
mV
mA/mV
µA
mA
TRANSC
(3)
Output Transconductance
Notes:
(1)
These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolongued time periods
may affect device reliability. All voltages are with respect to ground.
(2) Thermal Characteristics (Θ
JA
) of TSOT-23 5-lead: 255°C/W
(3) This parameter is controlled by design and verified during product evaluation. It is not production tested.
Doc. No. MD-4007 Rev. P
2
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
CAT102
TYPICAL PERFORMANCE CHARACTERISTICS
Line Regulation (at 1mA)
0.4
Output Voltage Change (mV)
Output Voltage Change (mV)
6
5
4
3
2
1
0
Load Regulation
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
2
6
10
14
18
Supply Voltage (V)
1
5
10
15
20
Load Current (mA)
Supply current vs. Input Voltage
92
90
Power-Supply Rejection Ratio vs. Frequency
-50
-55
-60
PSRR (dB)
Supply Current (µA)
88
86
84
82
80
78
0
5
10
Input Voltage (V)
15
20
-65
-70
-75
-80
-85
-90
-95
-100
0.1
1
10
100
1000
10000 100000
F r e q u e n c y (H z )
Reference Voltage
630
620
Gain vs. Frequency
110
90
Reference Voltage (mV)
Gain (dB)
610
600
590
580
570
-40
70
50
30
10
-10
0
40
80
120
0.01
0.1
1
10
100
1000
10000
Junction Temperature (ºC)
Frequency (kHz)
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
3
Doc. No. MD-4007 Rev. P
CAT102
APPLICATIONS INFORMATION
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 20 mA with
V
OUT
at 0.3 V. The wide input supply range allows
the device to operate from 2.2 V to 18 V. 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 600 mV, the OUT
pin sinks up to 20 mA.
Figure 1 shows the CAT102 configured as a shunt
regulator. To generate an output voltage of 0.6 V,
the FB pin has to be directly connected to the OUT
pin. A 1.0 µF capacitor from OUT to GND is
recommended when the output voltage is 0.6 V. A
resistor-divider connected from OUT to GND is used
to produce a higher output voltage as set by the
following equation:
V
OUT
= (1 + R
1
/R
2
) x 0.6 V
The current limit can be adjusted by using a resistor R3
connected between the IN and OUT pins. For example,
a 3.3 V supply V
IN
is associated with R
3
= 135
Ω,
and a
10 V supply works best with R
3
= 470
Ω.
The CAT102
shunt regulator is limited to low-current applications with
the OUT pin capable of sinking up to 20 mA max.
Figure 1. Application circuits for 0.6 V output and 1.2 V output voltages
V
IN
3.3V
R
3
V
OUT
0.6V/20mA
5
C
1
0.1µF
IN
OUT
3
C
2
CAT102
2
GND
FB
1
1µF
V
IN
3.3V
R
3
V
OUT
= (1 + R
1
/R
2
) x 0.6V
1.2V/20mA
5
C
1
0.1µF
IN
OUT
3
R
1
C
2
1µF
CAT102
2
GND
FB
1
10kΩ
R
2
10kΩ
Doc. No. MD-4007 Rev. P
4
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
CAT102
TYPICAL APPLICATION
1V regulated
output
V
IN
V
OUT
Regulator
with
Isolation
V
CC
> 2.2V
Opto-isolator
R3
100Ω
R4
100kΩ
5
IN
OUT
3
C
1
0.1µF
C
2
CAT102
2
R1
22kΩ
GND
FB
1
1µF
R2
33kΩ
Figure 2. Opto-Feedback Application Circuit
In order to allow proper operation of the optocoupler and the CAT102, the supply voltage V
CC
must be greater
than 2.2 V.
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
5
Doc. No. MD-4007 Rev. P
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