CAT102
Precision, Adjustable Shunt Regulator
(600mV Reference)
FEATURES
Low voltage reference: 600mV
Low temperature coefficient reference: 25ppm
Accurate 600mV reference voltage:
+6mV at T
J
= 25ºC
High PSRR: 45dB at 300kHz
High line rejection: ±1mV (V
CC
from 2.2V to 18V)
Low supply current: 300µA
Open collector output
Directly drives optocouplers
Compact 5-lead SOT23 package
Industrial temperature range: -40ºC to 85ºC
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
600mV. Over a junction temperature from -40°C to
105°C the reference voltage is within 8mV of the
nominal 600mV. In addition, the error amplifier output
and the supply voltage pin are on separate pins.
Power supply rejection is a high 45dB at 300kHz. The
output, OUT, can sink 20mA at a maximum saturation
voltage of 250mV.
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 8.
FUNCTIONAL DIAGRAM
IN
Error
Amplifier
+
PIN CONFIGURATION
OUT
3
5
SOT-23 5L
Top View
FB
GND
OUT
1
1
2
2
4
3
4
5
NC
5
8
IN
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 20mA.
No connection
Positive supply
FB
GND
OUT
NC
IN
© 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc. No. 4007 Rev. M
CAT102
ABSOLUTE MAXIMUM RATINGS
(1)
Parameters
V
IN
Voltage
OUT Voltage
FB Voltage
V
IN
, OUT, FB Current
Operating Junction Temperature (10s)
Lead Soldering Temperature (10s)
Storage Temperature Range
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 with a
junction temperature from -40°C to +105°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
= 3V, FB = OUT, I
OUT
= 1mA.
Symbol
V
IN
I
IN
V
FB
Parameter
Supply Voltage Range
Quiescent Supply Current
FB Threshold Reference Voltage
Line Regulation
Load Regulation
T
CREF
I
FB
PSRR
A
V
BW
V
OUT
TRANSC
I
LEAK
I
OUT(MAX)
Reference Temperature Deviation
FB Input Current
Reference Power Supply Rejection
Error Amplifier Open Loop Gain
Unity Gain Frequency
Output Saturation voltage
Output Transconductance
Output Leakage Current
Maximum Output Current
Frequency = 300kHz
I
OUT
= 2mA, V
OUT
= 1V
I
OUT
= 2mA, V
OUT
= 1V
I
OUT
= 20mA, V
FB
= HIGH
I
OUT
= 1mA to 20mA
V
OUT
= 16V, V
FB
= 0
V
OUT
= 0.3V
20
V
OUT
=1V
T
J
= 25˚ C
-40ºC <T
J
<105ºC
V
IN
= 2.2V to V
IN
=18V
I
OUT
= 1mA to 10mA
-40ºC < T
J
< 105ºC
-500
35
60
1
45
80
2
100
2.5
200
400
250
594
592
0.5
4
25
Conditions
Min
2.2
0.3
600
Typ
Max
18
0.5
606
608
1
8
50
500
Units
V
mA
mV
mV
mV
ppm/ºC
nA
dB
dB
MHz
mV
mA/mV
nA
mA
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 SOT-23 5-lead: 255°C/W
Doc. No. 4007 Rev. M
2
© 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT102
TYPICAL PERFORMANCE CHARACTERISTICS
Line Regulation (at 1mA)
0.4
Output Voltage Change (mV)
Load Regulation
6
Output Voltage Change (mV)
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
2.2
6
10
14
18
5
4
3
2
1
0
1
5
10
15
20
Supply Voltage (V)
Load Current (mA)
Supply Current vs. Load Current
300
280
260
Supply Current (µA)
Power-Supply Rejection Ratio vs. Frequency
-50
-55
-60
PSRR (dB)
240
220
200
180
160
140
120
100
0
5
10
15
L o a d C u r re n t (m A )
20
-65
-70
-75
-80
-85
-90
-95
-100
0.1
1
10
100
1000
10000 100000
F re q u e n c y (H z )
© 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
3
Doc. No. 4007 Rev. M
CAT102
TYPICAL PERFORMANCE CHARACTERISTICS
FB Bias Current vs. Temperature (V
CC
= 2.5V)
0
Reference Voltage (V)
FB Bias Current (nA)
630
620
610
600
590
580
Reference Voltage
10mA
-10
-20
-30
-40
-50
-60
-70
-40
0
40
80
120
570
-40
0
40
80
120
Junction Temperature (ºC)
Junction Temperature (ºC)
Gain vs. Frequency
110
90
Gain (dB)
70
50
30
10
-10
0.01
0.1
1
10
100 1000 10000
Frequency (kHz)
Doc. No. 4007 Rev. M
4
© 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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 20mA with
V
OUT
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 1.0µF capacitor from OUT to GND is recommen-
ded 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:
V
OUT
= (1 + R
1
/R
2
) x 0.6V
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
IN
is associated with R
3
= 135Ω, and a
10V supply works best with R3 = 470Ω. The CAT102
shunt regulator is limited to low-current applications with
the OUT pin capable of sinking up to 20mA max.
Figure 1. Application circuits for 0.6V output and 1.2V 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
© 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
5
Doc. No. 4007 Rev. M
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