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Shunt Regulator With Open Collector Output
POWER MANAGEMENT Description
The SC4431 is a four terminal device for regulating an isolated power supply with output voltages down to 1.5V. It is intended to be used as a replacement for three terminal shunt regulators such as SC431L where the output voltage is too low for the device to function in conjunction with an opto-isolator. SC4431 achieves this by having seperate supply and output pins, allowing the output to sink current at voltages as low as 0.1V, while the supply pin still has sufficient voltage for the device to function. In this way, allowing for a 1.4V drop through an opto-isolator diode, regulation down to 1.5V out can be achieved. The SC4431 shunt regulator is available with three initial reference voltage accuracies (0.5%, 1.0% and 2.0%) in the space saving 5-lead SOT-23 package. The three voltage tolerances allow the designer the opportunity to select the proper cost/tolerance for their application.
SC4431
Features
Open Collector output drives Optoisolator with as little as 1.5V input voltage Trimmed bandgap design - initial accuracies to + 0.5% 40mA drive capability Regulates output as low as 50mV Wide supply voltage range - 1.5V to 15V Low supply current - typically 110A Full industrial temperature range SOT-23 5 lead package
Applications
Telecom Power Supplies Opto driver for very low output voltage (1.5V) isolated power supplies Battery operated applications Point of use power supplies
Typical Application Circuit
2V Output Isolated Power Supply
T1 VIN Primary Side Controller Secondary Side Rectification and Filtering R1 R2 5.1k C1 2V OUT
U1
C3 SC4431 1 VCC
33nF
R3 6.34k
5 4N25 C2 22nF OUT
4 REF R4 10k
3 NC 2 GND
Revision September 9 ,2003
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POWER MANAGEMENT Absolute Maximum Rating
Parameter Input Supply Voltage Vcc pin current Output Voltage Reference Voltage (1) Continuous Output Current Reference Input Current Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Thermal Impedance Junction to Ambient Thermal Impedance Junction to Case Power Dissipation at TA = 25C Lead Temperature (Soldering) 10 seconds ESD Rating (Human Body Model)
Shunt Regulator With Open Collector Output
Symbol V CC ICC VOUT VREF IOUT IREF TA TJ TSTG J A J C PD TLEAD ESD Maximum -0.5 to +16 8 -0.5 to VCC -0.5 to +4 40 5 -40 to +85 -40 to +150 -65 to +150 256 81 475 300 2 Units V mA V V mA mA C C C C/W C/W mW C kV
SC4431
(1) If Vref will be forced above 1.224V, a resistor must be placed in series with the Vcc to limit the Icc current below 5mA.
Electrical Characteristics
Unless specified, TA = 25C, VCC = 2V, IOUT = 2mA. Values in bold apply over full operating temperature range.
Parameter VCC Input Supply Voltage Input Supply Current Off State Input Supply Current REF Reference Voltage
Symbol VCC ICC ICC(OFF)
Test Conditions
MIN 1.5
T YP
MAX 15 200 100 150 1.231 1.243 1.236 1.250 1.250 1.261 15 20 28 36 0.5 1.0 75 100 300 400 1 10
Units V A A
VREF
VREF = VOUT = 1.187V, VOUT = 2V
110 65
VREF
SC4431-.5, VREF = VOUT SC4431-1, VREF = VOUT SC4431-2, VREF = VOUT
1.219 1.207 1.212 1.200 1.200 1.187
1.224 1.224 1.224 8 8 0.3
V V V mV mV A
Change in VREF due to change in Vcc Change in VREF due to change in IOUT Reference Input Current OUT Saturation Voltage
dVREF/dVCC dVREF/dIOUT IREF
VCC = 1.5V to 15V IOUT = 0.1mA to 40mA 0.1mA IOUT 10mA
VOUT(SAT)
IOUT = 5mA, ICC = 500A VREF = 1.261V, IOUT = 40mA
50 275 0.50
mV mV A
Off State Output Current
IOUT(OFF)
VREF = 1.187V, VOUT = 2V
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Shunt Regulator With Open Collector Output
POWER MANAGEMENT Pin Configurations
(TOP VIEW)
SC4431
Ordering Information
Part Number(1)(2) SC4431CSK-X P ackag e SOT-23-5
Notes: (1) Only available in tape and reel packaging. (Suffix `.TR' e.g. SC4431CSK-X.TR). (2) Where "-X" denotes initial reference voltage tolerance. Available options are 0.5% (-.5), 1% (-1) and 2% (-2).
Lead) (SOT-23-5 Lead
Pin Descriptions
Pin# 1 2 3 4 5 Pin Name VC C GND NC REF OUT Pin Function This is the input supply pin for the SC4431. A low ESR capacitor should be used to bypass this pin to GND right at the IC. Logic and power ground. No connection. This is connected to the non-inverting input of the error amplifier. This is the output pin of the device, essentially an open collector. Note: A 22nF low ESR (ceramic) capacitor is required from this pin to GND for stable operation.
Block Diagram
Marking Information
Top Mark
4431
Bottom Mark
yyww
yyww = Datecode (Example: 9908)
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POWER MANAGEMENT Typical Characteristics
V ref vs T a I u t = 2m A o
1 .2 2 8 1 .2 2 7 1 .2 2 6 1 .2 2 5 1 .2 2 4 1 .2 3 2 1 .2 3 0 1 .2 3 6
V c c = 1 .5 V V cc= 2V V cc= 5V V cc= 15V
Shunt Regulator With Open Collector Output
SC4431
V ref vs T a V cc = 2V
I u t= 4 0 m a o
1 .2 3 4
I u t= 2 m A o I u t= 1 0 0 u A o
V ref(V
1 .2 2 3 1 .2 2 2 1 .2 2 1 1 .2 2 0 1 .2 1 9 1 .2 1 8 -4 0 -3 0 -2 0 -1 0 0 10 20 30 40 50 60 70 80 T a(D e g . . C)
V ref(V
1 .2 2 8 1 .2 2 6
1 .2 2 4 1 .2 2 2 -4 0 -3 0 -2 0 -1 0 0 10 20 30 40 50 60 70 80 T a(D e g . . C)
Typical Vref vs Ta Io = 2mA
I O ff vs T a V o u t = 2V cc
7 0 E -6
I c_O f c f
Typical Vref vs Ta Vcc = 2V
I ref vs T a V o u t = 2V
1 3 E -9
If re
1 2 E -9 6 5 E -6 1 1 E -9 1 0 E -9
I O ff(A cc
I ref (A
-4 0 -3 0 -2 0 -1 0 0 10 20 30 40 50 60 70 80
9 E -9 8 E -9 7 E -9
6 0 E -6
5 5 E -6
6 E -9 5 E -9
5 0 E -6 T a(D e g . . C)
4 E -9 -4 0 -3 0 -2 0 -1 0 0 10 20 30 40 50 60 70 80 T a(D e g . . C)
Typical Icc Off vs Ta Vo = 2V
I ref vs T a V cc = 2V
4 5 E -9
I u t= 1 0 0 u A o I u t= 1 m A o
Typical Iout vs Ta Vo = 2V
V sat vs T a V cc = 2V
350
I u t= 4 0 m a o I u t= 5 m A o
I u t= 2 m A o
4 0 E -9
I u t= 5 m A o I u t= 1 0 m A o I u t= 1 5 m A o
300 250
I f(A ) re
V s a t(m V
3 5 E -9
200 150 100
3 0 E -9
2 5 E -9
50 0 0 10 20 30 40 50 60 70 80 -4 0 -3 0 -2 0 -1 0 0 10 20 30 40 50 60 70 80 T a(D e g . . C)
2 0 E -9
-4 0 -3 0 -2 0 -1 0
T a(D e g . . C)
Typical Iref vs Ta Vcc = 2V
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Typical Vsat vs Ta Vcc = 2V
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Shunt Regulator With Open Collector Output
POWER MANAGEMENT Typical Characteristics
3.5000 3.5000
SC4431
3.0000
3.0000
2.5000
2.5000
2.0000
2.0000
Icc(mA)
Icc(mA)
1.5000
1.5000
1.0000
1.0000
0.5000
0.5000
0.0000
0.0000
-0.5000 1.2248 1.2703 1.3048 1.7030 3.0182
-0.5000 1.2243 1.2700 1.3009 1.7073 3.0073
Vref(v)
Vcc=2V,Io=1.3mA Vcc=5V,Io=1.3mA Vcc=15V,Io=1.3mA Vcc=2V,Io=2mA
Vref(v)
Vcc=5V,Io=2mA Vcc=15V,Io=2mA
Typical Icc vs Vref, Io = 1.3mA, Ta = 25 Deg.C.
Typical Icc vs Vref, Io = 2mA, Ta = 25 Deg.C.
+VCC
J1 +Vref_Adjust 1 2 C1 10uF R1 4k
+V adj
C3
U1 1
Io
5
R2 3.9k C2 10uF J2 1 2
R4 1k J3 1 2 C4 10uF
Vref
4
Vo
C5 22nF
R5 1k
Vref
SC4431 2
Icc vs Vref Test Circuit
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POWER MANAGEMENT Typical Gain Phase
SC4431 Gain / Phase Vin = 2V, Iout = 2mA, Vout = 1.6V
70
Shunt Regulator With Open Collector Output
SC4431
200
60
50
Gain Phase
150
100
40 Phase (deg) Phase (deg)
C3 33n
Gain (dB)
30
50
20
0
10 -50 0 -100
-10
-20 10 100 1000 Freq (Hz) 10000 100000
-150 1000000
SC4431 Gain / Phase Vin = 4V, Iout = 2mA, Vout = 2V
80 70 60 50 100 40 Gain (dB) 30 20 0 10 0 -50 -10 -20 10 100 1000 Freq (Hz) 10000 100000 -100 1000000 200
Gain
150
Phase
50
R1
J1 A 12345
J2 R 12345
1k for 2mA U1 J3 1 4V IN 1 2 3 VCC GND NC SC4431 C1 10u C2 0.1u REF 4 OUT 5 2V OUT
R2 3.16k R3
C4 22u C7 22n J4 1 GND J5 1 2 3 4 5 Signal In
C5 22u
C6 22u
5.1k R4 4.99k
Gain Phase Test Circuit
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Shunt Regulator With Open Collector Output
POWER MANAGEMENT Typical Applications
+V Monitor +Vcc Power Good
SC4431
C1 R4
R1 U1 5
R2
R3
1
Q1 C3
4 C4 C2 R5
Vref
22nF
2
SC4431
Power good Circuit
+Vcc
+Vout Secondary C1 +Vprimary R2 R1
1 R3 U2 PWM disable
Vref
5 4 C3 C2 22n U1 SC4431
R4
R5
C4
2
Isolated OVP Circuit
+Vin +Vout
Q1
C1
R1 U1 5
R2 R3
1
4 C2 22nF R4 C3
Vref
2
SC4431
Linear Regulator Circuit
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POWER MANAGEMENT Outline Drawing
Shunt Regulator With Open Collector Output
SC4431
SOT SO T-23- 5L
881 ECN00 - 881
Land Pattern
SOT SOT- 23- 5L
881 ECN00 - 881
Contact Information
Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805)498-2111 FAX (805)498-3804
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