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ADJUSTABLE SHUNT REGULATOR
SC431
April 13, 1998
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
DESCRIPTION
The SC431 is a three terminal adjustable shunt regulator with thermal stability guaranteed over temperature. The output voltage can be adjusted to any value from 2.5V (VREF) to 36V with two external resistors. The SC431 has a typical dynamic output impedance of 0.25. Active output circuitry provides a very sharp turn on characteristic, making the SC431 an excellent replacement for zener diodes. The SC431 shunt regulator is available in three voltage tolerances (0.5%, 1.0% and 2.0%) and three package options (SOT-23-3, SO-8 and TO-92). The three voltage tolerances allow the designer the opportunity to select the proper cost/tolerance for their application.
FEATURES * Wide operating current range 100A to 150mA * Low dynamic output impedance 0.25 typ. * Trimmed bandgap design + 0.5% * Alternate for TL431, LM431 & AS431 APPLICATIONS * Linear Regulators * Adjustable Supplies * Switching Power Supplies * Battery Operated Computers * Instrumentation * Computer Disk Drives
PIN CONFIGURATIONS
SOT-23 -3 Lead (Top View)
BLOCK DIAGRAM
SOIC 8 Lead (Top View)
SYMBOL DIAGRAM
TO-92 (Top View)
1 (c) 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
ADJUSTABLE SHUNT REGULATOR
SC431
April 13, 1998
ABSOLUTE MAXIMUM RATINGS
Parameter Cathode Voltage Continous Cathode Current Reference Input Current Operating Junction Temperature Range Storage Temperature Range Thermal Resistance TO-92 SO-8 SOT-23 Power Dissipation at TA = 25C TO-92 SO-8 SOT-23 Lead Temperature (Soldering) 10 seconds Symbol VZ IZ IREF TJ TSTG JA Maximum 37 150 10 -40 to +150 -65 to +150 160 175 410 0.78 0.71 0.30 260 Units V mA mA C C C/W
PD
W
TLEAD
C
ORDERING INFORMATION
PACKAGE 0.5% SO-8
(1) (1)
TOLERANCE 1.0% SC431CS - 1 SC431CSK - 1 SC431CZ - 1 2.0% SC431CS - 2 SC431CSK - 2 SC431CZ - 2 T/R Quantity 2.5K 3K TR=3K, TA=2K
SC431CS - .5 SC431CSK - .5 SC431CZ - .5
SOT-23 TO-92
(1)(2)
Notes: (1) Add suffix `TR' for Tape & Reel. (2) Add suffix `TA' for Tape Ammo.
2 (c) 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
ADJUSTABLE SHUNT REGULATOR
SC431
April 13, 1998
ELECTRICAL CHARACTERISTICS
Unless specified, TA = 25C
SC431 0.5% Parameter Reference Voltage VREF Temp Deviation Ratio of Change in VREF to Change in Cathode Voltage Symbol VREF VDEV
V REF VZ
SC431 1% MIN TYP MAX
SC431 2% MIN TYP MAX UNITS V
Condition VZ = VREF IZ = 10mA (test circuit 1) TA = 25C
MIN
TYP
MAX
2.482 2.495 2.507 2.470 2.495 2.520 2.445 2.495 2.545
TA = -40 to +85C, VZ = VREF (test circuit 1) IZ = 10mA IZ = 10mA, VZ = 10V to VREF IZ = 10mA, VZ = 36V to 10V
8
17
8
25
15
30
mV
-0.5 -1.0 0.5
-2.7 -2.0 4
-0.5 -1.0 0.5
-2.7 -2.0 4
-0.5 -1.0 0.5
-2.7 mV/V -2.0 4 A
Reference Input Current
IREF
R1 = 10k, R2 = , IZ = 10mA (test circuit 2) TA = -40 to +85C, R1 = 10k, R2 = , IZ =10mA (test circuit 2) VREF = 0V, VZ = 36V (test circuit 3) f < 1kHz, VZ = VREF IZ = 100uA to 100mA (test circuit 1) VZ = VREF (test circuit 1)
IREF Temp Deviation
IREF(DEV)
0.4
1.2
0.4
1.2
0.4
1.2
A
Off State Cathode Current Dynamic Output Impedance Minimum Operating Current
IZ (off) rZ
0.04
0.5
0.04
0.5
0.04
0.5
A
0.25
0.5 100
0.25
0.5 100
0.25
0.5 100
A
IZ (min)
TEST CIRCUITS
Test Circuit 1: VZ = VREF
Test Circuit 2: VZ > VREF
Test Circuit 3: Off State Current
RECOMMENDED OPERATING CONDITIONS
Min Cathode Voltage, VZ Cathode Current, IZ VREF 0.1 Max 36 150 Symbol V mA 3 (c) 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
ADJUSTABLE SHUNT REGULATOR
SC431
April 13, 1998
TYPICAL CHARACTERISTICS
Cathode Current vs. Cathode Voltage
300 200 100 0 -100 -200 -300 -2 -1 0 VZ (V) 1 2 3 IZ (mA) IZ (A) VZ = VREF TA = 25 C
o
Cathode Current vs. Cathode Voltage
150 100 50 0 -50 -100 -150 -2 -1 0 VZ (V) 1 2 3 VZ = VREF TA = 25 C
o
Reference Voltage vs. Junction Temperature
2.515 2.510 2.505 2.500 2.495 2.490 2.485 -50 -25 0 25 50 TJ (C) 75 100 125 150 20 IREF (nA) VREF (V) 60 VZ = VREF IZ = 10mA 100 IZ = 10mA R1 = 10k R2 =
Reference Input Current vs. Junction Temperature
80
40
0 -50 -25 0 25 50 TJ (C) 75 100 125 150
Ratio of Delta Reference Voltage to Delta Cathode Voltage vs. Junction Temperature
0.5 IZ = 10mA VZ = 3V to 36V 100 VZ = 36V VREF = 0V
Off-State Cathode Current vs. Junction Temperature
0.4 VREF/VZ (-mV/V)
10
0.3 IZ(off) 0.2
1
0.1
0.1
0.01
0 -50 -25 0 25 50 TJ (C) 75 100 125 150
0.001 -50 -25 0 25 50 TJ (C) 75 100 125 150
4 (c) 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
ADJUSTABLE SHUNT REGULATOR
SC431
April 13, 1998
TYPICAL CHARACTERISTICS (Cont.)
Small-Signal Gain and Phase Shift vs. Frequency
80 70 60 50 AV (dB) 40 30 20 10 0 -10 -20 1.0E+02 1.0E+03 1.0E+04 f (Hz) 1.0E+05 IZ = 10mA TA = 25C -180 -225 -270 Phase Shift (deg) -315 -360 -405 -450 -495 -540 -585 -630 1.0E+06
Test Circuit For Small-Signal Gain and Phase Shift
Reference Impedance vs. Frequency
100 IZ = 10mA TA = 25C 10
rZ ()
1
0.1
Notes for Application Circuit:
0.01 1.0E+03 1.0E+04 1.0E+05 f (Hz) 1.0E+06 1.0E+07
1) Set VOUT according to the following equation:
R1 V OUT = V REF 1 + + IREF R1 R2
APPLICATION CIRCUIT
2) Choose the value for R as follows: * * The maximum limit for R should be such that the cathode current, IZ, is greater than the minimum operating current (100A) at VIN(min). The minimum limit for R should be such that IZ does not exceed 150mA under all load conditions, and the instantaneous turn-on value for IZ does not exceed 200mA. Both of the following conditions must be met:
R min VIN (max) 200 mA
(to limit instantaneous turn-on IZ) (to limit IZ under normal operating conditions)
R min
VIN (max) - V OUT IOUT (min) + 150 mA
5 (c) 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
ADJUSTABLE SHUNT REGULATOR
SC431
April 13, 1998
OUTLINE DRAWING SOT-23
OUTLINE DRAWING SO-8
OUTLINE DRAWING TO-92
6 (c) 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320

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