POWER MANAGEMENT
1 www.semtech.com
SC431
Adjustable Shunt Regulator
Description Features
Revision 7, May 2003
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 30V with two external
resistors. The SC431 has a typical dynamic output
impedance of 0.25Ω. 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 with four
voltage tolerances (0.5%, 1.0% and 2.0% over TA = -40°C
to +85°C and 0.5% over TA = -40°C to +125°C) and three
package options (SOT-23-3, SO-8 and TO-92). This
allows the designer the opportunity to select the
optimum combination of cost and performance for their
application.
Linear Regulators
Adjustable Supplies
Switching Power Supplies
Battery Operated Computers
Instrumentation
Computer Disk Drives
Wide operating current range 130µA to 150mA
Low dynamic output impedance 0.25 Ω typ.
Trimmed bandgap design + 0.5%
Alternate for TL1431, TL431, LM431 & AS431
Industrial temperature range
Available in SOT-23-3, SO-8 and TO-92 packages
Notes:
1) Set VOUT according to the following equation:
1RI
2R
1R
1VV REFREFOUT +
+=
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 (130µA) 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:
mA200
V
R(max)IN
min ≥ (to limit instantaneous turn-on IZ)
mA150I
VV
R
(min)OUT
OUT(max)IN
min +−
≥ (to limit IZ under normal
operating conditions)
Applications
Typical Application Circuit(1)(2)
2 2003 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC431
Absolute Maximum Ratings
Electrical Characteristics
retemaraP lobmySmumixaMstinU
egatloVedohtaC V
Z
13V
tnerruCedohtaCsuonitnoC I
Z
051Am
tnerruCtupnIecnerefeR I
FER
01Am
TtanoitapissiDrewoP
A
C°52=
3-32-TOS
8-OS
29-OT
P
D
73.0
87.0
59.0
W
ecnatsiseRlamrehT
3-32-TOS
8-OS
29-OT
θ
AJ
633
361
231
W/C°
egnaRerutarepmeTtneibmAgnitarepO
2-xC134CS,1-xC134CS,5.-xC134CS
QxC134CS
T
A
58+ot04-
521+ot04-
C°
egnaRerutarepmeTnoitcnuJgnitarepO T
J
051+ot04-C°
egnaRerutarepmeTegarotS T
GTS
051+ot56-C°
sdnoces01)gniredloS(erutarepmeTdaeL T
DAEL
003C°
)ledoMydoBnamuH(gnitaRDSE V
DSE
2Vk
,5.-xC134CS
QxC134CS
1-xC134CS
retemaraPlobmySnoitidnoCniMpyTxaMniMpyTxaMstinU
egatloVecnerefeRV
FER
V
Z
V=
FER
I,
Z
Am01=
)1(
284.2594.2705.2074.2594.2025.2V
V
FER
noitaiveDpmeTV
VED
V
Z
V=
FER
,I
Z
Am01=
)1(
871852Vm
niegnahCfooitaRI
Z
,Am01= ∆V
Z
VotV01=
FER
5.0-7.2-5.0-7.2-V/Vm
V
FER
VniegnahCot
Z
I
Z
,Am01= ∆V
Z
V01otV03=0.1-0.2-0.1-0.2-
tupnIecnerefeR
tnerruC
I
FER
k01=1R Ω=2R, ∞,
I
Z
Am01=
)2(
5.04 5.04Aµ
I
FER
erutarepmeT
noitaiveD
I
)VED(FER
k01=1R Ω=2R, ∞,
I
Z
Am01=
)2(
4.02.14.02.1 Aµ
edohtaCetatS-ffO
tnerruC
I
)FFO(Z
V
FER
V,V0=
Z
V03=
)3(
40.005.040.005.0Aµ
tuptuOcimanyD
ecnadepmI
r
Z
V,zHk1<f
Z
V=
FER
I
Z
Am001otAµ031=
)1(
52.005.052.005.0 Ω
gnitarepOmuminiM
tnerruC
I
)NIM(Z
V
Z
V=
FER
)1(
031031Aµ
Z
REF
V
V
∆
∆
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters
specified in the Electrical Characteristics section is not implied.
Unless specified:TA = 25°C. Values in bold apply over full operating ambient temperature range.
3 2003 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC431
Test Circuit 3
Off-State
Test Circuit 2
VZ > VREF
Test Circuit 1
VZ = VREF
Electrical Characteristics (Cont.)
2-xC134CS
retemaraPlobmySnoitidnoCniMpyTxaMstinU
egatloVecnerefeRV
FER
V
Z
V=
FER
I,
Z
Am01=
)1(
544.2594.2545.2V
V
FER
noitaiveDpmeTV
VED
V
Z
V=
FER
,I
Z
Am01=
)1(
5103Vm
VniegnahCfooitaR
FER
otI
Z
,Am01= ∆V
Z
VotV01=
FER
5.0-7.2-V/Vm
VniegnahC
Z
I
Z
,Am01= ∆V
Z
V01otV03=0.1-0.2-
tnerruCtupnIecnerefeRI
FER
k01=1R Ω=2R, ∞I,
Z
Am01=
)2(
5.04Aµ
I
FER
noitaiveDerutarepmeTI
)VED(FER
k01=1R Ω=2R, ∞,I
Z
Am01=
)2(
4.02.1 Aµ
tnerruCedohtaCetatS-ffOI
)FFO(Z
V
FER
V,V0=
Z
V03=
)3(
40.005.0Aµ
ecnadepmItuptuOcimanyDr
Z
V,zHk1<f
Z
V=
FER
I,
Z
Am001otAµ031=
)1(
52.005.0 Ω
tnerruCgnitarepOmuminiMI
)NIM(Z
V
Z
V=
FER
)1(
031Aµ
Z
REF
V
V
∆
∆
Unless specified:TA = 25°C. Values in bold apply over full operating ambient temperature range.
Notes:
(1) See Test Circuit 1 below.
(2) See Test Circuit 2 below.
(3) See Test Circuit 3 below.
niMxaMlobmyS
V,egatloVedohtaC
Z
V
FER
03V
I,tnerruCedohtaC
Z
031.0051Am
Test Circuits
Recommended Operating Conditions
4 2003 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC431
ecnareloT%5.0%5.0%0.1%0.2
egnaRerutarepmeTtneibmAC°58+otC°04-C°521+otC°04-C°58+otC°04-C°58+otC°04-
3-32-TOS
)1(
RT5.-KSC134CSRTQKSC134CSRT.1-KSC134CSRT.2-KSC134CS
3-32-TOS
)4(,)1(
TRT5.-KSC134CSTRTQKSC134CSTRT.1-KSC134CSTRT.2-KSC134CS
8-OS
)2(
RT5.-SC134CSRTQSC134CSRT.1-SC134CSRT.2-SC134CS
29-OT
)3(
AT5.-ZC134CSATQZC134CSAT.1-ZC134CSAT.2-ZC134CS
Pin Configurations
SO-8 (Top View) TO-92 (Top View)SOT-23-3 (Top View)
Block Diagram Symbol
Ordering Information
Notes:
(1) Only available in tape and reel packaging. A reel contains 3000 devices.
(2) Only available in tape and reel packaging. A reel contains 2500 devices.
(3) Only available in an ammo pack. An ammo pack contains 2000 devices.
(4) “T” at end of part number indicates “lead free”.
5 2003 Semtech Corp. www.semtech.com
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SC431
Marking Information
SO-8 (Top View) TO-92 (Top View)SOT-23-3 (Top View)
SO-8 (Bottom View)
xxxxx
4 3 1
SC
431
yyww
yyww = Datecode
(Example: 9815)
4 3 1
yyww = Datecode (Example: 0008)
xxxxx = Semtech Lot # (Example: 00101)
SC
431CS
yyww
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POWER MANAGEMENT
SC431
-300
-200
-100
0
100
200
300
-2-10123
VZ (V)
IZ ( A)
VZ = VREF
TA = 25 oC
-150
-100
-50
0
50
100
150
-2-10123
VZ (V)
IZ (mA)
VZ = VREF
TA = 25 oC
0
0.1
0.2
0.3
0.4
0.5
-50 -25 0 25 50 75 100 125 150
TJ (°C)
VREF/ VZ (-mV/V)
IZ = 10mA
∆VZ = 3V to 30V
2.485
2.490
2.495
2.500
2.505
2.510
2.515
-50 -25 0 25 50 75 100 125 150
TJ (°C)
VREF (V)
VZ = VREF
IZ = 10mA
0
20
40
60
80
100
-50 -25 0 25 50 75 100 125 150
TJ (°C)
IREF (nA)
IZ = 10mA
R1 = 10kΩ
R2 = ∞
0.001
0.01
0.1
1
10
100
-50 -25 0 25 50 75 100 125 150
TJ (°C)
IZ(off)
VZ = 30V
VREF = 0V
Cathode Current vs.
Cathode Voltage
Cathode Current vs.
Cathode Voltage
Reference Voltage vs.
Junction Temperature
Reference Input Current vs.
Junction Temperature
Ratio of Delta Reference Voltage to Delta Cathode
Voltage vs. Junction Temperature
Off-State Cathode Current
vs. Junction Temperature
Typical Characteristics
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SC431
0.01
0.1
1
10
100
1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07
f (Hz)
rZ ( )
IZ = 10mA
TA = 25°C
-20
-10
0
10
20
30
40
50
60
70
80
1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06
f (Hz)
AV (dB)
-630
-585
-540
-495
-450
-405
-360
-315
-270
-225
-180
Phase Shift (deg)
IZ = 10mA
TA = 25°C
Small-Signal Gain and Phase Shift
vs. Frequency
Reference Impedance
vs. Frequency
Typical Characteristics (Cont.) Test Circuit - Small-Signal Gain and Phase
Test Circuit - Stability
Stability Boundary Condition For Shunt Regulation
vs. Cathode Current and Load Capacitance
8 2003 Semtech Corp. www.semtech.com
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SC431
Land Pattern - SOT-23-3
Note:
(1) Grid placement courtyard is 8 x 8 elements (4mm x 4mm) in accordance with the international grid detailed in
IEC Publication 97.
Outline Drawing - SOT-23-3
Outline Drawing - SO-8
9 2003 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC431
Land Pattern - SO-8
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805)498-2111 FAX (805)498-3804
Contact Information
Outline Drawing - TO-92
