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April 2009 Rev. 2.0.0
Exar Corporation www.exar.com
48720 Kato Road, Fremont CA 94538, USA Tel. +1 510 668-7000 – Fax. +1 510 668-7001
GENERAL DESCRIPTION
The SPX431A is a three-terminal adjustable
shunt voltage regulator providing a highly
accurate bandgap reference.
The SPX431A acts as an open-loop error
amplifier with a 2.5V temperature
compensation reference. The SPX431A has
thermal stability, wide operating current of
150mA and broad temperature range of -40°C
to 125°C, making it suitable for a variety of
applications which require a low-cost, high
performance solution. The SPX431A tolerance
of 0.5% is proven to be sufficient to overcome
all other errors in the system to virtually
eliminate the need for trimming in the power
supply manufacturer's assembly line and
contribute a significant cost savings. The
output voltage may be adjusted to any value
between VREF and 36 volts with two external
resistors.
The SPX431A is available in RoHS compliant,
lead free TO-92 and SOT89 packages.
APPLICATIONS
• Charger
• Switching Power Supplies
• Graphic Cards
• Monitors, VCRs, TVs
FEATURES
• 0.5% Precise Output Voltage
− Adjustable up to 36V
• Wide Operating Current
− 1mA to 150mA
• Low Temperature Coefficient
at 30ppm/°C
• Extended Temperature Range
− -40°C to +125°C
• Improved Replacment for TL431
• RoHS Compliant, Lead Free
TO-92 and SOT-89 Packages
TYPICAL APPLICATION DIAGRAM
Fig. 1: SPX431A Application Diagram
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© 2009 Exar Corporation 2/11 Rev. 2.0.0
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of
the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect
reliability.
Cathode-Anode Reverse Breakdown Volt. VKA ............. 37V
Operating Cathode Current (cont.) IKA ................... 150mA
Reference Input Current Range IREF.........................10mA
Power Dissipation SOT-89-TO-92 (Cont. 25°C) PD.. 770mW
Junction Temperature .......................................... 150°C
Storage Temperature TSTG........................ -65°C to 150°C
ESD Rating (HBM - Human Body Model) .................... 2kV
OPERATING RATINGS
Cathode-Anode Reverse Breakdown Volt. VKA ............. 36V
Operating Cathode Current (cont.) IKA ................ <100mA
Ambient Temperature Range ....................-40°C to 125°C
ELECTRICAL SPECIFICATIONS
Specifications with standard type are for an Operating Ambient Temperature of TA = 25°C only; limits applying over the full
Operating Ambient Temperature range are denoted by a “•”. Minimum and Maximum limits are guaranteed through test,
design, or statistical correlation. Typical values represent the most likely parametric norm at TA = 25°C, and are provided
for reference purposes only.
Parameter Min. Typ. Max. Units Conditions
Reference Voltage 2.493 2.503 2.515 V
Test circuit 1
VKA=VREF, IKA=10mA
ΔVREF with temperature TC 4.5 8 mV
Test circuit 1
VKA=VREF, IKA=10mA, 0°C ≤ TA ≤ 70°C
ΔVREF with temperature TC 4.5 16 mV •
Test circuit 1
VKA=VREF, IKA=10mA
-2.7 -1.0 Test circuit 2
VREF ≤ ΔVKA ≤ 10V, IKA=10mA
Ratio of change in VREF to
Cathode Voltage ΔVREF / ΔVKA -2 -0.4
mV/V
Test circuit 2
10V ≤ ΔVKA ≤ 36V, IKA=10mA
Reference Input Current IREF 0.7 4 µA
Test circuit 2
IKA=10mA, R1=10kΩ, R2=∞
IREF Temperature Deviation ΔIREF 0.4 1.2 µA •
Test circuit 2
IKA=10mA, R1=10kΩ, R2=∞
Minimum IKA for Regulation
IKA(MIN) 0.4 1 mA
Test circuit 1
VKA=VREF
Off State Leakage IKA(OFF) 40 250 nA
Test circuit 3
VKA=0, VREF=36V
Dynamic Outout Impedance ZKA 0.15 0.5 Ω
Test circuit 1
fZ≤1KHz, IKA=1 to 100mA
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© 2009 Exar Corporation 3/11 Rev. 2.0.0
BLOCK DIAGRAM
Fig. 2: SPX431A Block Diagram
PIN ASSIGNEMENT
3-pin TO-92 (N)
3-pin SOT89 (M1)
Fig. 3: SPX431A Pin Assignement
ORDERING INFORMATION
Part Number Temperature
Range Marking Package Packing
Quantity Note 1 Note 2
SPX431AM1-L/TR -40°C≤TA≤+125°C SOT89 2.5K/Tape & Reel RoHS Compliant
Lead Free
SPX431AN-L/TR -40°C≤TA≤+125°C TO-92 2K/Tape & Reel
RoHS Compliant
Lead Free Ammo Pack
“YY” = Year – “WW” = Work Week – “X” = Lot Number
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© 2009 Exar Corporation 4/11 Rev. 2.0.0
TYPICAL PERFORMANCE CHARACTERISTICS
All data taken at TA = 25°C, unless otherwise specified - Schematic and BOM from Application Information section of this
datasheet.
Fig. 4: Cathode Current vs Cathode Voltage
Fig. 5: Reference Voltage vs Ambient Temperature
Fig. 6: Low Current Operating Characteristics
Fig. 7: Reference Input Current vs Ambient Temperature
Fig. 8: ΔReference Voltage to ΔCathode Voltage Ratio
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© 2009 Exar Corporation 5/11 Rev. 2.0.0
Fig. 9: Test Circuit for Gain vs Frequency Responce
Fig. 10: Small Signal Gain vs Frequency
Fig. 11: Test Circuit for Pulse Response
Fig. 12: Pulse Response
Fig. 13: Test Circuit for Stability
Fig. 14: Stability Boundary Conditions
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© 2009 Exar Corporation 6/11 Rev. 2.0.0
Fig. 15: Test Circuit for Dynamic Output Impedance
Fig. 16: Dynamic Output Impedance
Fig. 17: Off State Leakage
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© 2009 Exar Corporation 7/11 Rev. 2.0.0
TYPICAL APPLICATION SCHEMATICS
Fig. 18: Shunt Regulator VOUT=(1+R1/R2)VREF
Fig. 19: Constant Current Sink ISINK=VREF/R1
Fig. 20: Reference Amplifier for Isolated Feedback
in Offline DC-DC Coinverters
Fig. 21: Precision High Current Series Regulator
VOUT=(1+R1/R2)VREF
Fig. 22: High Current Shunt Regulator
VOUT=(1+R1/R2)VREF
Fig. 23: Single Supply Comparator
with Temperature Compensated Threshold
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© 2009 Exar Corporation 8/11 Rev. 2.0.0
TEST CIRCUITS
TEST CIRCUIT 1
Test circuit for VKA=VREF
TEST CIRCUIT 2
Test circuit for VKA > VREF
TEST CIRCUIT 3
Test circuit for IKOFF
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© 2009 Exar Corporation 9/11 Rev. 2.0.0
PACKAGE SPECIFICATION
SOT-89
Unit: mm (inch)
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© 2009 Exar Corporation 10/11 Rev. 2.0.0
TO-92
Unit: mm (inch)
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© 2009 Exar Corporation 11/11 Rev. 2.0.0
REVISION HISTORY
Revision Date Description
2.0.0 04/15/09
Reformat of Datasheet
Updated ordering part numbers
Updated application and block diagram
FOR FURTHER ASSISTANCE
Email: customersupport@exar.com
Exar Technical Documentation: http://www.exar.com/TechDoc/default.aspx?
EXAR CORPORATION
HEADQUARTERS AND SALES OFFICES
48720 Kato Road
Fremont, CA 94538 – USA
Tel.: +1 (510) 668-7000
Fax: +1 (510) 668-7030
www.exar.com
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve
design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein,
conveys no license under any patent or other right, and makes no representation that the circuits are free of patent
infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a
user’s specific application. While the information in this publication has been carefully checked; no responsibility, however,
is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or
malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its
safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in
writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all
such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
