1.0A Low Dropout Voltage Regulator
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Information 1.0A Low Dropout Voltage Regulator
Output Option Fixed
VOUT (V) 2.5, 3.3, 5.0
VOUT Adj MIN (V) -
VOUT Adj MAX (V) -
IOUT (mA) 1000
VIN MIN (V) 3.1
VIN MAX (V) 16
IQ (µA) 18000
Accuracy (%) 2%
Vdrop (mV) 280
Output Noise (µVRMS) 260
PSRR (dB) -
Junction Temp Range (°C) -40 to 125
Package SOT223-3, TO263-3
Features Reverse battery protection, Current limit and thermal protection
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The SPX3940 is a 1A, accurate voltage regulator with a low drop out voltage of 280mV (typical) at 1A.

These regulators are specifically designed for low voltage applications that require a low dropout voltage and a fast transient response. They are fully fault protected against overcurrent, reverse battery and positive and negative voltage transients.

The SPX3940 is offered in 3-pin SOT-223 and TO-263 packages. For a 3A version, refer to the SPX29300 datasheet.

  • 1% output accuracy SPX3940A
  • Guaranteed 1.5A peak current
  • Low quiescent current
  • Low dropout voltage of 280mV at 1A
  • Extremely tight load and line regulation
  • Extremely fast transient response
  • Reverse battery protection
  • Internal short-circuit current limit
  • Replacement for LM3940

Documentation & Design Tools

Type Title Version Date File Size
Data Sheets SPX3940 1A Low Dropout Voltage Regulator 1.0.1 July 2023 1.1 MB
Application Notes AN200, Downloading and Installing CAD Symbols and Footprints with Ultra Librarian April 2019 1.2 MB
Product Brochures Power Management Brochure October 2020 2.4 MB
Product FAQs SPX3940 FAQ 1.0.0 October 2006 169.8 KB
Symbols & Footprints SPX3940AM3-L-3-3 and SPX3940AM3-L-3-3/TR CAD File (.bxl) September 2018 24.9 KB
Symbols & Footprints SPX3940AM3-L-5-0/TR CAD File (.bxl) September 2018 24.9 KB
Symbols & Footprints SPX3940AT-L-3-3/TR CAD File (.bxl) September 2018 17.7 KB
Symbols & Footprints SPX3940M3-L-2-5/TR CAD File (.bxl) September 2018 24.9 KB
Symbols & Footprints SPX3940M3-L-5-0/TR CAD File (.bxl) September 2018 24.9 KB
Symbols & Footprints SPX3940T-L-3-3/TR CAD File (.bxl) September 2018 17.7 KB
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Quality & RoHS

Part Number RoHS | Exempt RoHS Halogen Free REACH TSCA MSL Rating / Peak Reflow Package
SPX3940AM3-L-3-3 N Y Y Y Y L1 / 260ᵒC SOT-223-3
SPX3940AM3-L-3-3/TR N Y Y Y Y L1 / 260ᵒC SOT-223-3
SPX3940AM3-L-5-0/TR N Y Y Y Y L1 / 260ᵒC SOT-223-3
SPX3940M3-L-5-0/TR N Y Y Y Y L1 / 260ᵒC SOT-223-3
SPX3940M3-L-2-5/TR N Y Y Y Y L1 / 260ᵒC SOT-223-3
SPX3940AT-L-3-3/TR N Y Y Y Y L3 / 245ᵒC TO-263-3
SPX3940T-L-3-3/TR N Y Y Y Y L3 / 245ᵒC TO-263-3

Click on the links above to download the Certificate of Non-Use of Hazardous Substances.

Additional Quality Documentation may be available, please Contact Support.

Parts & Purchasing

Part Number Pkg Code Min Temp Max Temp Status Suggested Replacement Buy Now Order Samples PDN
SPX3940AM3-1-8 SOT-223-3 OBS
SPX3940AM3-1-8/TR SOT-223-3 OBS
SPX3940AM3-2-5 SOT-223-3 OBS
SPX3940AM3-2-5/TR SOT-223-3 -40 125 OBS
SPX3940AM3-3-3 SOT-223-3 -40 125 OBS
SPX3940AM3-3-3/TR SOT-223-3 -40 125 OBS
SPX3940AM3-5-0 SOT-223-3 -40 125 OBS
SPX3940AM3-5-0/TR SOT-223-3 -40 125 OBS
SPX3940AM3-L-1-8 SOT-223-3 -40 125 OBS SPX3940AM3-L-1-8/TR
SPX3940AM3-L-1-8/TR SOT-223-3 -40 125 OBS
SPX3940AM3-L-2-5 SOT-223-3 -40 125 OBS SPX3940AM3-L-2-5/TR
SPX3940AM3-L-2-5/TR SOT-223-3 -40 125 OBS SPX3940M3-L-2-5/TR
SPX3940AM3-L-3-3 SOT-223-3 -40 125 OBS SPX3940AM3-L-3-3/TR
SPX3940AM3-L-3-3/TR SOT-223-3 -40 125 Active Order
SPX3940AM3-L-5-0 SOT-223-3 -40 125 OBS SPX3940AM3-L-5-0/TR
SPX3940AM3-L-5-0/TR SOT-223-3 -40 125 Active Order
SPX3940AT-1-8 TO-263-3 -40 125 OBS
SPX3940AT-1-8/TR TO-263-3 -40 125 OBS
SPX3940AT-2-5 TO-263-3 OBS
SPX3940AT-2-5/TR TO-263-3 OBS
SPX3940AT-3-3 TO-263-3 -40 125 OBS
SPX3940AT-3-3/TR TO-263-3 -40 125 OBS
SPX3940AT-5-0 TO-263-3 OBS
SPX3940AT-5-0/TR TO-263-3 OBS
SPX3940AT-L-1-8 TO-263-3 -40 125 OBS SPX3940AT-L-1-8/TR
SPX3940AT-L-1-8/TR TO-263-3 -40 125 OBS
SPX3940AT-L-2-5 TO-263-3 -40 125 OBS SPX3940AM3-L-2-5
SPX3940AT-L-2-5/TR TO-263-3 -40 125 OBS SPX3940AM3-L-2-5/TR
SPX3940AT-L-3-3 TO-263-3 -40 125 OBS SPX3940AT-L-3-3/TR
SPX3940AT-L-3-3/TR TO-263-3 -40 125 Active Order
SPX3940AT-L-5-0 TO-263-3 -40 125 OBS SPX3940AT-L-5-0/TR
SPX3940AT-L-5-0/TR TO-263-3 -40 125 OBS
SPX3940AU-1-8 TO-220-3 OBS
SPX3940AU-2-5 TO-220-3 OBS
SPX3940AU-3-3 TO-220-3 OBS
SPX3940AU-5-0 TO-220-3 OBS
SPX3940AU-L-1-8 TO-220-3 OBS
SPX3940AU-L-2-5 TO-220-3 OBS
SPX3940AU-L-3-3 TO-220-3 OBS
SPX3940AU-L-5-0 TO-220-3 -40 125 OBS
SPX3940M3-1-8 SOT-223-3 OBS
SPX3940M3-1-8/TR SOT-223-3 OBS
SPX3940M3-2-5 SOT-223-3 -40 125 OBS
SPX3940M3-2-5/TR SOT-223-3 OBS
SPX3940M3-3-3 SOT-223-3 -40 125 OBS
SPX3940M3-3-3/TR SOT-223-3 -40 125 OBS
SPX3940M3-5-0 SOT-223-3 -40 125 OBS
SPX3940M3-5-0/TR SOT-223-3 -40 125 OBS
SPX3940M3-L-1-8 SOT-223-3 -40 125 OBS SPX3940AM3-L-1-8
SPX3940M3-L-1-8/TR SOT-223-3 -40 125 OBS SPX3940AM3-L-1-8/TR
SPX3940M3-L-2-5 SOT-223-3 -40 125 OBS SPX3940M3-L-2-5/TR
SPX3940M3-L-2-5/TR SOT-223-3 -40 125 Active Order
SPX3940M3-L-3-3 SOT-223-3 -40 125 OBS SPX3940AM3-L-3-3/TR
SPX3940M3-L-3-3/TR SOT-223-3 -40 125 OBS SPX3940AM3-L-3-3/TR
SPX3940M3-L-5-0 SOT-223-3 -40 125 OBS SPX3940M3-L-5-0/TR
SPX3940M3-L-5-0/TR SOT-223-3 -40 125 Active Order
SPX3940T-1-8 TO-263-3 OBS
SPX3940T-1-8/TR TO-263-3 OBS
SPX3940T-2-5 TO-263-3 OBS
SPX3940T-2-5/TR TO-263-3 OBS
SPX3940T-3-3 TO-263-3 -40 125 OBS
SPX3940T-3-3/TR TO-263-3 -40 125 OBS
SPX3940T-5-0 TO-263-3 OBS
SPX3940T-5-0/TR TO-263-3 OBS
SPX3940T-L-1-8 TO-263-3 -40 125 OBS SPX3940AM3-L-1-8
SPX3940T-L-1-8/TR TO-263-3 -40 125 OBS SPX3940AM3-L-1-8/TR
SPX3940T-L-2-5 TO-263-3 -40 125 OBS SPX3940AM3-L-2-5
SPX3940T-L-2-5/TR TO-263-3 -40 125 OBS SPX3940AM3-L-2-5/TR
SPX3940T-L-3-3 TO-263-3 -40 125 OBS SPX3940T-L-3-3/TR
SPX3940T-L-3-3/TR TO-263-3 -40 125 Active Order
SPX3940T-L-5-0 TO-263-3 -40 125 OBS
SPX3940T-L-5-0/TR TO-263-3 -40 125 OBS
SPX3940U-1-8 TO-220-3 OBS
SPX3940U-2-5 TO-220-3 OBS
SPX3940U-3-3 TO-220-3 -40 125 OBS
SPX3940U-5-0 TO-220-3 -40 125 OBS
SPX3940U-L-1-8 TO-220-3 OBS
SPX3940U-L-2-5 TO-220-3 OBS
SPX3940U-L-3-3 TO-220-3 OBS
SPX3940U-L-5-0 TO-220-3 -40 125 OBS
Show obsolete parts
Part Status Legend
Active - the part is released for sale, standard product.
EOL (End of Life) - the part is no longer being manufactured, there may or may not be inventory still in stock.
CF (Contact Factory) - the part is still active but customers should check with the factory for availability. Longer lead-times may apply.
PRE (Pre-introduction) - the part has not been introduced or the part number is an early version available for sample only.
OBS (Obsolete) - the part is no longer being manufactured and may not be ordered.
NRND (Not Recommended for New Designs) - the part is not recommended for new designs.


Pkg Code Details Quantities Dimensions PDF
  • JEDEC Reference: TO-261
  • MSL Pb-Free: L1 @ 260ºC
  • MSL SnPb Eutectic: n/a
  • ThetaJA: 62.3ºC/W
  • Bulk Pack Style: Tube
  • Quantity per Bulk Pack: 78
  • Quantity per Reel: 2500
  • Quantity per Tube: 78
  • Quantity per Tray: n/a
  • Reel Size (Dia. x Width x Pitch): 330 x 12 x 8
  • Tape & Reel Unit Orientation: Heatsink by sprocket hole
  • Dimensions: mm
  • Length: 6.50
  • Width: 3.50
  • Thickness: 1.80
  • Lead Pitch: 2.30
  • JEDEC Reference: TO-220
  • MSL Pb-Free: n/a
  • MSL SnPb Eutectic: n/a
  • ThetaJA: 29.4ºC/W
  • Bulk Pack Style: Tube
  • Quantity per Bulk Pack: n/a
  • Quantity per Reel: n/a
  • Quantity per Tube: 50
  • Quantity per Tray: n/a
  • Reel Size (Dia. x Width x Pitch): n/a
  • Tape & Reel Unit Orientation: n/a
  • Dimensions: inch
  • Length: 0.355 max
  • Width: 0.420 max
  • Thickness: 0.190 max
  • Lead Pitch: 0.10
  • JEDEC Reference: TO-263
  • MSL Pb-Free: L3 @ 245ºC
  • MSL SnPb Eutectic: n/a
  • ThetaJA: 31.4ºC/W
  • Bulk Pack Style: Tube
  • Quantity per Bulk Pack: n/a
  • Quantity per Reel: 500
  • Quantity per Tube: 50
  • Quantity per Tray: n/a
  • Reel Size (Dia. x Width x Pitch): 330 x 24 x 16
  • Tape & Reel Unit Orientation: Tab away from sprocket hole.
  • Dimensions: inch
  • Length: 0.380 max
  • Width: 0.420 max
  • Thickness: 0.190
  • Lead Pitch: 0.10


Distribution Date Description File
05/08/2019 Product Discontinuation Notice
02/27/2018 Qualification of alternate assembly subcon, JCET.
07/11/2017 Product Discontinuation Notification
04/12/2017 Qualification of alternate assembly subcon, JCET.
08/16/2016 Addition of an alternate qualified location, JCET.
07/26/2016 Product discontinuation notification. Discontinued.
02/25/2016 Alternate assembly site. Addition of an alternate assembly supplier JCET.
02/05/2016 Alternate assembly site. Addition of an alternate assembly supplier Nantong Fujitsu (China)
10/05/2015 JCET as alternate assembly site Addition of qualified alternate assembly site and material change using copper wire or gold wire.
09/09/2013 Addition of an alternate qualified SOT-223 assembly site, Carsem (Malaysia) using Hitachi CEL9240 molding compound, in addition to the current qualified assembly site, Unisem (Ipoh) using Sumitomo G600 molding compound. Material Change & Alternate Assembly Site.
02/06/2012 Packing Change: The carrier tape size changed from 16x12 mm to 12x8 mm. Quantity per reel remains the same (2.5Ku per reel). Standardization and business consolidation.
03/04/2009 Notice of Obsolescence Discontinued by Exar Corporation due to low market demand
02/28/2007 Product Obsolescence Letter and Discontinuation Notification. Discontinued.
02/02/2006 Announcing transfer of certain Power Management and Interface Products from Hillview fabrication facility to wafer foundary BCD. See attached Product List Power Management and Interface products as listed are being transfer to external wafer foundry, due to cessation of operations of the sipex Hillview Fabrication manufacturing site

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