1.0A Low Dropout Voltage Regulator
Data Sheet


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



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

Parts & Purchasing

Part Number Pkg Code RoHS Min Temp Max Temp Status Buy Now Order Samples
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 Suggested:
SPX3940AM3-L-1-8/TR SOT-223-3 -40 125 OBS
SPX3940AM3-L-2-5 SOT-223-3 -40 125 OBS Suggested:
SPX3940AM3-L-2-5/TR SOT-223-3 -40 125 OBS Suggested:
SPX3940AM3-L-3-3 SOT-223-3 -40 125 OBS Suggested:
SPX3940AM3-L-3-3/TR SOT-223-3 -40 125 Active Order
SPX3940AM3-L-5-0 SOT-223-3 -40 125 OBS Suggested:
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 Suggested:
SPX3940AT-L-1-8/TR TO-263-3 -40 125 OBS
SPX3940AT-L-2-5 TO-263-3 -40 125 OBS Suggested:
SPX3940AT-L-2-5/TR TO-263-3 -40 125 OBS Suggested:
SPX3940AT-L-3-3 TO-263-3 -40 125 OBS Suggested:
SPX3940AT-L-3-3/TR TO-263-3 -40 125 Active Order
SPX3940AT-L-5-0 TO-263-3 -40 125 OBS Suggested:
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 Suggested:
SPX3940M3-L-1-8/TR SOT-223-3 -40 125 OBS Suggested:
SPX3940M3-L-2-5 SOT-223-3 -40 125 OBS Suggested:
SPX3940M3-L-2-5/TR SOT-223-3 -40 125 Active Order
SPX3940M3-L-3-3 SOT-223-3 -40 125 OBS Suggested:
SPX3940M3-L-3-3/TR SOT-223-3 -40 125 OBS Suggested:
SPX3940M3-L-5-0 SOT-223-3 -40 125 OBS Suggested:
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 Suggested:
SPX3940T-L-1-8/TR TO-263-3 -40 125 OBS Suggested:
SPX3940T-L-2-5 TO-263-3 -40 125 OBS Suggested:
SPX3940T-L-2-5/TR TO-263-3 -40 125 OBS Suggested:
SPX3940T-L-3-3 TO-263-3 -40 125 OBS Suggested:
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.

Quality Documents

Part Number MDS RoHS REACH
SPX3940AM3-L-3-3 Download Download Download
SPX3940AM3-L-1-8 Download
SPX3940AM3-L-2-5 Download
SPX3940AM3-L-5-0 Download
SPX3940AT-L-1-8 Download
SPX3940AT-L-3-3 Download
SPX3940AT-L-5-0 Download
SPX3940M3-L-2-5 Download
SPX3940M3-L-3-3 Download Download
SPX3940M3-L-5-0 Download Download
SPX3940T-L-3-3 Download
SPX3940T-L-5-0 Download
SPX3940AM3-L-1-8/TR Download
SPX3940AM3-L-3-3/TR Download
SPX3940AM3-L-5-0/TR Download
SPX3940AT-L-3-3/TR Download
SPX3940AT-L-5-0/TR Download
SPX3940M3-L-2-5/TR Download
SPX3940M3-L-5-0/TR Download
SPX3940T-L-3-3/TR Download
Additional Quality Documentation may be available, please contact customersupport@maxlinear.com.
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

Frequently Asked Questions

The best way to determine this is to go to exar.com and type the part into the search function. At or near the top of the results you should see something that looks like

In this example, we looked for XRA1201. When you hover over it, it will turn grey and you can click anywhere in the grey box. This brings you to the product page. For example:


Click on Parts & Purchasing, highlighted in yellow above. The screen changes to:


Notice the status column and the “Show obsolete parts” link:


A legend tells you the definition of the different statuses. Click on the “Show obsolete parts” link to see EOL or OBS part numbers along with the Active part numbers:


Another method to find out if a part is OBS or EOL is to click on SUPPORT:


And then Product Change Notifications


Type the part into the search, and click on one of the part numbers from the drop down menu. Then you can look for the Product Discontinuation Notice, which generally is at the top of the list, for example:


If you see this, it tells you that this particular orderable part has been discontinued and when the last order date is, or was. If you click on the file, then you can view the notice we sent about this if you purchased the part in the recent past. It may also advise of a replacement part. When an orderable part first becomes discontinued, Product Discontinuation Notices are sent are sent to those who have purchased the parts in the recent past, if purchased directly, with a dated opportunity to place a last order.

Yes. Try our Excel-based heat calculation spreadsheet ANP-03, Thermal Calculator
For further study, this spreadsheet is mentioned in the following helpful application note: ANP-02, Thermal Considerations for Linear Regulators