Features • Output voltage specified over temperature • Excellent load regulation • Guaranteed 1A output current • Requires only one external component • Built-in protection against excess temperature • Short circuit protected Description The LM3940 is a 1A low dropout regulator designed to provide 3.3V from a 5V supply. The LM3940 is ideally suited for systems which contain both 5V and 3.3V logic, with prime power provided from a 5V bus. Because the LM3940 is a true low dropout regulator, it can hold its 3.3V output in regulation with input voltages as low as 4.5V. The T0-220 package of the LM3940 means that in most applications the full 1A of load current can be delivered without using an additional heatsink. The surface mount TO-263 package uses minimum board space, and gives excellent power dissipation capability when soldered to a copper plane on the PC board. Applications • Laptop/Desktop Computers • Logic Systems

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Typical Application click for larger image	Connection Diagram click for larger image
Typical Performance click for larger image

Datasheet

Title		Size	Date	Other Language
	LM3940 1A Low Dropout Regulator for 5V to 3.3V Conversion	328 Kbytes	19-Jul-07	日本語

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	AN-1061: Application Note 1061 Power Conversion in Line-Powered Equipment	162 Kbytes	1-Oct-02	日本語

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Part Number(s) (NSID)	Top View	Availability	Current Reported Stock	Budgetary Pricing	Standard Pack Size
LM3940LD-3.3/NOPB LM3940LD-3.3 RoHS	LLP	Lifetime buy Lead Time: 8 weeks	Distributor Region Qty DIGIKEY Worldwide 0	$0.78 each at 1K+ pcs	reel of 1000
LM3940LDX-3.3 RoHS	LLP	Lifetime buy Lead Time: 12 weeks	Distributor Region Qty DIGIKEY Worldwide 0	$0.78 each at 1K+ pcs	reel of 4500
LM3940IMP-3.3/NOPB LM3940IMP-3.3 RoHS		Full production Lead Time: 8 weeks	Distributor Region Qty ARROW Worldwide 5000 AVNET-EM Worldwide 3970 DIGIKEY Worldwide 3198 FUTURE Worldwide 1100 KEIKONG Asia Pacific 26000 NEWARK Americas 1574 RS COMPONENTS Worldwide 347	$0.63 each at 1K+ pcs	reel of 1000
LM3940IMPX-3.3/NOPB LM3940IMPX-3.3 RoHS		Full production Lead Time: 8 weeks	Distributor Region Qty ARROW Worldwide 2000 DIGIKEY Worldwide 0 FUTURE Worldwide 1100 TECHMOSA Asia Pacific 4000	$0.63 each at 1K+ pcs	reel of 2000
LM3940IT-3.3/NOPB LM3940IT-3.3 RoHS		Full production Lead Time: 8 weeks	Distributor Region Qty ARROW Worldwide 659 AVNET-EM Worldwide 135 DIGIKEY Worldwide 209 FARNELL Europe and Asia 802 FUTURE Worldwide 1100 NEWARK Americas 886 RS COMPONENTS Worldwide 348	$0.81 each at 1K+ pcs	rail of 45
LM3940IS-3.3/NOPB LM3940IS-3.3 RoHS		Full production Lead Time: 8 weeks	Distributor Region Qty ARROW Worldwide 767 AVNET-EM Worldwide 996 DIGIKEY Worldwide 546 FUTURE Worldwide 1100 NEWARK Americas 382 RS COMPONENTS Worldwide 319	$0.83 each at 1K+ pcs	rail of 45
LM3940ISX-3.3/NOPB LM3940ISX-3.3 RoHS		Full production Lead Time: 8 weeks	Distributor Region Qty ARROW Worldwide 4500 AVNET-EM Worldwide 2500 DIGIKEY Worldwide 500 FUTURE Worldwide 1100 KEIKONG Asia Pacific 5000 NEWARK Americas 420 TAYLOR Americas 500	$0.83 each at 1K+ pcs	reel of 500

Obsolete Versions

Obsolete Part	Alternate Part or Supplier	Source	Last Time Buy Date
LM3940J-3.3-MPR	NONE	NONE	01 Dec 2004
LM3940J-3.3-QML	NONE	NONE	02 Jun 2004
LM3940J-3.3-SCD	NONE	NONE	01 Dec 2004
LM3940LD-3.3	NONE	NATIONAL SEMICONDUCTOR	01 Dec 2009
LM3940LDX-3.3	NONE	NATIONAL SEMICONDUCTOR	01 Dec 2009
LM3940WG3.3-MPR	NONE	NONE	01 Dec 2004
LM3940WG3.3-QML	NONE	NONE	02 Jun 2004
LM3940WG3.3-SCD	NONE	NONE	01 Dec 2004

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM3940IMP-3.3	SLM	0	44046	0	0	3532500	1	1002356520
LM3940IMPX-3.3	SLM	0	44046	0	0	3532500	1	1002356520
LM3940IS-3.3	SLM	0	44046	0	0	3532500	1	1002356520
LM3940ISX-3.3	SLM	0	44046	0	0	3532500	1	1002356520
LM3940IT-3.3	SLM	0	44046	0	0	3532500	1	1002356520
LM3940LD-3.3	SLM	0	44046	0	0	3532500	1	1002356520
LM3940LDX-3.3	SLM	0	44046	0	0	3532500	1	1002356520

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

For more information on Reliability Metrics, please click here.

Obsolete Versions

Obsolete Part	Alternate Part or Supplier	Source	Last Time Buy Date
LM3940J-3.3-MPR	NONE	NONE	01 Dec 2004
LM3940J-3.3-QML	NONE	NONE	02 Jun 2004
LM3940J-3.3-SCD	NONE	NONE	01 Dec 2004
LM3940LD-3.3	NONE	NATIONAL SEMICONDUCTOR	01 Dec 2009
LM3940LDX-3.3	NONE	NATIONAL SEMICONDUCTOR	01 Dec 2009
LM3940WG3.3-MPR	NONE	NONE	01 Dec 2004
LM3940WG3.3-QML	NONE	NONE	02 Jun 2004
LM3940WG3.3-SCD	NONE	NONE	01 Dec 2004