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Reliability
Obsolete
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
Also Recommended
LM2677 Higher Efficiency & Better Transient Response
LM2678 Higher Efficiency & Better Transient Response
LP38690▲ Lower Supplu Current , Stable With Ceramic Capacitor
LP38692▲ Lower Quiescent Current, Stable With Ceramic Output Capacitors & Enable Pin
LP3872▲ Improved Output Current, Fast Response, Lower Supply Current
Also Recommended
LM2677 Higher Efficiency & Better Transient Response
LM2678 Higher Efficiency & Better Transient Response
LP38690▲ Lower Supplu Current , Stable With Ceramic Capacitor
LP38692▲ Lower Quiescent Current, Stable With Ceramic Output Capacitors & Enable Pin
LP3872▲ Improved Output Current, Fast Response, Lower Supply Current
Paramaters / Values LM3940 LP38690 LP38692 LP3872
Output Current 1000 mA
1000 mA
1000 mA
1500 mA
Output Min 3.3 Volt
1.8, 5.0, 2.5, 3.3 Volt
1.8, 5.0, 2.5, 3.3 Volt
1.8, 2.5, 3.3, 5 Volt
Input Max Voltage 7.5 Volt
10 Volt
10 Volt
7 Volt
Dropout Voltage 0.31 Volt
0.45, 0.95, 0.8, 0.65 Volt
0.2 Volt
0.38 Volt
Adjustable Output No
No
No
No
Quiescent Current 0.11 mA
0.055 mA
0.055 mA
6 mA
On/Off Pin No
No
Yes
Yes
Error Flag No
No
No
Yes
RegType LDO
LDO
LDO
LDO
Temperature Min -40 deg C
-40 deg C
-40 deg C
-40 deg C
Temperature Max 125 deg C
125 deg C
125 deg C
125 deg C
Output Voltage 3.3 Volt
1.8, 5.0, 2.5, 3.3 Volt
1.8, 5.0, 2.5, 3.3 Volt
1.8, 2.5, 3.3, 5 Volt
Output Max 3.3 Volt
1.8, 5.0, 2.5, 3.3 Volt
1.8, 5.0, 2.5, 3.3 Volt
1.8, 2.5, 3.3, 5 Volt
Datasheet
Featured Application Notes
More Application Notes
Part Number(s) (NSID) Top View Availability Current Reported Stock Budgetary Pricing Standard Pack Size
LM3940LD-3.3/NOPB LM3940LD-3.3RoHS
LLP Lifetime buy Lead Time: 8 weeks Distributor Region Qty
DIGIKEY Worldwide 0
$0.78 each at 1K+ pcs reel of 1000
LM3940LDX-3.3RoHS
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-3.3RoHS
Full production Lead Time: 8 weeks
$0.63 each at 1K+ pcs reel of 1000
LM3940IMPX-3.3/NOPB LM3940IMPX-3.3RoHS
Full production Lead Time: 8 weeks
$0.63 each at 1K+ pcs reel of 2000
LM3940IT-3.3/NOPB LM3940IT-3.3RoHS
Full production Lead Time: 8 weeks
$0.81 each at 1K+ pcs rail of 45
LM3940IS-3.3/NOPB LM3940IS-3.3RoHS
Full production Lead Time: 8 weeks
$0.83 each at 1K+ pcs rail of 45
LM3940ISX-3.3/NOPB LM3940ISX-3.3RoHS
Full production Lead Time: 8 weeks
$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