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LM3940 IC – 1A – Low Dropout Regulator IC for 5V to 3.3V Conversion

210.00 Excluding tax

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The LM3940 is a 1-A low-dropout regulator designed to provide 3.3 V from a 5-V supply.

The LM3940 is ideally suited for systems which contain both 5-V and 3.3-V logic, with prime power provided from a 5-V bus.

Because the LM3940 is a true low dropout regulator, it can hold its 3.3-V output in regulation with input voltages as low as 4.5 V.

The TO-220 package of the LM3940 means that in most applications the full 1 A of load current can be delivered without using an additional heat sink.

The surface mount DDPAK/TO-263 package uses minimum board space, and gives excellent power dissipation capability when soldered to a copper plane on the PC board.


  • Input Voltage Range: 4.5 V to 5.5 V
  • Output Voltage Specified over Temperature
  • Excellent Load Regulation
  • Specified 1-A Output Current
  • Requires only One External Component
  • Built-in Protection against Excess Temperature
  • Short-Circuit Protected


Parameter Specification
Part number LM3940
Output options  Fixed Output
Iout (Max) (A) 1
Vin (Max) (V) 5.5
Vin (Min) (V) 4.5
Vout (Max) (V) 3.3
Vout (Min) (V) 3.3
Fixed output options (V) 3.3
Package Group DDPAK/TO-263 | 3, TO-220 | 3, SOT-223 | 4
Regulated outputs (#) 1
Operating temperature range ( C ) -40 to 125
Thermal resistance θJA (°C/W) 23
Noise (uVrms) 150
Rating See Data Sheet
PSRR @ 100 KHz (dB) 32
Accuracy (%) 2.5
Dropout voltage (Vdo) (Typ) (mV) 310
Iq (Typ) (mA) 0.11
Package size: mm2:W x L (PKG) 3DDPAK/TO-263: 155 mm2: 15.24 x 10.16 (DDPAK/TO-263 | 3)
3TO-220: 47 mm2: 4.58 x 10.16 (TO-220 | 3)
4SOT-223: 46 mm2: 7 x 6.5 (SOT-223 | 4)

LM3940-IC Datasheet

* product image for illustration purposes only. actual product may vary.


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