LP3991 300-mA LDO for Digital Applications | TI.com

LP3991 (ACTIVE) 300-mA LDO for Digital Applications



Operating from a minimum input voltage of 1.65 V, the LP3991 LDO has been designed to provide fixed stable output voltages for load currents up to 300 mA. This device is suitable where accurate low voltages are required from low input voltage sources and is therefore suitable for post regulation of switched mode regulators. In such applications, significant improvements in performance and EMI can be realized, with little reduction in overall efficiency. The LP3991 provides fixed outputs as low as 1.2 V from a wide input range from 1.65 V to 4 V Using the enable (EN) pin, the device may be controlled to provide a shutdown state, in which negligible supply current is drawn.

The LP3991 is designed to be stable with space-saving ceramic capacitors as small as 0402 case size.

Performance is specified for a –40°C to +125°C junction temperature range. For output voltage options, contact your local Texas Instruments sales office.

For all available packages, see the orderable addendum at the end of the datasheet.


  • Input Voltage From 1.65 V to 4 V
  • Output Voltage From 0.8 V to 3 V
  • 1% Accuracy at Room Temperature
  • 125-mV Dropout at 300-mA Load
  • 50-µA Quiescent Current at 1-mA Load
  • Inrush Current Controlled to 600 mA
  • PSRR 65 dB at 1 kHz
  • 100-µs Start-Up Time for 1.5-V VOUT
  • Stable With Ceramic Capacitors as Small as 0402
  • Thermal-Overload and Short-Circuit Protection


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Part number Order Output options Iout (Max) (A) Vin (Max) (V) Vin (Min) (V) Vout (Max) (V) Vout (Min) (V) Fixed output options (V) Package Group Features Regulated outputs (#) Operating temperature range (C) Thermal resistance θJA (°C/W) Noise (uVrms) Approx. price (US$) Rating Output capacitor type PSRR @ 100 KHz (dB) Accuracy (%) Vdo (Typ) (mV) Iq (Typ) (mA) Package size: mm2:W x L (PKG)
LP3991 Order now Fixed Output     0.3     3.6     1.65     3     1.2     1.2
DSBGA | 4     Enable     1     -40 to 125     190     280     0.23 | 1ku     Catalog     Ceramic     25     2     75     0.05     See datasheet (DSBGA)    
LP3981 Order now Fixed Output     0.3     6     2.7     3.3     2.5     2.5
WSON | 6    
Enable     1     -40 to 125     57     35     0.20 | 1ku     Catalog     Ceramic     25     1     132     0.07     8VSSOP: 15 mm2: 4.9 x 3 (VSSOP | 8)
See datasheet (WSON)