LP3991_15 Datasheet, PDF (10/25 Pages) Texas Instruments – LP3991 300-mA Linear Voltage Regulator for Digital Applications

LP3991
SNVS296I – DECEMBER 2006 – REVISED AUGUST 2015
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Feature Description (continued)
7.3.2 Maximum Supply Voltage and Thermal Considerations
Maximum recommended input voltage is 3.6 V. The device may be operated at 4-V V_IN if proper care is given to
the board design in regard to thermal dissipation. As a guide, refer to Table 1 for ambient temperature at two
input voltages and two load currents for the example board types.
R_θJA
189ºC/W
160ºC/W
Table 1. Example Board Ambient Temperatures
V_IN
3.6 V
4V
3.6 V
4V
V_OUT
2.8 V
2.8 V
2.8 V
2.8 V
I_OUT
160 mA
250 mA
160 mA
250 mA
160 mA
250 mA
160 mA
250 mA
P_D
0.13 W
0.20 W
0.19 W
0.30 W
0.13 W
0.20 W
0.19 W
0.30 W
AMBIENT TEMPERATURE
100ºC
87ºC
89ºC
68ºC
104ºC
93ºC
94ºC
77ºC
7.4 Device Functional Modes
7.4.1 Enable Control
The LP3991 features an active high enable (EN) pin, which turns the device on when pulled high. When not
enabled the regulator output is off and the device typically consumes 2 nA.
If the application does not require the enable switching feature, the EN pin must be tied to V_IN to keep the
regulator output permanently on.
To ensure proper operation, the signal source used to drive the EN input must be able to swing above and below
the specified turnon/off voltage thresholds listed in Typical Characteristics under V_IL and V_IH.
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