LP2951JAN_15 Datasheet, PDF (15/25 Pages) Texas Instruments – Series of Adjustable Micropower Voltage Regulators

LP2951JAN
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SNVS408A – NOVEMBER 2010 – REVISED APRIL 2013
Reducing Output Noise
In reference applications it may be advantageous to reduce the AC noise present at the output. One method is to
reduce the regulator bandwidth by increasing the size of the output capacitor.
Noise can be reduced fourfold by a bypass capacitor across R₁, since it reduces the high frequency gain from 4
to unity. Pick
(2)
or about 0.01μF. When doing this, the output capacitor must be increased to 3.3μF to maintain stability. These
changes reduce the output noise from 430μV to 100μV rms for a 100kHz bandwidth at 5V output. With the
bypass capacitor added, noise no longer scales with output voltage so that improvements are more dramatic at
higher output voltages.
Typical Applications
Figure 36. 1A Regulator with 1.2V Dropout
Figure 37. 300mA Regulator with 0.75V Dropout
*Minimum input-output voltage ranges from 40mV to 400mV, depending on load current. Current limit is typically
160mA.
Figure 38. Wide Input Voltage Range Current Limiter
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