LP2950_08 Datasheet, PDF (10/17 Pages) Texas Instruments – ADJUSTABLE MICROPOWER VOLTAGE REGULATORS WITH SHUTDOWN

Micrel, Inc.
Noise can be reduced fourfold by a bypass capacitor
across R₁, since it reduces the high frequency gain from
4 to unity. Pick:
C_BYPASS
≅
1
2πR₁ • 200Hz
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
100µVrms for a100kHz 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.
LP2950/2951
Figure 1. ERROR Output Timing
Figure 2. Adjustable Regulator
September 2008
10
M9999-091208