LP2967 Datasheet, PDF (14/20 Pages) National Semiconductor (TI) – Dual Micropower 150 mA Low-Dropout Regulator in micro SMD Package

Application Hints
EXTERNAL CAPACITORS
The LP2967 low dropout regulator requires two external
capacitors, C_IN and C_OUT to assure the device’s output
stability. C_BYPASS may be used to reduce output noise. The
capacitors must be correctly selected with respect to capaci-
tance values for all three capacitors and ESR value for
C_OUT.
Input Capacitor
An input capacitor with a minimum capacitance value of 1µF
is required between the LP2967 input and ground (the
amount of capacitance may be increased without limit). This
capacitor must be located a distance of not more than 0.5
inches from the input pin and returned to a clean analog
ground. Any good quality ceramic or tantalum may be used
for this capacitor.
Output Capacitor
The output capacitor must meet the requirement for mini-
mum capacitance value of 2.2 µF and also have an appro-
priate ESR (equivalent series resistance) value. The LP2967
is actually designed to work with ceramic or tantalum output
capacitors, utilizing circuitry which allows the regulator to be
stable with an output capacitor whose ESR is as low as 4
mΩ. It may also be possible to use a film capacitor at the
output, but this type is not as attractive for reasons of size
and cost.
Important: The output capacitor must maintain its ESR in
the stable region over the full operating temperature range of
the application to assure stability. The minimum required
amount of output capacitance is 2.2 µF. Output capacitor
size can be increased without limit. It is important to remem-
ber that capacitor tolerance and variation with temperature
must be taken into consideration when selecting an output
capacitor so that the minimum required amount of output
capacitance is provided over the full operating temperature
range.
LP2967-3.3V Region of Stability with 10 µF C_OUT
LP2967-3.3V Region of Stability with 4.7 µF C_OUT
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LP2967-2.5V Region Of Stability with 10 µF C_OUT
10114209
LP2967-2.5V Region Of Stability with 4.7 µF C_OUT
10114208
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10114210
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