AP2201 datasheet(10/12 Pages) BCDSEMI

10 / 12 page

150mA RF ULDO REGULATOR

AP2201

Preliminary Datasheet

Jun. 2005 Rev. 1. 0

BCD Semiconductor Manufacturing Limited

Application Information

External Capacitors

The AP2201 requires external capacitors for regula-

tor stability. These capacitors must be correctly

selected for good performance.

Input Capacitor

If there is more than 10 inches of wire between the

input and the AC filter or if a battery is used as the

input, at least a 1

µF capacitor should be placed from

IN to GND.

Output Capacitor

It is required to prevent oscillation. 1.0

µF minimum

is recommended when CBYP is not used. 2.2µF mini-

mum is recommended when CBYP is 470pF. The out-

put capacitor may be increased without limit for large

values to improve transient response.

The output capacitor should have an ESR of about

5Ω or less. In most cases, tantalum or aluminium

electrolytic capacitors are adequate.

Noise Bypass Capacitor

Bypass capacitor is connected to the internal voltage

reference. A 680pF capacitor connected from BYP to

GND make this reference quiet, resulting in a

significant reduction in output noise. When using

CBYP, output capacitors of 2.2µF or greater are

required for better stability.

The start-up speed of the AP2201 is inversely

proportional to the value of reference bypass

capacitor. In some cases if output noise is not a major

concern and rapid turn-on is necessary, omit CBYP

and leave BYP open.

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