AP2201 Datasheet, PDF (10/12 Pages) BCD Semiconductor Manufacturing Limited – 150mA RF ULDO REGULATOR

150mA RF ULDO REGULATOR
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 1µF capacitor should be placed from
IN to GND.
Output Capacitor
It is required to prevent oscillation. 1.0µF minimum
is recommended when C_BYP is not used. 2.2µF mini-
mum is recommended when C_BYP is 470pF. The out-
put capacitor may be increased without limit for large
values to improve transient response.
Preliminary Datasheet
AP2201
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
C_BYP, 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 C_BYP
and leave BYP open.
Jun. 2005 Rev. 1. 0
BCD Semiconductor Manufacturing Limited
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