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PT2253A V2.8

- 4 -

December, 2005

Electronic Volume Controller IC

PT2253A

FUNCTION DESCRIPTION

ATTENUATION SETTING

The Attenuation can be increased or decreased depending on the state of the U/D Pin (either “H” or “L”

Level) by actuating the built-in oscillator. When power is applied, the attenuation is automatically set at

-40dB.

POWER SUPPLY

U/D

OSC

-30dB

-32dB

-34dB

-36dB

-38dB

-40dB

When the DOWN Key is pressed, the U/D Pin goes to the “L” Level and the oscillator is actuated in the

down state. Thus, attenuation is increased.

Conversely, when the UP Key is pressed, the U/D Pin goes to the “H” Level and the oscillator is

actuated in the up state. Thus, attenuation is decreased.

Oscillation frequency (fosc) is dependent on the Cx and the Rx and is determined by the following

equation:

Hz

(Cx)(Rx)

0.7

1

fosc

=

where: Rs ≥ 3Rx