MSM7503 datasheet(8/41 Pages) OKI

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MSM7503

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TPBI, TO

TPBI is the input and TO is the output of the transmit pre-amplifier (B).

When the handset is used, TPBI is connected to the transmit pre-amplifier (A) output pin (TPAO).

If adjustment of frequency characteristics on the transmit path is required, insert a circuit for

adjustment of characteristic between TPAO and TPBI. Through processor control, the signal

applied to this pin is output via the TO pin on the transmit path and its side tone via the RPO pin.

During the whole system power down mode, TO is at an analog ground level. The typical gain

between TPBI and TO is +17.7 dB. Through processor control, a gain between +17.7 dB and +8.7

dB is also settable at 3 dB steps.

The typical gain between TPBI and RPO is +3.0 dB. Through processor control, a gain between

–9 dB and +9 dB is variable in 3 dB steps. Changing the gain between TPBI and TO may change

the gain between TPBI and RPO. TPBI is a high impedance input, so insert an about 100 kW

resistor between TPBI and SGT.

TPAO

TPBI

SGT

A circuit example for adjustment of frequency characteristics

MPAI, MPAO

Handfree microphone pre-amplifier (A) input and output.

MPAI is the input and MPAO is the output. The speech path between MPAI and MPAO is always

active regardless of processor control. During the whole system power saving mode, MPAO is

at an analog ground level. The gain between MPAI and MPAO is typically +20 dB. Through

processor control, gains between +14 dB and +11 dB are also settable. MPAI is a high impedance

input, so insert an about 100 kW between MPAI and SGT.

MPBI, MPBO

The handfree microphone (B) input and output.

MPBI is the inverted input and MPBO is the output. With an external resistor, the amplifier gain

is adjusted in the range between –25 dB and +25 dB. A signal on the MPBO is output via the TO

pin through processor control. During the whole system power down mode, MPBO is at an

analog ground level. The gain between MPBO and TO is fixed to 0 dB.

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