MSM7557 데이터 시트보기 (PDF) - Oki Electric Industry

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MSM7557

Single Chip MSK Modem with Compandor for Cordless Telephone

Oki Electric Industry 

¡ Semiconductor

MSM7557

PIN DESCRIPTION

Name

Description

Transmit data input.

The data on SD pin are took into MSK modulator and the data are available on the positive edge of ST.

ME

SD input

tMS

SD

ST

Modulator

input data

In order to synchronize a receive modem, more than 18bits bit-synchronous signal should be

transmitted before data transmission. If S/N ratio of the receive signal is always good, more than

11bits bit-synchronous signal synchronizes the receiver.

Transmit data timing clock output.

ST

When digital "0" is put on ME pin, ST is fixed to digital "1" level.

Emphasis path selection.

EMP

Transmit side

Receive side

EMP

0

Pre-emphasis circuit is bypassed to the De-emphasis circuit is bypassed to the

path

path

Pre-emphasis circuit is connected to the De-emphasis circuit is connected to the

1

path

path

Deviation limiter control.

Voice signal maximum Rf modulation level is controlled by connecting external reference voltage to

this pin.

Input impedance of this pin is about 200 kW.

When this pin is left open, internal reference voltage is used as the clamp level.

LIM Internal clamp level is as follows.

DYN

Internal clamp level

Limiter level

0

0.50 V

–9 dBV

1

1.26 V

–1 dBV

This internal clamp level is made by internal reference voltage which is unrelated with VDD.

Negative clamp level is made by internal operational amplifier and the voltage is reversed at VSG.

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