MSM7557 View Datasheet(PDF) - Oki Electric Industry

Part Name

Description

Manufacturer

MSM7557

Single Chip MSK Modem with Compandor for Cordless Telephone

Oki Electric Industry 

¡ Semiconductor

MSM7557

(Continued)

Name

CMPI

DYN

SG

GND

TAO

Description

Compressor circuit input.

A 0.47 mF capacitor should be connected between CMPI and TVIO.

Dynamic range control input.

For an application of which VDD is always higher than 4.5 V (Base station), by setting DYN = "1",

modem transmit carrier level, typical input signal level, limiter clamp level and compandor

standard input level are up about 8dB to improve S/N ratio.

For an application of which VDD is lower than 4.5 V (Hand-set) DYN shall be digital "0".

To make easier interface with the RF part, one solution is to put digital "0" on DYN pin for both Base

station and Handset.

Built-in analog signal ground. The DC voltage is half of VDD.

To make this voltage source impedance lower and to ensure the device performance, it is necessary to

put a bypass capacitor of more than 1mF between SG and VDD in close physical proximity to the device.

Ground pin, (0V).

Transmit analog signal output.

According to control data on ME and TVE, TAO is set as follows.

ME

TVE

TAO

0

0

No signal output (potential = SG)

0

1

Voice signal output

1

X

MSK modulator output

X : Don't care

Receive voice signal output.

RVO pin state is defined by RVE control.

RVO

RVE

RVO

0

Output disable (potential = SG)

1

Output enable

CE1

CE2

CE3N

CE3P

RAIO

RAI

CSH

Capacitor connection pins to remove DC offset of the expander.

A 1 mF capacitor between SG pin and each pin should be connected.

Capacitor connection pins for the expander attack time and recovery time.

When DYN is digital "0" level, a 0.22 mF capacitor should be connected between CE3N and CE3P.

And when DYN is digital "1" level, a 0.47 mF capacitor should be connected between them.

Receive side amplifier input (RAI) and output (RAIO).

Second order RC-active filter is needed like TVIO and TVI.

Refer to TVIO and TVI pin description.

Capacitor connection pin to remove DC offset of the modem shaper circuit.

A 1 mF capacitor should be connected between GND pin and CSH.

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