msm7557 Oki Semiconductor, msm7557 Datasheet - Page 4

• Manufacturer Part Number: msm7557
• Description: Single Chip Msk Modem With Compandor For Cordless Telephone
• Manufacturer: Oki Semiconductor

¡ Semiconductor
PIN DESCRIPTION
Name
SD
ST
EMP
LIM
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.
When digital "0" is put on ME pin, ST is fixed to digital "1" level.
Emphasis path selection.
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.
Internal clamp level is as follows.
This internal clamp level is made by internal reference voltage which is unrelated with V
Negative clamp level is made by internal operational amplifier and the voltage is reversed at VSG.
Transmit data input.
The data on SD pin are took into MSK modulator and the data are available on the positive edge of ST.
EMP
DYN
0
1
0
1
Modulator
input data
SD input
Pre-emphasis circuit is bypassed to the
path
Pre-emphasis circuit is connected to the
path
ME
ST
Internal clamp level
Transmit side
0.50 V
1.26 V
t
MS
Description
De-emphasis circuit is bypassed to the
path
De-emphasis circuit is connected to the
path
Limiter level
Receive side
–9 dBV
–1 dBV
DD
.
MSM7557
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