ST5088D View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'ST5088D' PDF : 33 Pages View PDF
ST5088
GENERAL DESCRIPTION
ST5088 PIAFE is a combined PCM CODEC/FIL-
TER device optimized for ISDN Terminals and Digi-
tal Telephone applications. This device is A-law
and Mu-law selectable and offers a number of pro-
grammable functions accessed through a serial
control channel.
Depending on mode selected, channel control is
provided by means of a separate serial channel
control MICROWIRE compatible or multiplexed
with the PCM voice data channel in a GCI com-
patible format requiring only 4 digital interface
pins. When separate serial control interface is se-
lected, PCM interface is compatible with Combo I
and Combo II families of devices such as
ETC5057/54, TS5070/71.
PIAFE is built using SGS-THOMSON’s advanced
HCMOS process.
Transmit section of PIAFE consists of an amplifier
with switchable high impedance inputs followed
by a programmable gain amplifier, an active RC
antialiasing pre-filter to provide attenuation of high
frequency noise, an 8th order switched capacitor
band pass transmit filter and an A-law/Mu-law se-
lectable compandig encoder.
Receive section consist of an A-law/Mu-law se-
lectable expanding decoder which reconstructs
the analog sampled data signal, a 3400 Hz low
pass filter with sin X/X correction followed by two
separate programmable attenuation blocks and
two power amplifiers: one can be used to drive an
earpiece, and the other to drive a 50 Ω loud-
speaker or a piezo transducer up to 600nF.
When the loudspeaker section is set up with
maximum gain (+27dB) the device provide inter-
nally a programmable digital anticlipping system
to avoid output distortion.
Programmable functions on PIAFE include a
Ring/Tone generator which provides one or two
tones and can be directed to earpiece or to loud-
speaker (or buzzer).
A simple ringer control interface can bypass µP
control of sweep frequency and ring ON/OFF
phases.
A separate programmable gain amplifier allows
gain control of the signal injected. Ring/Tone gen-
erator provides sinewave or squarewave signal
with precise frequencies which may be also di-
rected to the input of the Transmit amplifier for
DTMF tone generation.
An auxiliary analog input (EAIN) is also provided
to enable for example the output of an external
band limited Ring signal to the Loudspeaker.
Transmit signal may be fed back into the receive
ampifier with a programmable attenuation to pro-
vide a sidetone circuitry.
A switchable anti-accoustic feed-back system
cancels the larsen effect in speech monitoring ap-
plication.
Two additional pins are provided for insertion of
an external Handfree function in the Loudspeaker
receive path.
An output latch controlled by register program-
ming permits external device control.
PIN FUNCTIONS
SO
PLCC
1,2
1,2
3,4
3,4
5
5
6,7
6,7
Name
HFI, HFO
VFr+, VFr–
VCC
LS-,LS+
Description
Hands free I/Os:
These two pins can be used to insert an external Handfree circuit
such as the TEA 7540 in the receive path. HFO is an output which
provides the signal issued from output of the receive low pass filter
while HFI is a high impendance input which is connected directly to
one of the inputs of the Loudspeaker amplifier.
Receive analog earpiece amplifier complementary
outputs, capable of driving load impedances between 100
and 400 Ω or a piezo ceramic transducer up to 150nF.
These outputs can drive directly earpiece transductor. The
signal at this output can drive be the summ of:
- Receive Speech signal from DR,
- Internal Tone Generator,
- Sidetone signal.
Positive power supply input for the digital section. +5 V + 10%.
Receive analog loudspeaker amplifier complementary outputs,
intended for driving a Loudspeaker: 80 mW on 50Ω load
impedance can be provided at low distorsion meeting
specifications.
Alternatively this stage can drive a piezo transducer up to
600nF. The signal at these outputs can be the sum of:
- Receive Speech signal from DR,
- Internal Tone generator,
- External input signal from EAIN input.
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