MC145554 Datasheet, PDF (1/20 Pages) Motorola, Inc – PCM Codec-Filter

MOTOROLA
SEMICONDUCTOR TECHNICAL DATA
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PCM Codec-Filter
The MC145554, MC145557, MC145564, and MC145567 are all per channel
PCM Codec–Filters. These devices perform the voice digitization and
reconstruction as well as the band limiting and smoothing required for PCM
systems. They are designed to operate in both synchronous and asynchronous
applications and contain an on–chip precision voltage reference. The
MC145554 (Mu–Law) and MC145557 (A–Law) are general purpose devices
that are offered in 16–pin packages. The MC145564 (Mu–Law) and MC145567
(A–Law), offered in 20–pin packages, add the capability of analog loopback and
push–pull power amplifiers with adjustable gain.
These devices have an input operational amplifier whose output is the input
to the encoder section. The encoder section immediately low–pass filters the
analog signal with an active R–C filter to eliminate very–high–frequency noise
from being modulated down to the pass band by the switched capacitor filter.
From the active R–C filter, the analog signal is converted to a differential signal.
From this point, all analog signal processing is done differentially. This allows
processing of an analog signal that is twice the amplitude allowed by a
single–ended design, which reduces the significance of noise to both the
inverted and non–inverted signal paths. Another advantage of this differential
design is that noise injected via the power supplies is a common–mode signal
that is cancelled when the inverted and non–inverted signals are recombined.
This dramatically improves the power supply rejection ratio.
After the differential converter, a differential switched capacitor filter band
passes the analog signal from 200 Hz to 3400 Hz before the signal is digitized
by the differential compressing A/D converter.
The decoder accepts PCM data and expands it using a differential D/A
converter. The output of the D/A is low–pass filtered at 3400 Hz and sinX/X
compensated by a differential switched capacitor filter. The signal is then filtered
by an active R–C filter to eliminate the out–of–band energy of the switched
capacitor filter.
These PCM Codec–Filters accept both long–frame and short–frame industry
standard clock formats. They also maintain compatibility with Motorola’s family
of TSACs and MC3419/MC34120 SLIC products.
The MC145554/57/64/67 family of PCM Codec–Filters utilizes CMOS due to
its reliable low–power performance and proven capability for complex
analog/digital VLSI functions.
MC145554/57 (16–Pin Package)
• Fully Differential Analog Circuit Design for Lowest Noise
• Performance Specified for Extended Temperature Range of – 40 to + 85°C
• Transmit Band–Pass and Receive Low–Pass Filters On–Chip
• Active R–C Pre–Filtering and Post–Filtering
• Mu–Law Companding MC145554
• A–Law Companding MC145557
• On–Chip Precision Voltage Reference (2.5 V)
• Typical Power Dissipation of 40 mW, Power Down of 1.0 mW at ± 5 V
MC145564/67 (20–Pin Package) — All of the Features of the MC145554/57 Plus:
• Mu–Law Companding MC145564
• A–Law Companding MC145567
• Push–Pull Power Drivers with External Gain Adjust
• Analog Loopback
MC145554
MC145557
MC145564
MC145567
16
1
16
1
16
1
L SUFFIX
CERAMIC PACKAGE
CASE 620
MC145554/57
P SUFFIX
PLASTIC DIP
CASE 648
MC145554/57
DW SUFFIX
SOG PACKAGE
CASE 751G
MC145554/57
L SUFFIX
20
CERAMIC PACKAGE
1
CASE 732
MC145564/67
20
1
20
1
P SUFFIX
PLASTIC DIP
CASE 738
MC145564/67
DW SUFFIX
SOG PACKAGE
CASE 751D
MC145564/67
REV 1
9/95 (Replaces ADI1517)
©_MOMo_Tto_Oro_Rla,_OIn_Lc._A1995
MC145554•MC145557•MC145564•MC145567
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