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MC145484 Datasheet, PDF (1/26 Pages) Motorola, Inc – 5V PCM CODEC-FILTER | |||
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MOTOROLA
SEMICONDUCTOR TECHNICAL DATA
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MC145484
Advance Information
5 V PCM Codec-Filter
The MC145484 is a general purpose per channel PCM CodecâFilter with pin
selectable MuâLaw or AâLaw companding, and is offered in 20âpin SOG and
SSOP packages. This device performs the voice digitization and reconstruction
as well as the band limiting and smoothing required for PCM systems. This
device is designed to operate in both synchronous and asynchronous
applications and contains an onâchip precision reference voltage.
This device has an input operational amplifier whose output is the input to the
encoder section. The encoder section immediately lowâpass filters the analog
signal with an active RâC filter to eliminate very high frequency noise from being
modulated down to the passband by the switched capacitor filter. From the
active RâC 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 singleâended
design, which reduces the significance of noise to both the inverted and
nonâinverted signal paths. Another advantage of this differential design is that
noise injected via the power supplies is a commonâmode signal that is
cancelled when the inverted and nonâinverted signals are recombined. This
dramatically improves the power supply rejection ratio.
After the differential converter, a differential switched capacitor filter bandâ
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 lowâpass filtered at 3400 Hz and sinX/X
compensated by a differential switched capacitor filter. The signal is then filtered
by an active RâC filter to eliminate the outâofâband energy of the switched
capacitor filter.
The MC145484 PCM CodecâFilter has a high impedance VAG reference pin
which allows for decoupling of the internal circuitry that generates the
midâsupply VAG reference voltage, to the VSS power supply ground. This
reduces clock noise on the analog circuitry when external analog signals are
referenced to the power supply ground. This device is optimal for electronic
SLIC interfaces.
The MC145484 PCM CodecâFilter accepts a variety of clock formats,
including Short Frame Sync, Long Frame Sync, IDL, and GCI timing
environments. This device also maintains compatibility with Motorolaâs family of
Telecommunication products, including the MC14LC5472 and MC145572
UâInterface Transceivers, MC145474/75 and MC145574 S/TâInterface Trans-
ceivers, MC145532 ADPCM Transcoder, MC145422/26 UDLTâ1,
MC145421/25 UDLTâ2, and MC3419/MC33120 SLICs.
The MC145484 PCM CodecâFilter utilizes CMOS due to its reliable
lowâpower performance and proven capability for complex analog/digital VLSI
functions.
20
1
DW SUFFIX
SOG PACKAGE
CASE 751D
SD SUFFIX
SSOP
20
CASE 940C
1
ORDERING INFORMATION
MC145484DW
MC145484SD
SOG Package
SSOP
PIN ASSIGNMENT
VAG Ref 1
ROâ 2
PI 3
POâ 4
PO+ 5
VDD 6
FSR 7
DR 8
BCLKR 9
PDI 10
20 VAG
19 TI+
18 TIâ
17 TG
16 Mu/A
15 VSS
14 FST
13 DT
12 BCLKT
11 MCLK
⢠Single 5 V Power Supply
⢠Typical Power Dissipation of 15 mW, PowerâDown of 0.01 mW
⢠FullyâDifferential Analog Circuit Design for Lowest Noise
⢠Transmit BandâPass and Receive LowâPass Filters OnâChip
⢠Active RâC PreâFiltering and PostâFiltering
⢠MuâLaw and AâLaw Companding by Pin Selection
⢠OnâChip Precision Reference Voltage of 1.575 V for a â 0 dBm TLP @ 600 â¦
⢠PushâPull 300 ⦠Power Drivers with External Gain Adjust
⢠MC14LC5480EVK is the Evaluation Kit for This Device
This document contains information on a new product. Specifications and information herein are subject to change without notice.
REV 0
2/97 TN97022700
©MOMoTtoOroRla,OInLc.A1997
MC145484
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