Freescale Semiconductor, Inc.
SEMICONDUCTOR TECHNICAL DATA
Order this document
by MC145484/D
The MC145484 is a general purpose per channel PCM Codec–Filter with pin
selectable Mu–Law or A–Law companding, and is offered in 20–pin SOG,
SSOP, and TSSOP 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 on–chip precision reference
voltage.
DW SUFFIX
SOG PACKAGE
CASE 751D
20
1
SD SUFFIX
SSOP
This device has 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 passband 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.
20
CASE 940C
1
DT SUFFIX
TSSOP
CASE 948E
20
1
ORDERING INFORMATION
MC145484DW
MC145484SD
MC145484DT
SOG Package
SSOP
TSSOP
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.
PIN ASSIGNMENT
The MC145484 PCM Codec–Filter has a high impedance V
reference pin
AG
which allows for decoupling of the internal circuitry that generates the
mid–supply V reference voltage, to the V power supply ground. This
AG
SS
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 Codec–Filter accepts a variety of clock formats,
including Short Frame Sync, Long Frame Sync, IDL, and GCI timing
environments. This device also maintains compatibility with Motorola’s family
of Telecommunication products, including the MC14LC5472 and MC145572
U–Interface Transceivers, MC145474/75 and MC145574 S/T–Interface Trans-
ceivers, MC145532 ADPCM Transcoder, MC145422/26 UDLT–1,
MC145421/25 UDLT–2, and MC3419/MC33120 SLICs.
The MC145484 PCM Codec–Filter utilizes CMOS due to its reliable
low–power performance and proven capability for complex analog/digital VLSI
functions.
•
•
•
•
•
•
•
•
•
Single 5 V Power Supply
Typical Power Dissipation of 15 mW, Power–Down of 0.01 mW
Fully–Differential Analog Circuit Design for Lowest Noise
Transmit Band–Pass and Receive Low–Pass Filters On–Chip
Active R–C Pre–Filtering and Post–Filtering
Mu–Law and A–Law Companding by Pin Selection
On–Chip Precision Reference Voltage of 1.575 V for a – 0 dBm TLP @ 600 Ω
Push–Pull 300 Ω Power Drivers with External Gain Adjust
MC14LC5480EVK is the Evaluation Kit for This Device
REV 2
3/98
TN98031100
MC145484
For More Information On This Product,
Go to: www.freescale.com
1