MTC-20144TQ-I AMI Semiconductor, Inc., MTC-20144TQ-I Datasheet - Page 9

• Manufacturer Part Number: MTC-20144TQ-I
• Description: Integrated ADSL CMOS Analog Front-End Circuit
• Manufacturer: AMI Semiconductor, Inc.

MTC-20144 RX PATH
Speech Filter
An external bidirectional LC filter for up
and downstream POTS service splits out
the speech signal to the analog
telephone circuit on both the NT and LT
sides of the line.
The ADSL analog front end Integrated
circuit does not contain any circuitry for
the POTS service but guarantees that the
POTS bandwidth is not disturbed by
spurious signals from the ADSL-
spectrum.
RX Common-mode Voltage
AGC of RX Path
The AGC gain in the RX-path is
controlled through a 5-bits digital code.
Four inputs are provided for RX input
and the selection is made with the
RXMUX bits of the CTRLIN interface. This
can be used to make lower gain paths
in case of high input signal.
The AGC characteristics are :
RX Filters
The combination of the external filter (an
LC ladder filter typically) with the
integrated lowpass filter provides :
- echo reduction to improve dynamic
range
- DMT sidelobe and out of band (anti-
aliasing) attenuation.
- Anti alias filter (60 dB rejection @
image freq.)
Description
Common mode signal VCM at RXIN1 and RXIN2 :
Description
Input refered noise (max. gain)
Max. input level
Gain range :
Gain and step accuracy:
Channel Filters
The purpose of these external analog
circuits is to provide partial echo
cancellation by an analog filtering of the
receive signal for both ATU_R
(Reception of downstream channel) and
ATU_C (Reception of upstream channel).
This is feasible because the upstream
and the downstream data can be
modulated on separate carriers (FDM).
Value/Units
1.6V < VCM < 1.7V
Value/Units
< 20 nVHz -1/2 (an external gain is needed)
1 Vpd
0 dB ... 31 dB with step = 1 dB
+- 0.3 dB
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MTC-20144