September 1994
TP3040, TP3040A PCM Monolithic Filter
General Description
Features
Y
Designed for D3/D4 and CCITT applications
b
The TP3040/TP3040A filter is a monolithic circuit contain-
ing both transmit and receive filters specifically designed for
PCM CODEC filtering applications in 8 kHz sampled sys-
tems.
Y
Y
a
Low power consumption:
5V, 5V power supplies
45 mW (0 dBm0 into 600X)
30 mW (power amps disabled)
Power down mode: 0.5 mW
20 dB gain adjust range
The filter is manufactured using microCMOS technology
and switched capacitor integrators are used to simulate
classical LC ladder filters which exhibit low component sen-
sitivity.
Y
Y
Y
Y
Y
Y
Y
No external anti-aliasing components
Sin x/x correction in receive filter
50/60 Hz rejection in transmit filter
TTL and CMOS compatible logic
All inputs protected against static discharge due to
handling
TRANSMIT FILTER STAGE
The transmit filter is a fifth order elliptic low pass filter in
series with a fourth order Chebyshev high pass filter. It pro-
vides a flat response in the passband and rejection of sig-
nals below 200 Hz and above 3.4 kHz.
RECEIVE FILTER STAGE
The receive filter is a fifth order elliptic low pass filter de-
signed to reconstruct the voice signal from the decoded/de-
multiplexed signal which, as a result of the sampling pro-
cess, is a stair-step signal having the inherent sin x/x fre-
quency response. The receive filter approximates the func-
tion required to compensate for the degraded frequency re-
sponse and restore the flat passband response.
Block Diagram
TL/H/6660–1
FIGURE 1
C
1995 National Semiconductor Corporation
TL/H/6660
RRD-B30M115/Printed in U. S. A.