Datasheet

DS_1x66B_001 73M1866B/73M1966B Data Sheet
Rev. 1.6 49
8.6 Transmit Path Signal Processing
8.6.1 General Description
In the transmit path, data is first sent by the host DSP through a serial interface to the 73M1x66B then
interpolated by an interpolation filter, serialized and transmitted across barrier interface to the Line-Side
Device, which is floating relative to the Host-Side Device earth ground. The data received on the
Line-Side Device is then de-serialized and digitally sigma-delta modulated to a one-bit data stream of
1.536 Mbps for a sample frequency of 8 kHz or 3.072 Mbps for a sample frequency of 16 kHz. The signal
is further filtered first by a switched capacitor filter and then a continuous time anti-aliasing circuit.
• The 0.2 dB pass-band ripple frequency is from dc to 3.422 kHz for an 8 kHz sample rate or 6.844 kHz
for a 16 kHz sample rate.
• The 3 dB bandwidth is 3.65 kHz for an 8 kHz sample rate or 7.299 kHz for a 16 kHz sample rate.
8.6.2 Total Transmit Path Response
Figure 26 and Figure 27 show the transmit path frequency response. The response shape is the same,
but the frequencies double for a 16 kHz sample rate.
0 1 2 3 4 5 6 7 8
100
90
80
70
60
50
40
30
20
10
0
10
Transmit Path Overall Frequency Response
Freq(kHz)
Gain (dB)
10
100−
composite x( )
80
x 16⋅
com
iplo
xo u
xo u
Figure 26: Transmit Path Overall Frequency Response to Fs of 8 kHz
0 0.5 1 1.5 2 2.5 3 3.5 4
1
0.8
0.6
0.4
0.2
0
0.2
0.4
0.6
0.8
1
Transmit Passband Response
Freq(kHz)
Gain (dB)
1.
1.0−
composite x( )
40
x 16⋅
Figure 27: Transmit Path Passband Response for an 8 kHz Sample Rate