AMIS-49587 Datasheet, PDF (16/59 Pages) ON Semiconductor – Power Line Carrier Modem

AMIS−49587
Received
C₂
Signal
R2
RX_OUT ₂
C₁
RX_IN 3
LOW NOISE
OPAMP
Receiver (S−FSK Demodulator)
TO AGC
R₁
REF_OUT 4
CDREF
REF
1, 65 V
V SSA
Figure 10. External Component Connection for 50/60 Hz Suppression Filter
RX_IN is the positive analog input pin of the receiver low
noise input op−amp. Together with the output RX_OUT an
active high pass filter is realized. This filter removes the
main frequency (50 Hz or 60 Hz) from the received signal.
The filter characteristics are determined by external
capacitors and resistors. Typical values are given in
Table 23. For these values and after this filter, a typical
attenuation of 80 dB at 50 Hz is obtained. Figure 9
represents external components connection. In a typical
application the coupling transformer in combination with a
parallel capacitance forms a high pass filter with a typical
attenuation of 60 dB. The combined effect of the two filters
decreases the voltage level of 230 Vrms at the mains
frequency well below the sensitivity of the AMIS−49587.
Figure 11. Transfer Function of 50 Hz Suppression Circuit
REF_OUT is the analog output pin which provides the
voltage reference used by the A/D converter. This pin must
be decoupled from the analog ground by a 1 mF ceramic
capacitance (C_DREF). It is not allowed to load this pin.
The low noise operational amplifier can be bypassed and
powered down by setting the bit R_RX_MOD[7] to 1. In this
mode the pin RX_OUT must be used as input of the AGC.
Table 23. VALUE OF THE RESISTORS AND
CAPACITORS
Component
Value
Unit
C₁
1.5
nF
C₂
1.5
nF
C_DREF
1
mF
R₁
22
kW
R₂
11
kW
The analog part of AMIS−49587 works with an analog
ground of REF_OUT
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