AMIS-49587 Datasheet, PDF (15/59 Pages) ON Semiconductor – Power Line Carrier Modem

AMIS−49587
level. The evaluation of the level is done during 1
CHIP_CLK period.
Depending on the value of peak level on ALC_IN the
attenuation is updated:
− Vp_{ALC_IN} < VTL_ALC: Increase the level with 1 step
− VTL_ALC ≤ Vp_{ALC_IN} ≤ VTH_ALC: Don’t change the
level
− Vp_{ALC_IN} > VTH_ALC: Decrease the level with 1 step
The gain changes in the next CHIP_CLK period.
An evaluation phase and a level adjustment takes 2
CHIP_CLK periods. ALC operation is enabled only during
the first 16 CHIP_CLK cycles after a hard or soft reset or
after going into transmit mode.
The automatic level control can be disabled by the ARM
by setting R_ALC_CTRL[3] to 1. In case the transmitter
outputs the programmed level in the register
R_ALC_CTRL[2:0]. See Appendix C.
The analog part of AMIS−49587 works with an analogue
ground REF_OUT. When connecting AMIS−49587 to
external circuitry working with another ground one must
make sure to place a decoupling capacitor.
RECEIVER PATH DESCRIPTION
Receiver Block Diagram
The receiver section is active when TX_RXB = 0. The
operation mode and the baud rate are made according to the
setting in R_CONF[9:0], R_FS[15:0] and R_FM[15:0]. See
Appendix C. The receive signal is applied first to a high pass
filter. Therefore AMIS−49587 has a low noise operational
amplifier at the input stage which can be used to make a high
pass active filter to attenuate the mains frequency. This high
pass filter output is followed by a gain stage which is used
in an automatic gain control loop. This block also performs
a single ended input to differential output conversion. This
gain stage is followed by a continuous time low pass filter
to limit the bandwidth. A 4^th order sigma delta converter
converts the analog signal to digital samples. A quadrature
demodulation for f_S and f_M is than performed by the ARM
micro, as well the handling of the bits and the frames.
RX_OUT
RX_IN
LOW NOISE
OPAMP
Receiver (Analog Path)
FROM
DIGITAL
Gain
LPF
4th
Order
SD AD
TO
DIGITAL
REF_OUT
REF
1.65 V
Figure 8. Analog Path of the Receiver
FROM
ANALOG
Noise
Shaper
Receiver (Digital Path)
1^st
Decimator
Compen−
sator
TO
GAIN
AGC
Control
Abs
value
accu
sin(fM )
2 ^nd
Decimator
cos(fM )
2 ^nd
Decimator
sin(fS)
2 ^nd
Decimator
cos(f S)
2 ^nd
Decimator
Quadrature Demodulator
Sliding
Filter
fM
Sliding
Filter
Sliding
Filter
Sliding
Filter
fS
SOFTWARE
Figure 9. Digital Path of the Receiver ADC and Quadrature Demodulation
50/60 Hz Suppression Filter
AMIS−49587 receiver input provides a low noise input
operational amplifier in a follower configuration which can
be used to make a 50/60 Hz suppression filter with a
minimum number of external components. This low noise
operational amplifier is enabled when R_RX_MOD[7] = 0.
See Appendix C. The pin RX_IN is the positive input and
RX_OUT is the output of the input low noise operational
amplifier. The pin REF_OUT can be use as an analog ground
(1.65 V) for the external circuitry.
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