ST-PLC-AFE Datasheet, PDF (13/58 Pages) STMicroelectronics – Power-line communication, analog front-end

ST-PLC-AFE
General description
Single to differential gain through the filter is equal to 1. If the single-ended input voltage
amplitude is 1 Vpp, then the output voltage in differential mode is also equal to 1 Vpp.
Figure 8 shows the single-ended to differential gain conversion.
Figure 8. PGA filter connection
2.3
Rx block
The Rx block consists of:
• Two programmable gain amplifiers (Rx PGA1 and Rx PGA2)
• A fourth-order, low-pass filter
• A selectable high-pass filter
The input sensing mode can be differential mode for better noise immunity or single mode
for the lowest BOM.
The Rx PGA1 can be configured through the SPI to operate as either an attenuator or an
amplifier. The gain steps of the Rx PGA1 are -3 dB, 3 dB, 9dB, and 15 dB. The gain can be
programmed through the RX_PGA1<1:0> bits in the Gain register. Configuring the Rx PGA1
as an attenuator (at gains less than 0 dB) is useful for applications where large interference
signals are present within the signal band. Attenuating large interference allows these
signals to pass through the analog Rx signal chain without causing an overload; the
interference signal can then be processed and removed within the microprocessor as
necessary. The gain steps of the Rx PGA2 are -6 dB, 6 dB, 18 dB, and 30 dB. The gain can
be programmed through the RX_PGA2<1:0> bits in the Gain register.
The Rx filter is a very low-noise, unity-gain, fourth-order low-pass filter. Its cutoff frequency
is selectable between CENELEC A or CENELEC B, C, or D bands. The selection of the
band is achieved through the BAND_SEL bit in the Enable register.
The 35 kHz high-pass filter is activated by the HP_EN bit in the Enable register.
Recommended connections for the Rx signal chain are shown in Figure 9, Figure 10, and
Figure 11.
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