ST-PLC-AFE datasheet(11/58 Pages) STMICROELECTRONICS

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ST-PLC-AFE

General description

2.2

Tx block

The Tx block is divided into an internal DAC, an internal fourth-order filter, a programmable

amplifier, and a power liner driver. There are two ways to drive this transmission line:

The internal DAC driving mode, achieved through the SPI interface and the internal

10-bit DAC.

Using an external driving mode where the signal received by the ST-PLC-AFE is purely

analog, coming from an external MCU DAC. This signal is applied on the TX_INP input

pin.

Tx PGA can be configured through the SPI to operate as an attenuator or to work in

follower. The gain steps of the Tx PGA are 6 dB, 0 dB, -18 dB, and -36 dB. The gain can be

programmed through the TX_PGA1<1:0> bits in the Gain register.

The Tx_filter is a unity-gain, fourth-order, low-pass filter. Its cutoff frequency is selectable

between CENELEC A or CENELEC B, C, or D modes. The selection of the band is

achieved through the BAND_SEL bit in the Enable register.

2.2.1

Internal DAC driving mode

The ST-PLC-AFE accepts serial data from the microprocessor and writes the data to the

internal DAC registers. Operating in DAC mode results in the lowest distortion signal

injected onto the AC mains. DAC mode is selected by setting the DAC_EN bit in the Enable

internal DAC in differential mode and in single-ended mode respectively.

Figure 5. Connection to the power line in differential mode

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