Analog front-end (AFE)

ST7580

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DocID022644 Rev 2

5.2

Transmission path

Figure 6 shows the transmission path block diagram. It is mainly based on a digital to analog

converter (DAC), capable of generating a linear signal up to its full scale output. A gain

control block before the DAC gives the possibility to scale down the output signal to match

the desired transmission level.

Figure 6. Transmission path block diagram

The amplitude of the transmitted signal can be set on a 32-step logarithmic scale via the

TX_GAIN parameter, introducing an attenuation ranging from 0 dB (typ.), corresponding to

the TX_OUT full range, down to -31 dB (typ.).

The signal level set by the TX_GAIN parameter can be calculated using the following

formula:

Equation 1 output attenuation A [dB] vs. TX GAIN

5.3

Power amplifier

The integrated power amplifier is characterized by very high linearity, required to comply

with the different international regulations (CENELEC, FCC, etc.) limiting the spurious

conducted emissions on the mains, and a current capability of I(PA_OUT) MAX that allows

the amplifier to drive even very low impedance points of the network.

All pins of the power amplifier are accessible, making it possible to build an active filter

network to increase the linearity of the output signal.

AM02506v1

TX AFE

DAC

Gain

Control

TX_OUT

TX_GAIN

BPF

BPF

 



TOL

GAIN

_

TX

31

GAIN

_

TX

dB

A





