ST7570

Analog front end (AFE)

Doc ID 17526 Rev 2

13/26

5

Analog front end (AFE)

5.1

Reception path

Figure 4 shows the block diagram of the ST7570 input receiving path. The main blocks are a

wide input range analog programmable gain amplifier (PGA) and the analog to digital

converter (ADC).

Figure 5.

reception path block diagram

The PGA is controlled by an embedded loop algorithm, adapting the PGA gain to amplify or

attenuate the input signal according to the input voltage range for the ADC.

The PGA gain ranges from -18 dB up to 30 dB, with steps of 6 dB (typ.), as described in

Table 5.

5.2

Transmission path

Figure 5 shows the transmission path block diagram. it is mainly based on a digital to analog

converter (DAC), capable to generate 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.

Table 6.

PGA gain table

PGA code

PGA gain (typ) [dB]

RX_IN max range [V p-p]

0-18

16

1-12

8

2-6

4

302

461

5

12

0.500

6

18

0.250

7

24

0.125

8

30

0.0625