ST7590

Analog front end (AFE)

Doc ID 18349 Rev 1

15/24

4.2

Transmission path

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

converter (DAC), capable to generate a very 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

According to PRIME Specifications the output level can be set on a 8-step logarithmic scale

between a Maximum Output Level (MOL) and a minimum output level (MOL - 21dB), with

steps of 3dB (typical). The maximum level corresponds to the TX_OUT full range.

4.3

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 1Arms (typical) that allows

the amplifier driving 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.

4.4

Thermal shutdown and temperature control

The ST7590 performs an automatic shutdown of the power amplifier circuitry when the

internal temperature exceeds 170 °C. After a Thermal shutdown event, the temperature

must get below 125 °C before the ST7590 power amplifier comes back to operation.

Moreover a digital thermometer is embedded to identify the internal temperature among four

zones, as indicated in Table 6.

Table 6.

Temperature zones

Temperature zone

Temperature range (Typ.)

1

4