Analog front-end (AFE)

ST7580

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DocID022644 Rev 2

The CL_SEL pin can be used to switch automatically the RCL resistor value according to

the used modulation. If FSK modulation is selected, CL_SEL is forced to GND, while if PSK

modulation is selected, CL_SEL is in high impedance state.

5.5

Thermal shutdown and temperature control

The ST7580 performs an automatic shutdown of the power amplifier circuitry when the

internal temperature exceeds T_TH4. After a thermal shutdown event, the temperature must

go below T_TH3 before the ST7580 power amplifier comes back into operation.

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

zones, as indicated in Table 9.

Table 9. Temperature zones

5.6

Zero crossing comparator

The ST7580 device embeds an analog comparator with hysteresis, used for optional zero

crossing detection and synchronization. It requires a bipolar (ac) analog input signal,

synchronous to the mains voltage.

Temperature zone

Temperature value

1

T < T_TH1

2T_TH1 < T < T_TH2

3T_TH2 < T < T_TH3

4

T > T_TH3