EVALST7590-1 Datasheet, PDF (15/24 Pages) STMicroelectronics – Narrow-band OFDM power line networking PRIME compliant system-on-chip

ST7590
Analog front end (AFE)
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
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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
1
2
3
4
Temperature range (Typ.)
T < T_TH₁
T_TH₁ < T < T_TH₂
T_TH₂ < T < T_TH₃
T > T_TH₃
Doc ID 18349 Rev 1
15/24