STWLC38 VRECT over-voltage clamping resistor

[Ryoma]

Hello experts, 

I have a question about how to determine the resistance value.
In STEVAL-WLC38RX circuit schematic, R4 = 200, R5 = 200, R6 = NA.
What is the idea behind the values you set?

The electrical characteristics in the datasheet for STWLC38 state Imax = 0.3[A](*1) when Vrect = 5 to 10[V].
   (*1)Non-repetitive 100 ms rectangular pulse

Are the resistance values based on these ratings?
Or is it set based on an experiment?

For now, I plan to use two of the same resistors as on the evaluation board.
Note that only the BPP will be implemented.

Regards, 
Ryoma

[Didier HERROUIN]

Hello,

These resistors are part of the Over-Voltage Protections.

Indeed, when the VRECT voltage exceeds the programmed threshold (VOUT + SOVP THRES), the resistors are grounded through internal switch to protect the circuit.

For your next requests, do not hesitate to open a case on st.com (https://www.st.com/content/st_com/en/support/support-home.html#), I will be able to support you directly.