Analog RSSI input ('SB', pin 103) voltage?

Hi, Can anyone please advise what voltage the analog RSSI input on a Pixhawk expects to see for 100% RSSI? Is it 3.3v?

I realise that RSSI_PIN_HIGH can be adjusted up to 5v in mission planner, but my tests seem to suggest that any voltage over 3.3v sent to this pin is ignored - so it appears to have a max allowable voltage of 3.3v. I identified this today with a Receiver who’s filter provides a 5v based RSSI analog signal. I set RSSI_PIN_HIGH to 5 and the max value displayed is 64. If I set RSSI_PIN_HIGH to 3.3, then it displays 99. This is no good in my case as its unlikely to drop below 99 until the voltage drops below 3.3v (which is actually an RSSI of 66, and not 99).