What is the maximum allowable voltage on analogue inputs (measured between pin and VSS) of SD24 inside MSP430AFE2xx, especially when PGA gain is set to values different than default 1?
I've read the datasheet, but I'm still confused about that. Differential full scale input voltage range should be between -Vref/2GAIN and +Vref/2GAIN. For GAIN = 1 we have +/-500mV, and for example for GAIN = 32 we have +/-15mV. I have a signal which sometimes is around 300mV and sometimes around 3mV, so I'd like to implement autoranging, when I measure the signal with GAIN = 32 and detect overflow (SD24_MEM constantly at 0xFFFF) the PGA should change to GAIN = 1, and then if measured voltage is below some value, the PGA should back to GAIN = 32.
The question is: what will happen if I set GAIN = 32 and then apply 300mV voltage on SD_24 input pin? Will it lead only to overflow of SD24_MEM register or physical damage of the input? I assume that until voltage at the pin not exceed Absolute ratings there is no way to destroy the chip.
Another confusing parameter: on page 16, in Absolute Maximum Ratings table, there is stated: Voltage applied to any pin: -0.3 V to V CC + 0.3 V. So if my VCC = 3.3V minimum voltage is -0.3V and maximum voltage is 3.6V. On the other hand, on page 29 there is table for SD24_A Input Range. From this table we can read that Absolute input voltage range should be between AVSS-1 and AVCC. So if tie digital VCC to analogue AVCC, and digital VSS do analogue AVSS absolute voltages on SD_24 inputs should be from -1V to 3.3V range - which is beyond limits from Absolute Maximum Ratings.
