" To avoid 'latch-up' effect at power-on:
Vss-0.5V<'voltage on any pin at any time'<Vdd+0.5V"
You are write...
One nights work, straight to garbish...
How did I miss that?
First thoughts:
I could apply the negative voltage after power-on (whith a switch for example) :)
Playing with op-amps is a good idea...
I can use a Full Wave Precision Rectifier to get only positive voltages...
But then, how could I distinguish between a positive and a negative value in the ADC?(for display purposes)