Quad ADC needs +5V and -5V supplies. Are there any constraints about power up
and power down sequence of these supplies.
If you refer to the absolute max ratings in the AD7874 datasheet, both VDD and
VSS ratings are referenced to AGND, with the result that you can deduce that
the max voltage range for VDD to VSS = -0.3 volts to +14 volts.Therefore you
can apply a -5Volts to VSS ahead of +5Volts to VDD or vice versa , apply +5V to
VDD ahead of -5Volts to VSS.