User`s manual
XP850026 s I/O Configurations
selected. The normal operating current of the A/D converter chip is 1 mA
to 2.5 mA. This consumption drops to 4 µA to 25 µA when the chip is in a
power-down mode. The reduction represents only about 1020 percent of
the XP8500 boards analog supply current and none of its digital supply
current
Drift
The AD680JT voltage reference experiences a voltage drift of 10 ppm/°C
(typ) to 30 ppm/°C (max). This drift corresponds to 25 mV/°C to 75mV/°C,
or 1.75 mV to 5.25 mV over the temperature range of 0°C to 70°C.
The LMC660C op-amp has an offset-voltage drift of 1.3 µV/°C (typ), or
91 µV over the temperature range of 0°C to 70°C.
A greater contribution to overall drift arises from differences in the
temperature coefficients of the gain and bias resistors, and the fixed 10 kΩ
resistors in resistor packs RP3 and RP4. These resistor networks and the
one used for the ratiometric voltage divider have a temperature coefficient
of 200 ppm/°C. Because the packages are small, the resistors within each
package are always at essentially the same temperature and their deviations
track closely.