AD7715_15 datasheet(25/40 Pages) AD

25 / 40 page

AD7715

Rev. D | Page 25 of 40

If the part is used in unipolar mode with a required span of

0.8 × VREF/GAIN, then the offset range which the system

calibration can handle is from −1.05 × VREF/GAIN to +0.25 ×

VREF/GAIN. If the part is used in unipolar mode with a required

span of VREF/GAIN, then the offset range which the system

calibration can handle is from −1.05 × VREF/GAIN to +0.05 ×

VREF/GAIN. Similarly, if the part is used in unipolar mode and

required to remove an offset of 0.2 × VREF/GAIN, then the span

range which the system calibration can handle is 0.85 ×

VREF/GAIN.

If the part is used in bipolar mode with a required span of ±0.4 ×

VREF/GAIN, then the offset range which the system calibration

can handle is from −0.65 × VREF/GAIN to +0.65 × VREF/GAIN. If

the part is used in bipolar mode with a required span of ±VREF/

GAIN, then the offset range which the system calibration can

handle is from −0.05 × VREF/GAIN to +0.05 × VREF/GAIN.

Similarly, if the part is used in bipolar mode and required to

remove an offset of ±0.2 × VREF/GAIN, then the span range

which the system calibration can handle is ±0.85 × VREF/GAIN.

Power-Up and Calibration

On power-up, the AD7715 performs an internal reset that sets

the contents of the internal registers to a known state. There are

default values loaded to all registers after a power-on or reset.

The default values contain nominal calibration coefficients for

the calibration registers. However, to ensure correct calibration

for the device a calibration routine should be performed after

power-up.

The power dissipation and temperature drift of the AD7715

are low, and no warm-up time is required before the initial

calibration is performed. However, if an external reference is

being used, this reference must have stabilized before calibration is

initiated. Similarly, if the clock source for the part is generated

from a crystal or resonator across the MCLK pins, the start-up

time for the oscillator circuit should elapse before a calibration

is initiated on the part (see the Clocking and Oscillator Circuit

section).

AD7715 Datasheet(PDF) 25 Page - Analog Devices