Datasheet

Data Sheet AD7798/AD7799
Rev. B | Page 5 of 28
Parameter AD7798B/AD7799B
1
Unit Test Conditions/Comments
SYSTEM CALIBRATION
2
Full-Scale Calibration Limit 1.05 × FS V max FS = Full-scale analog input. When V
REF
= AV
DD
, the
differential input must be limited to (0.9 × V
REF
/gain)
if the in-amp is active.
Zero-Scale Calibration Limit
−1.05 × FS
V min
Input Span 0.8 × FS V min
2.1 × FS V max
POWER REQUIREMENTS
7
Power Supply Voltage
AV
DD
GND 2.7/5.25 V min/max
DV
DD
GND 2.7/5.25 V min/max
Power Supply Currents
I
DD
Current 140 µA max Unbuffered mode, 110 µA typ @ AV
DD
= 3 V,
125 µA typ @ AV
DD
= 5 V
180 µA max Buffered mode, gain = 1 or 2, 130 µA typ @ AV
DD
= 3 V,
165 µA typ @ AV
DD
= 5 V
400 µA max AD7798: gain = 4 to 128, 300 µA typ @ AV
DD
= 3 V,
350 µA typ @ AV
DD
= 5 V
500
µA max
DD
440 µA typ @ AV
DD
= 5 V
I
DD
(Power-Down Mode) 1 µA max
1
Temperature range is40°C to +105°C. At the 19.6 Hz and 39.2 Hz update rates, the INL, power supply rejection (PSR), common-mode rejection (CMR), and normal
mode rejection (NMR) do not meet the data sheet specification if the voltage on the AIN(+) or AIN(−) pins exceeds AV
DD
− 1.6 V typically. When this voltage is
exceeded, the INL, for example, is reduced to 18 ppm of FS typically and the PSR is reduced to 69 dB typically. Therefore, for guaranteed performance at these update
rates, the absolute voltage on the analog input pins needs to be below AV
DD
− 1.6 V.
2
Specification is not production tested, but is supported by characterization data at initial product release.
3
Following a calibration, this error is in the order of the noise for the programmed gain and update rate selected.
4
Recalibration at any temperature removes these errors.
5
Full-scale error applies to both positive and negative full-scale and applies at the factory calibration conditions (AV
DD
= 4 V, gain = 1, T
A
= 2C).
6
FS[3:0] are the four bits used in the mode register to select the output word rate.
7
Digital inputs equal to DV
DD
or GND.