AD7798 datasheet(3/28 Pages) AD

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Data Sheet

AD7798/AD7799

Rev. B | Page 3 of 28

SPECIFICATIONS

AVDD = 2.7 V to 5.25 V; DVDD = 2.7 V to 5.25 V; GND = 0 V; REFIN(+) = AVDD; REFIN(−) = 0 V. All specifications TMIN to TMAX, unless

otherwise noted.

Table 1.

Parameter

AD7798B/AD7799B1

Unit

Test Conditions/Comments

ADC CHANNEL

Output Update Rate

4.17 − 470

Hz nom

No Missing Codes2

Bits min

AD7799: fADC < 242 Hz

Bits min

AD7798

Resolution

See Table 5 to Table 8

Output Noise and Update Rates

See Table 5 to Table 8

Integral Nonlinearity

±15

ppm of FSR max

Offset Error3

±1

µV typ

Offset Error Drift vs. Temperature4

±10

nV/°C typ

Full-Scale Error3, 5

±10

µV typ

Gain Drift vs. Temperature4

±1

ppm/°C typ

Power Supply Rejection

100

dB min

AIN = 1 V/gain, gain ≥ 4

ANALOG INPUTS

Differential Input Voltage Ranges

±VREF/gain

V nom

VREF = REFIN(+) – REFIN(–), gain = 1 to 128

Absolute AIN Voltage Limits2

Unbuffered Mode

GND − 30 mV

V min

Gain = 1 or 2

AVDD + 30 mV

V max

Buffered Mode

GND + 100 mV

V min

Gain = 1 or 2

AVDD – 100 mV

V max

In-Amp Active

GND + 300 mV

V min

Gain = 4 to 128

AVDD − 1.1

V max

Common-Mode Voltage, VCM

0.5

V min

VCM = (AIN(+) + AIN(−))/2, gain = 4 to 128

Analog Input Current

Buffered Mode or In-Amp Active

Average Input Current2

±1

nA max

Gain = 1 or 2, update rate < 100 Hz

±250

pA max

Gain = 4 to 128, update rate < 100 Hz

±1

nA max

AIN3(+)/AIN3(−), update rate < 100 Hz

Average Input Current Drift

±2

pA/°C typ

Unbuffered Mode

Gain = 1 or 2

Average Input Current

±400

nA/V typ

Input current varies with input voltage

Average Input Current Drift

±50

pA/V/°C typ

Normal Mode Rejection2

@ 50 Hz, 60 Hz

dB min

80 dB typ, 50 ± 1 Hz, 60 ± 1 Hz (FS[3:0] = 1010)6

@ 50 Hz

dB min

90 dB typ, 50 ± 1 Hz (FS[3:0] = 1001)6

@ 60 Hz

dB min

100 dB typ, 60 ± 1 Hz (FS[3:0] = 1000)6

Common-Mode Rejection

@ DC

100

dB min

AIN = 1 V/gain, gain ≥ 4

@ 50 Hz, 60 Hz2

100

dB min

50 ± 1 Hz, 60 ± 1 Hz (FS[3:0] = 1010)6

@ 50 Hz, 60 Hz2

100

dB min

50 ± 1 Hz (FS[3:0] = 10016), 60 ± 1 Hz

(FS[3:0] = 10006)

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