AD7785 datasheet(4/32 Pages) AD

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AD7785

Rev. 0 | Page 4 of 32

Parameter

AD7785B1

Unit

Test Conditions/Comments

REFERENCE

Internal Reference

Internal Reference Initial Accuracy

1.17 ± 0.01%

V min/max

AVDD = 4 V, TA = 25°C

Internal Reference Drift2

ppm/°C typ

ppm/°C max

Power Supply Rejection

dB typ

External Reference

External REFIN Voltage

2.5

V nom

REFIN = REFIN(+)

− REFIN(−)

Reference Voltage Range2

0.1

V min

AVDD

V max

When VREF = AVDD, the differential input must be

limited to 0.9 × VREF /gain if the in-amp is active

Absolute REFIN Voltage Limits2

GND

− 30 mV

V min

AVDD + 30 mV

V max

Average Reference Input Current

400

nA/V typ

Average Reference Input Current

Drift

±0.03

nA/V/°C typ

Normal Mode Rejection

Same as for analog inputs

Common-Mode Rejection

100

dB typ

EXCITATION CURRENT SOURCES

(IEXC1 and IEXC2)

Output Current

10/210/1000

μA nom

Initial Tolerance at 25°C

±5

% typ

Drift

200

ppm/°C typ

Current Matching

±0.5

% typ

Matching between IEXC1 and IEXC2; VOUT = 0 V

Drift Matching

ppm/°C typ

Line Regulation (VDD)

%/V typ

AVDD = 5 V ± 5%

Load Regulation

0.2

%/V typ

Output Compliance

AVDD

− 0.65

V max

10 μA or 210 μA currents selected

AVDD

− 1.1

V max

1 mA currents selected

GND

− 30 mV

V min

TEMPERATURE SENSOR

Accuracy

Sensitivity

±2

0.81

°C typ

mV/°C typ

Applies if user calibrates the temperature sensor

BIAS VOLTAGE GENERATOR

VBIAS

AVDD/2

V nom

VBIAS Generator Start-Up Time

See Figure 10

ms/nF typ

Dependent on the capacitance on the AIN pin

INTERNAL/EXTERNAL CLOCK

Internal Clock

Frequency2

64 ± 3%

kHz min/max

Duty Cycle

50:50

% typ

External Clock

Frequency

kHz nom

A 128 kHz external clock can be used if the

divide-by-2 function is used

(Bit CLK1 = CLK0 = 1)

Duty Cycle

45:55 to 55:45

% typ

Applies for external 64 kHz clock; a 128 kHz

clock can have a less stringent duty cycle

LOGIC INPUTS

CS2

VINL, Input Low Voltage

0.8

V max

DVDD = 5 V

VINH, Input High Voltage

0.4

2.0

V max

V min

DVDD = 3 V

DVDD = 3 V or 5 V

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