Datasheet AD7798, AD7799 (Analog Devices) - 3

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Data Sheet AD7798/AD7799 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 24 Bits min AD7799: fADC < 242 Hz 16 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 65 dB min 80 dB typ, 50 ± 1 Hz, 60 ± 1 Hz (FS[3:0] = 1010)6 @ 50 Hz 80 dB min 90 dB typ, 50 ± 1 Hz (FS[3:0] = 1001)6 @ 60 Hz 90 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) Rev. B | Page 3 of 28 Document Outline Features Interface Applications Functional Block Diagram General Description Revision History Specifications Timing Characteristics Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Output Noise and Resolution Specifications AD7798 AD7799 Typical Performance Characteristics On-Chip Registers Communication Register RS2, RS1, RS0 = 0, 0, 0 Status Register RS2, RS1, RS0 = 0, 0, 0; Power-On/Reset = 0x80 (AD7798)/0x88 (AD7799) Mode Register RS2, RS1, RS0 = 0, 0, 1; Power-On/Reset = 0x000A Configuration Register RS2, RS1, RS0 = 0, 1, 0; Power-On/Reset = 0x0710 Data Register RS2, RS1, RS0 = 0, 1, 1; Power-On/Reset = 0x0000(00) ID Register RS2, RS1, RS0 = 1, 0, 0; Power-On/Reset = 0xX8 (AD7798)/0xX9 (AD7799) IO Register RS2, RS1, RS0 = 1, 0, 1; Power-On/Reset = 0x00 Offset Register RS2, RS1, RS0 = 1, 1, 0; Power-On/Reset = 0x8000(AD7798)/0x800000 (AD7799) Full-Scale Register RS2, RS1, RS0 = 1, 1, 1; Power-On/Reset = 0x5XXX (AD7798)/0x5XXX00 (AD7799) ADC Circuit Information Overview Digital Interface Single-Conversion Mode Continuous-Conversion Mode Continuous Read Circuit Description Analog Input Channel Instrumentation Amplifier Bipolar/Unipolar Configuration Data Output Coding Burnout Currents Reference Reference Detect Reset AVDD Monitor Calibration Grounding and Layout Applications Information Weigh Scales Outline Dimensions Ordering Guide