Datasheet AD7798, AD7799 (Analog Devices)

3-Channel, Low Noise, Low Power, 16-/24-Bit, Σ-Δ ADC with On-Chip In-Amp Data Sheet AD7798/ AD7799 FEATURES FUNCTIONAL BLOCK DIAGRAM RMS noise: GND AVDD REFIN(+) REFIN(–) 27 nV at 4.17 Hz (AD7799) REFERENCE 65 nV at 16.7 Hz (AD7799) DETECT AD7798/AD7799 40 nV at 4.17 Hz (AD7798) 85 nV at 16.7 Hz (AD7798) AIN1(+) AVDD AIN1(–) Current: 380 µA typical AIN2(+) DOUT/RDY SERIAL Power-down: 1 µA maximum AIN2(–) MUX INTERFACE DIN Σ-Δ AIN3(+)/P1 IN-AMP AND ADC Low noise, programmable gain, instrumentation amp SCLK CONTROL AIN3(–)/P2 LOGIC CS Update rate: 4.17 Hz to 470 Hz 3 differential inputs GND DVDD PSW INTERNAL AD7798: 16-BIT Internal clock oscillator CLOCK AD7799: 24-BIT
001
GND Simultaneous 50 Hz/60 Hz rejection
04856-
Reference detect
Figure 1.
Low-side power switch Programmable digital outputs GENERAL DESCRIPTION Burnout currents Power supply: 2.7 V to 5.25 V
The AD7798/AD7799 are low power, low noise, complete
–40°C to +105°C temperature range
analog front ends for high precision measurement applications.
Independent interface power supply
The AD7798/AD7799 contains a low noise, 16-/24-bit ∑-∆
16-lead TSSOP package
ADC with three differential analog inputs. The on-chip, low noise instrumentation amplifier means that signals of small
INTERFACE
amplitude can be interfaced directly to the ADC. With a gain
3-wire serial
setting of 64, the rms noise is 27 nV for the AD7799 and 40 nV
SPI®, QSPI™, MICROWIRE™, and DSP compatible
for the AD7798 when the update rate equals 4.17 Hz.
Schmitt trigger on SCLK
On-chip features include a low-side power switch, reference
APPLICATIONS
detect, programmable digital output pins, burnout currents,
Weigh scales
and an internal clock oscillator. The output data rate from the
Pressure measurement
part is software-programmable and can be varied from 4.17 Hz
Strain gauge transducers
to 470 Hz.
Gas analysis
The part operates with a power supply from 2.7 V to 5.25 V.
Industrial process control
The AD7798 consumes a current of 300 µA typical, whereas the
Instrumentation
AD7799 consumes 380 µA typical. Both devices are housed in a
Portable instrumentation
16-lead TSSOP package.
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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