AD7781 Datasheet | Analog Devices

20-Bit, Pin-Programmable, Low Power Sigma-Delta ADC AD7781 Features Pin-programmable filter response Update rate: 10 Hz or 16.7 Hz Pin-programmable in-amp gain Pin-programmable power-down and reset Status function Internal clock oscillator Internal bridge power-down switch Current 115 μA typical (gain = 1) 330 μA typical (gain = 128) Simultaneous 50 Hz/60 Hz rejection Power supply: 2.7 V to 5.25 V - 40°C to +105°C temperature range Independent interface power supply Packages 14-lead, narrow body SOIC 16-lead TSSOP 2-wire serial interface (read-only device) SPI patible Schmitt trigger on SCLK FUNCTIONAL BLOCK DIAGRAM GND AVDD GAIN REFIN(+) REFIN(- ) AIN(+) G=1 OR 128 AIN(- ) BPDSW INTERNAL CLOCK 20-BIT Σ-Δ ADC DOUT/RDY SCLK DVDD 08162-001 FILTER PDRST Figure 1. Table 1. Parameter Output Data Rate RMS Noise C Grade B Grade P-P Resolution C Grade B Grade Settling Time Gain = 128 10 Hz 16.7 Hz 44 n V 55 n V 17.6 17.3 300 ms 65 n V 90 n V 17.1 16.6 120 ms 10 Hz Gain = 1 16.7 Hz 2.7 μV 2.7 μV 18.7 18.7 120 ms 2.4 μV 2.4 μV 18.8 18.8 300 ms APPLICATIONS Weigh scales Pressure measurement Industrial process control Portable instrumentation .. GENERAL DESCRIPTION The AD7781 is a plete, low power front-end solution for bridge sensor products, including weigh scales, strain gages, and pressure sensors. It contains a precision, low power, 20-bit sigma-delta (Σ-Δ) ADC, an on-chip, low noise programmable gain amplifier (PGA), and an on-chip oscillator. Consuming only 330 μA, the AD7781 is particularly suitable for portable or battery-operated products where very low power is required. The AD7781 also has a power-down mode that allows the user to switch off the power to the bridge sensor and power down the AD7781 when not converting, thus increasing the battery life of the product. For ease of use, all the Features of the AD7781 are controlled by dedicated pins. Each time that a data read occurs, eight status bits are appended to the 20-bit...