AD7175-2BRUZ

The AD7175-2BRUZ from Analog Devices is a high-precision 24-bit sigma-delta analog-to-digital converter optimized for precision measurement applications. The device combines 24-bit resolution with a maximum data rate of 250kSPS, providing both high accuracy and fast conversion speed in a single chip. The flexible 8-channel input multiplexer can be configured as 8 single-ended inputs or 4 fully differential inputs, or combinations thereof, allowing the same device to handle multiple sensor types. A key differentiator is the true rail-to-rail analog input capability, which allows the ADC to measure signals from 0V to VREF without the common-mode range restrictions typical of many precision ADCs. The integrated 2.5V bandgap reference offers 2ppm/C typical temperature drift, eliminating the need for an external precision reference in many applications. The sigma-delta modulator with a 3rd-order digital filter provides programmable filter settings (Sinc5+Sinc1, Sinc3, or enhanced 50/60Hz rejection) that allow trade-offs between noise performance, data rate, and settling time. The SPI interface supports clock rates up to 20MHz with optional CRC error checking for robust communication in noisy industrial environments. Multiple ADC channels can be sequentially scanned with per-channel configuration (different filter settings, bipolar/unipolar mode, and reference selection for each channel). The 6mW power consumption at 5kSPS makes it suitable for battery-powered precision instruments.

The AD7175-2BRUZ operates as a 24-bit sigma-delta ADC with configurable input multiplexer. Key subsystems include: (1) Sigma-Delta Modulator – a 3rd-order modulator oversamples the analog input at a high internal clock rate (up to 20MHz); the modulator outputs a 1-bit data stream whose average value represents the analog input; the oversampling ratio (OSR) determines the effective resolution: higher OSR = lower noise = more effective bits but slower data rate; (2) Digital Filter – the modulator output is processed by a programmable digital filter; the Sinc5+Sinc1 filter provides the fastest settling (1 data period); the Sinc3 filter provides better noise performance at lower data rates; the enhanced 50/60Hz rejection filter provides >80dB rejection at 50Hz and 60Hz simultaneously for industrial environments; (3) Input Multiplexer – an 8-channel analog mux connects any combination of inputs to the ADC; channels can be configured as single-ended (AINx to AINCOM) or differential (AINx+ to AINx-); each channel has its own configuration register for setup, bipolar/unipolar, and reference selection; (4) Reference – an internal 2.5V bandgap reference with 2ppm/C drift is available; alternatively, an external reference (up to VDDA) can be used for higher accuracy applications; a reference buffer allows using high-impedance external references; (5) SPI Interface – a 4-wire SPI interface (CS, SCLK, DIN, DOUT) with 8/24/32-bit frame formats; optional 8-bit CRC on the data frame detects communication errors; the RDY pin indicates when new data is available; multiple devices can share the SPI bus.

• Precision weight scale: 4 differential channels for 4 load cells, 24-bit for 0.1ug resolution, sinc5 filter for fast settling in multi-cell scanning
• Process control: 8 single-ended channels monitor temperatures (RTDs) and pressures, 50/60Hz rejection for factory floor noise immunity
• Medical ECG: 4 differential channels for 4-lead ECG, rail-to-rail input for DC-coupled measurement, low power for battery operation