Reference Design For Precision Sign Chain In Digital Multimeters

This design provides good DC efficiency and excessive accuracy in DC measurements, making it superb for functions that require exact voltage readings. 

This reference design offers a complete overview of the speculation, design, and testing of a high-performance sign chain optimised for DC measurements. Whereas the first utility for this design is digital multimeters (DMMs), it is usually extremely appropriate for different functions akin to information acquisition (DAQ) and situation monitoring programs. This reference design is good for digital multimeters (DMMs), information acquisition programs (DAQ), and situation monitoring functions, the place precision and reliability in DC measurements are essential. The straightforward acquire choice and large enter vary additional improve its adaptability for numerous high-accuracy measurement duties.

The design TIDA-010945 by Texas Devices (TI) delivers distinctive DC accuracy by integrating a high-performance 24-bit analog-to-digital converter (ADC), the ADS127L21, and a low-noise programmable acquire amplifier (PGA), the PGA855. These parts are particularly chosen for his or her superior efficiency traits, together with a typical nonlinearity of ±2.4ppm and minimal drift over temperature. The excessive degree of integration in these units simplifies the general sign chain design, making it simpler to attain the specified efficiency. The combination of the ADS127L21 ADC and PGA855 amplifier simplifies the sign chain, enhancing each reliability and ease of implementation.

The design features a programmable acquire stage that helps a broad enter vary, making it notably appropriate for functions like digital multimeters (DMMs) that must deal with numerous enter ranges. The design incorporates key parts that contribute to its superior efficiency. The ADS127L21 is a 24-bit delta-sigma (ΔΣ) ADC that includes a programmable digital filter and helps information charges as much as 512kSPS with a wideband filter or as much as 1365kSPS with a low-latency filter. Its excessive decision and configurable filter settings allow a superb signal-to-noise ratio (SNR) of 110dB when utilizing the Sinc4 filter, all whereas eliminating the necessity for high-speed ADC enter drivers and reference buffers. The PGA855 amplifier is a high-bandwidth, programmable acquire instrumentation amplifier that provides absolutely differential outputs and eight binary acquire settings, starting from an attenuating acquire of 0.125V/V to a most of 16V/V. These acquire settings are managed via three digital acquire choice pins, offering flexibility in sign conditioning. 

The REF70 collection, recognized for its high-precision voltage references, delivers industry-leading low noise (0.23ppmp-p), minimal temperature drift (2ppm/°C), and excessive accuracy (±0.025%). These references additionally supply wonderful energy provide rejection ratio (PSRR), low dropout voltage, and excellent load and line regulation, guaranteeing constant efficiency beneath various situations. When it comes to efficiency specs, the design achieves a complete unadjusted error (TUE) of ±6ppm and integral nonlinearity (INL) of ±2.4ppm at 25°C after calibration, with most estimated values of TUE ±32ppm and INL ±12.2ppm. The design additionally demonstrates low offset drift (350nV/°C) and acquire drift (1.5ppm/°C), guaranteeing secure efficiency throughout a large temperature vary. 

Texas Devices (TI)has examined this reference design. It comes with a invoice of supplies (BOM), schematics, meeting drawing, printed circuit board (PCB) format, and extra. The corporate’s web site has further information concerning the reference design. To learn extra about this reference design, click on right here.