Texas Instruments ADS1231ID

Overview

ADS1231ID from Texas Instruments is a precision 24-bit delta-sigma ADC with integrated PGA (G = 128), internal oscillator, low-side bridge power switch, and sinc⁴ digital filter - designed specifically for bridge sensor front-ends. It delivers 35nV_rms noise at 10SPS, simultaneous 50Hz/60Hz rejection, and ±19.5mV full-scale input range when VREF = AVDD = 5V, enabling high-accuracy weigh scale and load cell measurement.

For engineers reviewing the ADS1231ID datasheet, ADS1231ID pinout, ADS1231ID application, or ADS1231ID equivalent, key selection criteria include its ratiometric reference support up to 5V, pin-driven control (no register programming), two-wire serial interface with DRDY/DOUT dual-function pin, and SOIC-16 package compatibility with MSP430 microcontrollers in isolated industrial sensing designs.

Technical Context

The ADS1231ID implements a third-order ΔΣ modulator with fourth-order sinc⁴ digital filtering, achieving 24-bit no-missing-codes resolution and 110dB common-mode rejection. Its internal chopper-stabilized amplifier uses matched resistors and EMI-filtered inputs to suppress 1/f noise and external interference.

Timing is governed by either the onboard 4.9152MHz oscillator (selectable via CLKIN tie-low) or an external clock (1–6MHz), with data rate set by SPEED pin: 10SPS (full 50/60Hz notch rejection) or 80SPS. The DRDY/DOUT pin transitions low to signal valid conversion, then shifts out 24-bit two's-complement data MSB-first on SCLK rising edges.

Key Specifications

Pinout & Package

ADS1231ID is housed in a 16-pin SOIC (D package) with exposed pad thermal performance (θ_JA = 79.5°C/W). Pin functions are dedicated and non-programmable, supporting simple microcontroller interfacing without configuration overhead.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar precision bridge-sensor ADC applications.

Compared with ADS1232IPW, ADS1231ID offers superior bridge power management via SW pin but requires external reference; versus HX711, it delivers 4× lower noise, guaranteed 50/60Hz rejection, and full industrial temperature qualification - making it the only option for metrology-grade weighing systems.

Availability

ADS1231ID is available at Aetrix Electronics and suitable for weigh scales, load cells, and industrial process control systems requiring stable component supply, long-term calibration retention, and certified metrological performance.

Supply support for ADS1231ID includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision data acquisition and sensor interface ICs.

The ADS1231ID belongs to TI's high-accuracy delta-sigma ADC product line, engineered specifically for bridge-based transducers in metrology, industrial weighing, and structural monitoring applications where noise, drift, and line-frequency interference must be rigorously controlled.

FAQ

What is the full-scale input range of the ADS1231ID at 5V reference?

The ADS1231ID has a full-scale differential input range of ±19.5mV when VREF = AVDD = 5V and PGA gain is set to 128. This is calculated as ±0.5 × VREF / 128. At 3V reference, the range scales to ±11.7mV. The device accepts inputs within the common-mode range of GND + 1.5V to AVDD – 1.5V, ensuring compatibility with typical bridge sensor biasing schemes. This range directly supports standard load cell outputs without external attenuation or amplification.

How does the ADS1231ID achieve simultaneous 50Hz and 60Hz rejection?

The ADS1231ID achieves simultaneous 50Hz and 60Hz rejection through its fixed sinc⁴ digital filter architecture operating at 10SPS data rate. The filter's frequency response places deep notches exactly at integer multiples of the data rate - so at 10SPS, notches occur at 10Hz, 20Hz, 30Hz, etc., inherently rejecting both 50Hz and 60Hz line frequencies. This hardware-based rejection requires no firmware intervention and remains effective across temperature and supply variations, unlike adaptive digital filtering methods.

Can the ADS1231ID operate without an external reference voltage?

No - the ADS1231ID requires external VREFP and VREFN connections to define its reference voltage (VREF = VREFP – VREFN), with support for 1.5V to 5V. It does not contain an internal reference. However, it supports true ratiometric operation: if VREF is derived from the same supply as the bridge excitation (e.g., AVDD), gain errors due to supply drift cancel out. This makes the ADS1231ID ideal for systems where reference stability is managed at the system level rather than on-chip.

What is the purpose of the CAP pins on the ADS1231ID?

The CAP pins (5 and 6) connect to an external 0.1μF NPO/C0G capacitor that forms a first-order low-pass filter with an internal resistor (R_INT). This filter has a corner frequency of ~720Hz and serves two critical roles: (1) band-limiting the input signal to prevent aliasing by the ΔΣ modulator, and (2) attenuating chopper-stabilization residue to improve DC accuracy and temperature drift performance. Placement of this capacitor within 2mm of the CAP pins is mandatory for optimal noise and drift behavior.

How does the SW pin function in bridge sensor applications?

The SW pin is a low-side power switch that connects the bridge sensor's negative leg to GND during active conversion and opens (high-impedance) during standby or power-down modes. This eliminates continuous current flow through the bridge when measurements are not being taken, reducing self-heating, power consumption, and associated thermal drift. For a typical 350Ω load cell with 5V excitation, this cuts idle power from 71mW to near zero - essential for battery-powered portable scales.