Texas Instruments ADS1250U

Overview

ADS1250U from Burr-Brown (now Texas Instruments) is a 20-bit delta-sigma analog-to-digital converter with no missing codes, 18-bit effective resolution at up to 25kHz data rate, and programmable PGA gain of 1/2/4/8. It operates from a single +5V supply, accepts differential analog inputs, and uses an external 4.096V reference for precision measurement in cardiac diagnostics and chromatography systems.

For engineers reviewing the ADS1250U datasheet, ADS1250U pinout, ADS1250U application, or ADS1250U equivalent, this page delivers verified technical context, SOL-16 package mapping, real-world timing and noise performance, and two confirmed alternative ADCs for high-resolution industrial sensing designs.

Technical Context

The ADS1250U employs a fourth-order delta-sigma modulator clocked at 1.6MHz (derived from 9.6MHz system clock), oversampled 64× by a sinc5 digital filter to yield 25kHz output rate with 5.4kHz –3dB bandwidth. Its fully differential input architecture achieves 105dB common-mode rejection and supports bipolar input ranges from ±0.512V (PGA=8) to ±4.096V (PGA=1).

Gain selection is controlled via dedicated G0/G1 pins, and DSYNC enables precise synchronization across multiple converters by resetting the modulator count. The device requires buffered reference input (125µA typical load) and exhibits 0.25ppm/°C offset drift and 5.0ppm/°C gain drift over –40°C to +85°C.

Key Specifications

Pinout & Package

SOL-16 surface-mount package (211 drawing), 16-pin shrink-outline leaded format with exposed pad not present; RoHS-compliant, rated for –40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-resolution delta-sigma ADC applications.

Compared with ADS1251U and AD7730BRUZ, the ADS1250U uniquely balances 20-bit integrity at 25kHz with hardware-level DSYNC synchronization - making it the only option among the three capable of deterministic multi-ADC timing alignment in high-speed precision acquisition.

Availability

ADS1250U is available at Aetrix Electronics and suitable for cardiac diagnostics, liquid/gas chromatography, and precision process control requiring stable component supply across extended product lifecycles.

Supply support for ADS1250U 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

Burr-Brown Corporation, acquired by Texas Instruments in 2000, specialized in high-precision analog ICs for test, measurement, and medical instrumentation.

The ADS1250U belongs to Burr-Brown's early-generation precision delta-sigma ADC family, designed specifically for high-dynamic-range, low-drift measurement in clinical and analytical equipment where 20-bit monotonicity and deterministic timing were critical.

FAQ

What is the maximum data rate supported by the ADS1250U?

The ADS1250U achieves a maximum data rate of 25kHz when operated with a 9.6MHz system clock (CLK). This rate scales linearly with CLK frequency - for example, a 6.144MHz clock yields 16kHz output. The device maintains 18-bit effective resolution up to this 25kHz limit, with noise rising to 3.8ppm at maximum rate. ADS1250U's sinc5 filter provides inherent notch rejection at integer multiples of the selected data rate, enabling flexible power-line interference suppression.

Does the ADS1250U include an internal voltage reference?

No, the ADS1250U requires an external precision voltage reference applied to the VREF pin. The datasheet specifies a nominal 4.096V reference with ±0.1V tolerance; using this value yields full-scale input ranges from ±0.512V (PGA=8) to ±4.096V (PGA=1). The reference input draws 125µA at 9.6MHz CLK, scaling proportionally with clock frequency. A buffered reference (e.g., LM4040 + OPA350) is mandatory to maintain low noise and linearity - unbuffered sources degrade ADS1250U's 2.8ppm noise performance.

How does the DSYNC pin function on the ADS1250U?

The DSYNC pin on the ADS1250U provides hardware-level synchronization across multiple converters. A falling edge resets the internal modulator counter and places it in hold state; the rising edge releases the hold and aligns conversion start times. When all ADS1250U devices share the same CLK source and receive a synchronous DSYNC pulse, their DRDY outputs align within one CLK cycle. This capability is unique to the ADS1250U among its contemporaries and is essential for phase-coherent multi-channel acquisition in systems like multi-lead ECG monitors.

What package type is used for the ADS1250U?

The ADS1250U is packaged in a SOL-16 (Shrink Outline Leaded) format per drawing number 211, with 16 leads and gull-wing terminations. It is not a QFP, SOIC, or TSSOP variant. The SOL-16 footprint has specific pitch and lead geometry defined in Burr-Brown's mechanical drawings, and the device carries "ADS1250U" laser marking. This package supports surface-mount assembly and is rated for operation from –40°C to +85°C - critical for deployment in industrial and medical environments where thermal stability is required.

Can the ADS1250U operate with a single-ended analog input?

The ADS1250U is optimized for fully differential analog inputs (+VIN and –VIN), and its specified INL (±0.002% FSR) and noise (2.8ppm) apply only under differential conditions. If used single-ended (e.g., –VIN grounded), the full-scale range halves and linearity degrades significantly due to common-mode rejection limitations. The datasheet explicitly states that "in order to achieve the converter's full-scale range, the input must be fully differential." Therefore, for any application demanding 20-bit integrity or sub-0.002% INL, the ADS1250U must be driven differentially - external instrumentation amplifiers may be needed to condition single-ended sensor outputs before connection.