Texas Instruments ADS1251UG4

Overview

ADS1251UG4 from Texas Instruments is a 24-bit delta-sigma analog-to-digital converter (ADC) with no missing codes, 19-bit effective resolution at 20.8 kHz data rate, and 1.5 ppm rms noise. It operates from a single +5 V supply, accepts differential analog inputs up to ±VREF, and features an external reference input (0.5 V to 5 V). It is used in high-precision cardiac diagnostics, chromatography, and industrial process control systems requiring stable low-noise digitization.

For engineers reviewing the ADS1251UG4 datasheet, ADS1251UG4 pinout, ADS1251UG4 application, or ADS1251UG4 equivalent, this page delivers verified technical context, SO-8 package mapping, real-world timing and noise performance, and validated alternative options for precision measurement designs.

Technical Context

The ADS1251UG4 implements a 4th-order delta-sigma modulator with fixed 64× oversampling ratio and a Sinc5 digital filter, delivering notch rejection at integer multiples of the data output rate. Its modulator clock is derived by dividing the system CLK by 6 (e.g., 8 MHz CLK → 1.333 MHz modulator clock).

It supports synchronous serial communication via CMOS-compatible SCLK and DOUT/DRDY pins, uses offset binary two's complement data format, and enables synchronization or power-down by holding SCLK HIGH for defined numbers of DRDY cycles - four for sync, twenty for power-down.

Key Specifications

Pinout & Package

ADS1251UG4 is housed in an SO-8 surface-mount package (package code D), with gull-wing leads, 1.27 mm pitch, and JEDEC MS-012AC compliant outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS1252U and ADS1253IPW, the ADS1251UG4 provides the lowest power consumption per channel at ≤20.8 kHz while maintaining identical noise and linearity specs - making it the preferred choice for battery-powered or thermally constrained single-input measurement nodes.

Availability

ADS1251UG4 is available at Aetrix Electronics and suitable for cardiac diagnostics, chromatography instrumentation, and industrial process control systems requiring stable component supply with long-term manufacturability assurance.

Supply support for ADS1251UG4 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 heritage in precision data converters and industrial-grade signal chain solutions.

The ADS1251UG4 belongs to TI's precision delta-sigma ADC family designed specifically for high-dynamic-range, low-noise measurement applications in medical, analytical, and process control equipment where 24-bit integrity and 19-bit effective resolution are non-negotiable.

FAQ

What is the maximum data rate supported by the ADS1251UG4?

The ADS1251UG4 supports a maximum data rate of 20.8 kHz when operated with an 8 MHz system clock. This rate is fixed by the internal 64× oversampling ratio and 6:1 modulator clock divider. Reducing the system clock proportionally lowers the data rate - e.g., 4.9152 MHz CLK yields 12.8 kHz - enabling flexible trade-offs between speed and digital filter rejection depth.

Does the ADS1251UG4 require an external reference voltage?

Yes, the ADS1251UG4 requires an external reference voltage applied to the VREF pin. It accepts 0.5 V to 5 V, draws 32 µA at 8 MHz CLK, and directly sets the full-scale differential input range (±VREF). A buffered reference such as REF3040 with OPA350 is recommended to maintain 1.5 ppm noise performance and avoid loading-induced drift.

How does the ADS1251UG4 achieve 50 Hz or 60 Hz line-frequency rejection?

The ADS1251UG4 achieves 50/60 Hz rejection through its Sinc5 digital filter's inherent notch response at integer multiples of the data output rate. Setting the data rate to exactly 50 Hz (via 19.2 MHz CLK) or 60 Hz (via 23.04 MHz CLK) places the first notch at that frequency. For dual rejection, a 10 Hz data rate (3.84 MHz CLK) provides deep attenuation at both 50 Hz and 60 Hz.

Can multiple ADS1251UG4 devices be synchronized for simultaneous sampling?

Yes, multiple ADS1251UG4 devices can be synchronized by holding the SCLK pin HIGH for at least four consecutive DOUT/DRDY cycles. Upon the falling edge of SCLK, all devices release their modulator reset simultaneously, ensuring aligned conversion start times. Layout must minimize SCLK skew across devices to maintain sub-cycle timing alignment.

What is the meaning of "no missing codes" in the ADS1251UG4 specification?

"No missing codes" means the ADS1251UG4 guarantees monotonic transfer function across its entire 24-bit output range (–2²³ to +2²³–1) under all specified conditions - including full temperature range (–40°C to +85°C) and supply voltage variation. This ensures every possible digital code appears at least once during a full-scale ramp, eliminating non-monotonic behavior critical for closed-loop control and calibration.