Very Low Noise, 24-Bit Analog-to-Digital Converter

FEATURES

►24 Bits, No Missing Codes

− All Data Rates and PGA Settings

►Up to 23 Bits Noise-Free Resolution

►±0.0010% Nonlinearity (max)

►Data Output Rates to 30kSPS

►Fast Channel Cycling

− 18.6 Bits Noise-Free (21.3 Effective Bits) at 1.45kHz

►One-Shot Conversions with Single-Cycle Settling

►Flexible Input Multiplexer with Sensor Detect

− Four Differential Inputs (ADS1256 only)

− Eight Single-Ended Inputs (ADS1256 only)

DESCRIPTION

The ADS1255 and ADS1256 are extremely low-noise, 24-bit analog-to-digital (A/D) converters. They provide complete high-resolution measurement solutions for the most demanding applications.

The converter is comprised of a 4th-order, delta-sigma (∆Σ) modulator followed by a programmable digital filter. A flexible input multiplexer handles differential or single-ended signals and includes circuitry to verify the integrity of the external sensor connected to the inputs. The selectable input buffer greatly increases the input impedance and the low-noise programmable gain amplifier (PGA) provides gains from 1 to 64 in binary steps. The programmable filter allows the user to optimize between a resolution of up to 23 bits noise-free and a data rate of up to 30k samples per second (SPS). The converters offer fast channel cycling for measuring multiplexed inputs and can also perform one-shot conversions that settle in just a single cycle.

Communication is handled over an SPI-compatible serial interface that can operate with a 2-wire connection. Onboard calibration supports both self and system correction of offset and gain errors for all the PGA settings. Bidirectional digital I/Os and a programmable clock output driver are provided for general use. The ADS1255 is packaged in an SSOP-20, and the ADS1256 in an SSOP-28.

APPLICATIONS

1. Weigh Scales

2. Scientific Instrumentation

3. Industrial Process Control

4. Medical Equipment

5. Test and Measurement

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