ADS1255
ADS1256
SBAS288D − JUNE 2003 − REVISED AUGUST 2004
Very Low Noise, 24 Bit
Analog to Digital Converter
FEATURES
D
24 Bits, No Missing Codes
D
D
D
Data Output Rates to 30kSPS
D
Fast Channel Cycling
− All Data Rates and PGA Settings
Up to 23 Bits Noise-Free Resolution
±0.0010%
Nonlinearity (max)
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.
VREFP
VREFN
DVDD
XTAL1/CLKIN
XTAL2
RESET
SYNC/PDWN
DRDY
General
Purpose
Digital I/O
Serial
Interface
SCLK
DIN
DOUT
CS
AGND
D3 D2
ADS1256
Only
D1 D0/CLKOUT
DGND
− 18.6 Bits Noise-Free (21.3 Effective Bits)
at 1.45kHz
D
One-Shot Conversions with Single-Cycle
Settling
D
Flexible Input Multiplexer with Sensor Detect
D
D
D
Self and System Calibration for All PGA
Settings
− Four Differential Inputs (ADS1256 only)
− Eight Single-Ended Inputs (ADS1256 only)
Chopper-Stabilized Input Buffer
Low-Noise PGA: 27nV Input-Referred Noise
D
D
D
D
5V Tolerant SPI-Compatible Serial Interface
Analog Supply: 5V
Digital Supply: 1.8V to 3.6V
Power Dissipation
− As Low as 38mW in Normal Mode
− 0.4mW in Standby Mode
AVDD
ADS1256 Only
APPLICATIONS
D
Weigh Scales
D
Scientific Instrumentation
D
Industrial Process Control
D
Medical Equipment
D
Test and Measurement
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AINCOM
Mux
and
Sensor
Detect
1:64
Buffer
PGA
4th−Order
Modulator
Programmable
Digital Filter
Clock
Generator
Control
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Products
conform to specifications per the terms of Texas Instruments standard warranty.
Production processing does not necessarily include testing of all parameters.
Copyright
2003−2004, Texas Instruments Incorporated
www.ti.com
BURR-BROWN [ BURR-BROWN CORPORATION ]
