8-Channel, 24-Bit

ANALOG-TO-DIGITAL CONVERTER

with FLASH Memory

FEATURES

q 24 BITS NO MISSING CODES

q 0.0015% INL

q 22 BITS EFFECTIVE RESOLUTION

(PGA = 1), 19 BITS (PGA = 128)

q 4K BYTES OF FLASH MEMORY

PROGRAMMABLE FROM 2.7V TO 5.25V

q PGA FROM 1 TO 128

q SINGLE CYCLE SETTLING MODE

q PROGRAMMABLE DATA OUTPUT RATES

UP TO 1kHz

q PRECISION ON-CHIP 1.25V/2.5V REFERENCE:

ACCURACY: 0.2%

DRIFT: 5ppm/

q EXTERNAL DIFFERENTIAL REFERENCE

OF 0.1V TO 2.5V

q ON-CHIP CALIBRATION

q PIN COMPATIBLE WITH ADS1216

q SPI™ COMPATIBLE

q 2.7V TO 5.25V

q < 1mW POWER CONSUMPTION

DESCRIPTION

The ADS1218 is a precision, wide dynamic range, delta-sigma, Analog-to-

Digital(A/D)converterwith24-bitresolutionandFLASHmemoryoperating

from 2.7V to 5.25V supplies. The delta-sigma, A/D converter provides up to

24 bits of no missing code performance and effective resolution of 22 bits.

The eight input channels are multiplexed. Internal buffering can be selected

to provide a very high input impedance for direct connection to transducers

or low-level voltage signals. Burn out current sources are provided that allow

for the detection of an open or shorted sensor. An 8-bit Digital-to-Analog (D/

A) converter provides an offset correction with a range of 50% of the FSR

(Full-Scale Range).

The PGA (Programmable Gain Amplifier) provides selectable gains of 1 to

128 with an effective resolution of 19 bits at a gain of 128. The A/D

conversion is accomplished with a second-order delta-sigma modulator and

programmable sinc filter. The reference input is differential and can be used

for ratiometric conversion. The on-board current DACs (Digital-to-Analog

Converters) operate independently with the maximum current set by an

external resistor.

The serial interface is SPI compatible. Eight bits of digital I/O are also provided

thatcanbeusedforinputoroutput.TheADS1218isdesignedforhigh-resolution

measurementapplicationsinsmarttransmitters,industrialprocesscontrol,weight

scales, chromatography, and portable instrumentation.

APPLICATIONS

q INDUSTRIAL PROCESS CONTROL

q LIQUID /GAS CHROMATOGRAPHY

q BLOOD ANALYSIS

q SMART TRANSMITTERS

q PORTABLE INSTRUMENTATION

q WEIGHT SCALES

q PRESSURE TRANSDUCERS

ADS1218

SPI is a registered trademark of Motorola.

ADS1218

SBAS187 – SEPTEMBER 2001

www.ti.com

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 © 2001, Texas Instruments Incorporated

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.

BUF

PGA

A = 1:128

+

1.25V or

2.5V

Reference

Clock Generator

Registers

Serial Interface

2nd-Order

Modulator

RAM

4K Bytes

FLASH

AGND

AV

DD

IN+

IN–

R

DAC

V

REFOUT

V

RCAP

V

REF+

V

REF–

X

IN

X

OUT

DSYNC

PDWN

RESET

DRDY

BUFEN

DGND

DV

DD

WREN

Digital I/O

Interface

D7

...

D0

SCLK

POL

D

IN

D

OUT

CS

MUX

A

A

A

A

A

A

A

A

A

INCOM

IDAC1

Controller

Program-

mable

Digital

Filter

2

µA

AV

DD

8-Bit

IDAC

IDAC2

8-Bit

IDAC

Offset

DAC

AGND

2

µA