ADS1218
ADS
121
8
SBAS187 – SEPTEMBER 2001
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/
°
C
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
AGND
DESCRIPTION
The ADS1218 is a precision, wide dynamic range, delta-sigma, Analog-to-
Digital (A/D) converter with 24-bit resolution and FLASH memory operating
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
that can be used for input or output. The ADS1218 is designed for high-resolution
measurement applications in smart transmitters, industrial process control, weight
scales, chromatography, and portable instrumentation.
AV
DD
R
DAC
V
REFOUT
V
RCAP
V
REF+
V
REF–
X
IN
X
OUT
APPLICATIONS
q
INDUSTRIAL PROCESS CONTROL
q
LIQUID /GAS CHROMATOGRAPHY
q
BLOOD ANALYSIS
q
SMART TRANSMITTERS
q
PORTABLE INSTRUMENTATION
q
WEIGHT SCALES
q
PRESSURE TRANSDUCERS
SPI is a registered trademark of Motorola.
IDAC2
8-Bit
IDAC
1.25V or
2.5V
Reference
Clock Generator
IDAC1
AV
DD
8-Bit
IDAC
2µA
Offset
DAC
A
IN
0
A
IN
1
A
IN
2
A
IN
3
A
IN
4
A
IN
5
A
IN
6
A
IN
7
A
INCOM
POL
Serial Interface
SCLK
D
IN
D
OUT
CS
D0
... D7
PDWN
DSYNC
RESET
DRDY
MUX
IN+
IN–
BUF
+
PGA
2nd-Order
Modulator
A = 1:128
Program-
mable
Digital
Filter
Registers
RAM
4K Bytes
FLASH
Controller
WREN
2µA
AGND
DV
DD
DGND
BUFEN
Digital I/O
Interface
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.
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
www.ti.com
BURR-BROWN [ BURR-BROWN CORPORATION ]
