8-Channel, 24-Bit
ANALOG-TO-DIGITAL CONVERTER
with FLASH Memory
FEATURES
a71 24 BITS NO MISSING CODES
a71 0.0015% INL
a71 22 BITS EFFECTIVE RESOLUTION
(PGA = 1), 19 BITS (PGA = 128)
a71 4K BYTES OF FLASH MEMORY
PROGRAMMABLE FROM 2.7V TO 5.25V
a71 PGA FROM 1 TO 128
a71 SINGLE CYCLE SETTLING MODE
a71 PROGRAMMABLE DATA OUTPUT RATES
UP TO 1kHz
a71 PRECISION ON-CHIP 1.25V/2.5V REFERENCE:
ACCURACY: 0.2%
DRIFT: 5ppm/°C
a71 EXTERNAL DIFFERENTIAL REFERENCE
OF 0.1V TO 2.5V
a71 ON-CHIP CALIBRATION
a71 PIN COMPATIBLE WITH ADS1216
a71 SPI™ COMPATIBLE
a71 2.7V TO 5.25V
a71 < 1mW POWER CONSUMPTION
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.
APPLICATIONS
a71 INDUSTRIAL PROCESS CONTROL
a71 LIQUID/GAS CHROMATOGRAPHY
a71 BLOOD ANALYSIS
a71 SMART TRANSMITTERS
a71 PORTABLE INSTRUMENTATION
a71 WEIGHT SCALES
a71 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
DSYNCPDWN RESET DRDYBUFENDGNDDV
DD
WREN
Digital I/O
Interface
D7...D0
SCLK
POL
D
IN
D
OUT
CS
MUX
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
IDAC1
Controller
Program-
mable
Digital
Filter
2µA
AV
DD
8-Bit
IDAC
IDAC2
8-Bit
IDAC
Offset
DAC
AGND
2µA