REV.0
a
AD7719
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 2001
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
Low Voltage, Low Power,
Factory-Calibrated 16-/24-Bit Dual H9018-H9004 ADC
FEATURES
HIGH RESOLUTION H9018-H9004 ADCs
Two Independent ADCs (16- and 24-Bit Resolution)
Factory-Calibrated (Field Calibration Not Required)
Output Settles in One Conversion Cycle (Single
Conversion Mode)
Programmable Gain Front End
Simultaneous Sampling and Conversion of Two
Signal Sources
Separate Reference Inputs for Each Channel
Simultaneous 50 Hz and 60 Hz Rejection at 20 Hz
Update Rate
ISOURCE Select
TM
24-Bit No Missing Codes—Main ADC
13-Bit p-p Resolution @ 20 Hz, 20 mV Range
18-Bit p-p Resolution @ 20 Hz, 2.56 V Range
INTERFACE
3-Wire Serial
SPI
TM
, QSPI
TM
, MICROWIRE
TM
and DSP-Compatible
Schmitt Trigger on SCLK
POWER
Specified for Single 3 V and 5 V Operation
Normal: 1.5 mA Typ @ 3 V
Power-Down: 10 H9262A (32 kHz Crystal Running)
ON-CHIP FUNCTIONS
Rail-Rail Input Buffer and PGA
4-Bit Digital I/O Port
On-Chip Temperature Sensor
Dual Switchable Excitation Current Sources
GENERAL DESCRIPTION
The AD7719 is a complete analog front end for low frequency
measurement applications. It contains two high resolution sigma-
delta ADCs, switchable matched excitation current sources,
low-side power switches, digital I/O port, and temperature
sensor. The 24-bit main channel with PGA accepts fully differen-
tial, unipolar, and bipolar input signal ranges from 1.024 ×
REFIN1/128 to 1.024 × REFIN1. Signals can be converted
directly from a transducer without the need for signal condi-
tioning. The 16-bit auxiliary channel has an input signal range
of REFIN2 or REFIN2/2.
The device operates from a 32 kHz crystal with an on-chip
PLL generating the required internal operating frequency. The
output data rate from the part is software programmable. The
peak-to-peak resolution from the part varies with the programmed
gain and output data rate.
The part operates from a single 3 V or 5 V supply. When oper-
ating from 3 V supplies, the power dissipation for the part is
4.5 mW with both ADCs enabled and 2.85 mW with only the
main ADC enabled in unbuffered mode. The AD7719 is housed
in 28-lead SOIC and TSSOP packages.
Low-Side Power Switches
Reference Detect Circuit
APPLICATIONS
Sensor Measurement
Temperature Measurement
Pressure Measurements
Weigh Scales
Portable Instrumentation
4–20 mA Transmitters
ISOURCE Select is a trademark of Analog Devices.
SPI and QSPI are trademarks of Motorola Inc.
MICROWIRE is a trademark of National Semiconductor Corporation.
FUNCTIONAL BLOCK DIAGRAM
MUX
AV
DD
IEXC1
200H9262A
IEXC2
200H9262A
AV
DD
AGND
BUF PGA
MUX1
TEMP
SENSOR
I/O PORT
AV
DD
MAIN CHANNEL
24-BIT H9018-H9004 ADC
AUXILIARY CHANNEL
16-BIT H9018-H9004 ADC
REFERENCE
DETECT
OSC. AND
PLL
SERIAL
INTERFACE
AND
CONTROL
LOGIC
DV
DD DGND
IOUT1
IOUT2
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AV
DD
AGND REFIN2 PWRGND P1/SW1 P2/SW2 P3 P4
DOUT
DIN
SCLK
CS
RDY
RESET
XTAL1 XTAL2REFIN1(+) REFIN1(–)
AD7719
MUX2