PRELIMINARY TECHNICAL DATA
16-Bit Sigma Delta ADC with Current Sources,
a
Preliminary Technical Data
SwitchableReferenceInputsandI/OPort
AD7709
FEATURES
G E NE R AL D E S C R IP T IO N
16-BIT SINGLE CHANNEL SIGMA DELTA-ADC
Factory Calibrated (field calibration not required)
Output settles in one conversion cycle (single conver
sion m ode)
Program m able Gain Front End
16-bit No Missing Codes
13-bit Pk-Pk Resolution @ 20Hz, 20m V Range
16-bit Pk-PK Resolution @ 20Hz, 2.56V Range
INTERFACE
T he AD7709 is a complete analog front-end for low
frequency measurement applications. T he AD7709
contains a 16-bit sigma delta ADC with PGA and can be
configured as 2 fully-differential input channels or 4
pseudo-differential input channels. Inputs signal ranges
from 20mV to 2.56V can be directly converted using the
AD7709. T hese signals can be converted directly from a
transducer without the need for signal conditioning. Other
on-chip features include three software configurable
current sources, switchable reference inputs, low side
power switches and a 4-bit digital I/O port.
Three-Wire Serial
SPITM, QSPITM, MICROWIRETM and DSP Com patible
Schm itt Trigger on SCLK
T he device operates from a 32kHz crystal with an on-
board PLL generating the required internal operating
frequency. T he output data rate from the part is software
programmable. T he pk-pk resolution from the part varies
with the programmed gain and output data rate.
POWER
Specified for Single 3V and 5V operation
Norm al : 2m A @ 3V
Pow erdow n : 20uA (32kHz Crystal Running)
On-Chip Functions
T he part operates from a single +3V or +5V supply.
When operating from +3V supplies, the power dissipation
for the part is XmW. T he AD7709 are housed in a 24-
pin SOIC and T SSOP packages.
Rail-to-Rail Input Buffer and PGA
Sw itchable Reference Inputs
3 Configurable Current Sources
Low Side Pow er Sw tches
Digital I/ O Port
APPLICATIONS
Industrial Process Control
Instrum entation
FUNC TIO NAL BLO C K D IAGRAM
REFIN2(+) REFIN1(+)
REFIN2(-) REFIN1(-)
XTAL1 XTAL2
VDD
Pressure Transducers
Portable Instrum entation
OSC
&
.
I2
I3
I1
PLL
IOUT 1
IOUT 2
DOUT
DIN
SERIAL
INTERFACE
&
CONTROL
LOGIC
AIN1
AIN2
16-BIT
Σ−∆ ADC
BUF
PGA
SCLK
CS
MUX
AIN3 / P3
AIN4 / P4
RDY
RESET
AINCOM
AD7709
VDD
I/O PORT
GND
PWRGND
SW1/P1 SW2/P2
®
SPIand QSPI are a Registered Trademark of Motorola Inc.
REV. PrA January 2001
® MICROWIRE is a Registered Trademark of National Semiconductor Corp.
Inform ation furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assum ed by Analog Devices for its
use, nor for any infringem ents of patents or other rights of third parties
which m ay result from its use. No license is granted by im plication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norw ood, MA 02062-9106, U.S.A.
Tel: 781/ 329-4700
World Wide Web Site: http:/ / w w w.analog.com
Analog Devices, Inc., 2001
Fax: 781/ 326-8703