AD7709 Datasheet, PDF (1/17 Pages) Analog Devices – 16-Bit Sigma Delta ADC with Current Sources, Switchable Reference Inputs and I/O Port

PRELIMINARY TECHNICAL DATA
a 16-Bit Sigma Delta ADC with Current Sources,
Switchable Reference Inputs and I/O Port
Preliminary Technical Data
AD7709
FEATURES
16-BIT SINGLE CHANNEL SIGMA DELTA-ADC
Factory Calibrated (field calibration not required)
Output settles in one conversion cycle (single conver
sion mode)
Programmable Gain Front End
16-bit No Missing Codes
13-bit Pk-Pk Resolution @ 20Hz, 20mV Range
16-bit Pk-PK Resolution @ 20Hz, 2.56V Range
INTERFACE
Three-Wire Serial
SPI^TM, QSPI^TM, MICROWIRE^TM and DSP Compatible
Schmitt Trigger on SCLK
POWER
Specified for Single 3V and 5V operation
Normal : 2mA @ 3V
Powerdown : 20uA (32kHz Crystal Running)
On-Chip Functions
Rail-to-Rail Input Buffer and PGA
Switchable Reference Inputs
3 Configurable Current Sources
Low Side Power Swtches
Digital I/O Port
GENERAL DESCRIPTION
The AD7709 is a complete analog front-end for low
frequency measurement applications. The 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. These 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.
The device operates from a 32kHz crystal with an on-
board PLL generating the required internal operating
frequency. The output data rate from the part is software
programmable. The pk-pk resolution from the part varies
with the programmed gain and output data rate.
The part operates from a single +3V or +5V supply.
When operating from +3V supplies, the power dissipation
for the part is XmW. The AD7709 are housed in a 24-
pin SOIC and TSSOP packages.
APPLICATIONS
Industrial Process Control
Instrumentation
Pressure Transducers
Portable Instrumentation
IOUT 1
FUNCTIONAL BLOCK DIAGRAM
VDD
REFIN2(+) REFIN1(+) REFIN2(-) REFIN1(-) XTAL1 XTAL2
I1
I2
I3
OSC.
&
PLL
IOUT 2
AIN1
AIN2
AIN3 / P3
AIN4 / P4
AINCOM
MUX
BUF
PGA
16-BIT
Σ−∆ ADC
SERIAL
INTERFACE
&
CONTROL
LOGIC
DOUT
DIN
SCLK
CS
RDY
RESET
AD7709
VDD
I/O PORT
GND
PWRGND
SW1/P1 SW2/P2
REV. PrA January 2001
® SPIand QSPI are a Registered Trademark of Motorola Inc.
® MICROWIRE is a Registered Trademark of National Semiconductor Corp.
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
which may result from its use. No license is granted by implication or
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© Analog Devices, Inc., 2001