2
LC MOS
16-Bit A/D Converter
a
AD7701
FEATURES
Monolithic 16-Bit ADC
FUNCTIO NAL BLO CK D IAGRAM
AVDD DVDD AVSS DVSS
15
SC1
4
SC2
17
0.0015% Linearity Error
14
7
6
On-Chip Self-Calibration Circuitry
Program m able Low -Pass Filter
0.1 Hz to 10 Hz Corner Frequency
0 V to +2.5 V or ؎2.5 V Analog Input Range
4 kSPS Output Data Rate
Flexible Serial Interface
AD7701
CALIBRATION
CALIBRATION
SRAM
13
CAL
MICROCONTROLLER
16-BIT A/D CONVERTER
AIN
9
12
11
BP/UP
SLEEP
Ultralow Pow er
6-POLE GAUSSIAN
LOW-PASS
DIGITAL FILTER
ANALOG
MODULATOR
VREF
10
APPLICATIONS
Industrial Process Control
Weigh Scales
Portable Instrum entation
Rem ote Data Acquisition
AGND
DGND
8
5
20 SDATA
SCLK
CLOCK
GENERATOR
SERIAL INTERFACE
LOGIC
19
3
2
1
16
18
DRDY
CLKIN CLKOUT MODE
CS
GENERAL D ESCRIP TIO N
P RO D UCT H IGH LIGH TS
T he AD7701 is a 16-bit ADC which uses a sigma-delta conver-
sion technique. T he analog input is continuously sampled by an
analog modulator whose mean output duty cycle is proportional
to the input signal. T he modulator output is processed by an
on-chip digital filter with a six-pole Gaussian response, which
updates the output data register with 16-bit binary words at
word rates up to 4 kHz. T he sampling rate, filter corner fre-
quency and output word rate are set by a master clock input
that may be supplied externally, or by a crystal-controlled on-
chip clock oscillator.
1. T he AD7701 offers 16-bit resolution coupled with outstand-
ing 0.0015% accuracy.
2. No missing codes ensures true, usable, 16-bit dynamic range,
removing the need for programmable gain and level-setting
circuitry.
3. T he effects of temperature drift are eliminated by on-chip
self-calibration, which removes zero and gain error. External
circuits can also be included in the calibration loop to
remove system offsets and gain errors.
4. A flexible synchronous/asynchronous interface allows the
AD7701 to interface directly to UART s or to the serial ports
of industry-standard microcontrollers.
T he inherent linearity of the ADC is excellent, and endpoint
accuracy is ensured by self-calibration of zero and full scale
which may be initiated at any time. T he self-calibration scheme
can also be extended to null system offset and gain errors in the
input channel.
5. Low operating power consumption and an ultralow power
standby mode make the AD7701 ideal for loop-powered
remote sensing applications, or battery-powered portable
instruments.
T he output data is accessed through a flexible serial port, which
has an asynchronous mode compatible with UART s and two
synchronous modes suitable for interfacing to shift registers or
the serial ports of industry-standard microcontrollers.
CMOS construction insures low power dissipation, and a power
down mode reduces the idle power consumption to only 10 µW.
REV. D
© Analog Devices, Inc., 1996
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.
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