3 V/5 V, ± ±1 V ꢀInpu ꢁRIꢂg, ± ꢃm
3-ChRIIgl ±6-Biu, SiꢂꢃR-DgluR ADC
AD7717
FUNCTIONAL BLOCK DIAGRAM
FEATURES
DV
AV
DD
DD
REF IN(–)
REF IN(+)
Charge balancing ADC
AD7707
16 bits, no missing codes
0.003ꢀ nonlinearity
CHARGE
BALANCING
A/D CONVERTER
High level ( 10 V) and low level ( 10 mV) input channels
True bipolar 100 mV capability on low level input
Channels without requiring charge pumps
Programmable gain front end
Gains from 1 to 128
3-wire serial interface
AIN1
AIN2
Σ-Δ
MODULATOR
BUF
PGA
MUX
LOCOM
30kΩ
5kΩ
A = 1 ≈ 128
AIN3
DIGITAL FILTER
VBIAS
5kΩ
SPI, QSPI™, MICROWIRE™ and DSP compatible
Schmitt trigger input on SCLK
Ability to buffer the analog input
2.7 V to 3.3 V or 4.75 V to 5.25 V operation
Power dissipation 1 mW at 3 V
15kΩ
30kΩ
HICOM
SERIAL INTERFACE
REGISTER BANK
SCLK
CS
MCLK IN
DIN
CLOCK
GENERATION
Standby current 8 μA maximum
20-lead SOIC and TSSOP packages
MCLK OUT
DOUT
GENERAL DESCRIPTION
AGND
DGND
DRDY RESET
Figure 1.
The AD7707 is a complete analog front end for low frequency
measurement applications. This 3-channel device can accept
either low level input signals directly from a transducer or high
level (±±0 V) signals and produce a serial digital output. It employs
a Σ-Δ conversion technique to realize up to ±6 bits of no missing
codes performance. The selected input signal is applied to a
proprietary programmable gain front end based around an analog
modulator. The modulator output is processed by an on-chip
digital filter. The first notch of this digital filter can be pro-
grammed via an on-chip control register allowing adjustment
of the filter cutoff and output update rate.
for 3-wire operation. Gain settings, signal polarity and update
rate selection can be configured in software using the input
serial port. The part contains self-calibration and system calibra-
tion options to eliminate gain and offset errors on the part itself
or in the system.
CMOS construction ensures very low power dissipation, and the
power-down mode reduces the standby power consumption to
20 μW typical. This part is available in a 20-lead wide body (0.3
inch) small outline (SOIC) package and a low profile 20-lead TSSOP.
PRODUCT HIGHLIGHTS
The AD7707 operates from a single 2.7 V to 3.3 V or 4.75 V to
5.25 V supply. The AD7707 features two low level pseudo differen-
tial analog input channels, one high level input channel and a
differential reference input. Input signal ranges of 0 mV to 20 mV
through 0 V to 2.5 V can be accommodated on both low level input
channels when operating with a VDD of 5 V and a reference of
2.5 V. They can also handle bipolar input signal ranges of ±20 mV
through ±2.5 V, which are referenced to the LCOM input. The
AD7707, with a 3 V supply and a ±.225 V reference, can handle
unipolar input signal ranges of 0 mV to ±0 mV through 0 V to
±.225 V. Its bipolar input signal ranges are ±±0 mV through ±±.225 V.
±. The AD7707 consumes less than ± mW at 3 V supplies and
± MHz master clock, making it ideal for use in low power
systems. Standby current is less than 8 μA.
2. On-chip thin-film resistors allow ±±0 V, ±5 V, 0 V to ±0 V,
and 0 V to 5 V high level input signals to be directly accom-
modated on the analog inputs without requiring split supplies
or charge-pumps.
3. The low level input channels allow the AD7707 to accept
input signals directly from a strain gage or transducer
removing a considerable amount of signal conditioning.
4. The part features excellent static performance specifications
with ±6 bits, no missing codes, ±0.003ꢀ accuracy, and low
rms noise. Endpoint errors and the effects of temperature
drift are eliminated by on-chip calibration options, which
remove zero-scale and full-scale errors.
The high level input channel can accept input signal ranges of ±±0 V,
±5 V, 0 V to ±0 V and 0 V to 5 V. The AD7707 thus performs all
signal conditioning and conversion for a 3-channel system.
The AD7707 is ideal for use in smart, microcontroller or DSP-
based systems. It features a serial interface that can be configured
Rev. B
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. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2000–2010 Analog Devices, Inc. All rights reserved.
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