参数资料
型号: AD7746
厂商: ANALOG DEVICES INC
元件分类: 温度/湿度传感器
英文描述: DIGITAL TEMP SENSOR-SERIAL, 24BIT(s), 2Cel, RECTANGULAR, SURFACE MOUNT
封装: MO-153AB, TSSOP-16
文件页数: 1/17页
文件大小: 232K
代理商: AD7746
24-bit Capacitance to Digital Converter
with Temperature Sensor
Preliminary Technical Data
AD7745/AD7746
Rev. PrF, 3. March 2005
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
registered trademarks are the property of their respective companies.
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
2005 Analog Devices, Inc. All rights reserved.
FEATURES
Capacitance to Digital Converter (CDC)
Standard One Chip Solution
Interfaces to Single or Differential Floating Sensors
Resolution: 20 aF (i.e. 19-bit) at 16.6 Hz
Accuracy: 2 fF
Linearity: 0.01%
Input Range: ±4 pF
Offset / Common Capacitance Removal: up to 17 pF
Update rate: 5 Hz to 90 Hz
Simultaneous 50 Hz and 60 Hz rejection at 16.6 Hz
Tolerant of ground capacitance and ground leakage
current
Temperature sensor on chip
Resolution: 0.1°C, accuracy: ±2°C
Voltage input channel
Internal clock oscillator
2-Wire Serial Interface (I2C-Compatible)
Power
2.7 V to 5.25 V Single-Supply Operation
1 mA Current Consumption
Operating temperature: -40°C to +125°C
Package: 16-lead TSSOP
APPLICATIONS
Automotive, Industrial and Medical Systems for:
Pressure Measurement
Position Sensors
Level Sensors
Flowmeters
Humidity Sensors
Impurity Detection
GENERAL DESCRIPTION
The AD7745/AD7746 is a high-resolution Σ capacitance to
digital converter (CDC). The capacitance to be measured is
connected directly to the device inputs. The architecture
features inherent high resolution (24-bit no missing codes,
19-bit effective resolution at 16.6 Hz data rate), high linearity
(±0.01%) and high accuracy (±2 fF factory calibrated).
The AD7745/AD7746 capacitance input range is ±4 pF
(changing), while it can accept up to 17 pF absolute capacitance
(not changing), which is compensated by an on-chip digital to
capacitance converter (CAPDAC).
The AD7745 has one capacitance input channel, while the
AD7746 has two channels. Each channel can be configured as
single ended or differential. The AD7745/AD7746 is designed
for floating capacitive sensors. For capacitive sensors with one
plate connected to ground, the AD7747 is recommended.
The parts have an on-chip temperature sensor with resolution
of 0.1°C and accuracy of ±2°C. The on-chip voltage reference
and the on-chip clock generator eliminate the need for any
external components in most capacitive sensor applications.
The parts have a standard voltage input, which together with the
differential reference input allows easy interface to an external
temperature sensor, such as an RTD, thermistor or diode.
The AD7745/AD7746 has a 2-wire, I2C compatible serial
interface. Both parts operate from a single 3 V or 5 V power
supply. They are specified over the automotive temperature
range of -40°C to +125°C and are housed in a 16-lead TSSOP
package.
FUNCTIONAL BLOCK DIAGRAMS
Figure 1.
Figure 2.
CLOCK
GENERATOR
TEMP
SENSOR
EXC1
MUX
DIGITAL
FILTER
SCL
SDA
VDD
24-BIT
Σ-
MODULATOR
I2C
SERIAL
INTERFACE
CAP DAC
EXCITATION
AD7746
CIN1(+)
CIN1(-)
CAP DAC
VIN(+)
VIN(-)
GND
EXC2
RDY
CIN2(+)
CIN2(-)
CONTROL LOGIC
CALIBRATION
GND
REFIN(+)
REFIN(-)
VOLTAGE
REFERENCE
CLOCK
GENERATOR
TEMP
SENSOR
EXCA
MUX
DIGITAL
FILTER
SCL
SDA
VDD
24-BIT
Σ-
MODULATOR
I2C
SERIAL
INTERFACE
CAP DAC
EXCITATION
AD7745
CIN1(+)
CIN1(-)
CAP DAC
VIN(+)
VIN(-)
GND
REFIN(+)
REFIN(-)
EXCB
CONTROL LOGIC
CALIBRATION
RDY
VOLTAGE
REFERENCE
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