AD7745ARUZ-REEL Analog Devices Inc, AD7745ARUZ-REEL Datasheet - Page 24

• Manufacturer Part Number: AD7745ARUZ-REEL
• Description: IC,Converter, Other/Special/Miscellaneous,TSSOP,16PIN
• Manufacturer: Analog Devices Inc
• Type: Capacitance-to-Digital Converterr

Specifications of AD7745ARUZ-REEL

• Design Resources: Extending the Capacitive Input Range of AD7745/AD7746 (CN0129)
• Resolution (bits): 24 b
• Data Interface: Serial
• Voltage Supply Source: Single Supply
• Voltage - Supply: 2.7 V ~ 5.25 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Sampling Rate (per Second): -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD7745/AD7746
If the capacitive sensor can be considered to be at the same
temperature as the AD7745/AD7746 chip, the internal
temperature sensor can be used as a system temperature sensor.
That means the complete system temperature drift
compensation can be based on the AD7745/AD7746 internal
temperature sensor without need for any additional external
components. See the typical performance characteristics in
Figure 18.
EXTERNAL TEMPERATURE SENSOR
The AD7745/AD7746 provide the option of using an external
transistor as a temperature sensor in the system. The ∆V
method, which is similar to the internal temperature sensor
method, is used. However, it is modified to compensate for the
serial resistance of connections to the sensor. Total serial
resistance (R
The VIN(–) pin must be grounded for proper external
temperature sensor operation.
The AD7745/AD7746 are factory calibrated for
Transistor 2N3906 with the ideality factor n
See the typical performance characteristics shown
in Figure 19.
TYPICAL APPLICATION DIAGRAM
2N3906
TEMPERATURE
∆V
EXTERNAL
SENSOR
BE
Figure 41. Transistor as an External Temperature Sensor
R
R
S1
S2
S1
+ R
VIN (+)
VIN (–)
S2
in Figure 41) up to 100 Ω is compensated.
CIN1(+)
CIN1(–)
VIN(+)
VIN(–)
EXCA
EXCB
MODULATOR
GENERATOR
REFERENCE
24-BIT Σ-∆
VOLTAGE
CLOCK
V
DD
SENSOR
TEMP
CAP DAC
CAP DAC
EXCITATION
Figure 43. Basic Application Diagram for a Differential Capacitive Sensor
f
SCALING
DIGITAL
= 1.008.
FILTER
AND
MUX
REFIN(+) REFIN(–)
DATA
MODULATOR
GENERATOR
24-BIT Σ-∆
BE
CLOCK
Rev. 0 | Page 24 of 28
VDD
DIGITAL
REFERENCE
FILTER
VOLTAGE
CONTROL LOGIC
CALIBRATION
VOLTAGE INPUT
The AD7745/AD7746 Σ-Δ core can work as a high resolution
(up to 21 ENOB) classic ADC with a fully differential voltage
input. The ADC can be used either with the on-chip high
precision, low drift, 1.17 V voltage reference, or an external
reference connected to the fully differential reference input pins.
The voltage and reference inputs are continuously sampled by a
Σ-Δ modulator during the conversion. Therefore, the input
source impedance should be kept low. See the application
example in Figure 42.
V
Along with converting external voltages, the AD7745/AD7746
Σ-Δ ADC can be used for monitoring the V
voltage from the VDD pin is internally attenuated by 6.
GND
AD7745
DD
R
Figure 42. Resistive Temperature Sensor Connected to the Voltage Input
REF
R
INTERFACE
MONITOR
T
0.1µF
SERIAL
I
2
RTD
C
REFIN(+)
REFIN(–)
+
VIN(+)
VIN(–)
10µF
SDA
SCL
RDY
10kΩ
ANALOG TO DIGITAL CONVERTER
MODULATOR
10kΩ
GENERATOR
24-BIT Σ-∆
CLOCK
3V/5V
POWER SUPPLY
SYSTEM
HOST
VDD
(ADC)
GND
REFERENCE
DIGITAL
DD
FILTER
VOLTAGE
voltage. The
DATA