AD7745 Analog Devices, AD7745 Datasheet - Page 7

• Manufacturer Part Number: AD7745
• Description: 24-bit, 1 Channel Capacitance to Digital Converter
• Manufacturer: Analog Devices

Specifications of AD7745

• Resolution (bits): 24bit
• # Chan: 1
• Sample Rate: n/a
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: Diff-Uni,SE-Uni
• Ain Range: (2Vref) p-p,± 4 pF (Delta C)
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
Table 4. Pin Function Descriptions
Pin No.
1
2
3, 4
5, 6
7
8
9, 10
(AD7745)
9
(AD7746)
10
(AD7746)
11, 12
13
14
15
16
Figure 4. AD7745 Pin Configuration (16-Lead TSSOP)
Mnemonic
SCL
RDY
EXCA, EXCB
REFIN(+),
REFIN(–)
CIN1(–)
CIN1(+)
NC
CIN2(+)
CIN2(–)
VIN(+), VIN(–)
GND
VDD
NC
SDA
REFIN(+)
REFIN(–)
CIN1(+)
CIN1(–)
EXCA
EXCB
RDY
SCL
NC = NO CONNECT
1
2
3
4
5
6
7
8
(Not to Scale)
AD7745
TOP VIEW
Description
Serial Interface Clock Input. Connects to the master clock line. Requires pull-up resistor if not already
provided in the system.
Logic Output. A falling edge on this output indicates that a conversion on enabled channel(s) has been
finished and the new data is available. Alternatively, the status register can be read via the 2-wire serial
interface and the relevant bit(s) decoded to query the finished conversion. If not used, this pin should be left
as an open circuit.
CDC Excitation Outputs. The measured capacitance is connected between one of the EXC pins and one of the
CIN pins. If not used, these pins should be left as an open circuit.
Differential Voltage Reference Input for the Voltage Channel (ADC). Alternatively, the on-chip internal
reference can be used for the voltage channel. These reference input pins are not used for conversion on
capacitive channel(s) (CDC). If not used, these pins can be left as an open circuit or connected to GND.
CDC Negative Capacitive Input in Differential Mode. This pin is internally disconnected in single-ended CDC
configuration. If not used, this pin can be left as an open circuit or connected to GND.
CDC Capacitive Input (in Single-Ended Mode) or Positive Capacitive Input (in Differential Mode). The
measured capacitance is connected between one of the EXC pins and one of the CIN pins. If not used, this pin
can be left as an open circuit or connected to GND.
Not Connected. This pin should be left as an open circuit.
CDC Second Capacitive Input (in Single-Ended Mode) or Positive Capacitive Input (in Differential Mode). If not
used, this pin can be left open circuit or connected to GND.
CDC Negative Capacitive Input in Differential Mode. This pin is internally disconnected in a single-ended CDC
configuration. If not used, this pin can be left as an open circuit or connected to GND.
Differential Voltage Input for the Voltage Channel (ADC). These pins are also used to connect an external
temperature sensing diode. If not used, these pins can be left as an open circuit or connected to GND.
Ground Pin.
Power Supply Voltage. This pin should be decoupled to GND, using a low impedance capacitor, for example
in combination with a 10 µF tantalum and a 0.1 µF multilayer ceramic.
Not Connected. This pin should be left as an open circuit.
Serial Interface Bidirectional Data. Connects to the master data line. Requires a pull-up resistor if not provided
elsewhere in the system.
16
15
14
13
12
11
10
9
SDA
NC
VDD
GND
VIN(–)
VIN(+)
NC
NC
Rev. 0| Page 7 of 28
Figure 5. AD7746 Pin Configuration (16-Lead TSSOP)
REFIN(+)
REFIN(–)
CIN1(–)
CIN1(+)
EXCA
EXCB
RDY
SCL
NC = NO CONNECT
1
2
3
4
5
6
7
8
(Not to Scale)
AD7746
TOP VIEW
16
15
14
13
12
11
10
9
AD7745/AD7746
SDA
NC
VDD
GND
VIN(–)
VIN(+)
CIN2(–)
CIN2(+)