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AD7747
Rev. 0 | Page 7 of 28
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
05
46
9-
00
3
SCL
RDY
SHLD
TST
REFIN(+)
CIN1(–)
REFIN(–)
CIN1(+)
1
2
3
4
5
7
6
8
SDA
NC
VDD
GND
VIN(–)
VIN(+)
NC
16
15
14
13
12
11
10
9
AD7747
TOP VIEW
(Not to Scale)
NC = NO CONNECT
Figure 3. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
Mnemonic
Description
1
SCL
Serial Interface Clock Input. Connects to the master clock line. Requires pull-up resistor if not already provided
in the system.
2
RDY
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.
3
SHLD
Capacitive Input Active AC Shielding. To eliminate the CIN parasitic capacitance to ground, the SHLD signal
can be used for shielding the connection between the sensor and CIN. If not used, this pin should be left as an
open circuit.
4
TST
This pin must be left as an open circuit for proper operation.
5, 6
REFIN(+),
REFIN()
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.
7
CIN1()
CDC Negative Capacitive Input. The measured capacitance is connected between the CIN1() pin and GND. If
not used, this pin should be left as an open circuit.
8
CIN1(+)
CDC Positive Capacitive Input. The measured capacitance is connected between the CIN1(+) pin and GND. If not
used, this pin should be left as an open circuit.
9, 10
NC
Not Connected. These pins should be left as an open circuit.
11, 12
VIN(+), VIN()
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.
13
GND
Ground Pin.
14
VDD
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.
15
NC
Not Connected. This pin should be left as an open circuit.
16
SDA
Serial Interface Bidirectional Data. Connects to the master data line. Requires a pull-up resistor if not provided
elsewhere in the system.