Preliminary Technical Data

AD7747

Rev. PrC| Page 7 of 20

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS

TOP VIEW

(Not to Scale)

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

AD7747

CIN1(+)

SCL

RDY

SHLD

TST

CIN1(

REFIN(

REFIN(+)

NC

SDA

NC

VDD

GND

NC

VIN(+)

VIN(

Figure 3. AD7747 Pin Configuration (16-Lead TSSOP)

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 to for shielding the connection between the sensor and CIN. See the max allowed capacitance. 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 in Differential Mode. This pin is internally disconnected in single-ended CDC

configuration. If not used, this pin should be left as an open circuit.

8

CIN1(+)

CDC capacitive input (in single ended mode) or positive capacitive input (in differential mode). The measured

capacitance is connected between one of the CIN pins 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.