AD7796/AD7797

Data Sheet

Rev. B | Page 8 of 24

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

NC = NO CONNECT

1

2

3

4

5

6

7

8

CLK

CS

NC

NC

AIN(–)

AIN(+)

SCLK

NC

16

15

14

13

12

11

10

9

DOUT/RDY

REFIN(–)

REFIN(+)

NC

GND

DIN

TOP VIEW

(Not to Scale)

AD7796/

AD7797

Figure 5. Pin Configuration

Table 5. Pin Function Descriptions

Pin No.

Mnemonic

Description

1

SCLK

Serial Clock Input. This serial clock input is for data transfers to and from the ADC. The SCLK has a Schmitt-

triggered input, making the interface suitable for opto-isolated applications. The serial clock can be continuous

with all data transmitted in a constant train of pulses. Alternatively, it can be a noncontinuous clock with the

information being transmitted to or from the ADC in smaller batches of data.

2

CLK

Clock In/Clock Out. The internal clock can be made available at this pin. Alternatively, the internal clock can be

disabled, and the ADC can be driven by an external clock. This allows several ADCs to be driven from a

common clock, allowing simultaneous conversions to be performed.

3

CS

Chip Select Input. This is an active low logic input used to select the ADC. CS can be used to select the ADC in

systems with more than one device on the serial bus or as a frame synchronization signal in communicating

with the device. CS can be hardwired low, allowing the ADC to operate in 3-wire mode with SCLK, DIN, and

DOUT used to interface with the device.

4

NC

No Connect.

5

AIN(+)

Analog Input. AIN(+) is the positive terminal of the differential analog input pair AIN(+)/AIN(−).

6

AIN(−)

Analog Input. AIN(−) is the negative terminal of the differential analog input pair AIN(+)/AIN(−).

7

NC

No Connect.

8

NC

No Connect.

9

REFIN(+)

Positive Reference Input/Analog Input. An external reference can be applied between REFIN(+) and REFIN(–).

10

REFIN(−)

Negative Reference Input/Analog Input. REFIN(−) is the negative reference input for REFIN. This reference input

11

NC

No Connect.

12

GND

Ground Reference Point.

13

Supply Voltage, 2.7 V to 5.25 V.

14

Digital Interface Supply Voltage. The logic levels for the serial interface pins are related to this supply, which is

15

DOUT/RDY

Serial Data Output/Data Ready Output. DOUT/RDY serves a dual purpose. It functions as a serial data output

pin to access the output shift register of the ADC. The output shift register can contain data from any of the on-

chip data or control registers. In addition, DOUT/RDY operates as a data ready pin, going low to indicate the

completion of a conversion. If the data is not read after the conversion, the pin goes high before the next

update occurs.

The DOUT/RDY falling edge can be used as an interrupt to a processor, indicating that valid data is available.

With an external serial clock, the data can be read using the DOUT/RDY pin. With CS low, the data/control word

information is placed on the DOUT/RDY pin on the SCLK falling edge and is valid on the SCLK rising edge.

16

DIN

Serial Data Input. This serial data input accesses the input shift register on the ADC. Data in this shift register is

transferred to the control registers within the ADC; the register selection bits of the communication register

identify the appropriate register.