AD7323

Rev. 0 | Page 9 of 36

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

DGND

DOUT

SCLK

AD7323

TOP VIEW

(Not to Scale)

DIN

DGND

AGND

REFIN/OUT

CS

Figure 3. TSSOP Pin Configuration

Table 5. Pin Function Descriptions

Pin No.

Mnemonic

Description

1

CS

Chip Select. Active low logic input. This input provides the dual function of initiating conversions on

the AD7323 and frames the serial data transfer.

2

DIN

Data In. Data to be written to the on-chip registers is provided on this input and is clocked into the

register on the falling edge of SCLK (see the Registers section).

3, 15

DGND

Digital Ground. Ground reference point for all digital circuitry on the AD7323. The DGND and AGND

voltages ideally should be at the same potential and must not be more than 0.3 V apart, even on a

transient basis.

4

AGND

Analog Ground. Ground reference point for all analog circuitry on the AD7323. All analog input signals

and any external reference signal should be referred to this AGND voltage. The AGND and DGND

voltages ideally should be at the same potential and must not be more than 0.3 V apart, even on a

transient basis.

5

REFIN/OUT

Reference Input/Reference Output. The on-chip reference is available on this pin for use external to the

AD7323. The nominal internal reference voltage is 2.5 V, which appears at this pin. A 680 nF capacitor

should be placed on the reference pin (see the Reference section). Alternatively, the internal reference

can be disabled and an external reference applied to this input. On power-up, the external reference

mode is the default condition.

6

Negative Power Supply Voltage. This is the negative supply voltage for the analog input section.

7, 8, 10, 9

Analog Input 0 to Analog Input 3. The analog inputs are multiplexed into the on-chip track-and-hold.

The analog input channel for conversion is selected by programming the Channel Address Bit ADD1

and Bit ADD0 in the control register. The inputs can be configured as four single-ended inputs, two true

differential input pairs, two pseudo differential inputs, or three pseudo differential inputs. The config-

uration of the analog inputs is selected by programming the mode bits, Bit Mode 1 and Bit Mode 0, in

the control register. The input range on each input channel is controlled by programming the range

register. Input ranges of ±10 V, ±5 V, ±2.5 V, and 0 V to +10 V can be selected on each analog input

channel when a +2.5 V reference voltage is used (see the Registers section).

11

Positive Power Supply Voltage. This is the positive supply voltage for the analog input section.

12

Analog Supply Voltage, 2.7 V to 5.25 V. This is the supply voltage for the ADC core on the AD7323.

This supply should be decoupled to AGND.

13

Logic Power Supply Input. The voltage supplied at this pin determines at what voltage the interface

14

DOUT

Serial Data Output. The conversion output data is supplied to this pin as a serial data stream. The bits

are clocked out on the falling edge of the SCLK input, and 16 SCLKs are required to access the data. The

data stream consists of a leading ZERO, two channel identification bits, the sign bit, and 12 bits of

conversion data. The data is provided MSB first (see the Serial Interface section).

16

SCLK

Serial Clock, Logic Input. A serial clock input provides the SCLK used for accessing the data from the

AD7323. This clock is also used as the clock source for the conversion process.