AD7328

Data Sheet

Rev. C | Page 8 of 36

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

1

2

3

4

5

6

7

8

9

10

20

19

18

17

16

15

14

13

12

11

DIN

DGND

AGND

REFIN/OUT

CS

DGND

DOUT

SCLK

AD7328

TOP VIEW

(Not to Scale)

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 AD7328 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, 19

DGND

Digital Ground. Ground reference point for all digital circuitry on the AD7328. The DGND and AGND

voltages should ideally 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 AD7328. All analog input signals

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

should ideally 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

AD7328. The nominal internal reference voltage is 2.5 V, which appears at the pin. A 680 nF capacitor

should be placed on the reference pin. Alternatively, the internal reference can be disabled and an

external reference can be applied to this input. On power-up, the external reference mode is the default

condition (see the Reference section).

6

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

7, 8, 14, 13, 9, 10,

12, 11

Analog Input 0 to Analog Input 7. 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 bits, ADD2

through ADD0, in the control register. The inputs can be configured as eight single-ended inputs, four

true differential input pairs, four pseudo differential inputs, or seven pseudo differential inputs. The

configuration 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

registers. 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 Reference section).

15

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

16

Analog Supply Voltage, 2.7 V to 5.25 V. This is the supply voltage for the ADC core on the AD7328.

17

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

18

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 three channel identification bits, the sign bit, and 12 bits of conversion data.

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

20

SCLK

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

AD7328. This clock is also used as the clock source for the conversion process.