Data Sheet

AD7490

Rev. D | Page 7 of 28

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS

AD7490

TOP VIEW

(Not to Scale)

28

27

26

NC

4

25

AGND

24

23

22

AGND

21

CS

20

DIN

19

NC

18

17

SCLK

16

DOUT

15

NC = NO CONNECT

ALL NC PINS SHOULD BE

CONNECTED STRAIGHT TO AGND

Figure 3. 28-Lead TSSOP Pin Configuration

NOTES

1. NC = NO CONNECT. ALL NC PINS

SHOULD BE CONNECTED STRAIGHT

TO AGND.

2. CONNECT EXPOSED PAD TO GND

AD7490

TOP VIEW

(Not to Scale)

1

2

NC

3

AGND

4

5

6

AGND

7

CS

8

DIN

24

23

22

21

20

19

18

17

NC

NC

Figure 4. 32-Lead LFCSP Pin Configuration

Table 4. Pin Function Descriptions

Pin No.

Mnemonic

Description

TSSOP

LFCSP

20

18

CS

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

conversions on the AD7490 and also frames the serial data transfer.

23

21

Reference Input for the AD7490. An external reference must be applied to this input. The

voltage range for the external reference is 2.5 V ± 1% for specified performance.

22

20

14, 21, 24

12, 19, 22

AGND

Analog Ground. Ground reference point for all circuitry on the AD7490. All analog/digital input

signals and any external reference signal should be referred to this AGND voltage. All AGND pins

should be connected together.

13 to 5,

3 to 1,

28 to 25

11 to 9,

7 to 2,

31 to 26,

24

Analog Input 0 through Analog Input 15. Sixteen single-ended analog input channels that are

multiplexed into the on chip track-and-hold. The analog input channel to be converted is

selected by using the address bits ADD3 through ADD0 of the control register. The address bits,

in conjunction with the SEQ and SHADOW bits, allow the sequence register to be programmed.

via the RANGE bit in the control register. Any unused input channels should be connected to

AGND to avoid noise pickup.

19

17

DIN

Data In. Logic input. Data to be written to the control register of the AD7490 is provided on this

input and is clocked into the register on the falling edge of SCLK (see the Control Register

section).

15

13

DOUT

Data Out. Logic output. The conversion result from the AD7490 is provided on this output as a

serial data stream. The bits are clocked out on the falling edge of the SCLK input. The data

stream consists of four address bits indicating which channel the conversion result corresponds

to, followed by the 12 bits of conversion data, which is provided by MSB first. The output coding

can be selected as straight binary or twos complement via the CODING bit in the control

register.

16

14

SCLK

Serial Clock. Logic input. SCLK provides the serial clock for accessing data from the part. This

clock input is also used as the clock source for the conversion process of the AD7490.

17

15

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

interface of the AD7490 operates.

N/A

EP

EPAD

Exposed Pad. Connect exposed pad to GND.