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PIN ASSIGNMENTS

23

BUSY

BDGND

+VBD

DB0

DB1

DB2

DB3

DB4

DB5

DB6

DB7

BDGND

13 14

1

2

3

4

5

6

7

8

9

10

11

12

REFIN

REFOUT

COMMOUT

+VA

AGND

+IN

−IN

AGND

CAP1

+VAREG

NC

AGND

15 16 17 18

47 46 45 44 43

48

42

40 39 38

41

19 20 21 22

36

35

34

33

32

31

30

29

28

27

26

25

24

37

ADS8422

SLAS512B – JUNE 2006 – REVISED DECEMBER 2006

PFB Package

(Top View)

A.

NC - No connection

B.

Pins 9 and 13 are internally regulated 3-V outputs and are externally to be connected to decoupling capacitors only.

C.

+VAREG can be connected to a 3-V to 5-V supply.

D.

Pin 3 outputs REFIN/2

E.

Pin 38 can be used for ADC powerdown and pin 37 for analog output powerdown.

TERMINAL FUNCTIONS

NAME

NO

I/O

DESCRIPTION

5, 8, 12, 14,

AGND

–

Analog ground

15, 44, 45

BDGND

25, 35

–

Digital ground for bus interface digital supply

BUSY

36

O

Status output. High when a conversion is in progress.

Byte select input. Used for 8-bit bus reading.

BYTE

39

I

0: No fold back

1: Low byte D[7:0] of the 16 most significant bits is folded back to high byte of the 16 most significant pins DB[15:8].

This pin outputs REFIN/2 and can be used to set the common-mode voltage of the differential analog input, (+IN +

COMMOUT

3

O

–IN)/2.

CONVST

40

I

Convert start. This input is low true and can act independent of the CS input.

CS

42

I

Chip select.

CAP1, CAP2

9, 13

O

Decoupling of internally generated 3-V supply. Add 1-

µF capacitor from these pins to AGND.

8-BIT BUS

16-BIT BUS

Data Bus

BYTE = 0

BYTE = 1

BYTE = 0

DB15

16

O

D15 (MSB)

D7

D15 (MSB)

DB14

17

O

D14

D6

D14

DB13

18

O

D13

D5

D13

DB12

19

O

D12

D4

D12

DB11

20

O

D11

D3

D11

DB10

21

O

D10

D2

D10

7

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