ADS8284

PIN FUNCTIONS (continued)

PIN

I/O

DESCRIPTION

NO

NAME

14

VCMO

O

This pin outputs REFIN/2 and can be used to set common-mode voltage of differential analog inputs.

15

BUF-REF

O

Buffered reference output. Useful to level shift bipolar signals using external resistors.

POWER CONTROL PINS

21

PD-RBUF

I

High on this pin powers down the reference buffer (BUF-REF).

MULTIPLEXER CONTROL PINS

33

AUTO

I

High level on this pin selects auto mode for multiplexer scanning. Low level selects manual mode of multiplexer scanning

In auto mode (AUTO = 1) multiplexer channel selection is reset to CH0 on rising edge of MXCLK while C3 = 1. The pin is do

34

C3

I

not care in manual mode.

Acts as multiplexer address bit when AUTO = 0 (manual mode). In auto mode (AUTO = 1) C2 and C1 select the last

35

C2

I

multiplexer channel (channel count) in the auto scan sequence.

Acts as multiplexer address LSB when AUTO = 0 (manual mode). In auto mode (AUTO = 1) C2 and C1 select the last

36

C1

I

multiplexer channel (channel count) in the auto scan sequence.

Multiplexer channel is selected on rising edge of MXCLK irrespective of whether it is auto or manual mode. Device BUSY

37

MXCLK

I

output can be connected to MXCLK so that device selects next channel at the end of every sample.

ADC DATA BUS

8-BIT BUS

16-BIT BUS

18-BIT BUS

42-49,

Data Bus

BYTE = 0

BYTE = 1

BYTE = 1

BYTE = 0

BYTE = 0

BYTE = 0

52-61

BUS18/16 = 0

BUS18/16 = 0

BUS18/16 = 1

BUS18/16 = 0

BUS18/16 = 1

BUS18/16 = 0

42

DB17

O

D17 (MSB)

D9

All ones

D17 (MSB)

All ones

D17 (MSB)

43

DB16

O

D16

D8

All ones

D16

All ones

D16

44

DB15

O

D15

D7

All ones

D15

All ones

D15

45

DB14

O

D14

D6

All ones

D14

All ones

D14

46

DB13

O

D13

D5

All ones

D13

All ones

D13

47

DB12

O

D12

D4

All ones

D12

All ones

D12

48

DB11

O

D11

D3

D1

D11

All ones

D11

49

DB10

O

D10

D2

D0 (LSB)

D10

All ones

D10

52

DB9

O

D9

All ones

All ones

D9

All ones

D9

53

DB8

O

D8

All ones

All ones

D8

All ones

D8

54

DB7

O

D7

All ones

All ones

D7

All ones

D7

55

DB6

O

D6

All ones

All ones

D6

All ones

D6

56

DB5

O

D5

All ones

All ones

D5

All ones

D5

57

DB4

O

D4

All ones

All ones

D4

All ones

D4

58

DB3

O

D3

All ones

All ones

D3

D1

D3

59

DB2

O

D2

All ones

All ones

D2

D0 (LSB)

D2

60

DB1

O

D1

All ones

All ones

D1

All ones

D1

61

DB0

O

D0 (LSB)

All ones

All ones

D0 (LSB)

All ones

D0 (LSB)

ADC CONTROL PINS

62

BUSY

O

Status output. This pin is held high when device is converting.

64

BUS18_16

I

Bus size select input. Used for selecting 18-bit or 16-bit wide bus transfer. Refer to ADC DATA BUS description above.

1

BYTE

I

Byte Select Input. Used for 8-bit bus reading. Refer to ADC DATA BUS description above.

2

CONVST

I

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

3

RD

I

Synchronization pulse for the parallel output.

4

CS

I

Chip select.

DEVICE POWER SUPPLIES

22

VEE

Negative supply for OPA (OP1, OP2)

23, 24

VCC

Positive supply for OPA (OP1, OP2, BUF-REF)

5, 7,

13, 38,

+VA

Analog power supply.

40

6, 12,

26, 39,

AGND

Analog ground.

41

50, 63

+VBD

Digital power supply for ADC bus.

10

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