REV. A

AD7675

–6–

PIN FUNCTION DESCRIPTIONS (continued)

Pin No.

Mnemonic

Type

Description

21

DATA[8]

DO

When SER/

PAR is LOW, this output is used as the Bit 8 of the Parallel Port Data Output Bus.

or SDOUT

When SER/

PAR is HIGH, this output, part of the serial port, is used as a serial data output

synchronized to SCLK. Conversion results are stored in an on-chip register. The AD7675

provides the conversion result, MSB first, from its internal shift register. The DATA

format is determined by the logic level of OB/

2C. In serial mode, when EXT/INT is LOW,

SDOUT is valid on both edges of SCLK. In serial mode, when EXT/

INT is HIGH: If

INVSCLK is LOW, SDOUT is updated on SCLK rising edge and valid on the next falling

edge. If INVSCLK is HIGH, SDOUT is updated on SCLK falling edge and valid on the next

rising edge.

22

DATA[9]

DI/O

When SER/

PAR is LOW, this output is used as the Bit 9 of the Parallel Port Data Output Bus.

or SCLK

When SER/

PAR is HIGH, this pin, part of the serial port, is used as a serial data clock input

or output, dependent upon the logic state of the EXT/

INT Pin. The active edge where the

data SDOUT is updated depends upon the logic state of the INVSCLK Pin.

23

DATA[10]

DO

When SER/

PAR is LOW, this output is used as the Bit 10 of the Parallel Port Data Output Bus.

or SYNC

When SER/

PAR is HIGH, this output, part of the serial port, is used as a digital output frame

synchronization for use with the internal data clock (EXT/

INT = Logic LOW). When a read

sequence is initiated and INVSYNC is LOW, SYNC is driven HIGH and remains HIGH

while SDOUT output is valid. When a read sequence is initiated and INVSYNC is HIGH,

SYNC is driven LOW and remains LOW while SDOUT output is valid.

24

DATA[11]

DO

When SER/

PAR is LOW, this output is used as the Bit 11 of the Parallel Port Data Output Bus.

or RDERROR

When SER/

PAR is HIGH and EXT/INT is HIGH, this output, part of the serial port, is used

as an incomplete read error flag. In slave mode, when a data read is started and not complete

when the following conversion is complete, the current data is lost and RDERROR is pulsed high.

25–28

DATA[12:15]

DO

Bit 12 to Bit 15 of the Parallel Port Data output bus. These pins are always outputs regardless

of the state of SER/

PAR.

29

BUSY

DO

Busy Output. Transitions HIGH when a conversion is started, and remains HIGH until the

conversion is complete and the data is latched into the on-chip shift register. The falling edge

of BUSY could be used as a data ready clock signal.

30

DGND

P

Must Be Tied to Digital Ground

31

RD

DI

Read Data. When

CS and RD are both LOW, the interface parallel or serial output bus is enabled.

32

CS

DI

Chip Select. When

CS and RD are both LOW, the interface parallel or serial output bus is

enabled.

CS is also used to gate the external serial clock.

33

RESET

DI

Reset Input. When set to a logic HIGH, reset the AD7675. Current conversion if any is aborted.

34

PD

DI

Power-Down Input. When set to a logic HIGH, power consumption is reduced and conver-

sions are inhibited after the current one is completed.

35

CNVST

DI

Start Conversion. If

CNVST is HIGH when the acquisition phase (t

falling edge on

CNVST puts the internal sample/hold into the hold state and initiates a

conversion. This mode is the most appropriate if low sampling jitter is desired. If

CNVST is

state and a conversion is immediately started.

36

AGND

P

Must Be Tied to Analog Ground

37

REF

AI

Reference Input Voltage

38

REFGND

AI

Reference Input Analog Ground

39

IN–

AI

Differential Negative Analog Input

43

IN+

AI

Differential Positive Analog Input

NOTES

AI = Analog Input

DI = Digital Input

DI/O = Bidirectional Digital

DO = Digital Output

P = Power