Data Sheet

AD7951

Rev. A | Page 9 of 32

Pin No.

Mnemonic

Type1

Description

11, 12

D[0:1] or

DI/O

In parallel mode, these outputs are used as Bit 0 and Bit 1 of the parallel port data output bus.

DIVSCLK[0:1]

Serial Data Division Clock Selection. In serial master read after convert mode (SER/PAR = high,

EXT/INT = low, RDC/SDIN = low) these inputs can be used to slow down the internally generated serial

data clock that clocks the data output. In other serial modes, these pins are high impedance outputs.

13

D2 or

DI/O

In parallel mode, this output is used as Bit 2 of the parallel port data output bus.

EXT/INT

Serial Data Clock Source Select. In serial mode, this input is used to select the internally generated

(master) or external (slave) serial data clock for the AD7951 output data.

When EXT/INT = low, master mode; the internal serial data clock is selected on SDCLK output.

When EXT/INT = high, slave mode; the output data is synchronized to an external clock signal (gated

by CS) connected to the SDCLK input.

14

D3 or

DI/O

In parallel mode, this output is used as Bit 3 of the parallel port data output bus.

INVSYNC

Serial Data Invert Sync Select. In serial master mode (SER/PAR = high, EXT/INT = low). This input is used

to select the active state of the SYNC signal.

When INVSYNC = low, SYNC is active high.

When INVSYNC = high, SYNC is active low.

15

D4 or

DI/O

In parallel mode, this output is used as Bit 4 of the parallel port data output bus.

INVSCLK

In all serial modes, invert SDCLK/SCCLK select. This input is used to invert both SDCLK and SCCLK.

When INVSCLK = low, the rising edge of SDCLK/SCCLK are used.

When INVSCLK = high, the falling edge of SDCLK/SCCLK are used.

16

D5 or

DI/O

In parallel mode, this output is used as Bit 5 of the parallel port data output bus.

RDC or

Serial Data Read During Convert. In serial master mode (SER/PAR = high, EXT/INT = low) RDC is used to

select the read mode. Refer to the Master Serial Interface section.

When RDC = low, the current result is read after conversion. Note the maximum throughput is not

attainable in this mode.

When RDC = high, the previous conversion result is read during the current conversion.

SDIN

Serial Data In. In serial slave mode (SER/PAR = high EXT/INT = high) SDIN can be used as a data input to

daisy-chain the conversion results from two or more ADCs onto a single SDOUT line. The digital data

level on SDIN is output on SDOUT with a delay of 16 SDCLK periods after the initiation of the read sequence.

17

OGND

P

Input/Output Interface Digital Power Ground. Ground reference point for digital outputs. Should be

connected to the system digital ground ideally at the same potential as AGND and DGND.

18

OVDD

P

Input/Output Interface Digital Power. Nominally at the same supply as the supply of the host interface

2.5 V, 3 V, or 5 V and decoupled with 10 μF and 100 nF capacitors.

19

DVDD

P

Digital Power. Nominally at 4.75 V to 5.25 V and decoupled with 10 μF and 100 nF capacitors. Can be

supplied from AVDD.

20

DGND

P

Digital Power Ground. Ground reference point for digital outputs. Should be connected to system

digital ground ideally at the same potential as AGND and OGND.

21

D6 or

DO

In parallel mode, this output is used as Bit 6 of the parallel port data output bus.

SDOUT

Serial Data output. In all serial modes this pin is used as the serial data output synchronized to SDCLK.

Conversion results are stored in an on-chip register. The AD7951 provides the conversion result, MSB

first, from its internal shift register. The data format is determined by the logic level of OB/2C.

When EXT/INT = low (master mode), SDOUT is valid on both edges of SDCLK.

When EXT/INT = high (slave mode):

When INVSCLK = low, SDOUT is updated on SDCLK rising edge.

When INVSCLK = high, SDOUT is updated on SDCLK falling edge.

22

D7 or

DI/O

In parallel mode, this output is used as Bit 7 of the parallel port data output bus.

SDCLK

Serial Data Clock. In all serial modes, this pin is used as the serial data clock input or output, dependent

on the logic state of the EXT/INT pin. The active edge where the data SDOUT is updated depends on

the logic state of the INVSCLK pin.