AD7709

–9–

REV. PrA

January 2001

PRELIMINARY TECHNICAL DATA

11

REFIN2(-)

Negative reference input. This reference input can lie anywhere between GND

12

P2/SW2

GND or as a low-side power switch to PWRGND..

13

PWRGND

Ground point for the low-side power switches SW2 and SW1. PWRGND

must be tied to GND.

14

P1/SW1

or as a low-side power switch to PWRGND.

15

RESET

Digital input used to reset the ADC to its power-on-reset status. This pin has

16

SCLK

Serial clock input for data transfers to and from the ADC. The SCLK has a

schmitt triggered input making the interface suitable for opto-isolated applica-

tions. The serial clock can be continuous with all data transmitted in a con-

tinuous train of pulses. Alternatively, it can be noncontinuous clock with the

information being transmitted to or from the AD7709 in smaller batches of

data.

17

CS

Chip Select Input. This is an active low logic input used to select the

AD7709.

CS can be used to select the AD7709 in systems with more than one

device on the serial bus or as a frame synchronisation signal in communicating

with the device.

CS can be hardwired low allowing the AD7709 to be operated

in three-wire mode with SCLK, DIN and DOUT used to interface with the

device.

18

RDY

RDY is a logic low status output from the AD7709. RDY is low if the ADC

has valid data in its data register. This output returns high on completion of a

read operation from the data register. If data is not read,

RDY will return high

prior to the next update indicating to the user that a read operation should not

be initiated.

19

D O U T

Serial data output with serial data being read from the output shift register of

the ADC. The output shift register can contain data from any of the on-chip

data, calibration or control registers.

20

D I N

Serial Data Input with serial data being written to the input shift register on

the AD7709. Data in this shift register is transferred to the control registers

within the ADC depending on the selection bits of the Communications regis-

ter.

21

G N D

Ground Reference point for the AD7709.

22

Supply voltage, 3V or 5V nominal.

23

XTAL2

Output from the 32kHz crystal oscillator inverter.

24

XTAL1

Input to the 32kHz crystal oscillator inverter.