AD7933/AD7934

Rev. B | Page 10 of 32

Pin No.

Mnemonic

Description

20

WR

Write Input. Active low logic input used in conjunction with CS to write data to the control register.

21

RD

Read Input. Active low logic input used in conjunction with CS to access the conversion result. The conversion

result is placed on the data bus following the falling edge of RD read while CS is low.

22

CS

Chip Select. Active low logic input used in conjunction with RD and WR to read conversion data or write data to

the control register.

23

AGND

Analog Ground. This is the ground reference point for all analog circuitry on the AD7933/AD7934. All analog input

signals and any external reference signal should be referred to this AGND voltage. The AGND and DGND voltages

should ideally be at the same potential and must not be more than 0.3 V apart, even on a transient basis.

24

Reference Input/Output. This pin is connected to the internal reference and is the reference source for the ADC.

The nominal internal reference voltage is 2.5 V, and this appears at this pin. It is recommended to decouple the

25 to

28

Analog Input 0 to Analog Input 3. Four analog input channels that are multiplexed into the on-chip track-and-

hold. The analog inputs can be programmed as four single-ended inputs, two fully differential pairs, or two pseudo

differential pairs by appropriately setting the MODE bits in the control register (see Table 10). Select the analog

input channel to be converted either by writing to Address Bit ADD1 and Address Bit ADD0 in the control register

prior to the conversion, or by using the on-chip sequencer. The input range for all input channels can either be 0 V

and CODING bits in the control register. To avoid noise pickup, connect any unused input channels to AGND.