AD7933/AD7934

Preliminary Technical Data

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. This pin can be overdriven by an

external reference. The input voltage range for the external reference is 0.1 V to 3.5 V for differential mode and

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 to be four single ended inputs, two fully differential pairs or two

pseudo-differential pairs by setting the MODE bits in the control register appropriately (see Table 9). The

analog input channel to be converted can either be selected by writing to the address bits (ADD1 and ADD0) in

the control register prior to the conversion, or the on-chip sequencer can be used. The input range for all input

depending on the states of the RANGE and CODING bits in the control register. Any unsed input channels

should be connected to AGND to avoid noise pickup.

Rev. PrG | Page 10 of 32