AD9433 datasheet(19/20 Pages) AD

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AD9433

Rev. A | Page 19 of 20

A multilayer board is recommended to achieve best results. It is

highly recommended that high quality, ceramic chip capacitors be

used to decouple each supply pin to ground directly at the device.

The pinout of the AD9433 facilitates ease of use in the imple-

mentation of high frequency, high resolution design practices.

All of the digital outputs and their supply and ground pin

connections are segregated on one side of the package, with

the inputs on the opposite side for isolation purposes.

Care should be taken when routing the digital output traces.

To prevent coupling through the digital outputs into the analog

portion of the AD9433 (VCC, AIN, and VREF), minimal capacitive

loading should be placed on these outputs.

It is recommended that a fanout of only one gate be used for all

AD9433 digital outputs.

The layout of the encode circuit is equally critical and should be

treated as an analog input. Any noise received on this circuitry

results in corruption in the digitization process and lower over-

all performance. The encode clock must be isolated from the

digital outputs and the analog inputs.

REPLACING THE AD9432 WITH THE AD9433

The AD9433 is pin-compatible with the AD9432, although there

are two control pins on the AD9433 that are do not connect (DNC)

and supply (VCC) connections on the AD9432 (see Table 10).

Table 10. AD9432/AD9433 Pin Differences

AD9432

AD9433

APPLICATIONS INFORMATION

LAYOUT INFORMATION

DNC

DFS

VCC

SFDR MODE

Using the AD9433 in an AD9432 pin assignment configures the

AD9433 as follows:

•

The SFDR improvement circuit is enabled.

•

The DFS pin floats low, selecting twos complement coding

for the digital outputs. (Twos complement coding is the

only output coding available on the AD9432.)

Table 11 summarizes the differences between the AD9432 and

AD9433 analog and encode input common-mode voltages.

These inputs can be ac-coupled so that the devices can be used

interchangeably.

Table 11. AD9432/AD9433 Analog and Encode Input

Common-Mode Voltages

Input Pins

Common-Mode Voltage

AD9432

AD9433

ENCODE/ENCODE

1.6 V

3.75 V

AIN/AIN

3.0 V

4.0 V

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