AD9834 help required!

[saurabh17g]

I am planning to select the registers FSELECT and PSELECT using software. So what do i need to connect to the pins Fselect(pin no. 9) and pselect(pin no 10) is it DVDD or DGND or AVDD or AGND. According to pg no 7, they have mentioned that we can connect these pins to vdd or gnd. it sounds confusing.
Is it that these pins should be connected to ground through a resistance of 10k (refer the circuit diagram given on pg 29)?

Do i need to build separate power supply for AVDD and DVDD or one power supply with output of 5V is enough?

 

[NickS]

Datasheet Page 1:
The device operates with a power supply from 2.3 V to 5.5 V.
The analog and digital sections are independent and can be run
from different power supplies, for example, AVDD can equal
5 V with DVDD equal to 3 V.

From what I read on pages 1, 7 and 16 the reason they give you separate analog and digital power inputs is merely a convenience. Both can operate on the same range input. However supplying the lower voltage (3v) to the digital section means that the internal regulator(2.5v) does not have to drop as far. Also if you are concerned with noise on the power then you may choose to separate them for better isolation/performance(perhaps).

All that said you should re-read page 25. It clearly discusses the how to tie your grounds together at one point(star ground). And it specifies how to handle decoupling for the single input situation.

FSELECT and PSELECT are part of the digital operations so you connect them to DGND through a 10k pull down resistor. Are you familiar with the concept of pull-up and pull down resistors?

Hope that helps.