AD5781 hardware and software setup

Hi,

1) No need to use a pull-down resistor between LDAC and GND. Are you going to use a microcontroller to communicate with the DAC? May I know the configuration of the digital lines' output? is it push-pull or open-drain?

2) If you do not plan to use /CLR pin, I highly suggest to tie this pin to IOVCC pin.

3) Yes you are correct, a value must be programmed on the DAC register before changing the output to normal operating mode if you want a predetermined output value once it goes to normal mode. 

Hope this helps!

Cheers,

Ivan

Hi, Ivan:

Thank you so much!

That is really helpful. I plan to use a Pic18f4553 to control the DAC.

I have another technical problem, I am wondering if you or someone could please help me to figure it out or not: suppose I have loaded the DAC register, then I load the control register to make it work under normal mode, here is the question: will the Vout automatically be set to the the DAC register determined value right after the control register is updated, or I have to control LDAC from high to low to activate the Vout after the control register is updated .

again, thank you a lot

Peter

Hi,

one more thing:

 I am also considering other DACs, but some DACs' package is 24-Lead LFCSP_VQ. it is very hard to use in a prototype, and it is also difficult to find a 24-Lead LFCSP_VQ to DIP adapter. is there anyone who knows how to solve such a problem.

Thank you

Peter

Hi Peter,

1)Write DAC register values 

2) pull LDAC pin to low or issue software LDAC (always low is also an option, please refer to page 20 of the datasheet for complete details)

3) set to normal mode

By doing this, you should expect that the output goes to the equivalent output voltage of the DAC register sent in step 1.

Do you mean it's difficult to install LFCSP packages on boards? I do agree that it is challenging, but you may want to check this thread with a video link on how to hand solder a LFCSP device. May I also know which 24-lead LFCSP DAC you are referring to?

Cheers,

Ivan

same problem i am not getting otput out_volage_raw (ushing ad5781 driver )