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DAC088S085: initialization of the DAC088S085

Alan Bayko
Prodigy 60 points

Part Number: DAC088S085

Tool/software:

I am having a bit of trouble with the DAC088 part.  I am trying to set one of the outputs but I have not been able to get it to configure properly.  It might be in the configuration data I am sending the device.  The instructions I have been sending as a configuration are the following:

0x8000 set wrm mode

0xD000 disable power down mode

0xE000 

0xF000

Then to set output A to 1VDC I have been sending 

0x0064

Then to transfer to the output registers

0xA0FF

Vref is set at 2.54V.  The logic bus is at 3.3V. 

 

In the scope plot the red trace is sync, the blue trace is DIN and the yellow trace is SCLK.  The message is the 0xA0FF dacup update command

On the output seems to be around 60mV.  This is happening on multiple boards.  A 10k resistor to 3.3V pulls the output up by only 10mV so this looks like I am driving an output pulling the line to ground.

It is probably worth noting that this is happening on multiple boards.

  • +1
    TI__Mastermind 42253 points

    Hi Alan, 

    Is this happening on multiple boards as in some boards work as you expect, or it is happening on all boards?

    I assume all boards because you are not writing the correct data. 

    This is an 8-bit DAC, so code 100 is correct to get 1V with a 2.54V reference, but the data is left aligned in a 12-bit register. You need to shift your data left by 4 bits. The bottom 4 bits in the 12-bit register are ignored. You are really writing code 6 which does correspond to a 60mV output that you are seeing. 

    Best,

    Katlynne Jones