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AD5320 DAC has no output

Hi ADIexpert

My customer is using AD5320 as a DAC to output different voltage for its motor control application

however, no output was found (always 0V at the Vout) for different data 

please see the SPI diagram from MCU and schematic below

Ch1: x1 probe for sync signal

Ch2: x10 probe for data signal

Ch3: x10 probe for clk signal

Ch4: x1 probe for Vout

also, please see the schematic below

The Vcc2 and Vcc is 5V . We have also tried to bypass U8 and change Vcc2 and Vcc to 3.3V and wired the SPI signals from MCU directly to AD5320, but the result was still the same.

I am wondering if the SCLK has any lower bound limit for sclk freq? I can only see the upper bound limit of 30Mhz from datasheet and my customer was operating at the rather low speed ( around 300Khz)

Any advice is appreciated

thank you

Ken

  • Hi ,

    300kHz should be fine.

    Can you please confirm if the signals were measured at the same net where the pins of AD5320 are connected to? For example, Channel 3 is indeed measured at point where pin 5 is connected and not in SCK.

    Are SYNC1 and SYNC2 connected to the controller? It seems to me that it's always pulled high in the schematic, just want to make sure.

    Can you try to change the mode of operation to different power modes to check if it responds by measuring the output resistance? That is with R30 and R35 removed.

    Cheers,

    Ivan

  • Hi Ivan

    thanks for the suggestion, the sync signal was connected to MCU as you can see from the waveform that sync was pulled low when data was going to transmit from MCU.

    I will ask customer to check if the behavior is correct for different DB13 and DB12 setting

    I will update the result to you ASAP.

    Again, thank you for the prompt response

    Ken