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DAC8775: Switching Frequency

PY (Pengyu) Song
Expert 5860 points
Part Number: DAC8775

Hi team,

  • What is the switching frequency for the DCDC Converter inside the DAC8775?
  • Do the switching frequency depend upon the Output mode (Voltage or Current) and/or the Range selected? 
  • Any guidance from TI, on how much longer a trace (15mil wide) from the DAC pins to the DC-DC Inductor can be tolerated on the PCB? Or since LN and LP pins will be connecting to the 100uH inductor, there isn't any stringent requirement on the trace which contributes some parasitic inductance only? 
  • +1
    TI__Guru* 97465 points

    PY


    There isn't a simple description of the switching frequency I can find for the state machine that drives the switching of the buck-boost. From the design reviews I was able to find, the switching depends on several factors such as the DAC output mode, the PVDD voltage and the load. For the latter two factors, this is mostly from whether the device is acting as a buck or a boost converter.

    Based on some of the original measurements that I found, I think the range of the apparent DC-DC ripple is from about 20kHz to 1MHz with the largest ripple at low load or no load conditions.


    Joseph Wu

  • +1 in reply to Joseph Wu
    TI__Guru* 97465 points

    PY,

    Also, we don't have much guidance on the trace length that can be tolerated from the device pins to the inductor. Looking at the trace width of 15mils and standard copper weights an inch of length is still in the low tens of uH. I would guess that that length would be acceptable.

    Joseph Wu