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DS90UH947-Q1: Internal Oscillator Range with no Ext PCLK

Kevin Schmidgall
Expert 4000 points
Part Number: DS90UH947-Q1

Hi,

I am trying to understand the internal oscillator setting when  auto-switch is enabled in "PCLK Auto" (bit 1 of 0x03) 

If PCLK is not externally present does the internal oscillator default to the OSC Clock Source set in 0x14 or does it set its internal timing based off the configuration settings of horizontal and vertical width, back porch, etc like for pattern generation?

Additionally, what is the range of internal oscillator? It looks like 25MHz - 100MHz.

  • 0
    TI__Mastermind 28680 points

    Hi Kevin,

    Thank you for posting your question. I will need a bit of time to look up the appropriate information. But I will definitely post a response by this Friday.

  • 0
    TI__Mastermind 28680 points

    Hi Kevin,

     

    If no external PCLK is present and “PCLK Auto” (0x03[1]) is set to 1, then the internal oscillator automatically selected will be the OSC Clock Source (0x14[2:1]). The frequency of the OSC Clock Source depends on its register value. The possible frequencies are set at 25MHz (11), 50MHz (00 or 01), and 100MHz (10).

     

    The programmable oscillator frequency of the Pattern Generator is only used for basic testing and debugging.

     

    Best,

    Justin Phan

  • 0
    TI__Mastermind 28680 points

    Hi Kevin,

    After running a test setup, I was able to confirm that bits 0x14[2:1] do not affect the Forward Channel frequency. These bits are for modifying the BIST clock frequency only. This is a typo in the datasheet, which will need to be revised. The functional test I performed shows that the automatically selected PCLK is set at 33MHz.

    Best,

    Justin Phan