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DS90UB927Q-Q1: Power supply requirements for the the serializer

Alexis Magana Lemus
Intellectual 1395 points

Part Number: DS90UB927Q-Q1

Hi,

Currently have a design for the 927 serializer and looking at what is needed for the supply to power. Noticed that there is a supply noise max and wanted to see if this is tolerance of the device for ripple in the output of the supply? 

I see that the EVM and reference designs typically have a LDO for POL to the fpd-link device probably due to lack of switching noise and PSRR  however due wanting to consolidate the power rails and only need one device for the 3.3V looking to use a switching regulator. 

Please let me know if this is understood correctly.

Best regards,

  • 0
    TI__Mastermind 42240 points

    Hi Alexis,

    The tolerance for each power supply rails are ±5% and the maximum power supply noise that it can be tolerated is 100mVpp. I wouldn't consolidate the VDDIO and VDD33, and we recommended to use the LDO. If you want to use the switching regulator, it should be fine, but you need to ensure that the noise will not interfere to the device or high-speed path.

    Aaron

  • 0 in reply to Aaron Heng
    TI__Intellectual 1395 points

    Hi Aaron,

    Can you share more information on why VDDIO and VDD33 wouldn't want to consolidated as didn't notice this on the datasheet? 

    Thanks and best regards.

  • 0 in reply to Alexis Magana Lemus
    TI__Mastermind 42240 points

    Hi Alexis,

    Let me investigate this and I will get back with you by Wednesday.

    Aaron

  • 0 in reply to Aaron Heng
    TI__Mastermind 42240 points

    Hi Alexis,

    I would like to add more point to the your thread regarding the use of LDO or switching regulator. The FPD-Link products doesn't dictate the use of LDO or switching regulator. It depends on the application that you want to design in. When you use the LDO, it is more quite, but power dissipation maybe an issue here. You need to make sure that the LDO can handle the load of the chip.

    The VDD33 analog pin is use to power up the FPD-Link and the interface input. These power supply needs to be stable without disrupt from other power supply such as VDDIO.

    Aaron