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DS90UH940N-Q1: Proper Pulldown Resistor value and TVS-Diode selection guide

Part Number: DS90UH940N-Q1

Hello E2E team, 

My customer is drawing schematic of DS90UH940N-Q1 for new automotive project. 

Here's couple of questions from the customer.  

1. For Immunity against ESD shock, TVS diode on FPD-Link is being considered. Because it's high speed line, the TVS diode with 0.25pF capacitance would be used. Is it okay? What is the capacitance allowed for FPD-Link pin? Any recommendation?

2. Unused pin like GPIO or I2S needs to be connected to external pull-down resistor according to the datasheet. What is the proper value for the pull-down resistor?

Can all unused pins which needs external pulldown resistors be tied to one pull down together? Or, each pin needs its own pulldown resistor?  

Please answer. Thank you.

  • Hello Kenneth,

    For the ESD protection, 0.25pF is sufficient for 940N. Generally I would suggest using as low capacitance as possible.

    For the unused pin pulldowns, there is no hard requirement for the resistance but less than ~5k should be sufficient. It is to combine multiple unused pins for pulldown.

    Best Regards,
    Casey