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Original question:

DS90UB934-Q1: HSYNC/VSYNC signals not present

DS90UB934-Q1: some questions about schematic design

Arie Li
Expert 3390 points
Part Number: DS90UB934-Q1

Hi team,

I have some questions about 934 schematic design.

1. Customer only use RIN0 as input, so the SEL pin should be low. Since this pin already has a 25k internal pulldown resistor, can customer leave it floating? Or they need to pull it down by external resistor?

2. Similarly, how to connect the BISTEN pin if customer would like to control the BIST function by software? There is also an internal pulldown resistor. So should they leave it floating or pull down by external resistor?

3. Can customer add 0ohm resistor at the ROUT signal trace as below? Will it bring big impact on the signal quality? If the impact is not too much,  customer prefer to reserve these 0 ohm resistors on the PCB.

Thanks.

Arie

  • 0
    TI__Guru** 103215 points

    Hello Arie,

    For questions 1 and 2 it is recommended to use an external pulldown resistor to connect directly to GND in order to ensure the best EMI immunity vs. leaving the pins floating. For the 3rd question, it is possible to add the 0 ohm resistors but I would recommend using the smallest case size possible in order to ensure the trace impedance has minimal impact going through these components. 

    Best Regards,

    Casey