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TUSB8041: Questions for TUSB8041 Powering On Timing Issues

Jacky Wang(QD)
Genius 11530 points
Part Number: TUSB8041

Hi Experts,

When you checking into the TUSB8041 datasheet regarding to power-up timing, we state that if only one capacitor connected from GRSTz pin to GND, the VDD must be stable minimum of 10us before the VDD33. But if you look at our EVM design, we generated the VDD from VDD3.3 by LDO, and we also only connected one capacitor on GRSTz pin, so is there any problem in here?

EVM design schematic:

 

  • 0
    TI__Guru 60870 points
    Hi Jacky,

    The datasheet is very conservative. As long as 3.3V and 1.1V rails ramp simultaneously there is no issue using an external capacitor on GRSTz. We tightened the requirement in the datasheet when we found some customer applications where there was a significant delay between 3.3V and 1.1V ramp or the ramp time was very slow and we saw insufficient power on reset timing.

    Regards,
    JMMN