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DS90UB947-Q1: POWER ON TIMING

Athos Zhao
Expert 7320 points
Part Number: DS90UB947-Q1

Hi Expert,

Our customer is using 2 pieces of DS90UB947 with just one DC/DC power supply. 

They want to use MOSFET to control the power on timing as below diagram.

But our datasheet PAGE 71 says the power supply ramp of trVDDIO and trVDD11 need to higher than 200us.

They concern about the ramp would be less than 200us while using MOSFET.

Is the 200us necessary? Or are there any recommendation to realize the power on timing?

Thank you very much!

  • +1
    TI__Mastermind 33555 points

    Hi Athos,

    If the 200us rise time is not met, we cannot guarantee operation or behavior. It is important for the customer to meet these specs.

    Athos Zhao said:
    Or are there any recommendation to realize the power on timing?

    There are DC/DC converters with adjustable soft-startup that will allow rise time to be met. If the DC/DC converters don't have this feature, an RC network can be added to delay voltage rise. 

    Regards,

    Jack