This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS22964C: tps22964

Part Number: TPS22964C
Other Parts Discussed in Thread: TPS22953

Hi,

My question is about the maximum load capacitance - I'm going to connect the switch to SSD connector with 150uF on its pins. Will the inrush current effect the switch input dip? And how to avoid the input power dip?

Regards,

Youry

  • Hi Youri,

    Welcome to E2E!

    The inrush current that occurs when enabling the switch onto a discharged can be characterized by multiplying the slew rate (dV/dt) times the output capacitance. The TPS22964C has a long rise time which helps mitigate the inrush current to avoid having an excessive voltage drop on the power supply. In order to calculate the inrush current would you be able to share the input voltage range on this application?

    The voltage drop on the power supply is caused by the supply not being able to supply a high transient current. Since the TPS22964C doesn't have adjustable slew rate I would suggest increasing the input capacitance (1-1 ratio if possible) to help further mitigate the voltage dip since the transient current will now be supplied from the input capacitors and not directly from the power supply.

    Let me know if there's any questions.

    Best regards,

    Andy Robles

  • Thank you, Andy,

    The input voltage range is 3.3V +-5%.

    1-1 ratio - do you mean if I have 150uF load capacitance, also Cin should be the same?

    Regards,

    Youry

  • Hi Youri,

    That would be correct. A 1-1 ratio would help mitigate the voltage dip seen on the power supply since the input capacitance would supply some of that transient inrush current, but in your case scenario it might not be needed.

    A VIN = 3.3V the load switch has a typical rise time of 715us. Our rise time is measure from 10% of VOUT to 90% of VOUT so from 0.33V to 2.97V when VIN = 3.3V making the change in voltage 2.64V in 715us. When plugged into the inrush current equation [ I = Cout * (dV/dt) ] you would see about 550mA from inrush current. Since this inrush current is not very high I doubt there will be much of a voltage dip on the supply.

    If they do encounter a voltage dip during testing the only way to minimize that voltage dip would be increase the input capacitance or change devices to one with a longer rise time to further mitigate the inrush current.

    Best regards,

    Andy Robles

  • Thank you Andy,

    Can you recommend the device with a longer rise time?

    Youry

  • Hi Youri,

    A similar device with low RON and adjustable rise time through the CT pin would be the TPS22953, but this device would not have QOD. Is QOD a requirement in this application? What are other features required from the load switch in this application?

    The TPS22953 is an alternative, but I don't predict there will be any problems with the input voltage dipping when using TPS22964C.

    Best regards,

    Andy Robles

  • Thank you, Andy

    I will take TPS22953 into consideration.

    Youry

  • Hi Youri,

    Do let me know if there's anymore questions on either device. If it's a different question than the one on this thread feel free to create a new post and tag the device in question.

    Best regards,

    Andy Robles