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TPS22916: for USB current limit switch

Howard Zou
Genius 12365 points
Part Number: TPS22916
Other Parts Discussed in Thread: TPS2553,

Hi,

my customer was using TPS2553 as 500mA USB current limit switch.

They need the reverse current blocking function which TPS2553 can't meet.

Case1: When they power VCC with 5V, they can observe 5V at VOUT. And then they connect VOUT to a 5V source, then power down VCC. They can still see 5V               at VIN, which is not wanted.

Case2: If they directly connect VOUT to 5V source when VCC is powered down at first, they will not see 5V at VIN.

They need the current limit switch to turn off the MOSFET at case1.

But none of the device in power interface team can meet the requirement.

Do any device of load switch can meet the requirement?

Besides, TPS2553 will limit the output current to 500mA when the load exceeds 500mA. But it seems that load switch device will cut off the MOSFET when the load exceeds, and the threshold is above 500mA.

  • 0
    TI__Genius 10855 points

    Hi Howard,

    Thanks for reaching out on E2E!

    Unfortunately, our power switch devices such as the TPS22916 will exhibit the same behavior. If the EN/ON pin is connected high to VIN, a power switch will exhibit case 1 behavior.

    Let me try to explain the scenario and offer a potential solution:

    With any output capacitance, the output voltage will remain high if VIN is removed. Since the gate of the TPss9216 hasn't had a chance to fully turn off (since ON is connected to VIN and not pulled down to GND), the input will follow the output through the body diode and remain high, leaving VIN up. This feeds back into the EN/ON pin, keeping the gate high, and keeps the cycle going. However, in this case, reverse current blocking will still function and prevent reverse current from flowing from VOUT to VIN if it passes -500mA.

    The way to avoid this would be to let VIN drop below VIL before removing VIN. Since the TPS22916 has a smart pull-down on the ON pin if VON drops below VIL, the input would be pulled to GND and disable the TPS22916. Then, the input would not follow the output. Otherwise, the only other way to prevent VOUT reflected on VIN is by having a separate enable signal on the ON pin.

    Thanks,

    Arthur Huang

    To find the latest information on Power Switches, visit www.ti.com/powerswitch

    Please click "This resolved my issue" button if this post answers your question.