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TPS25942A: About the condition of Reverse Current Protection

Tao_2199
Genius 5770 points

Hello,

 

Regarding to reverse current protection on TPS25942, my customer is asking a question.

According to 9.3.5 Reverse Current Protection(datasheet page 25), input reverse blocking current can block by fast reverse comparator.

( it is needed more than typical -238mA . (–10 mV/ 42mΩ))

But according to application report (SLVA811A : Figure 12.page 14), if using two TPS25942 for power MUXing,

then when the primary supply is disconnected, reverse current will be able to flow through the master device.

In this case, how should I understand? Could you please tell me more detail?

If reverse current is less than -235mA, is it will able to flow through master device?

 

 

Regards,

Tao2199

  • 0
    TI__Guru** 105361 points
    Hi Tao,

    Typical reverse current of 238mA (for short interval <3us) is needed to establish reverse voltage of 10mV for detection and turn-off the device. When the primary supply is disconnected, the output cap charges the input cap and helps to establish spiky reverse current for a short interval. But, in this process, if reverse current is less than -235mA, the device remains in ON position.
    We will take action to modify the sentences in the documents for clarity.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    Genius 5770 points

    Hello Rakesh,

     

    Thank you for reply.

    I have additional question.

    When the primary supply is disconnected, will reverse current be able to block by parasite diode

    on internal FET?

    It seems that it will be able to block from Simplified Schematic. (datasheet,page1)

    What is different between behavior of parasite diode and fast reverse comparator?

     

    Regards,

    Tao2199

  • 0 in reply to Tao_2199
    TI__Guru** 105361 points
    Hi Tao,

    The fast reverse comparator turns OFF the FET circled in your post and then the parasite diode block the reverse current flow.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    Genius 5770 points
    Hello Rakesh,

    Thank you for everything!
    I cuold make it clear and have informed to my customer.

    Regards,
    Tao2199