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LM5175: direction of valley current sense

Shinichi Inoue
Guru 21686 points
Part Number: LM5175
Other Parts Discussed in Thread: LM5176

Dear Specialists,

My customer is considering LM5175 and has a question about valley current sensing.

I would be grateful if you could advise.

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Regarding the overcurrent protection during the step-down operation of the LM5175 and LM5176,

On the detection of the low side (the valley side of the inductor ripple current), is it effective for bidirectional flow?

(background)

In the condition where the capacitance of the output side capacitor is large (eg 2200 uF × 3 etc.)

If the reverse current flows from the output capacitor side to the GND through the detection resistor when using the CCM in the step-down operation mode to release the OVP, it is concerned that detection can not be performed.

In the worst case, we are worried that the parts of this route will not break.

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I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Guru* 78270 points
    Hi Shinichi,

    I see your concern. Actually it is not the case. The LM5175/75 decides its operating mode depend on the real time VOUT and VIN conditions. There will never be a case that the circuit only operates in buck mode when Vout is still higher than Vin. So, the boost peak current limit is still in play and the reverse current will not run away to cause damage.

    Hope this clarifies.

    Thanks,
    Youhao
  • 0 in reply to Youhao Xi
    Guru 21686 points
    Hi youhao,

    Thank you for your reply.

    I'll share your answer with the customer.

    If he has an additional question, I consult you again.

    I appreciate your great help.

    Best regards,
    Shinichi