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LM5069: Surge and Noise countermeasures for LM5069 (especially VIN-SENSE voltage)

Shinichi Inoue
Guru 20506 points
Part Number: LM5069
Other Parts Discussed in Thread: , TPS2663, TPS2660

Dear Specialists,

My customer is interested in LM5069 and has questions.

They'd like to know about about surge and noise countermeasures.

---

We plan to perform EMC tests such as lightning surge tests in our application.
We are considering LM5069 for that project.

According to the data sheet, when the voltage between the VIN-SENSE terminals exceeds 55mV, the FET is turned off and the current is cut off.
55mV is a quite small voltage, and I'm concerned that it may be susceptible to noise.

At that time, noise should not be used to erroneously detect the voltage between the VIN-SENSE terminals and turn off the FET.

The standards that need to be met are as follows
EN61000-6-2
EN61000-4-2
EN61000-4-3
EN61000-4-4
EN61000-4-5
EN61000-4-6
EN61000-4-8

Could you please let us know the materials for surge and noise countermeasures.
A reference design would be helpful.

Regarding surge, I could find the description in LM5069EVM-627, if you have more detailed information, please provide it.

As for noise, I think it is necessary to install with an external filter.
However, I could not find it in the related materials of LM5069.
Could you please provide related application note.

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Guru** 103736 points

    Hi Shinichi,

    Thanks for reaching out!

    The TIDA https://www.ti.com/lit/ug/tidu415/tidu415.pdf provides more information. We need reverse current blocking controller such as LM5050 to make a robust solution for surge protection.

    What are the system specifications (voltage, current) and end-application?

    TPS2663 is more optimized solution for surge protection. It can handle all the transients and can be scalable for higher currents by paralleling the devices as covered in application note https://www.ti.com/lit/an/slvaf13/slvaf13.pdf 

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Guru 20506 points

    Hi Rakesh,

    Thank you for your reply and sending the application note.

    I confirmed the application note(tidu415).
    There was no mention of noise standards.
    Is it possible to think the EN61000-4-1 to EN41000-4-8 standards can be satisfied?
    In other words, will the voltage between VIN and SENSE never exceed 55mV due to external noise and keep operation?

    Customer specifications are
    Vin 22-26V
    Iout 8A

    The TPS2660 has a built-in FET and is easy to use, but the rated current is insufficient.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • +1 in reply to Shinichi Inoue
    TI__Guru** 103736 points

    Hi Shinichi,

    We evaluate for three most common tests: System ESD Immunity (IEC 61000-4-2), Electrical Fast Transient Immunity (EFT) (IEC 61000-4-4), and Lightning/Surge Immunity (IEC 61000-4-5) defined in https://www.ti.com/lit/an/slva711/slva711.pdf 

    Looks like the other standards are related to EMI which would be able to pass with our devices because our devices doesn't do continuous switching like power switching converters.

    Shinichi Inoue said:
    In other words, will the voltage between VIN and SENSE never exceed 55mV due to external noise and keep operation?

    The voltage between VIN and SENSE will exceed 55mV for noise transients (EFT, Surge) and turns-off the MOSFET due to circuit breaker event. To support the load during this interval, we need to buffer capacitance at the output.  

    Shinichi Inoue said:

    Customer specifications are
    Vin 22-26V
    Iout 8A

    The TPS2660 has a built-in FET and is easy to use, but the rated current is insufficient.

    TPS2663 supports 6A, you can use two devices in parallel as covered in application note https://www.ti.com/lit/an/slvaf13/slvaf13.pdf 

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Guru 20506 points

    HI Rakesh,

    Thank you for your reply.

    Your comment

    We evaluate for three most common tests: System ESD Immunity (IEC 61000-4-2), Electrical Fast Transient Immunity (EFT) (IEC 61000-4-4), and Lightning/Surge Immunity (IEC 61000-4-5) defined in https://www.ti.com/lit/an/slva711/slva711.pdf 

    -> Has these test been performed on the LM5069EVM-627 or do these obtain the same results?

    Your comment

    The voltage between VIN and SENSE will exceed 55mV for noise transients (EFT, Surge) and turns-off the MOSFET due to circuit breaker event. 

    -> Does this comment indicate that the MOSFET turns off when performing Electrical Fast Transient Immunity (EFT) (IEC 61000-4-4), Lightning/Surge Immunity (IEC 61000-4-5)? .

    TPS2663 supports 6A, you can use two devices in parallel as covered in application note https://www.ti.com/lit/an/slvaf13/slvaf13.pdf 

    -> I'll share your suggestion with the customer.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • +1 in reply to Shinichi Inoue
    TI__Guru** 103736 points

    Hi Shinichi,

    The TIDA design, LM5069EVM-627 and TPS2663 can handle the transients. The difference is in performance. All these solutions turns off the output for transients but TPS2663 recovers fast which helps to meet Class A system performance for transients 

    Best regards,

    Rakesh 

  • 0 in reply to Rakesh
    Guru 20506 points

    Hi Rakesh,

    Thank you for your reply.

    (1) Which standard does class-A support? Does it mean the class of IEC61000-3-2? 

    (2) How does the TPS2663 detect current?
    The LM5069 judges by the potential difference of the external sense resistor, so I would like to know the difference.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • +1 in reply to Shinichi Inoue
    TI__Guru** 103736 points

    Hi Shinichi,

    Class A system performance means that the output says reliable for all the transients.  For fast transients, LM5069 would switch-off the output and would require large COUT to meet Class-A performance.

    Below information is from Page-10 https://www.ti.com/lit/an/slva711/slva711.pdf 

    TPS2663 eFuse uses FET current mirror circuits to detect the load current

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Guru 20506 points

    Hi Rakesh,

    Thank you for your reply.

    I understand the means of class A.

    The customer starts to consider TPS2663 because of the fast switching at surge event.

    So let's this thread.

    And then I'll ask TPS2663, could you please continue to support. 

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi