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TPS628502: TPS628502 & LMR51610XDBVR

Kelvin Cheng
Prodigy 30 points

Part Number: TPS628502
Other Parts Discussed in Thread: TPS628501, TPS628301

Dear Sir/Madam,

 

I am using TPS628502 & LMR51610XDBVR in my new product, may I know if those DCDC convertor has any protection for reserve current? 

Thanks and Regards,

Kelvin

  • 0
    TI__Mastermind 26110 points

    Hello Kelvin,

    thanks for reaching out in E2E.

    Do you mean reverse current?

    If so, then no, the TPS628502 don't have a dedicated reverse current protection.

    The ESD diode of the SW pin would clamp reverse current to some extent, but VIN+0.3V is the absolute maximum rating for this clamp voltage.

    When the TPS628502 is operating in FPWM (MODE pin set to high) then it can regulate down a higher output voltage, but the current is limited by the low side FET current limit.

    When VIN is supplied but the EN pin is low on TPS628502 then the active output discharge resistance would bring down a small reverse supply.

    What conditions for reverse supply would you consider?

    The LMR51610XDBVR is supported by a different team. Please submit a separate E2E post, referencing this device. This will automatically forward the post to the right team.

    Best regards,

    Andreas.

  • 0
    Prodigy 30 points

    Hi Andreas, 

    Thanks for you quick response. 

    In my system, I have serval DCDC, such as 1pcs TPS6285018AQDRLRQ1, 1pcs TPS6285011HQDRLRQ1, 1pcs TPS6285010MQDRLRQ1 that connect to a same input 5V

    When there is a power loss in 5V, we are thinking if the reverse current will cause any problem. Also, even it is from the same 5V, we are not sure if the output stable time of those DCDC is the same and not sure if it will cause any problem. Could you please help to comment about that ?

    Thanks Kelvin 

  • 0
    TI__Mastermind 26110 points

    Hi Kelvin,

    if "power loss in 5V" means the common 5V rail is getting disconnected from the supply, then the three TPS628501 continue operating until the VUVLO is reached (ca. 2.6V) if the EN pins are connected to VIN. If the EN signals are controlled in a different way then the TPS628501 stop switching on which ever condition is reached first, EN < VEN,IL or VIN < VUVLO. Then the output discharge of each TPS628501 is getting activated and their outputs are getting discharged with ca. 100Ω. Ideally this keeps the output voltage of each TPS628501 below the input voltage. The minimum input voltage required for the discharge function to remain active typically is 2V. If the outputs are still not fully discharged then the remaining charge will deplete across the output load or partially across the body diode of the SW pins. I don't expect any issues with this scenario.

    The timing of the ramp down of each TPS628501 depends on the attached load and caps and on the voltage. So the timing might not be synchronous.

    If the EN pins are controlled in a way that they are getting disabled before the 5V is decreasing then all TPS628501 would stop simultaneously and discharge the outputs.

    We also have devices available with a higher output discharge current if needed. For example the TPS628301 would discharge the output with ca. 400mA.

    However, if "power loss in 5V" means sudden short between 5V VIN and GND then reverse current across the body diode of the high side FET might cause electrical over-stress and can damage the TPS628501. Such scenario should be avoided, as it can also damage the circuitry attached at the output side.

    Best regards,

    Andreas.

  • 0 in reply to Andreas Mueller
    Prodigy 30 points

    Hi Andreas,

    Power loss in 5V" means the common 5V rail is getting disconnected from the supply, or the Main AC supply is turned OFF

    In this case, that's mean we do not need to take care about the reverse current as the discharge function keep the output lower than the input voltage?

    Thanks 

    Kelvin

  • 0
    TI__Mastermind 26110 points

    Hi Kelvin,

    thanks for your feedback.

    Yes, I think there should be no issue. Even if the discharge stops at too low VIN, then the FET body diode can handle the relatively slow depleting of the outputs.

    Best regards,

    Andreas.

  • 0 in reply to Andreas Mueller
    Prodigy 30 points

    Hi Andreas,

    I am coming back to this topic.

    Do you have any idea/suggested method how to measure the reverse current and how to prove it has no issue on the IC?

    Best regards,

    Kelvin

  • 0
    TI__Mastermind 26110 points

    Hi Kelvin,

    you could measure the inductor current with a current probe. It is a little tricky setup, as you would have to add some wire in series to the inductor, where you can place the current probe around. If the concern is more a external reverse powering then the output could be probed (might be easier to add small cable for a current probe or a resistor for voltage drop measurement in series). 

    Best regards,

    Andreas.