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Original question:

LM5060-Q1: OVP Seemingly Triggered by Driving EN Pin Low

LM5060-Q1: LM5060

Jason Petras
Intellectual 650 points
Part Number: LM5060-Q1
Other Parts Discussed in Thread: LM5060

Hello support, 

I would like to continue the conversation started by Froylan in the link below:

https://e2e.ti.com/support/power-management/f/196/t/818442?tisearch=e2e-sitesearch&keymatch=lm5060

I am seeing the same issue: The EN pin does not work near (but under) OVP = 2V. Instead, it works when OVP < 1.76V. I am expecting the EN pin to also work when 1.76V < OVP < 2.0V since OVP_th is 2.0V per the table in section 6.5 in the datasheet. 

OVP shutdown *does* work properly when OVP < 1.76V and then raised to OVP = 2.0V.  This is great!

Please confirm that EN does not work when 1.76V < OVP < 2.0V. Also, could you please update your datasheet to be very clear about this fact? It is a small, but important thing.  

Thank you !

Jason

  • 0
    TI__Guru** 105361 points

    Hi Jason,

    Thanks for reaching out!

    The max rising threshold of OVP is 2.12V to ensure that it shutdown for OVP event (considering process and temperature variation). Also, to release from OVP event, the OVP pin voltage has to drop below (2V-240mV) = 1.76V. Please refer Figure 12 in the datasheet.

    EN control does not work as long as the device stays in OVP event. I will take care to add a comment in next datasheet revision.

    BR, Rakesh

  • 0 in reply to Rakesh
    Intellectual 650 points

    Hi Rakesh

    Thanks for the quick reply!

    The issue I see is that EN does not work when OVP is above 1.76V and below 2.0V. I never reach OVP > 2.0V since I am using a bench supply and a controlled environment. Thus, I should not need to release from OVP state. I just cannot get EN to work when OVP is between 1.76V and 2.0V. Can you please confirm?

    Thanks!

    Jason

     

  • 0 in reply to Jason Petras
    TI__Guru** 105361 points

    Hi Jason,

    I would expect OVP to trigger anywhere between 1.88V to 2.12V. Can you please double check and confirm on the 1.76V threshold. Are you measuring using Digital multi-meter ? Is there any noise ?

    BR, Rakesh

  • 0 in reply to Rakesh
    Intellectual 650 points

    Hi Rakesh

    Yes, I can confirm the 1.76V threshold. I am using a bench supply and multimeter, both by Keysight. I can also confirm the 2.0V threshold because, once on, the device does OVP properly when OVP is 2.0V and reset at 1.76V - the reset voltage is the same as the voltage at which the EN locks out.

    Thoughts?

    Jason

  • 0 in reply to Jason Petras
    TI__Guru** 105361 points

    Hi Jason,

    Let me check at my end. Hope, you are measuring right across the device pins to avoid any ground shift effect.

    BR, Rakesh

  • 0 in reply to Rakesh
    TI__Guru** 105361 points

    Hi Jason,

    Your observation is correct. We need to look into the design to find the root cause. We will get back by middle of next week.

    What is your operating voltage range ? and desired VIN OVP cut-off threshold ?

    BR, Rakesh

  • 0 in reply to Rakesh
    Intellectual 650 points

    Hi Rakesh

    Thank you very much for testing! Also good news that the issue can be reproduced. My design has a OVP setting of 60V. This means that the enable pin is locked out at a little over VIN > 54V. UVLO is 16V. I use two separate voltage dividers.

    I understand that the part is not going to change. I can also solve this problem by raising OVP and changing some things downstream. That said, I would appreciate you confirming the issue and updating the data sheet to reflect this function.... of course, if you find a solution, I’d appreciate hearing about it too :)

    Thanks again Rakesh

    Jason

  • 0 in reply to Jason Petras
    TI__Guru** 105361 points

    Hi Jason

    We will root cause  the issue and keep you updated.

    BR, Rakesh

  • 0 in reply to Rakesh
    Intellectual 650 points

    Thank you Rakesh! Looking forward to hearing what you come up with

    Jason

  • 0 in reply to Jason Petras
    TI__Guru** 105361 points

    Hi Jason

    When the part is disabled (EN=0), the control logic shuts down all the internal circuit (including internal references) to minimize the quiescent current. When the part is re-enabled (EN=HIGH), the external OVP pin voltage has to be below the hysteresis voltage (1.88V-240mV = 1.64V) to keep the device out of OVP state. 

    In general, we have not faced any concern for LM5060 applications as the UVLO cut-off, nominal operating voltage and OVP cut-off are used well apart. I will take action to add comment in next datasheet revision.

    Please continue with your approach of raising OVP. Thanks! 

    BR, Rakesh

  • 0 in reply to Rakesh
    Intellectual 650 points

    Hi Rakesh, 

    Thank you for the clarification and the research! Well done!

    Jason