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LM73100EVM: Digital Switch

Marc
Prodigy 30 points
Part Number: LM73100EVM

Hi,

I wanted to change the OVP of U2 on LM73100EVM but did not get the result, please help to see what i had missed out for the below 6 steps?

1) Tested the default settings on EVM and is working for OVP=13.76V using R17=191K.

2) Using the Overvoltage Formula below with R14=2M, i calculated R17=113K  for OVP=22V (Vov).

Vov=1.2*[(2M+113K)/113K]

3) I replaced R17 from 191K to 113K on the EVM.

4) Connected Power Supply input to EVM and slowly increased 1V per step beginning from 3V.

5) When the Power Supply voltage level passes the default UV=10.84V setting, i can see LM73100 start to conduct power.

6) When the Power Supply voltage increased to 15V, i noticed the Power Supply voltage dropped to zero and maximum current was drawn (looks like short circuit).

Whereas I was expecting LM73100 continue to conduct power until the Power Supply voltage input reached 22V. 

Thank you,

  • 0
    TI__Guru 55300 points

    Hi Mark,

    I think TVS D18 went into breakdown.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 30 points

    Thanks Kunal,

    I removed D18 and proceed to test the LM73100EVB (Load Switch) and noticed the below issues:

    1) The Overvoltage (OV), Undervoltage (UV) and Power Good (PG) LED of LM73100EVB are working when it receives 20mA from the Power Supply. But when the Power Supply current is set to output 1A to LM73100EVB to retest OV UV and PG, the Load Switch cannot turn on (OV, UV and PG do not work), is there a setting for the Load Switch to work at high current 1A, 2A or 3A?

     

    2) For OV test:

    - Power Supply current is set to output 20mA to the Load Switch.

    - On LM73100EVB the J2 is jumper at pin1-2 for C6=3300pF.

    After the Power Supply exceed the OV=13.76V and voltage level is decrease to 12v and 11v, the Load Switch cannot recover on its own (cannot auto switch on). But the Load Switch can auto recover if the J2 jumper is used on pin3-4 or pin5-6 option (refer to picture below). May i know the reason if this is normal or otherwise?

     

    Below shows the Jumper settings of LM73100EVB when testing with Channel 1:

    Thank you

  • 0 in reply to Marc
    TI__Guru 55300 points

    Hi Mark,

    In you testing are you some load at output?

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 30 points

    Hello Kunal,

    Yes, the EVB board is connected to an Electronic Load (set at Continuous Current Mode) to simulate our device.

    Regards,

    Mark

  • 0 in reply to Marc
    TI__Guru 55300 points

    Okay. How much is load current?

  • 0 in reply to Kunal Goel
    Prodigy 30 points

    Hi Kunal,

    When i set Load Current to draw 10mA, the Load Switch can work.

    However when i set Load Current to accept 1A, the Load Switch cannot turn on.

    Regards,

    Mark

  • +1 in reply to Marc
    TI__Guru 55300 points

    Hi Marc,

    ELOAD in CC mode is not recommended to use with eFuse. Please use CR load.

    Regards

    Kunal Goel