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  • TI Thinks Resolved

LM5107: High side driver not used, how to connect HI, HB and HS?

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Replies: 2

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Part Number: LM5107

Dear all,

I am using the LM5107 and LM5101AMR MOSFET drivers within a boost converter to drive the switching NMOS via the low side driver. The high side driver is not used at all. From time to time the driver fails and seems to be shorted internally. Connection of LI to GND helped a lot, also connection of HB to VDD and HS to GND.

What would be the most save and most recommended connections for LI, HB and HS if the high side switch is not used?

I appreciate your answer, thanks in advance!

  • Hello Tim,

    I am an applications engineer with the high power drivers product line in TI and will work to answer your questions. If you are not using the floating high side driver in the application, it is recommended to terminate the driver pins  in a configuration that does not leave the high side ground reference floating.

    Please see the attached drawing. In the text you mention the LI pin, HB and HS; but I assume since you are using the low side driver you are inquiring about the HI pin, HB and HS.

    As you suggested as helped in your circuit, the best method to terminate the unused high side driver is to connect the HI and HS pins to ground, and connect HB to VDD. There should be no risk of the high side driver false triggering from noise on the un-terminated input  or the HS, and HB pins floating to an unknown potential.

    Regards,

    Richard HerringLM5101A_Low Side Only.pdf

    Richard Herring

  • In reply to Richard Herring:

    Hi Richard,

    thank you very much for your quick reply and the schematic.

    Kind regards,

    Tim

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