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LM76005: Whether NC pin connect to GND or not

Shuhei Goto
Expert 3530 points
Part Number: LM76005
Other Parts Discussed in Thread: LM76002, LM76003

Hi-team,

In data sheet of LM76005, NC pin no.7 and 23 are demand to float in order to maximize distance from the high level voltage input to ground.

On the other hand, in LM76002 and LM76003, all NC pin are demand to connect to GND.

Why are these different?

Best regards,

  • 0
    TI__Mastermind 25526 points

    Hi Shuhei

    The NC pins are not internally connected, so it's ok both for LM76002/LM76005 to leave the pins open or connect to GND.  Just like the datasheet specified,  Connect the pins  to ground copper on PCB can improve heat-sinking of the device and board level reliability, while floating them can maximize the distance between adjacent pins.  If leave the pin-7/23 floating, it also helps maximizing the distance from high voltage point to ground.

    Thanks

  • 0 in reply to Gui He
    TI__Expert 3530 points

    Hi Gui-san,

    Thank you for reply.

    I understood difference between floating and connecting to GND.

    Please let me ask more. Is there reason why description about NC pin in data sheet is different LM76002/LM76005 ?

    Best regards,

  • +1 in reply to Shuhei Goto
    TI__Mastermind 25526 points

    Hi Shuhei

    There is no specific reason. It's ok to connect either way. I would say recommend leave pin no.7 and 23 floating for both LM76005 and LM76002/3.  But since LM76002/3 can operate under higher fsw like 2.2MHz. So if the fsw is high and you have concern about the thermal performance, connect pin no.7 and 23 to ground might be good choice to improve heat-sinking.

    Thanks