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LM65680-Q1EVM: LM65680-Q1EVM

Wolfgang Klinger
Prodigy 30 points
Part Number: LM65680-Q1EVM
Other Parts Discussed in Thread: LM65680-Q1, LM65680

Tool/software:

Hi,

on the LM65680-Q1 EVM it is possible to switch from external to internal compensation.
The LM65680 data sheet states that the COMP pin must be connected to VCC for internal compensation.
But this is not possible on the evaluation board.
What are the consequences if the part is operated with internal compensation but the COMP pin cannot be connected to VCC?
Can the pin float in this case?

Thanks and regards

Wolfgang

  • +1
    TI__Guru 56345 points

    Hi Wolfgang,

    The LM65680-Q1 was setup to run at 400kHz so the EVM was configured for external compensation. It is possible to connected VCC to the COMP pin by connecting a short wire between the two pins.  

    Wolfgang Klinger said:
    What are the consequences if the part is operated with internal compensation but the COMP pin cannot be connected to VCC?
    Can the pin float in this case?

    The pin cannot float.

    Ben

  • 0 in reply to Ben C
    Prodigy 30 points

    Hi Ben,

    ok - so the evaluation board has a design error ...

    Thanks

    Wolfgang

  • +1 in reply to Wolfgang Klinger
    TI__Guru 56345 points

    Hi Wolfgang,

    No, the evaluation board was designed for 400kHz so external compensation was used. If the EVM was designed for 2MHz, then internal compensation would likely be used.

    Ben 

  • +1 in reply to Ben C
    Prodigy 30 points

    Hi Ben,

    In this case, however, there should be no jumper with which the level of the COMP pin can be changed, as there is no possibility of connecting the COMP pin to VCC.


    BTW is there a limit to the switching frequency above which internal or external compensation should be selected?

    Another question regarding the datasheet of the LM65680-Q1.Table 7-4 shows that connecting the DRSS/MODECOMM pin to VCC or leaving the pin unconnected leads both to the same behavior of DRSS and the Slew Rate Control.

    However, ‘Short to VCC’ contains a reference to a footnote that does not appear anywhere.
    What is meant by the reference (1)?

    Regards

    Wolfgang

  • +1 in reply to Wolfgang Klinger
    TI__Guru 56345 points

    Hi Wolfgang,

    Wolfgang Klinger said:
    BTW is there a limit to the switching frequency above which internal or external compensation should be selected?

    There is no limit but external compensation allows the user to have greater flexibility in adjusting the loop bandwidth and phase margin.

    Wolfgang Klinger said:

    Another question regarding the datasheet of the LM65680-Q1.Table 7-4 shows that connecting the DRSS/MODECOMM pin to VCC or leaving the pin unconnected leads both to the same behavior of DRSS and the Slew Rate Control.

    However, ‘Short to VCC’ contains a reference to a footnote that does not appear anywhere.
    What is meant by the reference (1)?

    Thanks for catching that issue. We will fixed the issue once the part is released to full production. The reference refers to: "This configuration is only valid for single-phase operation."

    Ben

  • +1 in reply to Ben C
    TI__Guru 56345 points

    Hi Wolfgang,

    If there are no further questions, please close the thread by clicking on "resolved" to my last post. Thanks!

    Ben