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LM5113: LM5113 Rev. H Datasheet Concerns

Sean Moorman
Prodigy 20 points
Part Number: LM5113
Other Parts Discussed in Thread: , LMG1205

Hello,

In January 2018, TI updated the LM5113 datasheet from Rev. G to Rev. H. In addition to being labeled with NRND status, several new requirements were introduced that have a serious impact on existing products I have in the field. Could you please help me understand the following changes? Referencing the Rev. H datasheet "Revision History" section.

-CHANGED THE FIRST PAGE KEY GRAPHIC: I have circled in RED the change from Rev. G to Rev. H datasheet. Image attached.

-CHANGED THE FUNCTIONAL BLOCK DIAGRAM: I have circled in RED the change from Rev. G to Rev. H datasheet. Image attached.

-ADDED CONTENT TO THE START-UP AND UVLO SECTION: I have circled in RED the change from Rev. G to Rev. H datasheet. Image attached.


QUESTION 1: Why was this change made? Was the internal bootstrap diode found to be insufficient? We have been observing a problem with the bootstrap capacitor (1uF in our application) not being sufficiently charged at startup and the high side gate voltage not being sufficiently level shifted to saturate our high-side GaN FET (GS61008T). When we add the external diode and resistor as depicted in the newly revised Rev. H datasheet, our observed problem goes away. We have been chasing this problem for a long time, and this appears to be a fix. 

NOTE: Although you made these changes to the Simplified Application Diagram, Functional Block Diagram, and Start-up & UVLO sections, you have not updated this new requirement in the "Typical Application" circuit in Figure 18. If this is indeed a new requirement, it should be updated in the application circuit schematic as well to avoid customer confusion.

QUESTION 2: Does PN: LM5113-Q1 also require this external resistor + diode? The LM5113-Q1 is a new product and in the same foot print that we need (10-WSON, we want to avoid the DSBGA package of the new LMG1205). The current LM5113-Q1 datasheet does not mention this new requirement anywhere. Does that imply that the external diode and resistor are not required? Or have you not updated the LM5113-Q1 datasheet with this new requirement?

 

 

  • 0
    TI__Expert 3225 points
    Hello Sean,

    Thank you for the inquiry. Here is my answer to your question:

    Answer to Q1: Yes in the first page simplified diagram, we have updated it with an external boot strap diode. LM5113 is our first generation of GaN driver, and we are keeping improving its performance. Just to enhance the startup voltage charging on the boot cap, we suggest to have an external diode to achieve faster charging.

    Thanks for bringing up the discrepancy on Fig. 18. We will consider updating it as well.

    Answer to Q2: LM5113-Q1 has identical circuit design as LM5113, but it is a Q100 certified version. In your case, I would suggest have the same modification by adding external diode+resistor to help have better startup.

    Please let us know if you have any other questions.

    Thanks and regards,
    Lixing
  • 0 in reply to Lixing Fu
    Prodigy 20 points

    Hi Lixing,

    Thanks for the prompt reply. Let me restate the question/answer so my understanding is clear, please correct my statements if incorrect.

    Statement 1: The new external diode and resistor requirement was added to the LM5113 (Rev. H) datasheet to improve the bootstrap capacitor charging at startup.

    Statement 2: LM5113-Q1 also requires the external and resistor diode to improve the bootstrap capacitor charging at startup.

    Follow up Question 1: Since the LM5113 and LM5113-Q1 are the same circuit, can we expect LM5113-Q1 to become NRND, too? Is there a End of Life date for either LM5113 or LM5113-Q1? We like the 10-WSON package and last I heard there were no plans offer the LMG1205 in this package.

    Follow up Question 2: Does the new LMG1205 require the external bootstrap diode and resistor like the LM5113 and LM5113-Q? The datasheet for the LMG1205 looks like a copy and paste job from the LM5113 (Rev. G) datasheet. There is no mention of the external diode and resistor requirement in either of the most recent LMG1205 or LM5113-Q1 datasheets. Based on your answer to my original Question 2, it seems like the datasheet for the LM5113-Q1 should also be revised to include this new external diode requirement (since the LM5113 and LM5113-Q1 are identical circuits). Accuracy and attention to detail on datasheets is vital to our success.

    Thanks again.

  • 0 in reply to Sean Moorman
    TI__Expert 3225 points
    Hi Sean,

    Thanks for the detailed follow up. Your two statements are true, and to answer your following questions:

    Follow up Q1: LM5113-Q1 is an automotive version that we have, and we do not have a plan to NRND it. For both LM5113 and LM5113Q1, we do not have a plan to stop manufacture so they are not the end of the life. You can continue to use them. But sorry that we will not have a WSON package for LM1205.

    Follow up Q2: The LMG1205 is an upgrade version from LM5113, and contains all the improvements from LM5113. This means that you will not need an external diode to have better startup. We would recommend LMG1205 for use if the package suits for you. With smaller package, actually the performance of driver should be better in terms of parasitics.

    We really appreciate your detailed examination of our datasheets, and we should come up to necessary changes on LM5113 and LM5113-Q1 datasheets.

    Best regards,
    Lixing
  • 0 in reply to Lixing Fu
    Prodigy 130 points

    Lixing,

    During a design review of a new power board based on an old LM5113 based power board design, I noticed it they lack the bootstrap diode required in the latest LM5113 online datasheet.  Surprised that I missed this previously,  I carefully reviewed the both the LM5113 and LMG1205 datasheets - it appears the bootstrap diode specifications and graphics are identical.

    To me there is a problem here:

    1) The diode in one component doesn't match its datasheet (datasheet it wrong)

    2) Some relevant aspect of the diode's behavior is absent from the datasheet.

    3) There is no real requirement to have the bootstrap in the LM5113.

    Which is it?  

    This new design was ready for fabrication and adding these components is problematic. 

    Thank you

    Chris

  • 0 in reply to Chris Barnhart87
    TI__Expert 3225 points
    Hi Chris,

    Thanks for asking. To answer your question, external bootstrap diode for LM5113 is not fully necessary for you to have it work, since there is an internal diode inside the IC. We suggested the added diode just to help achieve improved performance during startup.

    LMG1205 is an updated driver from LM5113 and have already implemented these improvements. So no diode is needed to have improved startup. It is pin-to-pin compatible with LM5113 in DSBGA package.

    Hope it helps. Thanks!

    Best regards,
    Lixing