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LMKDB1102: May I have some question regarding TI some document mention LMKDB1102?

TAlex Wu
Expert 1180 points
Part Number: LMKDB1102
Other Parts Discussed in Thread: CDCDB2000

Tool/software:

Dear SIR:

May I have some question regarding TI some  document mention LMKDB1102?

RC19XXX, 9QXL2001X vs. LMKDB1XXX, CDCDB2000 Drop-In Replacement Guide PAGE 25~26

https://www.ti.com/lit/ug/snaa410/snaa410.pdf?ts=1741316340363&ref_url=https%253A%252F%252Fwww.google.com%252F

Mention that LMKDB1102 can drop-in and show each pin compare result in the Guide PAGE 25~26.(Ti document)

base on the Guide (Ti document) create on JULY 2024.

Q1.

But compare LMKDB1102 Drop-In part both reference circuit (RC1900X old reference circuit) seems have "some different" as the Guide PAGE 25~26.(Ti document)

mention for example (Pin 6). So, I want double confirming the external circuit different (ex: Pin 6) . still can LMKDB1102 Drop-In?

Q2.

Base on RC1900X New reference circuit (create on 2024) seems LMKDB1102 reference circuit circuit "more different"(ex: power circuit),so  LMKDB1102 still can Drop-In as RC19XXX, 9QXL2001X vs. LMKDB1XXX, CDCDB2000 Drop-In Replacement Guide PAGE 25~26 mention ? or RC19XXX, 9QXL2001X vs. LMKDB1XXX, CDCDB2000 Drop-In Replacement Guide have new version ,too.

Would you have any advise regarding the different?base on LMKDB1102 reference circuit still can Drop-In both part ? (LMKDB1102 and RC1900X)or base on  RC1900X

New reference circuit still can Drop-In both part ? (LMKDB1102 and RC1900X)

(https://www.renesas.com/en/document/sch/rc19002-reference-schematic?r=25420406)

  • 0
    TI__Genius 12150 points

    Hi, 

    From page 25-26 of the drop in replacement guide you mentioned, the key difference between LMKDB1102 and RC19002 is that LMKDB1102 has a slew rate input requirement on OE1# (pin 15) while RC19002 does not mention this requirement on their datasheet. LMKDB1102 also requires pin 7 is pulled to GND, while the RC19002 can leave pin 7 floating. 

    On the reference design from Renesas that you linked, there are 2 changes needed to ensure LMKDB1102 can be used a drop-in replacement:

    1. Tie pin 7 to GND

    2. Decrease R14 to <1k Ohm to ensure the slew rate on OE1# (pin 15) is > 0.1V/ns. (assuming U4 might be pulled high at some point. If this switch will always be in the center position or pulled to GND no changes are needed). 

    Let me know if you have any other questions. 

    Regards, 

    Connor 

  • 0 in reply to Connor Lewis
    Expert 1180 points

    Dear sir:

    Thanks for your reply.

    But I want double confirming regarding below:

    according to LMKDB1102 reference board circuit as the link page 8  L1 design :

    https://www.ti.com/lit/ug/snau310/snau310.pdf?ts=1741574133369&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252Fzh-tw%252FLMKDB1102

    seems mapping to New reference circuit as the link page 1  R16(un-mounted and short):

    (https://www.renesas.com/en/document/sch/rc19002-reference-schematic?r=25420406)

    It still can Drop-In both part ? (meaning LMKDB1102 reference circuit L1 unnecessary and can short directly

    as https://www.renesas.com/en/document/sch/rc19002-reference-schematic?r=25420406 page 1 R16,Right?

    thanks

  • +1 in reply to TAlex Wu
    TI__Genius 12150 points

    Hi, 

    The ferrite bead on the power supply isn't strictly necessary for basic functionality, but it is recommended for better power supply isolation/filtering to achieve the best phase noise and jitter performance. Note that on the Renesas reference design, there's a ferrite bead on the USB power supply and an LDO which significantly attenuates high frequency power supply noise. The LMKDB1102 EVM interfaces directly with an external supply voltage (without an onboard LDO), so the ferrite bead is added for extra power supply filtering. LMKDB1102 will work with the power supply filtering setup used on the RC19002 reference schematic. 

    Regards, 

    Connor