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  • Case ID: 306828
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Replacement for QM12038 and support for multiple RFFE switches

FinKM

The nRF91 Thingy uses a pair of SD8T RF switches to tune the chip antenna to different LTE bands (and for GNSS). This setup uses two identical RF switches and the MAGPIO pins. Unfortunately, it seems the QM12038 is now discontinued and there are no clear drop-in (or even just functionally equivalent) parts available.

Info Request: Are there any recommended replacements for the QM12038, or a reference design using another topology?

The option for derivative designs is either to change the tuning network design completely which will add to development times and may degrade performance, or to find a suitable replacement. All production SP8T switches I can find use RFFE, which appears to be the preferred control solution for IOT devices going forward.

RFFE control using the same topology would require two switches with different (or hardware configurable) addresses to allow R/W operations to both. The Infineon BGS18MA12 looks like a good option as the device can change its address based on the connection of the SCK and SDA lines. This allows two identical chips to be placed back-to-back on the same RFFE bus without an address conflict.

The problem with this is that the nRF9160 AT Command %XMIPIRFFEDEV and %XMIPIRFFECTRL can only automatically control a single switch, not the two required for the Thingy-style tuning network.

Feature Request: Add modem firmware support for multiple RFFE switches (with different addresses) to be set when the modem changes between bands/modes

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  • 0

    Hi,

    You're correct, the RF Switch is discontinued, and at this point we are still looking for viable replacements. At this point, there isnt a alternative that we have tested and verified that I can suggest.

    The Infineon BGS18MA12 looks like a good option as the device can change its address based on the connection of the SCK and SDA lines. This allows two identical chips to be placed back-to-back on the same RFFE bus without an address conflict.

    I don't think that it's pin compatible? I think something like this would be closer to a replacement, but I see that it is also marked as discontinued..

    regards

    Jared 

  • 0 in reply to Jared

    Hi Jared,

    Okay, thanks for confirming.

    Yes, the BGS18MA12 is an RFFE part which leads to the second part of my question about enabling multi-switch RFFE control instead of using the MAGPIO lines. The footprint isn't identical of course, but with all the comms pins on one side f the package it should be a minor layout modification.

    Do let me know if you have any information on a potential RFFE implementation.

  • 0 in reply to FinKM

    Hi,

    Discussed this with our HW developers and they haven't really decided on anything yet but they doubt that they will do anything that would require a redesign of the matching network. They didn't really have anything to share regarding a potential RFFE implementation at this point.

    regards

    Jared 

  • 0 in reply to Jared

    Hi Jared,

    Okay not sure if it's the same team, but can you ask the SW/Firmware team about updating the modem firmware to allow multiple RFFE switches to be controlled automatically? This would allow us to progress the design in-house - we're happy to make the layout and tuning changes as required.

    Best,

    Finlay

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