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  1. #1
    New Member New Member mjkinfhtx is on a distinguished road
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    [SOLVED] Using the TLE987x to control 6 Relays

    I would like to use the TLE987x to independently manage 6 x 24V Relays.

    Is it possible set setup and configure the TLE987x to independently control 6 MOSEFT using the MOSFET Driver?

  2. #2
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    Hi mjkinfhtx,

    thank you for your interest in our products!
    The TLE987x can control three half-bridges independently, but not the corresponding high-side and low-side.
    Best,
    Fiz
    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

  3. #3
    New Member New Member mjkinfhtx is on a distinguished road
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    Hi Fiz,

    What about the statement in 27.2.2 of the UM (v1.3) 'In Normal Mode the output stage is fully controllable through the SFR registers CTRLx (x = 1, 2, 3)'?

    Or do I misunderstand its meaning?

    Regards,

    Mark.
    Last edited by mjkinfhtx; Jun 21st, 2019 at 12:02 AM.

  4. #4
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    Hi Mark,

    Yes in normal mode you can fully control each of the three half-bridge drivers via SFR CTRlL-3.
    But when you try to turn on the LS and the HS of a half-bridge at the same time, the TLE987x will prevent this due to its cross-current protection, which can not be disabled.
    You could use two TLE984x with its integrated relay-drivers + 4 external MOSFETs to manage your 6 relays independently.

    Best,
    Fiz
    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

  5. #5
    New Member New Member mjkinfhtx is on a distinguished road
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    Hi Fiz,

    The TLE984x seems like a much better match. The 6 relays is not fixed as this number was chose due to the 6x HS/LS of the TLE987x.

    The relays that I plan to use require a 24V PWM signal to energise the coils and require around 180mV. They are commercially available parts designed primarily for household wiring.

    The Low Side Switch modules can easily cope with this current, but not the High Side.

    To simplify the hardware and make use of the internal over current protection, can I use the two High Side Switches in parallel to provide the minim 180mV required by the relay coil?

    Regards,

    Mark.

  6. #6
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    Hi Mark,

    is you target application in the automotive or industrial area?
    Please check the max ratings of our devices and if they fit your application!

    Best,
    Fiz
    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

  7. #7
    New Member New Member mjkinfhtx is on a distinguished road
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    Hi Fiz,

    It's a concept / prototype for a 24V wired Home Automation system.

    There are very few devices available that can be powered directly from 24V and have 24V tolerant inputs and outputs, hence my (modified) choice of the TLE984x. These TLE984x result in a small BOM and provides good amount of diagnostics from the coil switching.

    I'm trying to make the most efficient use of the TLE984x, which is why I asked about using the High Side in parallel to achieve the current requirements for the relay coil as this would allow three relays to be controlled instead of two and no need for an external MOSFET.

    I'm aware that this is not part of the original use case / concept for the device, but appart from the high Side current it's a very good fit for my idea.

    If the High Side can be combined into a single parallel higher current device then I can realise 5 x 24V inputs (for switches), 3 x Relay (for light / power control), with LIN (also 24V) for communication.

    Regards,

    Mark.

  8. #8
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    Hi Mark,

    good to hear the TLE984x fits your needs!
    We have to look into driver capability of the HS more closely.
    Best,
    Fiz
    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

  9. #9
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    Hi Mark,

    you can use the TLE984x's HS driver for a relay, but you have to place a free-wheeling diode in parallel to the relay to prevent damaging the device due voltage drops, caused by the switching coil.
    Check the attachment for the placement of the diode.

    Best,
    Fiz
    Click image for larger version

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    ?????
    Last edited by Fiz; Jul 26th, 2019 at 06:18 AM.

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