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TIC10024-Q1: Operation with Vs 24V nominal

Wayne Meretsky
Prodigy 240 points
Part Number: TIC10024-Q1
Other Parts Discussed in Thread: TIC12400-Q1, , TIC12400

Previous questions asking about using TIC10024-Q1 and/or TIC12400-Q1 with Vs of 24V have replies that are specific to "Automotive Applications", in which one might presume that the 24V power source is a 24V battery also used for large loads such as engine starting and that may be subject to both high and low transients.

All that notwithstanding, each of these devices have a Recommended Operating Conditions specification 4.5 ≥ Vs ≥ 35 and not all applications are required to meet "Automotive" requirements.

Question:

Provided Vs remains within the range specified by the Recommended Operating Conditions, will TIC10024-Q1 and TIC12400-Q1 operate per their specifications when Vs has a nominal value in the range 20…30VDC?

  • 0
    TI__Genius 9132 points

    Hi Wayne,

    For both TIC12400-Q1 and the TIC10024-Q1, the VS supply is designed to be connected to a 12-V automotive battery (through a reverse blocking diode) with nominal operating voltage no greater than 16V

    The higher voltage rating of 35 V is for load dump and jump start conditions and more information is explained on pages 115-117 in the datasheet.

    What is your application where you are using this device with high power supply voltages? 

    Here is an alternative solution to MSDI using  the TMUX1308-Q1 with an input protection scheme. 

    Regards

    Saminah

  • 0 in reply to Saminah C
    Prodigy 240 points

    My application has a battery supply of 24V nominal, and an operating range of 20…30VDC.

    I understand and am not subject to the problems associated with transients in the automotive environment.

    The device has a Recommended Operation Condition for Vs of 4.5…35V and an Absolute Maximum for Vs of 40V.

    The footnote regarding nominal voltage of 16V makes exactly no sense. 16V in a 12V automotive environment is not nominal, the nominal voltage in a 12V automotive environment is 12, 13.6 or 14.4 - there's no real definition. And, we don't design to nominal voltages, we design to min and max. 

    What I'm hearing is that:

    • The Recommended Operating Condition for Vs is 4.5…16V
    • The footnote to that Recommended Operating Condition should read "Load Dump and Jump Start transients to 35V conforming to ISO 16750-2 and described in 10.3.1 are allowed"

    Is that correct?

  • 0 in reply to Wayne Meretsky
    Prodigy 240 points

    On further reflection, I can operate with Vs of 5V.

    The Absolute Maximum rating for the INx pins is -24…40V with a Recommended Operating Condition of 0…35V.

    However, the Recommended Operating Condition of 35V for INx is annotated with Footnote 1, which talks about operating voltage, not voltage on IO pins.

    Is the device useable with a Vs of 4.5…16V and IN00…09 seeing 30V?

  • 0 in reply to Wayne Meretsky
    TI__Genius 9132 points

    Hi Wayne,

    Can you explain your application in more detail - You mentioned you can operate at Vs of 5V and will have higher voltage upto 16V on INx pins.

    This will not blow up the part if you can explain what you are trying to accomplish, that will help. Also, I would consider the minimum VS requirement for comparator threshold for proper detection

    As I mentioned earlier, MSDI is is designed to be connected to a 12-V automotive battery  - Note 1 in the recommended operating conditions state the highest voltage recommended continuously is 16 V (on INx pins) for the lifetime of a 12-V  (Vs) battery.

    If your application is non-automotive, you could consider using the TIC12400, If your system is less than 85 deg you can operate Vs up to 24V.  If your system temperature is > 85 deg C we recommended only using up to 18V on Vs pin.   The INX pins can withstand up to 35 V.

    Regards

    Saminah

  • 0 in reply to Saminah C
    Prodigy 240 points

    Saminah,

    The details of my application are largely irrelevant. My supply voltage is 24V nominal and has a range of 20…30V as I have previously stated. It should be no surprise that there are numerous regulated voltage rails within any design such as 12V, 5V and 3.3V all with specs of about ±10%.

    It is not at all clear to me why anyone would choose to connect either the TIC10024 or TIC12400 directly to battery voltage in an automotive application when it could easily be run from such a regulated supply.

    So, for the sake of argument, let's say that Vs is a dedicated, regulated 5V or 12V; that the diode in the recommended power supply is replaced with a linear regulator. This seems to entirely resolve all questions of Vs and I cannot see any downside other than the cost of the linear regulator. Generally, this would seem to be desirable as it dramatically reduces the power dissipated by the wetting currents. Am I missing something here?

    This leaves only the question of allowed INx voltages. The data sheet says that the Recommended Operating Conditions for these pins is 0 to 35V with a foot note that says (emphasis mine) "[...] nominal operating voltage no greater than 16V […]". The operating voltage for the device is 5 or 12V as discussed above and so it seems that the INx inputs with are specified to behave well across a range of 0…35V.

    Questions

    1. Why would anyone choose to operate the TIC10024 or TIC12400 from unregulated battery voltage rather than a regulated power rail? Is there anything about the behavior of the device that would make this desirable?
    2. Provided that the operating voltage of the TIC10024 or TIC12400 remains less than 16V, will the INx pins perform as expected across an applied voltage range of 0…30VDC?

  • 0 in reply to Wayne Meretsky
    TI__Genius 9132 points

    Hi Wayne,

    Operating voltage includes INX pins.  They can be exposed to higher voltages for short periods of time per the automotive use case, but we do NOT guarantee 35V operation of the INx pins at DC for life.  35V on INx pins is intended as an ISO pulse protection mechanism, not as a supported operating case. So how you are using the TIC12400 in your application is important.

     

    • If you want to source wetting current from an INX pin that is pulled up to 35V with a low VS rail, you won’t be able to do it.

    • If you want to sink wetting current into an INX pin that is pulled up to 35V with a low VS rail, you should be able to do it.

     

    1. As for why automotive BCM designers don’t use a regulator, it is probably because of the power inversions that can happen if someone connects a car battery backwards accidentally.  A blocking diode can protect the BCM.  A regulator will not.  If you do not have that worry, then you can use a regulator.

     2. We still do not guarantee DC lifetime operation of INx pins pulled above 16V per our datasheet

    Regards

    Saminah

  • 0 in reply to Saminah C
    Prodigy 240 points

    I've changed my design to use the NXP MC33972.