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TPS1H000-Q1: Low current limit with a 24V rail

John Griffith
Mastermind 21471 points
Part Number: TPS1H000-Q1
Other Parts Discussed in Thread: TPS27SA08-Q1, TPS1HTC30-Q1,

Hello,

My customer is looking to set a 15-20mA current limit on a 24V rail and they want a HS switch that can be enabled by a 3.3V MCU GPIO pin. 

None of our load switches or HS switches that I can see that operate at 24V can set such a low current limit so I was thinking about using a current sense amplifier with an integrated comparator. Issue with this solution is that the comparator output is going to go from low to high when the output current exceeds the threshold and none of our 24V switches have active low enable. Was trying to figure out a way to do this without 3 devices and wanted to check if I was missing something. Lastly, they are hoping for a power good options to indicate if there is an overcurrent condition (I think with the comparator output they could just monitor that). 

Thanks!

John

  • 0
    TI__Mastermind 18530 points

    Hi John,

    I have two ideas:

    1. Attaching the CSA comparator output to the CL pin - that would keep the device enabled when current limit is not reached and disable the device when it is reached. And, if there is a capacitor connected to the DELAY pin, the device will be latched off even after the comparator output returns high. The MCU would then need to toggle EN from high to low to high.

    2. Using the SNS pin of another device such as TPS1HC100-Q1 connected to the MCU ADC, in which case everything then can be handled by the MCU.

    Do you think either of these could work?

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    TI__Mastermind 25055 points

    John,

    Is this for a 24V automotive system? Be mindful that the Hxx/HBxx devices would not support nominal 24V automotive applications. The TPS1HTC30-Q1 and TPS27SA08-Q1 are more nominal 24V systems, however as mentioned would not be able to support current limit measurement as low as you are looking for.

    Best Regards,
    Tim 

  • 0 in reply to Timothy Logan
    TI__Mastermind 21471 points

    This is a medical regulated 24V bus they distribute throughout the system. So won't have the cold crank, load dump, and ISO 7637 pulses you need to deal with. Should then be okay, right?

    Patrick, that is a cool idea, thanks! So the CL pin can just be "pulled low" and then when the comparator trips it goes to, lets say 3.3V, the current threshold immediately trips. Is 0.8V the threshold for the CL? There are a few voltage thresholds in the electrical parameters and it isn't immediately clear. 

    I think this idea could work. 

    John

  • 0 in reply to John Griffith
    TI__Mastermind 18530 points

    Hi John,

    Yes, that's fine - especially TPS1H000-Q1 which is rated for 40V anyway.

    And yes, the CL threshold is 0.8V. Great that it's promising, please keep us updated!

    Thanks,

    Patrick