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TPS1H100-Q1: What is the load current possible and recommended? [TPS2HB16-Q1]

Viraaj Somayajula
Intellectual 295 points
Part Number: TPS1H100-Q1
Other Parts Discussed in Thread: TPS2HB16-Q1, TPS1HB16-Q1

For TPS1H100-Q1, in the datasheet, the load current is internally limited to 10A. We can choose the external load current limitation as well. I have a load which uses 4.5A typically and sometimes upto 8A.

But in the recommended operating conditional "maximum nominal DC load currrent" is given as 4A. Is "TPS1H100-Q1" applicable for my application?

Also could you please verify the following schematic:

Thanks

Viraaj

  • 0
    TI__Mastermind 23410 points

    Hi Viraaj,

    Based on your steady state of 4.5A, the TPS1H100 is not recommended as the junction temperature will exceed the thermal shutdown threshold.

    In its place, I'd recommend the TPS1HB35, which can handle a continous load current of 5A and has a programmable current limit that can range from 2 to 10A for the A or C version and 5 A to 25A for the B version. 

    If there is more information about the output, such as resistance, inductance, or capacitance, I can give a better recommendation.

  • 0 in reply to Anthony P Pham
    Intellectual 295 points

    Hi Anthony,

    I want to use this for resistive loads and powering external modules (such as motor drivers). Can you please suggest a suitable IC for my use case. I would like to have some margin of error as well. Can you please suggest something which can withstand 7-8A continuous load current?

    EDIT:

    I was looking at the dual channel high side switch - TPS2HB16-Q1. Is this recommended for my use case?

    Which metric should we use to calculate junction temperature for thermal shutdown (To be precise, how is it related to the load current) ? Can you confirm that it depends only on Rdson (in mohms).

    How to calculate how long, it can sustain an increased amperage before thermal shutdown?

    Thanks

    Viraaj

  • 0 in reply to Viraaj Somayajula
    TI__Mastermind 23410 points

    Hi Viraaj,

    I want to use this for resistive loads and powering external modules (such as motor drivers). Can you please suggest a suitable IC for my use case. I would like to have some margin of error as well. Can you please suggest something which can withstand 7-8A continuous load current?

    The TPS1HB16-Q1 device is a single channel device that can handle a continuous load current of 7A.

    I was looking at the dual channel high side switch - TPS2HB16-Q1. Is this recommended for my use case?

    Would you be using both channels on the TPS2HB16-Q1? With a single channel in use, this device can handle a continuous load current of 7A. If now concerned for thermal behavior, both the TPS1HB16-Q1 and the TPS2HB16-Q1 will handle the 4.5A load current very well when considering just a single channel for the TPS2HB16-Q1.

    Which metric should we use to calculate junction temperature for thermal shutdown (To be precise, how is it related to the load current) ? Can you confirm that it depends only on Rdson (in mohms).

    For calculating junction temperature, it is related to load current through power dissipation. As well as power dissipation, it depends on the junction-to-ambient resistance of the device and the ambient temperature, along with the Rdson which you've already mentioned. 

    To get a more general sense of how to calculate whether the device temperature will stay below the thermal shutdown threshold, take a look at the How To Drive Resistive, Inductive, Capacitive, and Lighting Loads With Smart High Side Switches. It goes over how to calculate junction temperature on resistive loads as well as some conditions for the other characteristics of a load that I had asked about.

    How to calculate how long, it can sustain an increased amperage before thermal shutdown?

    For calculating the time, there is a bit of a loop as the Rdson of the device varies with temperature and how the device heats up will vary from device to device. I can provide some calculation for the device if there is a concern for thermal shutdown behavior during high current loads or provided the higher current load behavior, I can run the numbers and get back to you. 

  • 0 in reply to Anthony P Pham
    Intellectual 295 points

    Hi Anthony,

    Thank you for your detailed response.

    Yes, I am planning to use both the channels for two different loads with TPS2HB16-Q1. Although only one channel will be in use at a time, there is a possibility in extreme cases that the current on one of the load might go to 7-7.5A in our use case. Hence, the request for 7-8A.

    According to what you said above, it seems like TPS2HB16-Q1 is good for my use case.

    1. Could you please let me know one last piece of information. How long can the load sustain 8A and 9A current before thermal shutdown?
    2. I am also grounding the latch pin, so as far as I understand, the switch retries after Tretry time and if the junction temperature comes down (<150 degC), switch starts again. So, how long before the operation returns to normal?

    If you can provide this information, it will be really helpful.

    Thanks

    Viraaj

  • 0 in reply to Viraaj Somayajula
    TI__Mastermind 23410 points

    Hi Viraaj,

    According to what you said above, it seems like TPS2HB16-Q1 is good for my use case.

    Awesome, glad to hear! 

    Could you please let me know one last piece of information. How long can the load sustain 8A and 9A current before thermal shutdown?

    For your own reference, I've attached the excel workbook that I used to get the following numbers:

    Current Ambient Temperature = 25C Ambient Temperature = 105C
    8A Will not reach thermal shutdown 2 seconds
    9A Will not reach thermal shutdown 0.9 seconds

    Die power is calculated using the load current and the max Rds(on) which for the 2HB16 is 40mOhms (2.56 W for the 8A and 3.24 for the 9A)16PWP_TPS2HB16_RC_Network_2_CH_ON.xlsx

    I am also grounding the latch pin, so as far as I understand, the switch retries after Tretry time and if the junction temperature comes down (<150 degC), switch starts again. So, how long before the operation returns to normal?


    The TPS2HB16-Q1 will retry 3 or 7 times depending on the version depending on the fault but you are correct in that the same occurs in a thermal shutdown fault. I can attempt to look into this further but will need to know which version you'd like to try this with? 

     

  • 0 in reply to Anthony P Pham
    Intellectual 295 points

    Hi Anthony,

    Thank you so much for your detailed reply. I am using the version A (TPS2HB16AQPWPRQ1) in my design. The numbers you have shared are good for our use case. I shall proceed with this part. If you can just confirm the retry after fault part, it would be great. Thanks again.

    Regards

    Viraaj