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TPS1HTC100-Q1: Current limiting, analog value on ADC(SNS) pin.

Karthik Gokul
Prodigy 100 points
Part Number: TPS1HTC100-Q1
Other Parts Discussed in Thread: TPS1HTC30-Q1

Tool/software:

Hello Team,

I am using the TPS1HTC100 ic for controlling the auxilary power. I am going with a max load of 5.7A, my Rlim would be 8Kohms. And to avoid saturation at my 3.3V microcontroller i am going with a Vsns(max = @5.7A) = 3.1V. So then the load current is 5.7A the Vsns would be 3.1V, my Rsns = 435ohms. but what is there is a short circuit and the current exceeds that ? will the output voltage on the sns pin go above the intended 3.1V and if yes then how can i protect the microcontroller that can take a maximum of 3.3V on its input pins ?

Thanks, 

Karthik

  • 0
    TI__Expert 8211 points

    Hi Karthik,

    If you are concerned about a short to ground scenario on the output, then that should not affect the SNS pin. A short to ground fault will cause the SNS pin to output VSNSFH but this voltage is scaled based on what diagnostics is pulled high to. So, if DIAG_EN is pulled high to 3.3V then that is the highest voltage that SNS pin should see. Please see below for a more detailed explanation. 

    Please also keep in mind the typical nominal load current for this device is about 4A and other factors like temperature, board layout, etc. to make sure the device does not go into thermal shutdown. Also, RILIM can only be between 10kΩ–50kΩ. 

    Thanks,

    Rishika Patel 

  • 0 in reply to Rishika Patel
    Prodigy 100 points

    Hi Rishika,

    Before going ahead with the part I would like to know the following -

    1. In the datasheet of the smart switch it is written as "Current limit: 1A to 5A or 7.3A". Yes the nominal is given to be 4A and 60V of operating, but I wanted to know if there is any data regarding an over drive condition, suppose that I set the current limit to be 6A and draw 5A continously from the ic what could be the implication ? Is there any data to support this weather the ic would go into a thermal shutdown and then try a turn on after certain period of time(latch is NC) ?

    2. It is given that for TPS1HTC100, 7.3A is when the Ilim pin is grounded, on floating it is 4.2A and if a resistor connected it is programable, but as you have said not to go below 10K on the value of Rlim, would it not be possible for me to use the same TPS1HTC100 and have 5A at all ? If no, could you please clarify the 7.3A rating ?

    3. I also found out an alterntive ic that can handle 6A nominal (TPS1HTC30), but in the product page of the component there are 2 ratings for max current limit. One at 6A and the other at 16A. So is ^A a continous Imax limit and 16 a peak value ? And this ic seems to be a pin to pin compatable ic with the same footprint, much lower Rdson. (https://www.ti.com/product/TPS1HTC30-Q1)

    Thank you, 

    Karthik.

  • 0 in reply to Karthik Gokul
    TI__Expert 8211 points

    Hi Karthik,

    The nominal current specification vs. expected load current provides a good perspective on whether the device is likely to go into thermal shutdown. Latch has an internal pulldown so if you leave it floating, the device will operate in auto-retry mode in response to thermal shutdown. 

    Yes, the TPS1HTC30-Q1 device may be a better option especially for a slightly higher nominal load current. There are not two ratings for max current limit. The max nominal load current is related to the normal operation current that the load will draw. The 2-16A current limit range is dependent on how ILIM is configured - this is to set the overcurrent threshold so that any current greater than the set limit is considered a fault. You can set the current limit to 6A with this device. 

    Also, there will be more power dissipation when the device is in current limiting mode. 

    Thanks,

    Rishika Patel