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TPS4H160-Q1: Current limit

Big Bill
Expert 1980 points
Part Number: TPS4H160-Q1

Dear  experts:

          I used the TPS4H160-Q1 to control the loading,  i set the current limit 2A with the external current limit function, when i use the electronic load to pump 2A current, the Load current will  drop 250mA.

where is the problem ？ Looking  forward to your reply Thanks~

       As below is  the schematic and Testing tools  。

   

  

  • 0
    TI__Mastermind 28340 points

    Hello,

    The instruments in the picture show:

    1- Supply volatge 12.15V and current 256mA

    2- Electronic laod current set 2A and the voltage reading across the load is 0V

    That means the channel is in current limit. During current limit the FET can switch on/off due to thermal shutdown.

    Would you please check your meausrment with oscilloscope? You should see similar to the waveform in the attached file.

    RegardsTPSxHxxx-Q1 thermal behavior during over current.pptx

  • 0 in reply to Mahmoud Harmouch
    Expert 1980 points

    Dear  Mahmoud Harmouch：

        Thanks for your reply, I  forgot explain to the IC  temperature is as high as 135℃ on the 2A  limit  current   condition, why cause so high temperature?  

  • 0 in reply to Big Bill
    TI__Mastermind 28340 points
    Hello,

    What is the nominal load current? is it 2A? or the device is in current limit? If the device is in current limit the juntion temperature is reached and the device will turn on and off. You are measuring the case temperature I guess, so it is normal to see around 135C. It is lower than the junction temperature due to junction to case thermal resitance. Please send the scope picture for final answer and close your issue.
    Regards
  • 0 in reply to Mahmoud Harmouch
    Expert 1980 points
    Dear

    i measure the TPS4H160-Q1 surface temperature 135℃ in below condition

    1- Supply volatge 12.15V and current 256mA
    2- Electronic laod current set 2A and the voltage reading across the load is 0V
  • 0 in reply to Big Bill
    TI__Mastermind 28340 points
    Hello,

    According to your schematic the current limit per channel is 2A. The current limit has 15% accuracy so it can be limiting between 1.7A and 2.3A. I think the device is going into thermal shutdown before the current limit is reached because laoding 2A on each channel the power dissipation is Pd = 4 x square(2A) x Ron = 4 x 4 x 0.28 = 4.48W. The junction to ambient thermal resistance is 32.7C/W and this will cause the justion to rise 146.5C above ambient. At room temperature the device will thermally shutdown. The reading current is average and low becasue the dveice is in autoretry mode. That means it is switching on and off. Please lower your load current to around 1.6A and should be working at room temperature. I suppose the thermal pad is soldered to a coper ground plan.

    Regards
  • 0 in reply to Mahmoud Harmouch
    Expert 1980 points
    Dear Mahmoud Harmouch:

    I measure the surface temperature 135℃ on the condition that only one channel has loading not four channel. So what cause this issue？
  • 0 in reply to Mahmoud Harmouch
    Expert 1980 points
    Dear Mahmoud Harmouch:

    I measure the surface temperature 135℃ on the condition that only one channel has loading not four channel. So what cause this issue？

    the other question, the loading current is reach the 2A，why the IC limit the output current is 265ma? where is this value come from？

    thanks ~
  • 0 in reply to Big Bill
    TI__Mastermind 28340 points
    Hello,

    If only one channel is loaded with 2A and you measure DC average current 265mA, means it is in current limit. When the channel is in current limit the FET is in saturation region and the power dissipation before reaching the thermal shutdown is 12V x 2A = 24W. At this power dissiaption the thermal shutdown is triggered. Once the thermal shutdown is triggered, the current limit is at 70% of its original value. The THER pin is tied to GND means the device is in auto-retry mode. The FET is switching on and off and the average current is lower than 70% of the current limit set. For better understanding the situation, you need to use a scope with current probe and monitor the output current.
    You may check the setup by setting the electronic load at lower current 1.7A for example and see if it works as exepected.

    Regards
  • 0 in reply to Mahmoud Harmouch
    TI__Mastermind 28340 points
    Hello,

    The information, for resolving this issue, was provided. Based on that, I' m closing this thread and please let me know for further support.

    Regards