This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS7H2201-SP: TPS7H2201-SP

Part Number: TPS7H2201-SP
Other Parts Discussed in Thread: TPS7H2201EVM-CVAL

I used TPS7H2201-SP for GEO platform equipment development project. 

When I checked OCP and OVP states, load switch mosfets goes into on-off continuously. For this reason any error mode, load switch heat increases up to 135C.

I used thermal pad and vias, I changed RTIMER, SS and ILTIMER values but nothing changed. 

I also have, TPS7H2201EVM-CVAL demo board. Same problem occurs here too.

Both, TPS7H2201-SP datasheet and TPS7H2201EVM-CVAL datasheet, there are no recommendations regarding thermal improvement.

Could you help me?

Thank you. 

  • Hi,

    I want to make sure I'm understanding your problem correctly. Is the device constantly switching on and off once power is applied, or does the continuous on-off switching only occur after a certain event (like overvoltage, overcurrent, or after probing certain pins)? Have you confirmed whether the device is shutting down due to OCP or OVP? If you have any waveforms of the behavior, that would also be useful.

    I also have a few questions about your testing setup:

    1. What input voltage and load is your design using? 
    2. Could you share the schematic and an image of the development board you tested with? This will help me troubleshoot what the issue may be.
    3. Did you make any alterations to the TPS7H2201EVM-CVAL board or were you using the default components that the board comes with?

    Thanks,

    Sarah

  • Hi Sarah,

    Thermal problem only happens when testing the OCP and OVP states.

    Vin: 5.5V

    OCP occurs: 6A

    OVP occurs: 6V

    I do not have permission for sharing schematics but my schematic values same with TPS7H2201EVM-CVAL datasheet. (Page 20, Figure 18, I am use only 1 load switch)

    I haven't made any changes to the TPS7H2201EVM-CVAL eval board. I saw the same problem on eval board.

  • Thanks for the additional details about the design and schematic values you are using.

    Is testing being done at room temperature (25C)? How long does it take the device to reach 135C and how are you measuring the temperature? You said the device is constantly switching on and off during OCP tests. This is because you are not removing the fault condition and are allowing the device to constantly turn off and then restart through the timers, correct? Does the on-off switching occur for the OVP test if VIN is raised to 7V, or does the switching only occur if VIN is left at the voltage that trips OVP (~6V)?

    The Ron of this device under your conditions would be ~35 mOhms max at room temp, so power dissipation at 6A would be ~1.26W. This shouldn't be enough power to reach the temperatures you're seeing, but I will check with our designers to see if there may be special thermal considerations in either of the protection modes and possibly set up a board to test myself. 

    Thanks,

    Sarah

  • Our tests done at 25C @ room temperature. IC reach 135C in very short time period (ms) and I measure this temperature via thermal camera. 

    Is there any progress about the solution?

  • Hi, thanks for checking in.

    Looking back at your descriptions, it sounds most likely that the switching losses from the internal FETs turning on & off repeatedly are the main source of dissipated power, and therefore heat. You mentioned that you had been unable to make a difference by altering the timers and SS. What values did you try using? Lowering ILTIMER, increasing RTIMER, and increasing SS should theoretically help with this if the changes are large enough. I am receiving an EVM this week to check on the bench.

    Alternatively, connecting RTIMER to GND and using the EN pin to restart the device is another option that could be used to prevent the board from heating up so much. Would this be an option for your design?

    I also recommend this App Note (Load Switch Thermal Considerations) for more information about managing load switch power dissipation. Section 2.3 talks about different techniques for minimizing the thermal resistance of the PCB itself. 

    Thanks,

    Sarah

  • Hi, 

    Rtimer: 2.2nF/50V (1.1ms)

    Ltimer: 2.2nF/50V (1.1ms)

    SS: 100nF/25V (11ms) 

    (This values same with eval board application)

    I increased Rtimer up to 30ms but nothing changed. I do not have digital command so I can not use EN pin. 

    I will review app note. 

  • Thanks, I'll get back to you as soon as I receive the EVM and run tests this week. It's very odd that increasing Rtimer that much wouldn't have any effect.

  • Hi Elif,

    I was able to recreate results similar to what you observed. The device does reach fairly high temperatures when switching on and off due to over-current limit protection features. This took around 1-2 minutes on the default TPS7H2201-SP EVM I used.

    The methods outlined in the App Note I shared earlier could be applied to this board design to improve thermal performance, however, it's important to note that leaving the device to switch on and off in this fault mode indefinitely is not ideal regardless of the thermal impact.

    Depending on your design, the turn-off and restart behavior controlled by the TPS7H2201-SP ILTIMER and RTIMER pins may be enough to remove the overcurrent fault and prevent indefinite switching (which would prevent the higher temperatures). If this is the case, then it would be unlikely for the device to reach the temperatures we observed when forcing it to switching indefinitely. 

    Thanks,

    Sarah