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TPS22930A: Over-current detection in LTSpice simulation

Sebastian Bernal
Prodigy 40 points
Part Number: TPS22930A
Other Parts Discussed in Thread: TPS22950, TPS2595

Hello,

Not sure if I'm overlooking something simple in the datasheet, but I'm ultimately just trying to replicate the behavior found in Figure 9, the "Application Curves". Here with a load current of 3.3V/1Ohm = 3.3A, all I see at the output is ~500mV, and the FAULT_N line is still at 1V, despite the over-current condition. Note that R_LIM is set to 2.21k for a current-limit of 500mA, according to the datasheet. 

V2 is mimicking a logic HIGH on a GPIO signal. I tried setting the current-limit explicitly through a 2.21k resistor, but that doesn't affect the simulation results in any way.

Any advice as to fixing this issue? Appreciate any help, thank you.

  • 0
    TI__Genius 10652 points

    Sebastian, 

    My guess would be some nuance of the way the model was imported for LTspice, or possibly some unkown issue with using LTspice with our model. 

    If you can zip up your folder, including the model, i could potentially help with LTspice but we officially do not support our models with anything but TINA or 

    If i may, I would strongly recommend you to try using PSPICE for TI (basically our version of Orcad capture), this is available free.

    All of our models are included within PSPICE for TI library. Also, when you download one of our models it comes with the test bench which you can directly open up there. Importing external psipce model is also supported. 

    I have just simualated something close to your setup (1ohm load, 5V VIN), and varied RLIM from 2.5k to 1k. Current limit of the model is working correctly.

    Are you able to use PSPICE for TI? This may be a lot quicker than dealing with LTSPICE. 

    Best

    Dimitri

  • 0
    TI__Genius 10652 points

    Also, 

    In my testing, even when current is limited, FLT line stays at 1V regardless. This could be issue with model itself rather than simulator. 

    Best

    DImitri

  • 0 in reply to dimitri james
    Prodigy 40 points

    Hello again,

    Thanks for your clarifications, I wasn't aware of the incompatibility issues. 

    After learning how to actually use Pspice for TI, I came across the same issue with the fault line still being stuck at 1V.

    I'm not sure whether you can confirm that the TPS22950 specifically  has no fault reporting in the case of over-current? It seems that it only reports faults caused by exceeding a temperature threshold; refer to the image below. 

    If that's the case (that it has no fault reporting due to over-current condition), how would you suggest reporting such a fault to something like a microcontroller? I was thinking using a conventional current sense amp, but any other suggestions are appreciated.

  • 0 in reply to Sebastian Bernal
    TI__Genius 10652 points

    Sebastian, 

    You are correct. Overcurrent itself will not trip the FLT pin.

    Only thermal shutdown or reverse current condition will cause the FLT pin to fall. The truth table 8-1 shows the flt state according to input conditions. 

    if you need fault reporting during current limit this MUST be implemented externally or you must choose another device. I think choosing another device would be the simplest solution. Especically if implementing on PCB. Other devices can add even more functionality than that as well without increasing the pcb area/bom cost/count.. 

    I think you might just be in the stage of evaluating different parts? Depending on your application, i could recommend you take a look at TPS2595 eFuse or 

    virtually any high-side switch if those can meet your application. 

    We have a nice whitepaper here which goes into major features differences of those Power switches if that helps. 

    Moost if not all High-side switches have fault output on current limit exceeded. They are very sophisticated devices and have a lot more diagnostics features than this.

    Please let me know of any further questions on this. If you prefer to implement the solution discretely with external components let me know. 

    Best

    Dimitri