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Original question:

TPS1H200A-Q1: Fault Detection Issue

TPS1H200A-Q1: Fault Detection

Songzhen Guo
Intellectual 2840 points
Part Number: TPS1H200A-Q1

Hi Experts,

I am following the question about this one: 

I want to describe the issue again, please see the test environment：

18V_PRI is input voltage to TPS1H200A

18_SEC is the output voltage of TPS1H200A

IN is the IN of TPS1H200A

Current is sense by current sensor

Fault is the fault output of TPS1H200A

PWM is the flyabck working signal, it's meaning that the load is connected to the power bus

When the delay capacitor is 4.7nF, in latch-off mode, total delay time is tcl+tdl1+tdl2= 2.3ms. See the test waveform below:

In 0s, when the first current limitation occur and just continue 0.5ms , the fault just down for 0.1ms then go to high level.

In 2ms, now the time is less than 2.3ms, when the second current limitation occur and fault is down to low level and the output of TPS1H200A keep disable.

But if the second current limitation gap longer, the action of TPS1H200A is different: 

In 0s, when the first current limitation occur and just continue 0.5ms , the fault just down for 0.1ms then go to high level.

In 2.5ms, now the time is longer than 2.3ms, when the second current limitation occur and fault is down to low level, the second current limitation continue less than 2.3ms, the fault will go back to high level.

Could you comment on that? Customer has modified the power on sequence on the product, all the product are meet second picture waveform. Thanks.

Best Regards

Songzhen Guo

  • 0
    TI__Mastermind 32650 points

    Hi Songzhen,

    When the device turns on, it can hit thermal swing and thermal shutdown due to the current limiting. This means that the device thermally heats up and turns off. This can happen before the delay timing is complete. If the device thermally turns off before the delay timing, it ignores the latch and then retries. Then, if the device hits a thermal swing or shutdown after the tdl2 time expires, it will latch off the device. This is what the customer is seeing in the first picture.

    In the second picture, the delay timing from the first turn off even has expired (and the first LATCH event has been ignored). The device has also cooled down further. Then during the second turn on event, the heat generated is not enough to turn off the device since the output is partially charged. This leads to successful turn on. 

    This is expected behavior of the device and the customer work around to delay the power on sequence is acceptable. Another option(which will show different behavior) is to not use the delay latch mode and to use the auto retry mode of the device.

    Thanks,

    Shreyas