TMCS1100: input surge current capability

Hey Chen,

Thanks for using our forum. To better understand your issue, I need to first clarify a few things.  My understanding is that you want to know whether the TMCS1100 device is powered or not, will it survive a surge current and not suffer a degradation in performance. If so, there is not a simple answer for your concern.  The surge capability depends upon the surge current profile (current magnitude vs. time) as well as the customer layout.  Heat, the byproduct of large currents across a given resistance (the leadframe and input traces), is essentially what can damage the device.  However, heat has a slow response time and lags behind the current signal.  Consequently, current handling is inversely related to pulse duration as indicated by the Single-Pulse Leadframe Capability figure in the datasheet (figure 11 for this revision).  While this general behavior should also be observed on the customer's board, the actual limits will change according to layout. Large, heavy copper input planes will sink more heat and increase the current capability.  Your customer has the option to simulate or test on the bench to determine what load leads to a junction temperature that exceeds the absolute max specifications. We expect the case temperature to be approximately equivalent to junction temperature.