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Intelligent Power Switches Slide 12

In applications using an IPS, a key problem is the temperature and how to handle an over temperature event. Of course, when the design is made, the first choice is to choose an IPS with an Rdson low enough to avoid reaching the over temperature threshold. But with the constraints of space (up to 8 channels in the same package), cost and regulations like IP65 (where the electronics must be sealed), an over temperature event has a high probability to occur in the lifetime of the product. The IPS handle this stress smoothly by monitoring the junction temperatures of each channel and the case temperature. TJ is the junction temperature and TC the case temperature. When the junction temperature goes above TJSD, the current of a given channel is turned off and turns on again only when the junction temperature goes below TJR. After a few cycles like this, the case temperature is increasing. If the case temperature reaches TCD, all the channels are turned off and must decrease down TCR to turn on again. The temperature protection in an Intelligent Power Switch is not simply turn on and off of the channels based on the temperatures. An IPS can have up to 8 channels. When the junction over temperature threshold is reached, only one channel is turned off, and in the event of a case over temperature, all the channels are turned off. With that in mind, how does one turn on the channels to immediately prevent a new temperature shut down?

PTM Published on: 2011-09-07