uc2842 operate temperature is from -40c to 85c shows in our datasheet, i want to know what will happen if our ic operate in 125C temperature ? does uc2842 have over tempreture protection function? our customer find uc2842 will not work in 125C, that's way i ask this question? could you please give your comment here?
This question has been asked several times before. Because of this I have a response that was framed around a UCC3809 but it applies equally to the UC2842 family.
I hope this explains the problem sufficiently. Note that the temperatures are JUNCTION temperatures not ambient and that the junction will always be warmer than the ambient when the part is in operation.
The question on how to interpret the temperature listings on the data sheet keeps coming up and needs to be explained.
The data sheet usually has multiple parts listed at the top for instance the UCCx809 family consists of devices with 3 temperature ranges:
The UCC3809 has a temperature range of 0 C to 70 C.
The UCC2809 has a temperature range of -40 C to 85 C.
The UCC3809 has a temperature range of -55 C to 125 C.
These refer to the junction temperature of the device.
If the device’s junction temperature is within the temperature window for the device then the device will meet specification as per the data sheet. However, it does not mean that if you exceed the temperature window, either up or down, that the device will fail.
All three parts are made from the same pattern and can even come from the same wafer.
During the qualification process, the parts were initially tested in wafer form on a cold plate where the temperature was controlled. The tests were done in such a short time that the temperature of the junction is assumed to not have moved substantially. This data was then used to establish guard bands for each of the parameters so the tests could be done at room temperature. If the parameters fall within the identified guardbands, the part will operate within specification over the selected temperature range.
A part with a 0 C to 70 C temperature range may meet full specification with some guard bands right out to -39 C to -84 C, then again it may fail specification at -5 C or 75 C. For that reason, it would be marked for the 0 C to 70 C parts.
Since the parts are all from the same wafer/pattern exceeding the temperature range should not cause damage to the IC but things like thresholds, reference voltages, and frequencies will change and can cause problems in the circuit it is controlling.
Also note that there is a UC1842 version of this device that has been tested and qualified to operate over the wider temperature range than the UC2842 or UC3842.
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