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LM3886: Thermal protection

Guru 16770 points
Part Number: LM3886

Hi

1.
According to datahseet, the junction temperature is limited by 150℃ but thermal protection works at 165℃.
What is relationship between thermal protection and absolute junction temperature?

2.
Are there any impact for device performance if device works between 165℃ to 155℃?

3.
The "typical" electrical characteristics would be offerd in Ta=25℃.
What is temperature in "limit" characteristics?

4.
What is Tc (case temperature) when thermal protection works?
Do you have information?

BestRegards

  • Hello! The 150degC Junction temp max is just the maximum continuously operating temp spec at junction. The device can also support an instantaneous Safe Operating Area temperature of up to 250°C, however this is where the Thermal Protection of the overall die (not junction) can kick in. Per the DS... The LM3886 has a sophisticated thermal protection scheme to prevent long-term thermal stress to the device. When the temperature on the die reaches 165°C, the LM3886 shuts down. It starts operating again when the die temperature drops to about 155°C, but if the temperature again begins to rise, shutdown will occur again at 165°C. Therefore the device is allowed to heat up to a relatively high temperature if the fault condition is temporary, but a sustained fault will cause the device to cycle in a Schmitt Trigger fashion between the thermal shutdown temperature limits of 165°C and 155°C. This greatly reduces the stress imposed on the IC by thermal cycling, which in turn improves its reliability under sustained fault conditions. Since the die temperature is directly dependent upon the heat sink, the heat sink should be chosen as discussed in THERMAL CONSIDERATIONS, such that thermal shutdown will not be reached during normal operation. Using the best heat sink possible within the cost and space constraints of the system will improve the long-term reliability of any power semiconductor device.