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I'm going to be using a microcontroller and SDRAM IC in an enclosure that could, given some environmental variables that I have no control or knowledge of, get too hot for the devices to work properly. Redesigning the enclosure is not an option. However, I could notify the operator, if my microcontroller had a means of reading the temperature.

How can I monitor the temperature of a large IC? I'm using 54-pin TSOPs and 100-pin TQFPs. I've considered using a SMD thermistor and an ADC on the microcontroller, or using a prepackaged solution like this SOT-23-3 'active thermistor'. However, with either of these methods, I'm not sure how to thermally couple the devices. I'd like to avoid having components on the back-side of the board if possible.

Other possibilities include adhering a device on some long leads to the center of the IC, or monitoring the current used by the device, and extrapolate the power consumed to get an estimate of the temperature. Both of these seem like hack jobs, while a thermistor or temp sensor seems much cleaner.

What single-sided layout will simultaneously give be the best thermal properties to cool my devices, and allow the sensor to be thermally coupled with the die of the IC? Or, are there other methods that I'm not considering that would be better?

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I guess the cause of overheating is not power dissipation of your uC. That means you can just place thermistor close to uC and you'll get +-2C accurate readings.

Some uCs have internal thermistors connected to one of ADC input - check datasheet.

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  • \$\begingroup\$ What do you base the +-2C number on? \$\endgroup\$ – Kevin Vermeer Feb 12 '11 at 16:30
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    \$\begingroup\$ Just an estimation. In fact it will be better - it's all connected to same PCB and I don't see why uC will be constantly way hotter (given 0.1-0.5W power consumption) \$\endgroup\$ – BarsMonster Feb 12 '11 at 19:31

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