UCC28C40D

Hi Tai,

The UCC28C40 is only rated to -40 C.  Using the device outside of the datasheet's specifications can cause undesired behavior, or no operation as you have observed.

Silicon devices need to be kept within a certain temperature for proper operation due to physical properties of the material.  These properties includes carrier mobilities and electron-hole pair generation dominating charge carrier populations.

Regards,

Hi Rob,

Why the specification cited that Operating junction temperature range, TJ .. --55°C to 150°C?

Is this a fail statement or?

What about the figure 9 , Please advise why the offset can't be more than 1V at -25 degree C.

Thanks

Tai

Hi Rob,

Can you recommend  the replacement  part that can work at -45C?

Thanks

Tai

Hi Rob,

Figure 9 of the spec. sheet indicated that voltage at comp to CS should be below 1V at 25 degree C.Please advice how critical this parameter is?

Thanks in advanced.

Tai

Hi Again Tai,

The -55 to 150 C is the absolute maximum before the part is damaged.  If you read the note under that section, it says we do not guarantee the part will function in this range. 

From the datasheet: "These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied."

Figure 9 is a characterization graph, but again, does not guarantee the device will work at that low of a temperature.

We have a PWM controller that runs down to -55 C, but has a different UVLO threshold range.  The part is the UCC28C43-EP

Are you looking for the same voltage range?

Regards,

Hi Rob,

Thank you for your respond. Yes, we are using the same voltage range. Please review our schematic and suggest with your opinion.2451.Doc1.docx

Thanks

Tai

Hi Rob,

Review the bad part and we are seeing that the over current maybe the smoking gun to kill the part !

Please review the circuit and confirm?

Thanks

Tai

Hi Tai,

Over current will definitely do that.  Where are you seeing an OC condition on the part?

Regards,

We measured the bad part and found the CS pin was read very low ( diode reading),the 100 ohms connect to this pin was open. I believed that this indicated high current condition was happened at some instances!We also found the output gate resistor and the discharge gate resistor also open , the switching Fet also shorted.

Tai

Hi Rob,

My original assessment of temperature was wrong, the part only encountered the temp of -14 C  and not -45C.

I would like to send the part in for further Failure Analysis. It is very importance for our Customer to know why the part go bad!

we run this application at high amplitude 60,000ft. Do you see any issue to the part at this level??

Would you please review our circuit and feedback with your opinion?

2844.DZXRALTE-008L080F-GGL1.doc