topic Re: LPC1758 junction temperature (recommended values) in LPC Microcontrollers

LPC1758 junction temperature (recommended values)

max12 — Mon, 30 Sep 2024 08:59:48 GMT

The datasheet states a maximum ambient temperature of 85°C and a absolute maximum junction temperature of 150°C.

My question is:

What is the recommended maximum junction temperature for this chip? It is some value above 85°C but below 150°C. So it might be 105 or 125°C. Where can I find this information?

We need this to verify operation during a worst-case temperatur test. For this, we need to know that the chip operates inside the recommended conditions, not the maximum ratings. We get case temperatures a bit above 85°C.

Re: LPC1758 junction temperature (recommended values)

Pavel_Hernandez — Thu, 03 Oct 2024 00:33:41 GMT

Hello, my name is Pavel, and I will be supporting your case, is this information that what you mentioned? on datasheet mentions this Tamb = −40 °C to +85 °C, unless otherwise specified.

Could you let me know about where did you get that information?

Best regards,
Pavel

Re: LPC1758 junction temperature (recommended values)

max12 — Thu, 03 Oct 2024 06:19:55 GMT

Thanks for the answer, we use the LPC1758 datasheet Rev. 8.7.

We did a worst-case temperature test in a climate chamber at 50°C ambient temperature. The chip is located inside an enclosure. The board also contains power electronics. We measured a case temperature of 93°C. The board is slighlty above 85°C, the air is cooler (but hard to measure).

The 85°C ambient is valid for the maximum power draw of the chip. But we dont use maximum clock speed, maximum operating voltage and not all peripherals. So even if the ambient temperautre is slightly above 85°C, the chip may be a lot cooler then the maximum recommended junction temperature.

Using the power draw of the chip < 300mW and Rth(j-c), I can estimate the junction temperature at Tc+4°C (97°C). I need to determine, if this is inside the recommended ratings or not.

150°C junction temperature as stated in the maximum ratings is a stress rating only. Operation is not guaranteed.

Re: LPC1758 junction temperature (recommended values)

Pavel_Hernandez — Fri, 11 Oct 2024 23:56:14 GMT

Hello, thanks for the details about this case, my apologize for the delayed response, I'm researching more information.

Best regards,
Pavel

Re: LPC1758 junction temperature (recommended values)

Pavel_Hernandez — Fri, 08 Nov 2024 21:38:15 GMT

Hello, I reviewed the user manual, and I find this chapter.

But with the information have the Tj could be around 95C.
Tj = 85C + (6.769 * 1.5w).

Best regards,
Pavel