LM317MQ: The maximum operating junction temperature

Hi Ted,

The maximum operating temperature to avoid damage is 150'C. The maximum operating temperature to remain in spec is 125'C. Between 125'C and 150'C the part will not face damage, but its performance may be degraded and won't be guaranteed to be within the Electrical Characteristic table limits.

Best,

Gregory Thompson

Hi Gregory

Thanks for your comments. 

Would you help provide the measured junction-to-ambient thermal resistance in EVM board such as listed in tps6244x-Q1 datasheet?

Customer need it to do the thermal simulation. As you know the  junction-to-ambient thermal resistance based on JEDEC standard is usually bigger than one in EVM board. LM317MQ is in constant current application and charger the NiH battery in eCall application. 

Thanks 

Hi Ted,

The TPS6244x-Q1 is a different product line so I'll redirect to switching converters. But in my experience with LDOs the quoted thermal metric is determined through simulation as there is no good way to measure junction temperature inside the device while the device is on.

Lmk if there are any further questions about the LM317MQ.

Thanks,

Gregory Thompson

Hi Gregory

Can you measure the junction-to-ambient thermal resistance in EVM board in lab for LM317MQDCYR?

And pls double check if  the LM317MQ datasheet in Ti website is right. It seem that it is LM317 datasheet not LM317MQ for automotive application. The title is not LM317MQ but LM317 which is not the automotive grade device. Seems that it is just a simple copy of LM317 device. 

LM317MQ data sheet, product information and support | TI.com

Thanks 

Hi Ted, 

I'll double check the LM317MQ thermal shutdown behavior, but I doubt I can provide an accurate junction-to-ambient thermal resistance bench measurement as there is likely no reliable way to benchmark junction temperature for it (there are a lot of unknowns with BJT protection features). The chip does not have the same modern independent output voltage collapsing thermal shutdown as many of our other chips that we use to benchmark a consistent junction temperature.

The same datasheet is applicable to the LM317M as well the LM317MQ. The OPN listing in the packaging information section covers all OPNs from both:

They share the same specs, the only difference between the LM317M and LM317MQ appears to be the automotive qualification. However, I agree it is confusing. The draft of the next version of the datasheet (SLVS297Q, should release soon) makes its coverage of both the LM317M and LM317MQ clear on the front page.

Best,

Gregory Thompson