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Part Number: LM317A
I have a question about LM317.
Could you tell me about it?
In the datasheet p5 "7.4 Thermal Information" there is 23.3 (NDE: TO - 220 PKG) as "RθJA (Junction - to - ambient thermal resistance)".
What is the value of 23.3 specified in what mounting condition?
I think that this package called TO - 220 can be implemented as below.
· Attaching to the fin
· Direct mounting on board
By checking what kind of method is prescribed by your company,
We are considering whether customers can use it from the viewpoint of thermal characteristics.
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In reply to Ryan Eslinger:
Thank you for contacting.
I want to know is the following,
Q：What is the condition of specifing ”RθJA= 23.3" ?
In reply to Pokkun:
The measurement was taken with a thermal simulation with the device mounted on a standard JEDEC board.
The standard JEDEC board used to generate the standard datasheet thermal table is 114.3 x 76.2 x 1.6 mm and has 4 layers. The top and bottom layers are 2 oz Cu each and the buried layers are 1 oz each. There are thermal vias under the pad, the number of vias would be the maximum that would fit beneath the exposed pad based on 1.2 mm pitch.
In reply to Michael Hartshorne:
Thank you for your detailed answer.
By the way,
is this consideration OK that "the measurement conditions don' have heat radiation fins attached?"
The RTja is specified with the exposed pad soldered on to the board. If the device is mounted vertically, and a heat sink is used, the RTja can vary widely depending on the heat sink and connection to heat sink. We don't offer RTja values for these conditions, the heat sink vendor should be able to offer a value of the expected RTja when the heatsink is used.
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