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Hi,
I got a inquiry about Power dissipation(Pd).
I can find RθJA graph in the datasheet. But customer wanted to get a graph about power dissipation(Ambient temperature vs Pd, Pd according to package).
If you have any information about Pd, could you give me some information about it?
Thank you.
Best Regards,
Kevin Shin
Hi Kevin,
Soon we will have a thermal widget come online which will allow you to estimated thermal performance based on package and temperature. For now the best way to estimate this is with RθJA.
This is used as follows: TJ=TA+PD*RθJA Where:
TJ is the junction temperature
TA is the application Ambient temperature
P is the Power Dissipated (PD=(VIN-VOUT)*ILOAD)
and is from the below table:
Do this answer your question?
Hi Kevin,
I put together this simple spreadsheet to help predict maximum power dissipation:
This should apply to any LDO.
Does this work for you?
Hi John,
Thank you for your supply. It was very helpful to me.
I have another question about that graph.
I think that TJA = TJ - TA. Is that right?
So doesn't RθJA effect to this graph or is RθJA fixed in that graph? Is my understanding right?
How can I change the value of RθJA?
Thank you.
Best Regards,
Kevin Shin
Hi Kevin,
TJA is RθJA. I updated the spreadsheet to be clearer:
Does this help to clarify?
Hi Kevin,
The x-axis of the graph is the PCB ambient temperature. So for the above case, it can only deliver full power for the above case when the temperature is below 15C. LDO's work best when the delta between VIN and VOUT is minimized.
I hope this helps to clarify.