BQ24073:

Mannika Garg

Part Number: BQ24073

Hi,

I have noticed in the datasheet that the Junction-to-ambient thermal resistance (44.5 °C/W) for the device is lesser than the Junction-to-case (top) thermal resistance (54.2 °C/W). Can you please explain why is that so because my knowledge says that normally the former is higher.

Regards,

Mannika Garg

over 5 years ago

0 Anthony P Pham over 5 years ago

TI__Mastermind 23410 points

Hi Mannika,

This can be due to a few factors based on how the thermal resistance are measured. Junction-to-ambient allows for the heat to be dissipated across the package body. Junction-to-case however forces the dissipated heat across only a single surface of the package body.

You can reference the following document on how TI obtains the thermal metrics: http://www.ti.com/lit/an/spra953c/spra953c.pdf

0 Anthony P Pham over 5 years ago in reply to Anthony P Pham

TI__Mastermind 23410 points

Hi Mannika,

Did this help with your question? Haven't heard in a while and wanted to check in.

0 Mannika Garg over 5 years ago in reply to Anthony P Pham

Prodigy 30 points

Hi Anthony,

I am still confused. What could be the different ways of measuring it? I mean nominally junction-to-ambient thermal resistance is always higher.

0 Anthony P Pham over 5 years ago in reply to Mannika Garg

TI__Mastermind 23410 points

Hi Mannika,

In the junction-to-ambient case, efficiency can increase as the temperature increases, potentially resulting in lower ratios of temperature to power as described in section 1.7.

0 Anthony P Pham over 5 years ago in reply to Anthony P Pham

TI__Mastermind 23410 points

Hi Mannika,

Just wanted to see if this answer was helpful in your understanding.

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BQ24073: