LMZ31530: Thermal coefficients

Nir Flysher

Expert 3287 points

Part Number: LMZ31530

Dear Team,

Could you please advise the following thermal coefficients for the LMZ31530RLGT ?

Theta_JB - Junction to board

Theta_Jc_Top - Junction to top

Theta_Jc_Bot - Junction to bottom

In addition, would you recommend to add additional thermal VIAs at the center of the thermal pad (in addition to the via on pin 69) ?

Regards,

Nir.

over 5 years ago

0 Denislav Petkov over 5 years ago

TI__Mastermind 19101 points

Hello Nir,

The datasheet already contains thermal information in section 4.3. We use Psi JT and Psi JB parameters.
If the customer doesn't mind thermal vias inside the pads, I don't see a problem adding them.
As always, please check the recommended layout and component placement in section 8.2.

Cheers,
Denislav

0 Tima Koren over 5 years ago in reply to Denislav Petkov

Prodigy 20 points

The answer settles the thermal vias matter, but does not provide additional information on thermal resistances. I want the Theta values for a 2-R model of the component, so that it can be integrated in a bigger model of the PCB.
Many TI component datasheets contain Theta values, so I assume that those values have been measured.
Can you assist me by providing those values?

In addition is there a recommended value of junction temperature, Tj?
The only value listed in the DS is under Absolute Maximum Ratings. Is it applicable as the recommended maximum Tj?

Thanks,
Tima

0 Tima Koren over 5 years ago in reply to Denislav Petkov

Prodigy 20 points

Hi Denislav,

Can you please assist me with the Theta_jt and Theta_jb thermal resistance values?

They are required to construct a 2-resistor model for the component. Theta_jc (junction to case) may also be helpful.

Thank you,

Tima

0 Denislav Petkov over 5 years ago in reply to Tima Koren

TI__Mastermind 19101 points

Hello Tima,

The maximum operating junction temperature is 125C. This would be the maximum recommended temperature.

I will double check if the theta jt and jb numbers are available, but many devices have the psi numbers instead. Here is an app note providing more details: www.ti.com/.../spra953c.pdf

Cheers,
Denislav

0 Denislav Petkov over 5 years ago in reply to Denislav Petkov

TI__Mastermind 19101 points

Hi Tima,
We only have psi numbers available for this device.
Cheers,
Denislva

Power management

Power management forum

LMZ31530: Thermal coefficients