AM3352: Temperature considerations

Shivasharan Nagalikar

Part Number: AM3352

Hello team,

One of my customers looking for suggestions on PCB copper area calculation to maintain the junction temperature. Could you please advise ?

We have estimated the power consumption of 1.25W with optimum utilization of AM3352. According to (Tj=Ta+PD*Rja )formula...

Where Tj= Junction temperature, Ta= System inside ambient temperature of 70Degree, PD= Power dissipation of 1.25W, Rja= Junction to ambient thermal resistance of 24.2 degree/Watt

Tj = 70 + 1.25*24.2 = 100.25 degree

First, We are looking to reduce for 10 degree junction temperature, how much copper is need to reduce the temperature by 10C?”

If it s difficult to meet 90 degree at 70 degree ambient, how much POH will be de-rated with a junction temp of 100C? Our expected ambient inside the system is 70 degree.

Best Regards,

Shiv

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

Hi,

Please see this document: processors.wiki.ti.com/.../AM335x_Thermal_Considerations

0 Harsh Bhuva over 7 years ago in reply to Biser Gatchev-XID

Prodigy 20 points

Hi Biser,

We have gone through this link processors.wiki.ti.com/.../AM335x_Thermal_Considerations and found little useful.

We are targeting me maintain junction of processor by 90 degree. Can you please specify required copper area?
Can you please share heat-sink serface area calculation to maintain junction temperature?

0 Biser Gatchev-XID over 7 years ago in reply to Harsh Bhuva

TI__Guru**** 393215 points

There is no universal formula for this. This depends entirely on PCB stack-up and layout. A good practice is to have a solid GND plane on the first internal layer under the processor, with the GND plane covering the entire layer. You can study the AM335x reference designs to reach your own solution: processors.wiki.ti.com/.../AM335x_Boards

0 Harsh Bhuva over 7 years ago in reply to Biser Gatchev-XID

Prodigy 20 points

We have found PCB Thermal calculator for calculating required copper area to control junction temperature.

http://www.ti.com/adc/docs/midlevel.tsp?contentId=76735&DCMP=hpa_design_center&HQS=Tools+OT+pcbthermalcalc

But, we haven't found copper area calculation for AM3352ZCZ80 in this calculator. Can please you suggest how we can calculate it?

Following link have given basic idea about thermal management of high frequency board in general (i.e. use thermal pad, spread copper layer, use metal enclosure, air flow using fan etc.):

http://processors.wiki.ti.com/index.php/AM335x_Thermal_Considerations

We are trying to reduce temperature from 100 degreeC to 90 degreeC (10 degreeC control) by using PCB layout designing (using thermal pad and spreading copper layer around AM3352), can you suggest document in which they specified the copper area requirement v/s junction temperature and number of BGA thermal via v/s junction temperature?

0 kalpesh diyora over 7 years ago in reply to Harsh Bhuva

Intellectual 265 points

It is not clear on finalization of heatsink area to control the junction temperature.

Generally the processor will guide to derive the heat sink size to control the junction temperature.

Also,

There is two difference thermal resistance in datasheet for junction to case. And there is hugh difference in between these two. I think, this would be close to each other.

1) Junction to case = 10.2 c/w

2) Junction to Package top = 0.3 C/W

Please clarify

0 Biser Gatchev-XID over 7 years ago in reply to kalpesh diyora

TI__Guru**** 393215 points

This document explains the details of the Junction to Case parameter in section 2 and the Junction to Top of Package parameter in section 3:
www.ti.com/.../spra953c.pdf

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AM3352: Temperature considerations