LMK04832: Thermal heat issue

Hello Kathirvel,

Are you using the LMK04832EVM? If not, what is surrounding your LMK04832 on your board? What voltage are you providing to the supply pins?

Best,

Andrea

Supply voltage is 3.3V. The IC placed in the bottom side of the PCB only Resistors and capacitors are surrounded.

/cfs-file/__key/communityserver-discussions-components-files/48/0447.LMK04832_5F00_Sch.pdf

Hello Kathirvel,

What's the actual power consumption on the part (not just the estimate from TICS Pro)? Also, you measured the case temp of 71°C when ambient is 24°C, this number doesn't add up if the power is that high, could you please explain further? Thanks!

Best,

Andrea

We do not have any direct means to measure the power consumed by LMK04832 as the board has other components as well.The board is powered by single 5V supply.The current consumption without LM04832 configuration programming is around 1A.After programming when the clock outputs are stabilized after 30 minutes the current of the board is 1.5A and the heat on the LMK04832 case is close to 71'C.So we can say it consumes 2.5Watts.

Hi Kathirvel,

The power consumption seems to be in the expected range with your configuration, can you send us the register dump file/ticspro tcs file and we can take a look if anything can be optimized but looks like not much of room if you're to keep with the output format, # channels on etc.

Apart from that, is it possible for you to measure the device case temperature when the ambient is 70C? Also maybe include a measurement on the board just right next to the device when ambient is 70C, we can take a second look on the Junction estimate with Rjb and Rjc, which probably a more accurate estimate.  

Below is a link to an apps note on thermal metrics.

Semiconductor and IC Package Thermal Metrics (Rev. C) (ti.com)

Regards

CP

The ticspro tcs file is already attached.Please suggest if any improvements can be done to reduce power consumption.

/cfs-file/__key/communityserver-discussions-components-files/48/TICSPro_5F00_14_5F00_09_5F00_2023_5F00_40MHZ.tcs

We will try to measure the temperature at higher ambient temperatures  and update.

OK thanks Kathirvel, we'll take a look.

Hi Kathrivel, 

I checked your config on a LMK04832 EVM and I measured around 0.87A at 3.3V including all the other peripheral components, so a power consumption of 2.5W seems like a reasonable estimate. I was able to reduce the current consumption by around 40 mA by disabling SYSREF since it looks like you don't need that functionality. Besides that, there's not much else that can be done to reduce the power since most of it is being consumed by the VCO and output clocks.  

Like CP mentioned, I would recommend measuring the case temperature and using the Junction-to-case (top) thermal resistance parameter since it will be much more accurate compared to the junction-to-ambient parameter. The PCB design (overall thickness, number of layers, surrounding components, etc.) has a huge impact on the junction-to-ambient accuracy so the 24.3 C/W figure may not be a good estimate for your application. For reference, running your config on the EVM at room temperature, the case temperature on the LMK04832 only reached 43C which I measured by taping a thermocouple to the top of the device package. This would give an estimated junction temperature of around 60C and I would expect there to be plenty of margin at an ambient temperature of 70C. 

Regards, 

Connor 

TICSPro_14_09_2023_40MHZ_SYSREF_Disabled.tcs