TPS56528: temperature is too high when working

Hi Chase,

    What is the temperature of the IC that you call "normal working" at 60C ambient?

Regards,

Gerold

Hi Gerold,

The PCB is in the case, and inside the case it is 60℃ when device is working. and especially on the top of the IC(TPS56528), the temperature is 90.9℃.

we measured it attaching thermal coupler on the top of IC.

Best regards,

Chase

Hi  ,

what's the loading current for each rail ? 

and I try to get a quick check on thermal with WEBENCH . The Tc is around 68.5 under 12Vin-1vout -5A.

you can check below file exported from WEBENCH.

If wand to reduce the heat, you can try add more VIAs around IC , use thick layers...

WBOperatingValuesDesign102.csv

Hi,

Also recommend to add 0.1uF cap close to VIN-GND.

BRs,

Young

Hi Young,

you said that the temperature is 68.5℃. is it under room temperature with 25℃ ?

and could you check the temperature also with 0.8V output?

Best regards,

Chase

Hi ,

What's the loading for them ? The thermal is most related with the application conditions. 

 You can get the results by WEBENCH ,too.

WEBENCH link : <https://webench.ti.com/power-designer/switching-regulator%3E

BRs,

Young

Hi Young,

Now I am discussing this issue with my customer.

by the way, i simulated the circuit from WEBENCH, I could not find Tc(top case temperature), I only found junction temperature.

(please see the report attached)

in addition my report is created only pdf file. not txt like you.

could you tell me where can i check the top case temperature?

Best regards,

Chase

WBDesign8.pdf

Hi,

Normally we care the Tj more than Tc, that's why WEBENCH shows this data not Tc.

and I add the Tc data in the files for your reference . You can use a simple formula :Tc=Tj - ΨJT * Power, to get the Tc data .

ΨJT is Junction-to-top characterization parameter, 8.7 C/W for tps56528; Power is Total Power Dissipation, you can get it in WEBENCH .

And i find that you set Ta=60C, do customers need IC working at 60C environment ?

BRs,

Young

Hi Young,

Thank you for your reply.

as i said Ta=60C because the PCB is in the product case, inner ambient temperature is about 60C.

so i can calculate Tc as = 107.8-(8.7*1.428) = 95.38C

now what i am worried about is, of course this Tj and Tc temperatures are in-spec, but i think this is too hot.

this end equipment is L2 ethernet switching hub. and it has to be run all the time, all the year, day and night.

do you have any data of lifetime for this tough environment?

please check this issue. Thanks.

Best regards,

Chase

Hi,

may i know the thermal requirement for this case ? As you said, the IC will working in ~60C ambient temperature and all the time . 

Could you help confirm the typical application &  loading again ? 

For the lifetime , you can check the Qual memo (HTOL data) for reference .

BRs,

Young

Hi Young,

i asked to my customer about the thermal requirement. they said that there is not fixed values, just they check it to under the spec.

so whatever any situation, junction temperature is below 150C that will be fine with them.

but the problem is this device is always-on device so they cannot expect if the time is passed by. after 1 year and 2 years, they do not know what happens.

and the device is L2 ethernet switch. and problemed TPS56528 have 1.0V and 4.2A max output.

if you send me the lifetime in this hard(hot) condition, it would be very helpful to me.

please check this issue. Thanks.

Best regards,

Chase

Hi Chase,

We will check HTOL data and feedback to you next Monday. Thanks.