CCS/TPS65987DDJ: PD charge fail on NB of Dell_5370

Hello,

If you are looking for the Rdson vs. junction temperature, check out Figure 1 in the datasheet. There you can find the PPHVx Rdson vs Junction Temperature. 

I would need more information about the fail to understand it. Is the device going into thermal shutdown? Have you followed the layout recommendations for heat dissipation described in Section 11.6 of the datasheet? 

Thanks,

Emma

Hi,Emma:

yes,i am read the figure 1 in the datasheet, the RDSon VS Junction temp be direct ratio relationship. the RDSon resistance is increase  when the temp rise.

why is shutdown the Vbus when the temperature rise to 56°C? in theroy, it's  better withstand inrush when the RDSon increase .

could you help to me check the what's reason?

as below for i tested the docking rise temp when operating 1hour after, it seems doesn't  thermal shutdown,because the TA=56°C be shutdown.

together the RθJC(top)_65.4/W(56+3*3*0.025*65.4=70°C),doesn't touch the Tj(125°C).

if the docking be assembly test: it is charge OK when the temp fall to 32°C,but need to waiting 0.5hour after

if the docking has a PCBA loading , it handshake OK when wait for 3mins after,the temp fall to 39°C .

what 's it symptom?

 could you help to me confirm it?

PS: our layout be follow the datasheet,pls refer to the below capture.

thanks!

Hello,

I am not sure if the issue you are seeing is related to the TPS65987D. I was unable to reproduce this on an EVM. Can you try testing in parallel with an EVM to reproduce this issue?

Thanks,

Emma

Hi,Emma:

thanks!

accroding your suggestion,i tested the EVM ,loading 20V/5A condition, after 1hour,the TPS65987D was 57°C(see the below capture).

then connect it to Dell_5370 , it can reproduce the issue.but within 2mins check.

because the symptom hardly repeat if out of 2mins.

in this cause, it seem doesn't  touch the OTP of TPS65987D(5*5*0.025*65.4+57=98°C<125°C).

meanwhile, i try move the E-cap and MLCC(our docking has 100uF/25V,ESR=0.03R)after,then change it to EVM's Tantal Cap to test.

  same as condition loading after,re-check the PD charge.it work normal.

and i change the EVM's cap to 100uF/25V/0.03R(from our docking),same as loading test it again,

re-charge the NB, doesn't handshake OK,must waiting for the temperature colder(about 40°C)

upon these conclusion,this issue from E-cap or MLCC cap,due to the hot reason,will decrease the ESR.

if cover this NB, change to higher ESR E-cap is better.

if cover the NB of 100W PD(ie:lenevo Y9000K),must using the lower ESR E-cap,else to charge fail.

how to choose the E-cap for the compatibility,i am very confuse.

as below for our PD power solution(LM34936),show it to you reference.

hope to you give some suggestion to me reference for this issue.

thanks!

Hi,Emma:

re-upload the capture fail. maybe the server of TI be busy.

the PD power base on the EVM of LM34936.

thanks!

Hello,

Which capacitor are you referring to? Which pin on the TPS65987D is it on?

Thanks,

Emma

Hi,Emma:

 the location of capactiro is EC13(100uF/25V,ESR 30mR,don't care the 150uF of circuit);

the net name is TT3 for  GPIO pin of PDO_20V ,the 31# pin for this controll from TPS65987D,name is GPIO4.

BTW:

we have test  the final goods of our docking in chamber 40°C, the  temperature(TA) of TPS65987D reach to 74.5°C.

Operating ambient temperature, TA -10~75°C in the datasheet, like the test condition ,can i understand it enter OTP or not?

could you help to me clarify the TA and TJ(125°C.)

thanks!