TPS62046: TPS62046 output current is only 300mA

Hi Jianfeng,

thanks for your question.

Could you share your schematic with me, including the capacitor values that are used in your design? What kind of battery do you use?

Also, what are your operating conditions such as the temperature?

It would help a lot if you could also share an oscillator plot showing the issue you describe above.

Thanks and best regards,

Britta

hi，Britta：

        Thanks for you reply , the schematic and oscillator picture as attached and can find the values of the capacitors , please see the follow conditions for more detail:

1.  I use the 5 voltage as input insteaded of the battery ( when the 3.3V drop down but  the 5 voltage  works well  )
2.  The work temperature is just normal maybe 25 degress.
3. I also find that when have a heavy load before power on ,the TPS62046 can't work . but when power up then have a heavy load it can work normaly ,that 's so weird
4. 

issue for TI.pdf

Hi Jianfeng,

thanks for sharing those details. While I have a look at the schematic, could you please answer my follow-up questions:

With regards to your point 3: Does that mean you only see the issue during ramp up with max load? Could you please share an oscilloscope screenshot of the startup including the load?
Also, is your maximum load 300mA during startup or after Vout ramp? Please provide a plot that shows the behavior that you described in you initial post, including Vin, Vout and Iload. 

Thanks and best regards,

Britta

hi，Britta：

  thanks for your reply , below information may help you understand my issue :

1. This morning  i use a electronic load instead of resistances ,this time loading 300mA  works well ( both in startup and after Vout ramp), i don't know what happy .
2. i increase the load to 800mA ,it's also works well too(both in startup and after Vout ramp) ,see attached picture.
3. but when i increase to 900mA ,the issue happy again.(load to900mA in startup ) ,see attached picture , it;s similar for this issue.

Hi Jianfeng,

thanks for the details.

Am I correct that now you only the issues at 900 mA load current? Can you confirm that also when you increase the load to 900 mA and above after Vout ramp? Did you see this issue on one device or multiple?

I will try to also reproduce your measurements in the lab to understand what happens.

Thanks,

Britta

Hi，Britta :

    In the early days , when I load in 300mA  ,the volatge droped down  ,but  no happen again in the next days . so i icreased the load current to 900mA , the issue appears again . The load 900mA is in start upatatsue not in vout ramp , i just use one chip for this demo board . i am looking forward for your test record ,thanKs!

Hi Jianfeng,

thanks for the clarification.

I should be able to take the measurements either today or tomorrow and come back to you with results or recommendations beginning of next week.

Thanks for your patience,

Britta

Hi Jianfeng,

unfortunately I was not able to reproduce the issue that you are describing in this post.

Could you let me know how you are measuring the load current? Is it possible that the current temporarily exceeds the specified current limit? 

Also, do you have an EVM that you could test as well?

Best regards,

Britta

Hi，Britta :

         I not get a EVM board for double confirmation , but thanks  anyway,  since the TPS60246 is an old desige, Could you recommend an new similar chip for the new production,thanks !

Hi Jianfeng,

please note that TPS62046 should work without issues. However, TPS62082 is comparable (2.3-6 V Vin, fixed 3.3 V Vout and up to 1.2 A Iout).  It has the same functionality as TPS62046 with improved efficiency, lower output voltage ripple and a smaller solution size. Please note that it is not pin to pin compatible though.

Have you looked at my questions/ suggestions in the last post?

Best regards,

Britta

Hi ,Britta:

     yes ,  I have already checked your suggestion , I think the load current is not exceed the maximum current ,because the load is an electronic device and it's very stable. So  i will weld new board for test  or I will try to test the TPS62082.  thanks a lot for your patient answer in the recently days  and have a good weekend .