TPS631000: Extra SW node pulse in boost PFM?

Hi  TR,

it is an issue caused by unstable operation internal.  may be a feedforward capacitor will help. please take the attachment as ref.

thanks

Regards

Tao

Efficiency comparison test of TPS63805 and TPS631000.pptx

Thanks, Tao. They're evaluating the full range from 1.6Vin to 5.5Vin for 3.3Vout at about 20mA load but real input should be between 2V and 4.5V. Should they still target the 51pF Cff?

Hi Tao,

Can you test the 51pF for stability down to 2V and up to 4.5V? I received the EVM today and tested 47pF myself... looked ok down to 2.8V but then I started to see an additional pulse again. 

Bode plots would be great, too. I don't have that capability in my lab. 

Thank you,

TR

Hi TR，

sorry  i missed you update, and i will show you later.

Regards

Tao

Hi   TR,

just kindly reminder, it is unable to test bode plots during PFM working for there will be extra low frequency ripple.and loop is no longer work during PFM working.

Regards

Tao

Hi   TR,

Bad news, during my bench test with 51pf, i got same performance with you.

seems it is not a good solution for your application.

so, it is unacceptable for this additional ripple, right?

Regards

Tao

Is there a better value you'd recommend 10pF or 100pF?

The ripple difference when the additional pulse is there in your buck mode slides is pretty substantial. Looks like you also referenced that you tested ripple at lower Vins (boost mode) can you share those, too?

Their load is pretty small on the board <100mA max but it's connected to an IoT device which will make it pretty dynamic. We just want to make sure it's going to be stable.