TPS631000: IPFM_entry

Hello Dice-K,

It seems to be the output current, but we need to wait for the expert to be back in the office to know it for sure. Please expect an answer next week Wednesday.

Best regards,
Brigitte

Hi Brigitte,
Thank you for your reply.

I will wait for the answer next Wednesday.
I would also like the answer to the following:

The period during which 145mA is exceeded is just under 1ms.

Is the threshold for switching from PFM to PWM also 145mA?

↓ Enlarged view of the current waveform at peak

I would like to know how long period the threshold needs to be exceeded for the mode to switch.

Best regards,
Dice-K

Hello Dice-K,

Thank you for your patience.

Which current are you measuring? Is this the load current? If yes, I expect that the peak is coming from the output capacitor.

Best regards,
Brigitte

Hi Brigitte,
Thank you for your reply.

Yes, this is the load current.
If the peak current is generated from the output capacitor, won't it switch from PFM to PWM?

Best regards,
Dice-K

Hello Dice-K,

Do you have the capability to measure the inductor current? If yes, I think this helps to understand if the behavior is as expected or not.

Nevertheless, in general the converter is compensated and has to be compensated somewhere between 1/5th and 1/10th of the right-halfplane zero and therefore it is capable of switching several cycles before a change in current will be seen internally. So an overshoot at the beginning might be expected.

Best regards,
Brigitte

Hi Brigitte,

The period during which the output current exceeds 145mA is just under 1ms, which is nearly 2000 cycles.
How many cycles does the inductor average current have to exceed the threshold before the transition from PFM to PWM occurs?

Best regards,
Dice-K