(1) LM63610 moves between PWM and PFM as load changes when it is in AUTO mode, so the question is what is the condition for this mode transition(between PWM and PFM)? Does it occur when Iout_avg<0.5*IL_pkpk?
When Iout_avg<0.5*IL_pkpk, it operates in PFM.
When Iout_avg>0.5*IL_pkpk, it operates in PWM.
Correct?
(2) Besides, if stability need to be checked, how to perform the loop measurement?
Thanks.
Hi Jason,
Thank you for considering TI products. The PFM mode is triggered when the circuit runs into the min on time in DCM mode, and the frequency is slowed down to allow the duty cycle reduce from Vo/Vout to meet the output regulation requirement, otherwise Vout will rise above the setting point.
In DCM, the on time is determined by the following equation:
Ton = sqrt (2 x Io x Lo x Vo / ( Fsw x (Vin - Vo) x Vin ) )
Replacing Ton with the min ON time, and you can get the Fsw vs Io curve.
Regarding the stability, you need to follow the design guideline to select the components and you may check the full load Bode Plots with good margin, then at light load in PFM the circuit should remain stable. A quick bench verification is to run a step load from min load to max load and see the output response.
Hope this clarifies,
Best Regards,
Youhao
