BQ24259: PFM/CCM transition mechanism in OTG mode

Ann_Lien

Part Number: BQ24259
Other Parts Discussed in Thread: BQ25896

Hi expert,

My customer want to know the mechanism for transition between PFM and CCM in OTG mode. Does it depend on output loading only or also Vbat/Vbus relation? They counters VBUS ripple too high question on their factory side and they cannot know which one is okay and which one is fail one. Thanks a lot!!

Best regards,

Ann Lien

over 6 years ago

0 Joel Hernandez II over 6 years ago

TI__Mastermind 25800 points

Hey Ann,

The PFM and CCM transition in OTG mode depends on output power and efficiency. Realistically, the inductor current would be used to determine when to switch from PWM to PFM.

When they increase the load on VBUS, do they see the voltage ripple go down?

Regards,
Joel H

0 Ann_Lien over 6 years ago in reply to Joel Hernandez II

TI__Genius 14360 points

Hey Joel,

Thanks for reply!!
They did see ripple go down but their spec is under 5V/0.5A and tested with real device which means current would be 5V/0.3A~0.5A(in transition period). Do we have any chance to narrow the transition gap? Thanks a lot!

Best regards,
Ann Lien

0 Joel Hernandez II over 6 years ago in reply to Ann_Lien

TI__Mastermind 25800 points

Hey Ann,

We cannot narrow the gap on this device to reduce this ripple. However, the BQ25896 can support this by disabling PFM in OTG mode using the PFM_OTG_DIS bit.

Regards,
Joel H

Power management

Power management forum

BQ24259: PFM/CCM transition mechanism in OTG mode