LM25149-Q1: PFM/SYNC dynamic control

Shinji Tsuji

Part Number: LM25149-Q1

Hi team,

How is LM25149-Q1 output behaves if it changed from diode emulation mode to FPWM mode on the fly using PFM/SYNC pin control at light load (DCM) operation, or vice versa?

I would like to make sure OUT voltage is stable (no over/under shoot) during transition of the mode.

regards,

over 2 years ago

0 Hongjia-Wu over 2 years ago

TI__Expert 5280 points

Hi Shinji,

This will be determined by the L, Cout or the loop design. If the loop is good enough, there will be no issues.

Hongjia

0 Shinji Tsuji over 2 years ago in reply to Hongjia-Wu

TI__Genius 13268 points

Hi Hingjia-san,

Is there internal pull up or pull down bias on PFC/SYNC pin?

What does happen if this pin is OPEN? (from pin FMA, it continues to operate normal. does it mean stay in PFM or FPWM mode?)

regards,

0 Hongjia-Wu over 2 years ago in reply to Shinji Tsuji

TI__Expert 5280 points

Hi Shinji,

Let me check and reply to you later.

Hongjia

+1 Hongjia-Wu over 2 years ago in reply to Shinji Tsuji

TI__Expert 5280 points

Hi Shinji,

The is no pull-up, or pull-down on the PFM/SYNC pin. The input is digital logic, if the pin is left floating there is no guarantee what state it will be in.

Hongjia

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LM25149-Q1: PFM/SYNC dynamic control