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Original question:

LM5118: Possible load regulation issues at high end of transition mode

LM5118-Q1: LM5118-Q1 Buck to buck-boost mode transition issue at frequency more than ~460kHz

Prashant Patil1
Prodigy 10 points
Part Number: LM5118-Q1
Other Parts Discussed in Thread: LM5118

Hello Team,

I am using LM5118-Q1

Having following load requirements

Input Voltage Range: 6V to 32V

Output Voltage : 5V ± 3% tol

Expected Load current: 1.5Amps

 Regulator meets above requirement when switching frequency set as ~307 to 312kHz.

But when I change switching frequency to ~460 to 470kHz the regulator could provide regulation in buck mode till 8V input (decreasing input voltage from 32V) as I decrease input voltage further below 8V the transition from buck to buck-boost mode is not happening (buck-boost MOSFET is not getting gate pulse) & its loosing the regulation. (output going <3V and later getting turned OFF)

NOTE: I can not change switching frequency back to 307kHz or so. I need to have solution for load mentioned above with ~460 to 470kHz frequency only.