Synchronous buck allows for FPWM operation. Normally it is desired to have FPWM only in light load mode - not in full load mode. Hence, most synchronous buck converters have a much smaller negative inductor current limit than a positive inductor current limit. If an IC is chosen without sufficiently large negative inductor current limit for a sinking current application, the output power will be limited by the small negative inductor current limit.

Fortunately, some TI devices such as TPS548B22 and TPS548D22 perform both positive and negative inductor current limits with the same magnitudes, allowing the sinking current application the same large output current as the sourcing current application.