The LM6x4xx can have two behaviors while lightly loaded. One behavior, called auto mode operation, allows a seamless transition between normal current mode operation while heavily loaded and in highly-efficient light-load operation. The other behavior, called FPWM mode, maintains full frequency even when unloaded. Which mode the LM6x4xx operates in depends on the SYNC/MODE pin. When SYNC/MODE is high, the part is in FPWM. When SYNC/MODE is low, the part is in PFM.

In auto mode, light-load operation is employed in the LM6x4xx at load lower than approximately 1/10th of the rated maximum output current. Light-load operation employs two techniques to improve efficiency:

• Diode emulation, which allows DCM operation
• Frequency reduction

Note that while these two features operate together to create excellent light load behavior, they operate independently of each other.