Often it is desirable to synchronize the operation of multiple regulators in a single system. This technique results in better defined EMI and can reduce the need for capacitance on some power rails. The LM53600-Q1 and LM53601-Q1 devices provide a SYNC/MODE input, which allows synchronization with an external clock. The LM53600-Q1/LM53601-Q1 implements an in-phase locking scheme – the rising edge of the clock signal provided to the input of the LM53600-Q1 or LM53601-Q1 device corresponds to turning on the high side device within the LM53600-Q1 or LM53601-Q1. This function is implemented using phase locking over a limited frequency range eliminating large glitches upon initial application of an external clock. The clock fed into the LM53600-Q1 or LM53601-Q1 device replaces the internal free running clock but does not affect frequency fold-back operation. Output voltage will continue to be well regulated with duty factors outside of the normal 15% through 77% range though at reduced frequency.
The device remains in FPWM mode and operates in CCM for light loads when synchronization input is provided.