Each controller can be used in external synchronization mode by leaving the RT pin floating and applying a clock to the SYNC pin. Note than the RT pin configuration sets the oscillator mode of the controller and must be left floating for this mode of operation. The external clock that is applied must be set to twice the desired switching frequency (that is, a 1-MHz applied clock is needed for 500-kHz switching frequency). The external clock must be in the range of 200 kHz to 4 MHz with a duty cycle between 40% and 60%. It is recommended to use an external clock with 50% duty cycle. The controller will internally invert the clock signal that is applied at the SYNC pin during this mode. Since the controller does not perform any switching with RT floating, the applied clock must be present before OUTA and OUTB (where applicable) will become active for external synchronization mode. Figure 8-9 shows the switching waveforms for the controllers in external synchronization mode. Note that the OUTB waveform is only applicable for TPS7H5005-SEP and TPS7H5008-SEP.