A resistor from the RT pin to AVSS sets the switching frequency of the device. The TPS7H500x-SEP controller has a switching frequency range of 100 kHz to 2 MHz. In internal oscillator mode, the RT pin must be populated or the controller will not perform any switching. Equation 7 shows the calculation determining the RT value for a desired switching frequency. The curve in Figure 8-7 shows the RT value that corresponds to a given switching frequency for the TPS7H500x-SEP.

where:

• RT is in kΩ
• f_sw is in kHz

In this mode, the SYNC pin is configured as an output and produces a clock signal with a frequency that is twice that of the switching frequency set by RT. As such, this clock signal has a range of 200 kHz to 4 MHz. This SYNC output clock signal is in phase with the switching frequency of the device. Figure 8-8 shows typical waveforms for the controllers in this mode of operation. Note that the OUTB waveform is only applicable for TPS7H5005-SEP and TPS7H5008-SEP.