Two TPS7H500x-SP controllers can be operated in a primary-secondary mode by utilizing the SYNC pin. As mentioned in the Internal Oscillator section, when RT is selected to provide the desired switching frequency, SYNC outputs a clock signal at twice the switching frequency. As such, the clock input generated by the primary device be used as the clock input at SYNC for the secondary controller, which would operate in external synchronization mode. This means that the RT pin of the primary device should be populated while the corresponding pin of the secondary device would be left floating.

The primary-secondary mode would be useful in a couple of scenarios. The first is for two independent converters that need to be synchronized to the same switching frequency. In this instance, the converters can be two converters can have different operating conditions or topologies. Besides the shared SYNC signal, there are no connections between the two converters.

In a second scenario, two controllers can be used to design a single interleaved converter with phases in parallel. In this design, the VSENSE, COMP, SS, and HICC pins would need to be connected in addition to the shared SYNC connection.

When using two controllers in primary-secondary mode, it is important to note that secondary controller will invert the clock signal that it receives from the primary controller. As such, there will be phase shift between the switching outputs of the primary and secondary controllers. This phase shift from an output (i.e. OUTA) on the primary controller to the corresponding output on the secondary controller will be 90° or 270°, depending on when the secondary device synchronizes to its clock input. Note that in Figure 8-12, the waveforms for OUTB are only applicable for TPS7H5001-SP and TPS7H5004-SP.

The three operational modes for the controller are summarized in Table 8-1.