The SMB_CLK, SMB_DIO, and SMB_ALERT# pins are used for PMBus communication, an open-drain interface. TPS53676 is compatible with both 1.8-V and 3.3-V logic levels as shown in to Part I of the PMBus specification, revision v1.3.1. At least one external pull-up resistor is required for these pins. The 100 kHz, 400 kHz and 1 MHz modes of operation are supported. PMBus is a shared bus, where devices are assigned a communication address. Select the PMBus slave address as described in Section 7.4.4. The controller device stretches clock pulses during operation when more processing time is required. Clock stretching support in the PMBus master is mandatory. See the Section 7.8 section for more information about PMBus functionality.