When power is applied to TPS53676, an initialization procedure performs self-checks of internal memories, performs pin detection, and loads the values stored in non-volatile memory to operating memory. This procedure can take up to 20 ms to complete, during which time the device may not respond to PMBus commands. Initialization takes place the first time power is applied to the VCC pin and does not repeat unless the device is power cycled. Pin configuration is loaded during this time. Until initialization is complete, all pins remain high impedance, except for the AVR_RDY and BVR_RDY pins which are pulled low by default.

Once initialization is complete, the device waits for an enable condition specified by the ON_OFF_CONFIG command to begin power conversion. By default the device is configured to wait for the AVR_EN pin to be set high to enable channel A, and the BVR_EN pin to be set high to enable channel B. Once an enable condition is received, TPS53676 checks that the powerstage input supply (VIN_CSNIN pin) is above the VIN_ON value, and the powerstage driver is fully powered (e.g. that no TAO_LOW condition exists). This takes approximately 750 μs (up to 1.0 ms) to complete before the first PWM pulses are output by the controller. This process repeats each time power conversion is enabled for any reason, including enable cycling or fault shutdown.

Figure 7-1 Initialization process