Figure 7-13 shows a conceptual view of the TPS53676 output voltage control, and dynamic behavior.

Update the VOUT_COMMAND value through PMBus, to change the output voltage of each channel on-the-fly. Optionally, use the OPERATION command to toggle the output voltage bewteen the VOUT_MARGIN_HIGH, VOUT_MARGIN_LOW and VOUT_COMMAND values. This is described in more detail in Section 7.5.2. AVSBus may also control the output voltage and slew rate when configured to do so through OPERATION.

The VOUT_MAX and VOUT_MIN commands define the maximum and minimum allowed voltage, through any combination of offsets and voltage target commands. If commanded higher or lower than these limits, the output voltage transitions to these limits and stops.

The soft-start and soft-stop slew rates are calculated using the current output voltage target and TON_RISE and TOFF_FALL command values. All output voltage transitions which occur during normal power conversion follow the slew rate defined by VOUT_TRANSITION_RATE.

The VOUT_SCALE_LOOP parameter must be set properly, when an external output voltage divider is being used. This value is used internally to provide scaling for all output voltage related parameters.

Update the VOUT_TRIM value to apply a static offset to the output voltage target. This may be used to fine-tune the output voltage in production, or null any board related offsets.

Figure 7-13 Output voltage control conceptual view

TPS53676 provides several options to fine-tune the controller response to high speed output voltage transitions. For example, large output voltage steps upward cause an inrush current, required to charge the output capacitors for that channel. This inrush current combined with the DC load line setting make the output voltage appear to move more slowly than the commanded slew rate. Use the DVID_CONFIG command to configure dynamic loadlines and offsets which apply only during output voltage transitions. Typically, set the DC and AC load lines for upward moving transitions to a value equal or lower than the nominal. Similarly, typically, set the DC and AC loadlines to a value larger than the nominal value for downward moving transitions. Refer to the Technical Reference Manual for a register map of this command.

Figure 7-14 Dynamic load line and offset control

The DVID_CONFIG command also allows the user to configure dynamic offsets which are only applied during output voltage transitions. The configured recovery delays determine when the load line and offset values return to nominal settings, in terms of PWM (order 0) cycle counts. Figure 7-14 illustrates the dynamic load line, offset and recovery delay behavior of the controller.