SLVSH95 July 2024 TPS546C25
ADVANCE INFORMATION
The TPS546C25 offers VOUT_TRANSITION_RATE register to set slew rate when changing the output voltage levels.
During the output voltage transition, due to the quick charge or discharge to output capacitors, the power stage sees extra inrush current. This inrush current plus load current can trigger overcurrent protection when there is no sufficient room from OCL or NOC setting. For example, the positive inductor current during VOUT step-up transition goes higher than nominal operation. If the LS valley OCL threshold is set relatively low and doesn’t allow the extra inrush current, the inductor current is potentially limited by the cycle-by-cycle overcurrent limit feature, thus the actual step-up slew rate is lower than the desired value. Similar situation can happen to VOUT step-down transition with no load condition. The negative inductor current during VOUT step-down transition goes more negative than nominal operation. However, the inductor current is not allowed to go more negative than the Negative OC threshold. Thus, triggering NOC operation during VOUT step-down transition results that the actual step-down slew rate is lower than the desired value.