SLUSDW9A June 2020 – June 2020 TPS51215A
SLEW can be used to program the soft-start time and voltage transition timing. During soft-start operation, the current source used to program the SLEW rate is 4.5 µA (nominal). During VID transition, the current source is switched to a higher current of 45 µA.
In this design example, the requirement is to complete VID_00 to VID_11 transition within 120 µs, calculate the SLEW capacitance based on Equation 8.
For VOUT = 1.8 V, the soft start timing based on CSLEW is 1.2 ms.
The slower slew rate is desired to minimize large inductor current perturbation during startup and voltage transition, thus reducing the possibility of acoustic noise.