The preferred way to sequence power down is to have all the power supplies ramped down sequentially in the exact reverse order of the power-up sequencing. In other words, the power supply that has been ramped up first should be the last one that should be ramped down. This ensures there would be no spurious current paths during the power-down sequence. The VDDS power supply must ramp down after all 3.3-V VDDSHVx [1-6] power supplies.
If it is desired to ramp down VDDS and VDDSHVx [1-6] simultaneously, it should always be ensured that the difference between VDDS and VDDSHVx [1-6] during the entire power-down sequence is <2 V. Any violation of this could cause reliability risks for the device. TI recommends maintaining VDDS ≥1.5V as all the other supplies fully ramp down to minimize in-rush currents.
If none of the VDDSHVx [1-6] power supplies are configured as 3.3 V, the VDDS power supply may ramp down along with the VDDSHVx [1-6] supplies or after all the VDDSHVx [1-6] supplies have ramped down. TI recommends maintaining VDDS ≥1.5V as all the other supplies fully ramp down to minimize in-rush currents.