SWCS142 July 2018 TPS650861
PRODUCTION DATA.
BUCK1–BUCK6 support dynamic voltage scaling (DVS) for maximum system efficiency. The VR outputs can slew up and down in either 10-mV or 25-mV steps using the 7-bit voltage ID (VID) defined in Section 4.7 and Section 4.8. DVS slew rate is minimum 2.5 mV/µs. In order to meet the minimum slew rate, VID progresses to the next code at 3-µs (nom) interval per 10-mV or at 6-µs interval per 25-mV steps. When DVS is active, the VR is forced into PWM mode, unless BUCKx_DECAY = 1, to ensure the output keeps track of VID code with minimal delay. Additionally, PGOOD is masked when DVS is in progress. Figure 5-5 shows an example of slew down and up from one VID to another (step size of
10 mV).
As shown in Figure 5-6, if a BUCKx_VID[6:0] is set to 7b000 0000, its output voltage will slew down to the minimum VID value first, and then will drift down to 0 V as the SMPS stops switching. Subsequently, if a BUCKx_VID[6:0] is set to a value (neither 7b000 0000 nor 7b000 0001) when its output voltage is less than 0.5 V, the VR will ramp up to 0.5 V first with soft-start kicking in, then will slew up to target voltage in the slew rate aforementioned. It must be noted that a fixed 200 µs of soft-start time is reserved for VOUT to reach 0.5 V.