ZHCSG44G June 2017 – January 2025 TPS650864
PRODUCTION DATA
BUCK1–BUCK6 support dynamic voltage scaling (DVS) for maximum system efficiency. The VR outputs can slew up and down in 25mV steps for the converters, and either 10mV or 25mV steps for the controllers, using the 7-bit voltage ID (VID) defined in Section 6.7 and Section 6.8. DVS slew rate is minimum 2.5mV/μs. In order to meet the minimum slew rate, VID progresses to the next code at 3μs (nom) interval per 10mV or at 6μs interval per 25mV 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 7-19 shows an example of slew down and up from one VID to another (step size of
10 mV).
Figure 7-19 DVS Timing Diagram I (BUCKx_DECAY = 0)As shown in Figure 7-20, if BUCKx_VID[6:0] is set to 7b000 0000, its output voltage slews down to 0.5V first, and then drifts down to 0 V as the SMPS stops switching. Subsequently, if 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 ramps up to 0.5 V first with soft-start kicking in, then slews up to target voltage in the slew rate mentioned previously. A fixed 200μs of soft-start time is reserved for VOUT to reach 0.5 V. In this case, however, the SMPS is not forced into PWM mode as it otherwise causes VOUT to droop momentarily if VOUT might have been drifting above 0.5V for any reason.
Figure 7-20 DVS Timing Diagram II (BUCKx_DECAY = 0)