MC13892_1107 Datasheet, PDF (79/158 Pages) Freescale Semiconductor, Inc – Power Management Integrated

FUNCTIONAL DEVICE OPERATION
SUPPLIES
Table 49. DVS Control Logic Table for SW1 and SW2
STANDBY ⁽⁷²⁾
0
0
1
DVSx Pin
0
1
X
Set Point Selected by
SWx[4:0]
SWxDVS[4:0]
SWxSTBY[4:0]
Notes
72. STANDBY is the logical anding of STANDBY and STANDBYSEC
Table 50. DVS Speed Selection for SW1 and SW2
SWxDVSSPEED[1:0]
00
01 (default)
10
11
Function
25 mV step each 2.0 μs
25 mV step each 4.0 μs
25 mV step each 8.0 μs
25 mV step each 16 μs
Since the switchers have a strong sourcing capability but no active sinking capability, the rising slope is determined by the
switcher, but the falling slope can be influenced by the load. Additionally, as the current capability in PFM mode is reduced,
controlled DVS transitions in PFM mode could be affected. Critically timed DVS transitions are best assured with PWM mode
operation.
Note that there is a special mode of DVS control for Switcher Increment / Decrement (SID) operation described later in this
chapter.
DVS pin controls are not included for SW3 and SW4. However, voltage transitions programmed through the SPI will step in
increments of 25 mV per 4.0 μs, to allow SPI controlled voltage stepping with SWx[4:0]. Additionally, SW3 and SW4 include
Standby mode set point programmability.
Figure 20 shows the general behavior for the switchers when initiated with pin controlled DVS, SPI programming or standby
control.
Figure 20. SW1 Voltage Stepping with Pin Controlled DVS
Note that the DVSx input pins are reconfigured for Switcher Increment / Decrement (SID) control mode when SPI bit
SIDEN = 1. Refer to the SID description below for further details.
SWITCHER INCREMENT / DECREMENT
A scheme for incrementing or decrementing the operating set points of SW1 and SW2 is desirable for improved Dynamic
Process and Temperature Compensation (DPTC) control in support of fine tuning power domains for the processor supply tree.
An increment command will increase the set point voltage by a single 25 mV step. A decrement command will decrease the set
point by a single 25 mV step. The transition time for the step will be the same as programmed with SWxDVSSPEED[1:0] for DVS
Analog Integrated Circuit Device Data
Freescale Semiconductor
MC13892
79