Datasheet

Analog Integrated Circuit Device Data
Freescale Semiconductor 46
MC34708
Functional Block Description
In addition to controlling the operating mode in Standby, the voltage setting can be changed. The transition in voltage is handled
in a controlled slope manner, see
Dynamic Voltage Scaling for details. Each regulator has an associated set of SPI bits for
Standby mode set points. By default, the Standby settings are identical to the non-standby settings which are initially defined by
PUMSx programming.
The actual operating mode of the Switching regulators as a function of the STANDBY pin is not reflected through the SPI. In other
words, the SPI will read back what is programmed in SWxMODE[3:0], not the actual state that may be altered as described
previously.
Two tables follow for mode control in the low power Off states. Note that a low power Off activated SWx should use the Standby
set point as programmed by SWxSTBY[4:0]. The activated regulator(s) will maintain settings for mode and voltage until the next
startup event. When the respective time slot of the startup sequencer is reached for a given regulator, its mode and voltage
settings will be updated the same as if starting out of the Off state (except switching regulators active through a low power Off
mode will not be off when the startup sequencer is started).
In normal steady state operating mode, the SWxPWGD pin is high. When the SWx set point is changed to a higher or lower set
point, the SWxPWGD pin will go low and will go high again when the higher/lower set point is reached.
0100 APS Off
0101 PWM PWM
0110 PWM APS
0111 Off Off
1000 APS APS
1001 Reserved Reserved
1010 Reserved Reserved
1011 Reserved Reserved
1100 APS PFM
1101 PWM PFM
1110 Reserved Reserved
1111 PFM PFM
Table 33. Switching regulator Control In Memory Hold
SWxMHMODE Memory Hold Operational Mode
(44)
0 Off
1 PFM
Notes:
44. For Memory Hold mode, an activated SWx should use the
Standby set point as programmed by SWxSTBY[4:0].
Table 34. Switching regulator Control In User Off
SWxUOMODE User Off Operational Mode
(45)
0 Off
1 PFM
Notes:
45. For User Off mode, an activated SWx should use the Standby
set point as programmed by SWxSTBY[4:0].
Table 32. Switching regulator Mode Control for Normal and Standby Operation
SWxMODE[3:0] Normal Mode Standby Mode