Intel PXA27 Series Design Manual page 41

Figure 4-1. Minimal Voltage Regulator Power System Design Example
®
Intel PXA27x Processor Family Design Guide
1.3V
Regulator
Main battery
3.7V
1.8V
Regulator
(optional)
Supe
rCap
High Reference voltage**
* Battery level where system must enter deep sleep until main battery is
recharged.
** Battery level where system should save state and enter sleep.
Mixed Voltage Design Considerations
PWR_EN
ON
1.1V
Regulator
ON
ON
3.3V
Regulator
ON
3.3V
Regulator
Low
Reference
voltage*
VCC_SRAM
VCC_CORE
(drowsy)
VCC_PLL
SYS_EN
VCC_IO
VCC_MEM
VCC_BB
VCC_USIM
VCC_LCD
nReset
VCC_BATT
BATT_FAULT
VCC_FAULT
I:4-3