900844 Datasheet, PDF (51/118 Pages) Freescale Semiconductor, Inc – Integrated Power Management IC for Ultra-mobile and Embedded Applications

VBAT
VCOINCELL
RTC
STATE
ACTIVE
STATE
FUNCTIONAL DEVICE OPERATION
POWER STATES AND CONTROL
VPWR
VBOS
Keep Alive
Bandgap
1.2V
VCORERTC
1.2V
0.9V
CLOCK
RC/XTAL
Keep Alive
Registers
UVDET
EN
EN
VCOREREF
EN
VCOREDIG
VCORE
EN
1.5V
1.2V
Digital Supply Reference Supply
2.775V
Analog Supply
Closed when
VCOREDIG > 1.2V
Figure 17. 900844 Internal Power Tree Block Diagram
As part of the turn on sequence, the 900844 enables a set of internal supplies that provide power to the rest of the circuitry:
1. V_COREREF: This is the main bandgap and reference voltage for all internal circuitries.
2. V_CORE: This is the supply for the internal analog circuitry.
3. V_COREDIG: This is the supply for the internal digital circuitry.
Table 21 summarizes the voltage references on the 900844.
Table 21. 900844 Internal Power Supply Summary
Reference
VCOREREF
(Bandgap & Regulators Reference)
VCOREDIG
(Digital Core Supply)
VCORE
(Analog Core Supply)
Parameter
Output Voltage
Bypass Capacitor
Output Voltage
Bypass Capacitor
Output Voltage
Bypass Capacitor
Target
1.2 V
100 nF typ.
1.5 V
2.2 μF typ.
2.775 V
2.2 μF typ.
There is an internal node called the Best of Supply node (VBOS), which supplies the Real Time Clock and the Keep Alive
Registers. This ensures that power to these critical circuits is maintained for maximum life. VBOS represents the highest of the
VBAT and VCOINCELL input voltages. When VCOREDIG is > 1.2 V, an internal switch is closed, and the circuitry that was
powered from VBOS is now powered from VCOREDIG.
Analog Integrated Circuit Device Data
Freescale Semiconductor
900844
51