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5.4. Power Management Subsystem
U201
LCD
Memory
VMEM
SIMVCC
SIM
Circuit
RTC
Circuit
VMEM
Battery
NReset
U101
13 MHz
VCORE
VEXT
VRTC
Power detection
and latching
Charging
Circuit
VMEM
VCORE
VBAT
Figure 5.13. Power management Subsystem Block Diagram
5.4.1. Power Source
The battery comprises a single Lithium-Ion (Li-Ion) cell with a nominal voltage of 3.7 V and 780 mAh capacity.
This type of battery has an advantage in weight and size over Nickel Metal Hydride (NiMH) cells.
The voltage regulators and the reference are enabled based on the status of the battery and input from the user or software.
If U201 is in Deep Discharge Lockout (DDLO) or Under-Voltage Lockout (UVLO) only the Real-Time Clock regulator is active.
If U201 is in Thermal Shutdown only the Real-Time Clock regulator is active.
If the battery is not in Deep Discharge Lockout, Under-Voltage Lockout, or Thermal Shutdown, the Real-Time Clock regulator
and the reference are always enabled. The other regulators are enabled or disabled based on input from the user or software.
If the user presses the power-on key (KEYON), the regulators required to boot the software are enabled. If a charger is detected
(CHGDET) the regulators required to boot the software are enabled. If the software asserts the DBBON signal the regulators
required to maintain the software state are enabled. The VCXOEN signal enables the VCXO regulator.
The analogue regulators can be enabled and disabled using CSPORT.
Each power source is specified as follows.
■
Digital Core LDO (VCORE)
The digital core LDO supplies the baseband circuitry in the handset (baseband processor and baseband converter). The LDO
has been optimised for very low quiescent current at light loads as this LDO is on whenever the handset is switched on.
5.4.3. Voltage Regulation
5.4.2. Regulator Control