Panasonic GSM EB-A100 Service Manual

– 5-13 –5.4. Power Management SubsystemADP6537LCD MemoryVMEMSIMVCCSIMCircuitRTCCircuitVMEMBatteryNResetAD652513 MHzVCOREVEXTVRTCPower detectionand latchingChargingCircuitVMEMVCOREVBATFigure 5.13. Power management Subsustem Block Diagram5.4.1. Power SourceThe 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 the AD6537 is in Deep Discharge Lockout (DDLO) or Under-Voltage Lockout (UVLO) only the Real-Time Clock regulator isactive. If the AD6537 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 regulatorand the the reference are always enabled. The other regulators are enabled or disabled based on input from the user orsoftware. If the user presses the power-on key (KEYON), the regulators required to boot the software are enabled.If a charger isdetected(CHGDET) the regulators required to boot the software are enabled. If the software asserts the DBBON signal theregulators reguired to maintain the software state are enabled. The VCXOEN signal enables the VCXO regulator.The analog 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 LDOhas been optimized for very low quiescent current at light loads as this LDO is on whenever the handset is switched on.5.4.3. Voltage Regulation5.4.2. Regulator Control