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Regulator No 4 – VCXO power supply (located on the RF PCB)
Voltage
3.6 ± 2.5%
Current3mA max.
This regulator provides a very stable power supply for the VCXO
Regulator No 5 – SIM regulator
Voltage
5 ± 5%
Current10mA
This regulator provides 5V for SIM access
Regulator No 6 – LCD regulator
Voltage
3.5 ± 2.5%
Current20mA
This regulator provides 3.5V for LCD power
9.4.4 Battery Charging circuit
The CPU within the phone controls the battery charging. When external power is present the phone is automatically
switched on. If rechargeable cells are detected and the temperature is within specified limits the charger starts
rapid charge algorithm.
Charging is determined by - deltaV with time, temperature and voltage safe-guards.
Deeply Discharged batteries
When a battery is deeply discharged there may not be enough power to power on the phone for charging. In this
case the charging circuit must automatically detect if the batteries are rechargeable and start slow trickle charge
until there is enough power to switch on the phone.
9.4.5 Power Fail
The SIM card contains EEPROM, if power fails while the SIM is active the SIM may corrupt its memory as the
supply voltage drops out of specification.
The PWR_FAIL_INT is a non-maskable interrupt to the CPU, which forces exception processing whenever the
battery voltage drops below 3.6V.
Issue 1
Section 9
MCUK971001G8
Revision 0
9 - 6
Technical Guide
POWER SUPPLIES