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Figure 2:
Power supply block diagram
450-0902
9.4.2 Power On Circuit
There are two mechanisms for powering on the Hand-held, Power Key or External power. The Hand-held is kept
powered on by the CPU, stay alive, or external power. This means that the phone remains powered up all the time
that external power is present. To minimise drain on external power, for example while the phone is connected to a
car kit with ignition off the phone is put into sleep-mode to give an average power use of less than 2mA. For a
20AHr car battery this would give approximately 416 days before the battery would run flat, if left connected and the
phone powered off – assuming no battery self discharge.
9.4.3 Voltage Regulators
Using 4 cells with 3.0V logic gives no problems with high regulator voltage dropout, However the high voltage drop
means that thermal characteristics must be carefully considered.
To reduce the cost the minimum number of regulators are used.
Regulator No 1 – Baseband power supply
Voltage
3.0 ± 2.5%
Current200mA max.
This regulator provides all the power requirements for the base-band except the SIM and LCD.
Regulator No 2 – RF power supply
Voltage
3.6 ± 2.5%
Current200mA max.
This regulator provides the main power for the RF
Regulator No 3 – VCO power supply (located on the RF PCB)
Voltage
3.6 ± 2.5%
Current30mA max.
This regulator provides a very stable power supply for the VCOs
MCUK971001G8
Section 9
Issue 1
Technical Guide
9 - 5
Revision 0
POWER SUPPLIES
3.6V
30mA
3.6V
200mA
3.5V
20mA
3.0V
200mA
POR
VCO
RF
LCD
logic
power-up
logic
CPU
3.6V
3mA
VCXO
RF PCB
SIM
step-up
+ reg.
5.0V
10mA
3.6V det
On RF PCB
external power
8.0V, 1.5A