Power Distribution - Nokia 6255 Description And Troubleshooting

6255/6255i6256/6256i (RM-19)
Baseband Description and Troubleshooting
The charging control circuitry (CHACON) inside the UEME controls the charging current
delivered from the charger to the battery. The battery voltage rise is limited by turning
the UEME switch off when the battery voltage has reached 4.2V. The charging current is
monitored by measuring the voltage drop across a 220mOhm resistor.

Power Distribution

In normal operation, the baseband is powered from the mobile terminal's battery. The
battery consists of one Lithium-Ion cell capacity of 1070 mAh and some safety and
protection circuits to prevent harm to the battery.
The UEME ASIC controls the power distribution to the entire mobile terminal through the
BB and RF regulators. The battery feeds power directly to the following parts of the
system:
• UEME
• PA
• Vibra
• Display lights
• Keyboard lights
The heart of the power distribution to the mobile terminal is the UEME. The UEME
includes all the voltage regulators and feeds the power to the system. The UEME handles
hardware power-up functions so the regulators are not powered and the power-up reset
(PURX) is not released if the battery voltage is less than 2.8V.
The baseband is powered from five different UEME regulators (see Table 2):
Maximum
Regulator
Current (mA)
VCORE 300
DC/DC
VIO 150
VFLASH1 70
VFLASH2 40
VANA 80
VSIM 25
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Table 2: Baseband Regulators
Vout (V) Notes
1.35 The power-up default value is 1.35V. The output voltage is
selectable: 1.0V/1.3V/1.5V/1.8V.
(Note: If using D2800 processor version 1, the default is
1.57V.)
1.8 Enabled always except during power-off mode
2.78 Enabled always except during power-off mode
2.78 Enabled only when data cable is connected
2.78 Enabled only when the system is awake (off during sleep and
power-off modes)
3.0 Enabled during power-up mode and scanning for a SIM card
©2005 Nokia Corporation
Nokia Customer Care
Company Confidential Issue 2 05/2005