Nokia 1508 Manual page 10

1508(RM-388)
Baseband Description and Troubleshooting
(Temperature-compensated crystal oscillator) The CBP's TCXO clock input supports
the frequency 19.2 MHz +/-2ppm. An integrated PLL and digital divider inside the
CBP are used to create the required clock for the system.
The SLEEP_CLK provides a 32.768 kHz +/-20ppm clock source to drive the CBP
controller into sleep mode. At this mode, most of the CBP is powered down and the
TCXO is disabled.
Power Distribution
In normal operation, the baseband is powered by the mobile terminal's battery pack.
The battery pack consists of one lithium-ion cell with a capacity of 860 mA and safety
and protection circuits
The PMU ACT5805 IC controls the power distribution for the whole mobile terminal,
which includes the baseband and the RF regulators, but excludes the RF power
amplifier (RF PA) which drains power from the battery directly. The battery provides
power directly to the following parts of the system:
· PMU ACT5805
· RF PA
· Vibrator
· Keyboard & LCD backlights
· Audio Amplifier
The heart of the power distribution is the power control block inside the PMU
ACT5805. It includes all the voltage regulators and feeds the power to the entire
system. The PMU ACT5805 handles hardware power-up functions so that the
regulators are not powered on and the power up reset (NRST) is not released if the
battery voltage is less than 3.2V.
The baseband is powered by the following PMU ACT5805 regulators:
Regulator Voltage
Rating
Notes
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