Nokia 8208, Руководство по обслуживанию

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RM-384
System Module and User Interface
Issue1 Company Confidential Page 5-13
Copyright © 2009 Nokia. All rights reserved.
Figure 55
Charging Circuitry
The LP3919 is a complete Power Management Unit (PMU) designed for CDMA cellular phones. The
LP3919 PMU contains a Li-Ion battery charger, 9 low noise low dropout voltage regulators, 2 buck
regulators, a USB Transceiver, two comparators and a high speed serial interface to program on/off
conditions and output voltages of individual regulators, and to read status information of the PMU.
The Li-Ion charger requires few external components and integrates the power FET. Charging is
thermally regulated to obtain the most efficient charging rate for a given ambient temperature.
A built-in Over-Voltage Protection (OVP) circuit at the charger input protects the PMU from input
voltages up to +28V (LP3919A), eliminating the need for any external protection circuitry.
Buck regulators have an automatic switch to PFM mode at low load conditions
providing very good efficiency at low output currents.
Analog LDO regulators provide excellent PSRR and very low noise, 10 uV typ, ideally suited for
supplying voltage to RF section.
To accommodate different baseband requirements, the LP3919 has four different user selectable
default voltage settings and startup sequences.
Two general purpose comparators can be used for detecting external accessories like ear plug etc.