Power Block - LG L705ix Service Manual

3. TECHNICAL BRIEF

3.9 Power Block

3.9.1 General
MSM6280, included RF, is fully covered by PM6650(Qualcomm PMIC). PM6650 cover the power of
MSM6280, MSM memory, RF block, Bluetooth, Micro SD, USIM and TCXO.
Major power components are :
PM6650-3P (U301, Main PCB Bottom): Phone power supply
MAX8645Y (U400, Main PCB Top): LCD Backlight charge pump and Dual LDO
3.9.2 PM6650
The PM6650 device integrates all wireless handset power management, general housekeeping, and
user interface support functions into a single mixed signal IC. A block diagram of the device is shown
in Figure 3.9-1. Its versatile design is suitable for CDMA and non-CDMA handsets, as well as other
wireless products such as PC cards, modems, PDAs, etc.
The power management portion accepts power from common sources battery, external charger,
adapter, USB_VBUS, coin cell backup and generates all the regulated voltages needed to power the
appropriate handset electronics. It monitors and controls the power sources, detecting which sources
are applied, verifying that they are within acceptable operational limits, and coordinates battery and
coin cell recharging while maintaining the handset electronics supply voltages.
On-chip voltage regulators generate fifteen programmable output voltages using a combination of
switched-mode power supplies and low dropout voltage regulators, all derived from a common
trimmed voltage reference. Independent regulated power sources support various electronic functions
while avoiding signal corruption between diverse circuits, allow power management sequencing, and
meet different voltage level requirements.
The devices general housekeeping functions include a 16-position analog multiplexer that has eight
internal connections and supports connections to eighteen external pins. The eight internal
connections are used to monitor on-chip functions such as the temperature sensor. Six external
connections are hardwired to access input power nodes such as VCHG, VBAT, etc. The IC includes
twelve multi-purpose pins that can be configured as analog inputs that are routed by an analog switch
network to create five multiplexer inputs. These are available to monitor system parameters such as
temperature and battery ID. The multiplexer output.s offset and gain are adjusted, then buffered and
routed to the Mobile Station Modem. (MSM.) device for analogto- digital conversion. Various oscillator,
clock, and counter circuits are provided to initialize and maintain valid pulse waveforms and measure
time intervals for higher-level handset functions. A dedicated controller manages the TCXO warm-up
and signal buffering, and key parameters are monitored to protect against detrimental conditions.
Handset-level user interfaces are also supported. The IC includes four backlight or LED drivers with
brightness (current) control that could be used for keypad, LCD, camera flash, and generalpurpose
drivers. A vibration motor driver is used to alert handset users of incoming calls, and a speaker driver
with volume control can be used for audio alerts or speakerphone and melodyringer applications.
IC-level interfaces include the three-line serial bus interface (SBI) used by the MSM device to
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