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Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
3. TECHNICAL BRIEF
3.5.4 VCTCXO(X100 : TG-5010LH_19_2M_75A)
The Voltage Controlled Temperature Compensated Crystal Oscillator (VCTCXO) provides the reference
frequency for all RFIC synthesizers as well as clock generation functions within the MSM6280 IC. The
oscillator frequency is controlled by the MSM6280 IC.s TRK_LO_ADJ pulse density modulated signal in
the same manner as the transmit gain control TX_AGC_ADJ. A two-pole RC lowpass filter is
recommended on this control line.
The PM6650 IC controls the handset power-up sequence, including a special VCTCXO warm-up interval
before other circuits are turned on. This warm-up interval (as well as other TCXO controller functions) is
enabled by the MSM TCXO_EN line . The PM6650 IC VREG_TCXO regulated output voltage is used to
power the VCTCXO and is enabled before most other regulated outputs.
Any GSM mode power control circuits within the MSM6280 IC require a reference voltage for proper
operation and sufficient accuracy. Connecting the PM6650 IC REF_OUT directly to the MSM6275 IC
GSM_PA_PWR_CTL_REF provides this reference. This sensitive analog signal needs a 0.1
μ
F low
frequency filter near to MSM side, and isolate from digital logic and clock traces with ground on both sides,
plus ground above and below if routed on internal layers
Input power management
- Valid external supply attachment and removal detection
- Supports unregulated (closed-loop) external charger supplies and USB supplies as input power sources
- Supports lithium-ion main batteries
- Trickle, constant current, constant voltage, and pulsed charging of the main battery
- Supports coin cell backup battery (including charging)
- Battery voltage detectors with programmable thresholds
- VDD collapse protection
- Charger current regulation and real-time monitoring for over-current protection
- Charger transistor protection by power limit control
- Control drivers for two external pass transistors and one external battery MOSFET—MOSFET is optional
- Voltage, current, and power control loops
-Automated recovery from sudden momentary power loss
Output voltage regulation
- One boost (step-up) switched-mode power supply (SMPS) for driving white LEDs and hosting USBOTG
- Three buck (step-down) switched-mode power supplies that efficiently generate MSMC, MSME, and PA
(or second MSMC) supply voltages
- Supports dynamic voltage scaling (DVS) for MSMC and PA
- Eleven low dropout regulator circuits with programmable output voltages, implemented using three
different current ratings: 300 mA (two), 150 mA (six), and 50 mA (three). These can be used to power
MSMA, MSMP, RFRX1, RFRX2, RFTX, SYNT, TCXO, WLAN, MMC, USB, and RUIM circuits.
- All regulators can be individually enabled/disabled for power savings
- Low power mode available on MSMA and MSMP regulators
- All regulated outputs are derived from a common bandgap reference—close tracking
3.5.5 PMIC Functional Block Diagram(U503 : PM6650-3P)
