Samsung SCH-i830 Service Manual page 14

Circuit Description
2-6. PDA PART
The PDA logic part consists of power supply part, MPU & memory part, LCD part, audio part
and all the peripherals.
2-6-1. POWER SUPPLY
When the battery is inserted to the handset,
VBAT makes VCC_BATT, VCORE14, VPLL13, VSRAM11 via U405(MAX1587) which is a CPU voltage
VCC30 via U405(MAX1587) which is CPU & peripheral voltage,
VCC28 via U414(MIC5219-2.8BML) which is a DPRAM voltage,
VLCD33 via U413(MIC2211-SSBML) which is a LCD logic voltage,
VBT30 via U416(MIC2211-PPBML) which is a Buletooth voltage.
VBAIS30 via U416(MIC2211-PPBML) which is a MIC vias voltage.
VBAT33 via U413MIC2211-SSBML) which is a backup battery charging voltage,
VSD30 via U410(MIC2212) which is a SD-Card voltage.
VCC30 makes VCC18 via U412(MIC2211-JGBML) which is a M-DOC voltage,
VDD30 makes VDD18 via U411(MIC2211-JGBML) which is a SDRAM voltage,
VLCD33 makes AVDD5V, VON, VOFF via U1000(MAX1779) which is LCD pannel voltage.
Backup Battery
The SPH-i830 has a back-up battery(ML1220) that stores data of SDRAM when the battery
removed or becomes low battery state that is below 3.1V.
The low battery state is checked by voltage detector or R3111Q311C(U400).
If the battery level is below 3.1V, nPOWER_FAIL signal is asserted. Then the backup DC/DC
converter(U405, MAX1676) output path is connected to VDD30 which is MPU, SDRAM voltage.
Backup battery supply main voltage or VDD30. If backup battery voltage is below 2V, discharging
path is disabled.
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