Samsung SCH-1500 series Service Manual

Also see for SCH-1500 series: User guide

6. Circuit Description6-1 Logic SectionSamsung Electronics 6-16-1-1 Power SupplyWith the battery installed on the phone and bypressing the PWR key, the VBATT and ON_SWsignals will be connected. This will turn on Q110(2SC4081BR) and will drive DC-DC converter(U130) to output 5.2V. This in turn will be suppliedto regulators (U110 and U120), thus releasing themfrom the shut-down state to output regulated 3.3V.The VBATT applied to ON_SW will turn on Q111(DTC144EE) resulting in the signal ON_SW_SENSEto change state from HIGH to LOW. This will allowMSM to send out PS_HOLD (logical HIGH) to turnon Q110 even after the PWR key is released.The voltage (+3.3VD) from U120 is used in thedigital parts of MSM and BBA. The voltage(+3.3VA) from U110 is used in the analog part ofBBA and Audio circuit.6-1-2 Logic PartThe Logic part consists of internal CPU of MSM,RAM, ROM and EEPROM. The MSM receivesTCXO and CHIPX8 clock signals from the BBA andcontrols the phone during the CDMA and the FMmode. The major components are as follows:•CPU : INTEL 80186 core•FROM : U126 (MBM29LV800T) - 8MBITFLASH ROM•SRAM : U127 (KM68U2000LTGI) - 2MBITSTATIC RAM•EEPROM : U113 (AT24C128W) - 128KBITSERIAL EEPROMCPUINTEL 80186 CMOS type 16-bit microprocessor isused for the main processing. The CPU controls allthe circuitry. For the CPU clock, 27MHz resonator isused.FLASH ROM (U106)One 8 MBIT FROM is used to store the terminal'sprogram. Using the down-loading program, theprogram can be changed even after the terminal isfully assembled.SRAM (U107)One 2 MBIT SRAM is used to store the internal flaginformation, call processing data, and timer data.EEPROM (U108)One 128 KBIT EEPROM is used to store ESN, NAM,power level, volume level, and telephone number.KEYPADFor key recognition, key matrix is setup usingSCAN0-6 of STORE signals and KEY0-3 of inputports of MSM. Eight LEDs and backlight circuitryare included in the keypad for easy operation in thedark.LCD MODULELCD module contains a controller which willdisplay the information onto the LCD by 8-bit datafrom the MSM. It also consists a DC-DC converterto supply -3.5V for fine view angle and LCDreflector to improve the display efficiency.