Samsung SCH-A302 Service Manual page 45

10. SCH-A302 Circuit description & Circuit Diagrams
1. Logic Section
(1) Power Supply
For the POWER ON, with the battery installed on the phone and by pressing the PWR key, the VBAT
and ON_SW signals will be connected, also by connecting the TA(travel adaptor). This will turn on
Q507(2SC4617). This will turn on U501. This voltage is supplied to pin 6 and pin10 of PM(power
management) U501 , thus releasing them from the shut-down state to output regulated 2.8 V,
thus releasing them from the shut-down state to output regulated 2.8 V.
Simultaneously, VBAT applied to ON_SW will turn on Q508(DTC144EE/TR) resulting in the signal
ON_SW_SENSE to change state from HIGH to LOW. This will allow MSM to send out
PS_HOLD(logical HIGH) to turn on Q507(2SC4617) even after the PWR key is released.
For the POWER OFF, by pressing PWR_KEY of the keypad for few seconds the VBAT voltage will be
applied to the ON_SW and will drive Q508(DTC144EE/TR) to input LOW on the ON_SW_SENSE of
the MSM. The MSM will recognize this and will output LOW on the PS_HOLD.
The voltage(+2.8 V) from the pin 6 and pin10 of the U501 is used in the digital parts of MSM.
The voltage(+3.0 V) from the pin 20 of the U501 is used in the parts of IFR.
The voltage(+3.0 V) from the pin 15 of the U501 is used in the RX parts of RF.
The voltage(+3.0 V) from the pin 18 of the U501 is used in the TX parts of RF.
The voltage(+2.7 V) from U501 is used in the analog part.
(2) Logic Part
The logic part consists of internal CPU of MSM, Memory and EEPROM. The MSM receives TCXO and
CHIPX8 clock signals from the IFR and controls the phone during the CDMA and the FM mode.
The major components are as follows:
•
CPU : MSM3100C(U609)
•
Memory : U103(MB84VD2219EC-90PBS)
U101(KM616U4110CLZI-7L)
•
EEPROM : U106(AT24C256-10UI-2.7-T.R)
CPU
ARM7TDMI µ-processor is used for the main processing.
The CPU controls all the circuitry. For the CPU clock, 27 MHz resonator is used.
MEMORY (U103 and U101)
16M FLASH ROM(U103)and 4M SRAM(U101) packages are used to store the terminal's program,
the internal flag information, call processing data, data service, and timer data.
Using the down-loading program, the program can be changed even after the terminal is fully
assembled.
EEPROM(U106)
One 256KBIT EEPROM is used to store ESN, NAM, power level, volume level, and telephone number.
SAMSUNG Proprietary-Contents may change without notice
- ARM7TDMI µ-processor
- 16MBIT FLASH ROM
- 4MBIT SRAM
- 256KBIT SERIAL EEPROM
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