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SGH-N620E Circuit Description
2-2
Modulation Spectrum
200kHz offset
30 kHz bandwidth
GSM
-35dBc
DCS
-35dBc
400kHz offset
30 kHz bandwidth
GSM
-66dBc
DCS
-65dBc
600kHz ~ 1.8MHz offset
30 kHz bandwidth
GSM
-75dBc
DCS
-68dBc
2. Baseband Circuit description of SGH-N620E
1. Power Management
Four low-dropout regulators designed specifically for GSM applications power and help ensure optimal system performance
and long battery life. while a self-resetting, electronically fused switch supplies power to external accessories. Ancillary
support functions, such as RTC module and High Voltage Charge pump, Clock generator, aid in reducing both board area
and system complexity.
2. Clock Generato
r
The Clock Generator (CG) generates all clocks for internal and external usage. The 32768 Hz crystal oscillator provides an
accurate low clock frequency for the VP40578
.
3
. LCD
LCD is 4 grey LCD. Chip select signals in the U205, LCD_EN can enable LCD. B_LIGHT signal enables blue LED of
LCD. Blue LEDs use the 'LVCC' supply voltage.
"RST" signal initiates the Reset process of the LCD.
8-bit data lines(D(0)~D(7) transfers data and commands to LCD through bypass capacitor. Data and commands use
"A(0)" signal. If this signal is high, Inputs to LCD are commands. If it is low, Inputs to LCD are data. The signal which
informs the input or output state to LCD, is required. But this system is not necessary this signal. So "WR" signal is
used to write data or commands to LCD. Power signal for LCD is "VDD3.0".
4. Key
This is consisted of key interface pins among VP40578 (KEYBORD_ROW(0:7), KEYBOARD_COL(0:7)) . These signals
compose the matrix. Result of matrix informs the key status to key interface in the VP40578.
Eight key LEDs use the
"LED_3V3" supply voltage. "BACKLIGHT" signal enables LEDs with current control
5. IF connector
It is 18-pin connector. They are designed to use RS232_TXD, RS232_RXD, RS232_RTS, RS232_CTS, BOOT, SCL, SDA,
MIC2N, MIC2P, SPK2N, SPK2P, DCVOLT. They connected to power supply IC, microprocessor and signal processor IC.
6. Battery Charge Management
A complete constant-current/constant-voltage linear charger for single cell lithium-ion batteries. If ta connected to phone,
"DCVOLT" enable charger IC and supply current to battery. when fault condition caused, "CHG_ON" signal level change
low to high and charger IC stop charging process.
7. Audio
SPK2P and SPK2N from VP40578 are connected to the main receiver. MIC2P and MIC2N are connected to the main
