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Circuit Description
— Backlight LED Driver
The backlight LED driver is a low-side, programmable current source designed to control the brightness of the keyboard
illumination. LED1_DRV is controlled via LED1_[0:2] and can be programmed to sink from 15mA to 60mA in 7.5mA
steps. LED2_DRV is controlled via LED2_[0:2] and can be programmed to sink from 5mA to 40mA in 5mA steps.
Both LED drivers are capable of sinking their maximum output current at a worst-case maximum output voltage of 0.6V.
For efficient use, the LEDs is connected between the battery and the LED_DRV output.
— Vibrator Motor Driver
The vibrator motor driver is a independent voltage regulator to drive a small dc motor that silently alerts the user of an
incoming call. The driver is a 3.3V constant source while sinking up to 140mA and controlled by enable signal of main
chip. For efficient use and safety, the vibrator motor should be connected between the regulator output and the ground.
2-2-2. Connector
— JTAG Connector
Trident has two JTAG ports which are for ARM core and DSP core(DSP16000). So this system has two port connector
for these ports. Pins' initials for ARM core are 'CP_' and pins' initials for DSP core are 'DSP_'.
CP_TDI and DSP_TDI signal are used for input of data. CP_TDO and DSP_TDO signals are used for the output of the
data. CP_TCK and DSP_TCK signals are used for clock because JTAG communication is a synchronous. CP_TMS and
DSP_TMS signals are test mode signals. The difference between these is the RESET_INT signal which is for ARM core
RESET.
— Keypad connector
This is consisted of key interface pins in the trident, KEY_ROW[0~4] and KEY_COL[0~4]. These signals compose the
matrix. Result of matrix informs the key status to key interface in the trident. Some pins are connected to varistor for
ESD protection. And power on/off key is seperated from the matrix.
So power on/off signal is connected with CSP2200 to enable CSP2200.
Nine key LED use the +VBATT supply voltage. These are connected to BACKLIGHT signal in the CSP2200.
This signal enables LEDs with current control.
— EMI Filtering
This system uses the EMI Filter to reduce noise from LCD part. Some control signals are connected to LCD without EMI
filtering.
2-3
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