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SILICON TOUCH TECHNOLOGY INC

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16-channel 16-bit PWM Constant Current LED Driver

Version : A.003

Page 4

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DM634

Equivalent Circuit of Inputs and Outputs

1. DCK, DAI,

LAT , SOMODE/GCK terminals

2. DAO terminals

PCB Layout Consideration

To connect an external resistor to REXT pin and ground can determine the maximum output

current. If there is any disturbance occurred to REXT pin, the constant current output may be

unstable or noisy. Since REXT (pin23), DAO (pin22), and SOMODE/GCK (pin21) are next to each

other, the most possible interference is caused by DAO or SOMODE/GCK signal. Accordingly, it is

recommended that adding some shielding area within the above pins in PCB layout, or laying the

signal line of above pins on different PCB layer will prevent the noise problems effectively.