DM114 데이터 시트보기 (PDF) - Silicon Touch Technology Inc.

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DM114

8-Bit CONSTANT CURRENT LED DRIVERS

Silicon Touch Technology Inc. 

Vo

點晶科技股份有限公司

SILICON TOUCH TECHNOLOGY INC.

System Configuration Example

DM114、DM115

[1] Output current (IOUT)

Sink current is set by the external resistor as shown in figure (Iout vs. Rext).

[2] LED supply voltage (VLED) setup

VLED = VCE ( Tr Vsat ) + Vf ( LED forward voltage ) + VO ( IC supply voltage)

To prevent too much power dissipated by the device due to higher VLED , an additional R can

be used to reduce the Vout when the outputs consume current:

VDD

V LED = 3~4 (V )

SCAN

ENABLE

OUT0

CLOCK

LATCH

OUT7

R

S E R IA L-IN

R -E XT G N D

S E R IA L-O U T

CPU

ENABLE

CLOCK

LATCH

S E R IA L-IN

R -E XT G N D

OUT0

OUT7

S E R IA L-O U T

R = VLED − Vf − VO(min)

IO(max) • Bit(max)

Note

This device has only one ground pin shared by signal, output sink current, and power ground.

It is advisable to pattern the ground layout with minimized inductance such that the switching

noise induced by the input signals and the output sink current would not cause chip malfunction. To

prevent the drivers’ outputs from damage by overshoot stress, it is also advisable not to turn off the

drivers and scan transistors simultaneously.

8-BIT CONSTANT CURRENT LED DRIVERS with 3.3V~5V supply voltage

Preliminary

Version:A.002

Page 12

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