點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
新竹市科學園區展業一路9號7樓之1
9-7F-1, Prosperity RoadⅠ, Hsin-Chu, Taiwan, R.O.C.
DM634
Tel：886-3-5645656
Fax：886-3-5645626
Output Modulation Technique
DM634 provides a new LED drive technique of output modulation. It mixes traditional Pulse
Width Modulation (PWM) represented by LSB 12 bit with Sequential Split Modulation (SSM)
represented by MSB 4 bit. The main benefits of SSM are to drive LED with an equivalent higher
refresh rate (up to 380Hz in DM634 when FGCK = 25MHz) and change bit to next bit smoothly. The
relationships between PWM and SSM in time domain can be refer to the diagram below (not to
scale):
A complete modulation cycle
0
8
1
9
2
10
3
11
4
12
5
13
6
14
7
15
Sequential Split Modulation represented by Bit [15:12]
Traditional PWM Width represented by Bit [11:0]
Bit[11:0] (PWM)
t
Bit[15:0]
A complete modulation cycle
on
off
on
off
MSB
LSB
0000 XXXX,XXXXXXXX
Bit[11:0] (PWM)
MSB
LSB
0001 XXXX,XXXXXXXX
Bit[11:0] (PWM)
on
off
on
off
on
off
on
off
MSB
LSB
0110 XXXX,XXXXXXXX
Bit[11:0] (PWM)
MSB
LSB
0111 XXXX,XXXXXXXX
Bit[11:0] (PWM)
MSB
LSB
1000 XXXX,XXXXXXXX
Bit[11:0] (PWM)
MSB
LSB
1001 XXXX,XXXXXXXX
Bit[11:0] (PWM)
on
MSB
LSB
1110 XXXX,XXXXXXXX
off
on
off
Bit[11:0] (PWM)
MSB
LSB
1111 XXXX,XXXXXXXX
65536 clocks
t
Ultra High Resolution Current Outputs
DM634 could provide 16-bit linear PWM control current outputs for each channel. There are
two advantages for system design. One is DM634 has sufficient bit resolution (65536 steps), not
only LED color information but additional data such as global brightness, dot correction, and
gamma correction can be represented by the proper algorithms. The other is to reduce a lot of clock
and data rate compared to conventional ON-OFF type LED drivers.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.003
Page 16
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