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
High Accuracy Global Brightness Correction
DM634 has built-in global brightness Correction feature. It can save PCB space and cost of
system by eliminating the circuit of Rrext value adjusting or voltage drop adjusting across the
external resistors. The output current is calculating by following equation*1*2*3
:
Iout*1 = Vrext / Rext x M*2 x ( 1 + DGBC*3)/96
Global Brightness data and Open/Short Flag format
shift in first
DC[6]
MSB
DC[5]
DC[4]
DC [3]
DC [2]
DC [1]
DC [0]
O/S
LSB
The Shift in data sequence of GBC data and detection flag as above. Dc[6], Dc[5] to Dc[0] are
7-bit data of GBC value. The last bit O/S is the flag of detection. When O/S flag set “L”, the LED
open detection function be selected. Otherwise, if the flag set “H”, the LED short failure detection
function be selected. .
Global Brightness Control
The default GBC data (DGBC) is “1011111” (Iout = 75% Imax*4 ) after power-on. Users could
shift GBC data in by following timing sequence without changing luminous data. The sequence
shows four triggering latch pulses (LAT ) with high level clock (DCK), circuit switch into GBC
mode at falling edge of the 4th latch pulse (LAT ) then user can make eight triggering clock pulses to
set 7-bit GBC data and O/S flag. Notice that PWM data won’t be changed while GBC data is
latched.
1
2
254 255 256
1
2
3
4
5
6
7
8
DCK
LAT
1
2
3
4
t
Timing Combination to set GBC data and O/S flag
*1 Iout is the current value setting under 100% PWM duty cycle.
*2 Vrext/Rext * M as the equation in Page 9.
*3
D
GBC
is the data of global brightness correction. User can refer to Timing Sequence to know how to set DGBC on page 18.
*4 Imax means the GBC data is “1111111”.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.003
Page 17
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