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.

Tel：886-3-5645656

Fax：886-3-5645626

16-channel 16-bit PWM Constant Current LED Driver

Version : A.003

Page 17

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DM634

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

Global Brightness data and Open/Short Flag format

LSB

MSB

shift in first

O/S

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

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 4

set 7-bit GBC data and O/S flag. Notice that PWM data won’t be changed while GBC data is

latched.

DCK

LAT

Timing Combination to set GBC data and O/S flag

t

1

2

254 255 256

1

2

12

34

56

78

34

Iout

GBC