16-bit Constant Current LED Driver with Error Detection

Version:A.006

Page 13

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DM13C

Open

Short

or

Short

Open

useless clock pulse does not shift-in data

Real-time monitor

With the above operating principle, system could continuously retrieve LED status from

serial-out then compare with the last frame data one by one. Once there is any discrepancy

(‘1’‘0’), we can locate which channel is abnormal precisely. Since the process is ongoing and

without shifting between image mode and detection mode, it does not interrupt the image data flow

and the output display. The ‘real-time monitor’ method is suitable for LED Variable Message Signs

(VMS) system.

Clocks calculation

For large LED display applications, ‘real-time monitor’ could be a heavy loading for system

because it needs to compare the retrieved information with a lot of frame data. Therefore, to write

the image data of all channels to ‘1’, all failure status will be identified when there will be any ‘0’

retrieved. By calculating the numbers of clock pulses, the locations of abnormal channel could be

pointed out easily. The “clocks calculation” method helps to minimize the loading and memory

resources of system.

Selection of Open/Short Detection

The default detection type provided by DM13C is LED open detection after power-on. Users

could switch LED open to short detection (or short to open detection) by following timing sequence.

There are two alternative options could be selected. The option 1 shows triggering latch pulse when

the last clock of the frame data kept at high level. The option 2 shows sending one useless clock

pulse which will not shift-in data while the latch signal is kept at high level.

DCK

LAT

Normal Operation

t

DCK

LAT

option 1

t

DCK

LAT

t

option 2