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BD VFDs Application Note APN140
4. CONTROL PROCEDURE
4.2 Multiplex Drive Type
For a multiplex driven VFD, the grid scan data
must be formatted as well as the anode data. For this reason, the
software is difficult to create, including the data
transfer rate (speed), compared to the static drive.
Fig.16a Display Pattern Example of Multiplex Drive |
4.2.3 Important Precautions of Grid Scan
As for the grid scanning timing, the following aspects deserve
ATTENTION;
- To avoid flickering display, the refresh rate (repetition
frequency of T1 to T20 = 1/TR) must be 120Hz (Note 2) or higher. This
means the term of "Tn" has to be approx. 400 micro seconds
or shorter.
- The tp and tBK should be settled in one period of TR.
If not, the luminance of each digit may be uneven.
- The grid scan must be continuous, and never be interrupted
while the VFD is operating. If the grid scan is interrupted even momentarily,
the VFD may be permanently damaged.
To avoid this, we reccomend a protective circuit as in Fig.14a.
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Note 2) In cese of 50Hz or 60Hz AC filament drive.
If the filament is driven by higher frequency(kHz range), the refresh rate can be as
long as 60Hz. In any case, a higher refresh frequency is
recommended.
Back to APN140 INDEX 4-3. Full Dotmatrix Type
APN140
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