BD VFDs Application Note APN140

5. DESIGN GUIDANCE

5.1 Glass Package Size

For custom designed BD VFD, we recommend a package size from the standard line of displays packages. For standard glass packages, please refer to the application note APN101 or contact us for the latest information.

5.2 Lead Pins

Fig.20 Standard Lead Pin Form

The standard lead pin form of the BD VFDs is 6.0mm length and 2.0mm pitch. The dimensions of standard lead pin are shown in Figure 20. Custom lead pin design is also available upon request.

5.3 Segment Design

The rules described below should merely be regarded as prelimenary design guidance. In practice, these values may vary from one case to another. For details, please contact us for specific instruction.

5.3.1 General Design Rules for Static Drive

In the case of the static drive, there is no space required for grid division, which provides a higher degree of freedom in the segment design.
Normally, the area of a segment must not exceed 300mm2 due to limited current capacity of the driver chip.
The following basic rules are applicable.

Fig.21a Minimum Thickness and Gap between Segments

Fig.21b Same Color Segment on Separated Anode

Fig.21c Different Color Segment on Separated Anode

5.3.2 Rules on Segment Design for Multiplex Drive

For multiplex driving, some space for grid division is required. Figure 22 shows the required space for common grid division. Other basic design rules for the grid are the same as the static drive. The minimum value for this space is dependent on many factors, please consult our engineers.

Fig.22a Minimum Segment Gap for Grid Division in Multiplex Drive

Fig.22b Dot matrix in Multiplex Drive

5.4 Driver Selection

The following table shows the available built-in drivers and the maximum voltages (VDD2) including filament bias voltages.

Table 7 Driver Chip and Maximum Operating Voltage (as of July 1998)

Driver Number of Bit Maximum Operating Voltage (VDD2)

Type 1 96 bit 43V MAX, 58V MAX

Type 2 64+64 bit 72V MAX

5.5 Driving Voltage and Brightness

5.5.1 Static Drive

For static drive, the relationship between operating voltage and brightness is;

Table 8 Operating Voltage and Brightness in Static Drive

Ec VDD2 Ek Brightness (Blue- green)
13V 15V 2V 2000cd/m2 TYP.
13V 18V 2V 2500cd/m2 TYP.
13V 24V 2V 3500cd/m2 TYP.

5.5.2 Multiplex Drive

For a custom multiplex driven BD VFD, the number of grids will be limited due to the available voltage of the driver.
If the grid division can be a small number, the duty can be set at a large value and the operating voltage (VDD2) can be set lower and/or the brightness can be raised if necessary.
If high brightness is not critical, the number of grids can be increased. Table 9 shows the relationship between the voltage and the expected brightness level for multiplex driven BD VFD.

Table 9 Number of Grid and Driving Conditions

Target Brightness Number of grid VDD2 needed (Ek=5V)

1000 cd/m2 TYP. 10 30V

20 40V

40 52V

2000 cd/m2 TYP. 10 40V

20 52V

40 65V

3000 cd/m2 TYP. 10 52V

20 65V
Note: In case of large character dimensions, it may be necessary to divide a character into two or three parts, and assign a bit to each part due to the current(mA) capability of the driver.

5.5.3 Graphic in Multiplex Drive

The following information is for the design of a full-matrix (graphic) type BD VFDs.
Although the scan duty cannot be set too small due to the limited output voltage of the driver, the graphic type BD VFD is available with a lower voltage than conventional graphic VFDs and high brightness, if the grid scan is controlled properly. For details on the driving method, please consult our engineers.

Table 10 Summary of Graphic BD VFDs

Dot Config. Driver Grid Scan Duty Expected Brightness (VDD2)

G/A Hybrid G/A Independent

Grid Anode

64 x 8 96bit x 1 96bit x 1 96bit x 1 1/32 600cd/m2 TYP (40V)
900cd/m2 TYP (48V)
1200cd/m2 TYP (55V)

64 x 16 96bit x 1 96bit x 1 96bit x 1

64 x 32 - 96bit x 1 96bit x 1

128 x 8 128bit x 1 128bit x 1 128bit x 1 1/64 500cd/m2 TYP (55V)
600cd/m2 TYP (60V)
900cd/m2 TYP (70V)

128 x 16 128bit x 1 128bit x 1 128bit x 1

128 x 32 - 128bit x 1 128bit x 1

128 x 64 - 128bit x 1 128bit x 2

256 x 16 - 128bit x 1 128bit x 1 1/128 300cd/m2 TYP (60V)
450cd/m2 TYP (70V)

256 x 32 - 128bit x 1 128bit x 1

256 x 64 - 128bit x 1 128bit x 2

APN140 INDEX In Addition

APN140