CHAPTER 15 VFD CONTROLLER/DRIVER
330
User’s Manual U11302EJ4V0UM
<3> Pull-down resistor power dissipation:
Grid
(V
OD
– V
LOAD
)
2
×
No. of grids
×
Digit width (1 – Cut width) =
Pull-down resistor value
No. of grids + 1
(5.5 V – 2 V – (–35 V))
2
×
16 grids
×
(1 –
1
)
= 52.3 mW
25 k
Ω
16 grids + 1
16
Segment
(V
OD
– V
LOAD
)
2
×
No. of illuminated dots
×
Digit width (1 – Cut width) =
Pull-down resistor value
No. of grids + 1
(5.5 V – 0.4 V – (–35 V))
2
×
110 dots
×
(1 –
1
)
= 390.2 mW
25 k
Ω
16 grids + 1
16
Total power dissipation = <1> + <2> + <3> = 118.8 + 26.5 + 11.1 + 52.3 + 390.2 = 598.9 mW
In this manner, design the system so that the power dissipation does not exceed the allowable total power
dissipation rating.
Figure 15-24 shows a display example and display data for “dot type”.