Display Type In Which A Segment Spans Two Or More Grids (Display Mode 2: Dspm05 = 1) - NEC mPD780208 Subseries User Manual

15.10.3 Display type in which a segment spans two or more grids (display mode 2: DSPM05 = 1)

The calculation method for the total power dissipation in the case of the display example in Figure 15-26 is
described below.
Example Assume the following conditions:
= 5 V ±10%, 5.0 MHz oscillation
V
DD
Supply current (I
Display output: 23 segments × 7 patterns (cut width = 1/16: when DIMS1 to DIMS3 = 000B)
Display output voltage (V
Fluorescent display control voltage (V
Mask option pull-down resistor = 25 kΩ
By placing the above conditions in calculation <1> to <3>, the total dissipation can be worked out.
<1> CPU power dissipation: 5.5 V × 21.6 mA = 118.8 mW
<2> Output pin power dissipation:
(V – V
DD
<3> Pull-down resistor power dissipation:
Grid
Segment
Total power dissipation = <1> + <2> + <3> = 118.8 + 31.6 + 62.5 + 152.8 = 365.7 mW
In this example, the power dissipation problem is cleared because the total power dissipation does not exceed
the allowable total power dissipation rating shown in Figure 15-22.
Figure 15-25 shows the grid driving timing, and Figure 15-26 shows a display example and display data of a
display type in which a segment spans two or more grids.
332
CHAPTER 15 VFD CONTROLLER/DRIVER
) = 21.6 mA
DD
Maximum current at the display output pin is 15 mA.
) = V – 2 V (voltage drop of 2 V)
OD DD
LOAD
Total current value of each grid
) ×
OD
No. of grids + 1
15 mA × 9 grids
2 V × × (1 –
7 grids + 1
2
(V – V )
OD LOAD
×
Pull-down resistor value
2
(5.5 V – 2 V – (–35 V))
×
25 kΩ
2
(V – V ) No. of illuminated dots
OD LOAD
×
Pull-down resistor value
2
(5.5 V – 0.5 V – (–35 V))
×
25 kΩ
User's Manual U11302EJ4V0UM
) = –35 V
× Digit width (1 – Cut width) =
1
)
16
No. of grids
× Digit width (1 – Cut width) =
No. of grids + 1
9 grids 1
× (1 –
)
7 grids + 1 16
× Digit width (1 – Cut width) =
No. of grids + 1
22 dots 1
× (1 –
)
7 grids + 1 16
= 31.6 mW
= 62.5 mW
= 152.8 mW