M30218 Datasheet, PDF (138/179 Pages) Mitsubishi Electric Semiconductor – M30218 Group

Pull-down
Mitsubishi microcomputers
M30218 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Power Dissipation Calculating example 3
(when 2 or more digit is turned ON at same time, and used Toff invalid function)
Fixed number depending on microcomputer’s standard
• VOH output fall voltage of high-breakdown port 2 V (max.); | Current value | = at 18 mA
• Resistor value 68 kΩ (min.)
• Power dissipation of internal circuit (CPU, ROM, RAM etc.) = 5 V X 38 mA = 190 mW
Fixed number depending on use condition
• Apply voltage to VEE pin: Vcc – 50 V
• Timing number 11; digit number 12; segment number 24
• Ratio of Toff time corresponding Tdisp time: 1/16
• Turn ON segment number during repeat cycle: 114 ( for Toff invalid waveform;50)
• All segment number during repeat cycle: 264 (= 11 X 24)
• Total number of built-in resistor: for digit; 10, for segment; 22
• Digit pin current value: 18 (mA)
• Segment pin current value: 3 (mA)
(1) Digit pin power dissipation
[{18 X 10 X (1–1/16) X 2} + {18 X 2 X 2}] / 11 = 37.23 mW
(2) Segment pin power dissipation
[{3 X 64 X (1–1/16) X 2} + {3 X 50 X 2}] / 11 = 60.00 mW
(3) Pull-down resistor power dissipation (digit)
[{(50– 2)² / 68 X (10 X 10 / 12) X (1 – 1 / 16)} + {(50– 2)² / 68 X (2 X 10 / 12) } ] /11 = 29.20 mW
(4) Pull-down resistor power dissipation (segment)
[{(50– 2)² / 68 X (64 X 22 / 24) X (1 – 1 / 16)} + {(50– 2)² / 68 X (50 X 22 / 24) } ] / 11 = 310.59 mW
(5) Internal circuit power dissipation (CPU, ROM, RAM etc.) = 190.00 mW
(1) + (2)+ (3) + (4) + (5) = 627.02 mW (There is a limit of use temperature)
DIG0
DIG1
DIG2
DIG3
DIG4
DIG5
DIG6
DIG7
DIG8
DIG9
Timing
number
1
2
345
6
7
Repeat cycle
Figure S-3. Digit timing waveform (3)
89
10 11
Tscan
137