M38B5XMXH Datasheet, PDF (84/355 Pages) Mitsubishi Electric Semiconductor – 8-BIT SINGLE-CHIP MICROCOMPUTER

HARDWARE
MASK OPTION OF PULL-DOWN RESISTOR
Power Dissipation Calculating example 2
(when 2 or more digit is turned ON at same
time)
q 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 43 V / 900 µA = 48 kΩ (min.)
• Power dissipation of internal circuit (CPU, ROM, RAM etc.) = 5 V !
15 mA = 75 mW
q Fixed number depending on use condition
• Apply voltage to VEE pin: Vcc – 45 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
• All segment number during repeat cycle: 264 (= 11 ! 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 ! 12 ! (1–1/16) ! 2} / 11 = 36.82 mW
(2) Segment pin power dissipation
{3 ! 114 ! (1–1/16) ! 2} / 11 = 58.30 mW
(3) Pull-down resistor power dissipation (digit)
(45 – 2)² /48 ! (12 ! 10/12) ! (1 – 1/16) / 11 = 32.84 mW
(4) Pull-down resistor power dissipation (segment)
(45 – 2)² /48 ! (114 ! 22/24) ! (1 – 1/16) / 11 = 343.08 mW
(5) Internal circuit power dissipation (CPU, ROM, RAM etc.) = 75 mW
(1) + (2)+ (3) + (4) + (5) = 547 mW
DIG0
DIG1
DIG2
DIG3
DIG4
DIG5
DIG6
DIG7
DIG8
DIG9
Timing number
12
3
4
5
6
7
Repeat cycle
89
10 11
Tscan
Fig. 77 Digit timing waveform (2)
1-68
38B5 Group User’s Manual