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M38B71M1 Datasheet(PDF) 76 Page - Renesas Technology Corp |
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M38B71M1 Datasheet(HTML) 76 Page - Renesas Technology Corp |
76 / 110 page ![]() 38B7 Group SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER MITSUBISHI MICROCOMPUTERS 75 Fig. 83 Digit timing waveform (1) Power Dissipation Calculating Example 1 (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 µs = 48 kΩ (min.) • Power dissipation of internal circuit (CPU, ROM, RAM etc.) = 5 V ✕ 15 mA = 75 mW (Fixed number depending on use condition) • Apply voltage to VEE pin: Vcc – 45 V • Timing number 17; digit number 16; segment number 20 • Ratio of Toff time corresponding Tdisp time: 1/16 • Turn ON segment number during repeat cycle: 31 • All segment number during repeat cycle: 340 (= 17 ✕ 20) • Total number of built-in resistor: for digit, 16; for segment, 20 • Digit pin current value 18 (mA) • Segment pin current value 3 (mA) (1) Digit pin power dissipation {18 ✕ 16 ✕ (1 – 1 / 16) ✕ 2} / 17 = 31.77 mW (2) Segment pin power dissipation {3 ✕ 31 ✕ (1– 1 / 16) ✕ 2} / 17 = 10.26 mW (3) Pull-down resistor power dissipation (digit) [{45 – 2}2/ 48 ✕ (16 ✕ 16 / 16) ✕ (1 – 1 / 16)] / 17 = 33.94 mW (4) Pull-down resistor power dissipation (segment) [{45 – 2}2/ 48 ✕ (31 ✕ 20 / 20) ✕ (1 – 1 / 16)] / 17 = 65.86 mW (5) Internal circuit power dissipation (CPU, ROM, RAM etc.) = 75 mW (1) + (2)+ (3) + (4) + (5) = 217 mW DIG0 DIG1 DIG2 DIG3 DIG13 DIG14 DIG15 Timing number 12 3 16 17 15 14 Tscan Repeat cycle |