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ACPL-336J Datasheet, PDF (17/18 Pages) AVAGO TECHNOLOGIES LIMITED – Rail-to-rail output voltage
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Step 2: Check the ACPL-336J power dissipation and increase RG if necessary. The ACPL-336J total power dissipation (PT)
is equal to the sum of the LED power (PE), input IC power(PI) and the output IC power (PO).
PT = PE + PI + PO
Assuming operation conditions of IF(worst case) = 16 mA, RG = 11.8 Ω, Max Duty Cycle = 80%, QG = 1 µC, f = 10 kHz and
TA max = 95 °C.
Calculation of LED Power Dissipation
PE = IF • VF • Duty Cycle
= 16 mA • 1.95 V • 0.8 = 25 mW
Calculation of Input IC Power Dissipation
PI = ICC1(Max) * VCC1(Recommended Max)
= 6 mA * 5.5 V = 33 mW
Calculation of Input IC Power Dissipation
PO = PO(BIAS) + PO(SWITCHING)
= ICC2 • (VCC2-VEE2) + PHS + PLS
PHS = (VCC2*QG*f ) * RDS,OH(MAX) / (RDS,OH(MAX)+RG) / 2
PLS = (VCC2*QG*f ) * RDS,OL(MAX) / (RDS,OL(MAX)+RG) / 2
PHS = (30 V • 1µC • 10 kHz) • 4.5 Ω/(4.5 Ω +7.3 Ω)/2 = 44.6 mW
PLS = (30 V • 1µC • 10 kHz) • 3.6 Ω/(3.6 Ω+7.3 Ω)/2 = 38.0 mW
PO = 7.5 mA • 30 V + 44.6 mW +38.0 mW
= 307.6 mW < 600 mW (PO(MAX) @ 95 °C)
The value of 7.5 mA for ICC2 in the previous equation is the maximum ICC2 over the entire operating temperature range.
Since PO is less than PO(MAX), RG = 11.8 Ω is all right for the power dissipation.
Thermal Calculation
Application and environmental design for ACPL-336J needs to ensure that the junction temperature of the internal
ICs and LED within the gate driver optocoupler do not exceed 125 °C. The following equations calculate the maximum
power dissipation effect on junction temperatures.
LED Junction Temperature, TE = AEA*PE + AEI*PI + AEO*PO + TA
= 176.1 °C/W *25 mW + 35.4 °C/W *33 mW + 33.1 °C/W *307.6 mW + 95 °C
= 110.7 °C
Input IC Junction Temperature, TI = AEI*PE + AIA*PI + AIO*PO + TA
= 35.4 °C/W *25 mW + 92 °C/W *33 mW + 25.6*307.6 mW + 95 °C
= 106.8 °C
Output IC Junction Temperature, TO = AEO*PE + AIO*PI + AOA*PO + TA
= 33.1 °C/W *25 mW + 25.6 °C/W *33 mW + 76.7*307.6 mW + 95 °C
= 120.3 °C
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