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ACPL-W343-500E Datasheet, PDF (17/20 Pages) AVAGO TECHNOLOGIES LIMITED – 4.0 Amp Output Current IGBT Gate Drive Optocoupler | |||
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Selecting the Gate Resistor (Rg)
Step 1: Calculate Rg minimum from the IOL peak specification. The IGBT and Rg in Figure 28 can be analyzed as a simple
RC circuit with a voltage supplied by ACPL-P343/W343.
Rg ⥠VCC â VEE â VOL
IOLPEAK
= 15 V + 5 V â 2.9 V
4A
= 4.3 ï ï» 5 ï
The VOL value of 2.9 V in the previous equation is the VOL at the peak current of 4.0 A (see Figure 7).
Step 1: Check the ACPL-P343/W343 power dissipation and increase Rg if necessary. The ACPL-P343/W343 total power
dissipation (PT) is equal to the sum of the emitter power (PE) and the output power (PO).
PT = PE + PO
PE = IF ⢠VF ⢠Duty Cycle
PO = PO(BIAS) + PO(SWITCHING)
= ICC ⢠(VCC-VEE) + ESW(Rg;Cg) ⢠f
Using IF(worst case) = 16 mA, Rg = 5 ï, Max Duty Cycle = 80%, Cg = 25 nF, f = 25 kHz and TA max = 85° C:
PE = 16 mA ⢠1.95 V ⢠0.8 = 25 mW
PO = 3 mA ⢠20 V + 5 ïJ ⢠25 kHz
= 60 mW + 125 mW
= 185 mW < 700 mW (PO(MAX) @ 85° C)
The value of 3 mA for ICC in the previous equation is the maximum ICC over the entire operating temperature range.
Since PO is less than PO(MAX), Rg = 5 ï is alright for the power dissipation.
3.0E-05
2.5E-05
2.0E-05
VCC = 30 V
VCC = 20 V
VCC = 15 V
1.5E-05
1.0E-05
5.0E-06
0.0E+00
0
2
4
6
8
10
Rg - Gate Resistance - 7
Figure 31. Energy Dissipated in the ACPL-P343/W343 for each IGBT switching
cycle
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