HCPL-3180-500E Datasheet, PDF (12/16 Pages) AVAGO TECHNOLOGIES LIMITED – 2.5 Amp Output Current, High Speed, Gate Drive Optocoupler

Selecting the Gate Resistor (R_g) for HCPL-3180
Step 1: Calculate R_g minimum from the I_OL peak specification. The IGBT and
R_g in Figure 25 can be analyzed as a simple RC circuit with a voltage supplied
by the HCPL-3180.
R_{ g }≥_  ^VCC_IO^–_LP^V_EAOKL
  = ^{20 – 3}
     2
  = 8.5 Ω
The V_OL value of 3 V in the previous equation is the V_OL at the peak current of
2 A. (See Figure 6.)
Step 2: Check the HCPL-3180 power dissipation and increase R_g if necessary.
The HCPL-3180 total power dissipation (P_T) is equal to the sum of the emitter
power (P_E) and the output power (P_O).
PT = PE + PO
PE = IF * VF * Duty Cycle
PO = PO(BIAS) + PO(SWITCHING)
2.0
1.8
Q_g = 100 nC
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
10
20
30
40
50
R_g — GATE RESISTANCE — Ω
Figure 26. Energy dissipated in the HCPL-3180 and for
each IGBT.
= ICC * VCC + ESW (R_g;Q_g) * f
For the circuit in Figure 25 with IF (worst case) = 16 mA, R_g = 10 Ω, Max Duty
Cycle = 80%, Q_g = 100 nC, f = 200 kHz and T_AMAX = +75°C:
PE = 16 mA * 1.8 V * 0.8 = 23 mW
PO = 4.5 mA * 20 V + 0.85 µ * 200 kHz
= 260 mW ≥ 226 mW (PO(MAX) @ 75°C = 250 mW (5°C * 4.8 mW/°C))
The value of 4.5 mA for I_CC in the previous equation was obtained by derating
the I_CC max of 6 mA to I_CC max at +75°C. Since P_O for this case is greater than
the P_O(MAX), R_g must be increased to reduce the HCPL-3180 power dissipa-
tion.
PO(SWITCHING MAX)


= PO(MAX) – PO(BIAS)
= 226 mW – 90 mW
= 136 mW




ESW(MAX)
= PO(SWITCHING MAX)
f
= 136 mW
200 kHz
= 0.68 µW
For Q_g = 100 nC, a value of E_sw = 0.68 µW gives a R_g = 15 W.
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