HCPL-314J-300 HP [Agilent(Hewlett-Packard)], HCPL-314J-300 Datasheet - Page 13

• Manufacturer Part Number: HCPL-314J-300
• Description: 0.4 Amp Output Current IGBT Gate Drive Optocoupler
• Manufacturer: HP [Agilent(Hewlett-Packard)]

Selecting the Gate Resistor (Rg)
Step 1: Calculate R
IGBT and Rg in Figure 19 can be analyzed as a simple RC circuit with a
voltage supplied by the HCPL-J314.
The V
current of 0.6A. (See Figure 6).
Step 2: Check the HCPL-J314 power dissipation and increase Rg if
necessary. The HCPL-J314 total power dissipation (P
sum of the emitter power (P
P
P
P
= (I
where K
constant of 0.001 mA/(nC*kHz). For the circuit in Figure 19 with I
(worst case) = 10 mA, Rg = 32 Ω, Max Duty Cycle = 80%,
Qg = 100 nC, f = 20 kHz and T
P
P
0.4 µ J • 20 kHz = 80 mW
< 260 mW (P
The value of 3 mA for I
entire operating temperature range.
Since P
power dissipation.
T
E
O
E
O
= P
= I
= 10 mA • 1.8 V • 0.8 = 14 mW
= P
= (3 mA + (0.001 mA/(nC • kHz)) • 20 kHz • 100 nC) • 24 V +
CCBIAS
OL
F
E
O(BIAS)
O
ICC
• V
value of 5 V in the previous equation is the V
+ P
for this case is less than P
+ K
F
• Qg • f is the increase in I
O
• Duty Cycle
O(MAX)
+ P
ICC
Rg ≥
O(SWITCHING)
• Qg • f) • V
g
minimum from the I
@ 85°C)
=
= 32 Ω
CC
24 V – 5 V
V
I
in the previous equation is the max. I
CC
OLPEAK
0.6A
E
) and the output power (P
– V
CC
AMAX
= I
OL
+ E
O(MAX)
CC
= 85°C:
CC
SW
• V
OL
due to switching and K
, Rg = 32 Ω is alright for the
(Rg,Qg) • f
CC
peak specification. The
+ E
SW
OL
(Rg,Qg) • f
T
) is equal to the
O
).
at the peak
CC
ICC
over
F
is a
13
Figure 20. Energy Dissipated in the
HCPL-J314 and for Each IGBT
Switching Cycle.
LED Drive Circuit
Considerations for Ultra
High CMR Performance
Without a detector shield, the
dominant cause of optocoupler
CMR failure is capacitive
coupling from the input side of
the optocoupler, through the
package, to the detector IC
as shown in Figure 21. The
HCPL-J314 improves CMR
performance by using a detector
IC with an optically transparent
Faraday shield, which diverts the
capacitively coupled current away
from the sensitive IC circuitry.
However, this shield does not
eliminate the capacitive coupling
between the LED and opto-
coupler pins 5-8 as shown in
Figure 22. This capacitive
coupling causes perturbations in
the LED current during common
mode transients and becomes the
major source of CMR failures for
a shielded optocoupler. The main
design objective of a high CMR
LED drive circuit becomes
keeping the LED in the proper
state (on or off ) during common
mode transients. For example,
the recommended application
circuit (Figure 19), can achieve
10 kV/µs CMR while minimizing
component complexity.
Techniques to keep the LED in
the proper state are discussed in
the next two sections.
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
Rg – GATE RESISTANCE – Ω
20
40
60
Qg = 50 nC
Qg = 100 nC
Qg = 200 nC
Qg = 400 nC
80
100