11

Figure25.RecommendedLEDdriveandapplicationcircuitforHCPL-3180.

Figure24.CMRtestcircuitandwaveform.

ApplicationsInformationEliminatingNegativeIGBTGate

Drive

To keep the IGBT firmly off, the HCPL-3180 has a very

1 W (typical) on resistance in its pull down circuit. When

the HCPL-3180 is in the low state, the IGBT gate is shorted

inductance from the HCPL-3180 to the IGBT gate and

emitter (possibly by mounting HCPL-3180 on a small PC

board directly above the IGBT) can eliminate the need for

negative IGBT gate drive in many applications as shown

in Figure 25. Care should be taken with such a PC board

design to avoid routing the IGBT collector or emitter

traces close to the HCPL-3180 input as this can result in

unwanted coupling of transient signals into the input of

HCPL-3180 and degrade performance.

(If the IGBT drain must be routed near the HCPL-3180

input, then the LED should be reverse biased when in the

off state to prevent the transient signals coupled from the

IGBT drain from turning on the HCPL-3180.)

0.1

µF

10

Ω

1

3

+

–

+

–

2

4

8

6

7

5

250 KHz

50% DUTY

CYCLE

500

Ω

10 nF

10%

50%

90%

0.1

µF

1

3

+

–

+

–

2

4

8

6

7

5

A

+

B

5 V

∆t

0 V

∆t

δV

δt

=

+ HVDC

3-PHASE

AC

- HVDC

0.1

µF

1

3

+

–

2

4

8

6

7

5

270

Ω

+5 V

CONTROL

INPUT

Rg

Q1

Q2

74XXX

OPEN

COLLECTOR