11

+ HVDC

3-PHASE

AC

- HVDC

0.1 µF

1

3

+

–

2

4

8

6

7

5

HCPL-3140/HCPL-0314

Rg

Q1

Q2

270

Ω

+5 V

CONTROL

INPUT

74XXX

OPEN

COLLECTOR

Applications Information

Eliminating Negative IGBT Gate

Drive

To keep the IGBT firmly off,

the HCPL-3140/HCPL-0314 has a

specification of 1.0 V. Minimizing

Rg and the lead inductance from

the HCPL-3140/HCPL-0314 to

the IGBT gate and emitter

(possibly by mounting the

HCPL-3140/HCPL-0314 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 19. Care should be taken

with such a PC board design to

avoid routing the IGBT collector

or emitter traces close to the

HCPL-3140/HCPL-0314 input as

this can result in unwanted

coupling of transient signals into

the input of HCPL-3140/

HCPL-0314 and degrade

performance. (If the IGBT

drain must be routed near the

HCPL-3140/HCPL-0314 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-3140/

HCPL-0314.)

Figure 19. Recommended LED Drive and Application Circuit for HCPL-3140/HCPL-0314.