Open Drain Output
35 192-300300N1 GVI Frames C, D & E 2019-9
8.8.2. Protection
The Open Drain outputs are protected against inductive discharge with internal freewheeling diodes to
HIGH_SIDE_OUT/IN, internal short circuit detection and a capacitor to B- for ESD protection.
The Open Drain outputs are not protected against reverse polarity of the battery. A way to avoid this failure
mode is to activate the contactor only after the voltage over the DC-bus capacitors has reached the accepted
pre charge level (see picture in chapter 8.9.1).
NOTE
When driving inductive loads on PWM Open drain outputs there must always be a path for the
current to the freewheeling diodes. Do not connect any switch or fuse in series with the diode.
8.8.3. Circuit
CAUTION
Overvoltage sensitive equipment – risk of damage to equipment
Internal free-wheeling diodes are provided to protect the motor controller from overvoltage at
inductive load.
For Open drain 1, 2 & 3; internal free-wheeling diodes are connected to the HIGH_SIDE_OUT
pin.
For Open drain 4, 5 & 6; internal free-wheeling diode s are connected to the HIGH_SIDE_IN
pin.
Ensure that inductive loads are connected such that the path for the free-wheeling diode is
always intact (see chapter 8.9.1), or use an external free-wheeling diode if this is not possible.
Use of brushless fan or other loads with built-in capacitor can give high inrush current when
turned ON, which will give an Open Drain overcurrent trip. The inrush current must be below
the Open Drain peak current.
Figure 21 Schematic of the Open Drain 1, 2 and 3 Output circuit
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