Short Circuit Protection on XA2 DOUTs?

Ethan Zeman 5 years ago in Expansion modules / XA2, XS2 updated by Thomas Moberg (System support) 5 years ago 3

Pardon me if this information is already readily available but am having trouble finding it.

If the wiring for an XA2 DOUT is shorted to battery is there an internal protection strategy in the module that will protect the XA2 from being damage?



Satisfaction mark by Ethan Zeman 5 years ago

Yes, the DOUT:s are protected from short to battery. It is perhaps not so clear, in the Appendix A of the instruction book we list SCB (short to battery) under protection.


One thing that will happen if you short the DOUT to battery is that you introduce a point of reverse feed of the module. If you remove normal power supply (+BAT pin) and have the DOUT shorted to battery, the module will be powered through reverse feed of the high-side switch. 

Also the hardware of the XA2's have changed over the years, and we had issues with latched DOUT's that were not an issue for years. Since we did not have the diodes installed per the manual this was ultimately our fault, and installing the diodes per the manual solved the issue. Just frustrating that we had hundreds of XA2's out in the field with no issue, now every time we send a replacement out we have to send a diode kit to ensure we don't latch the outputs. There is a discussion somewhere on this forum discussing this issue, I might have even started it, I don't remember at this point. 

When you have a coil on a DOUT an deactivates it you will induce a negative transient current on that coil.

This transient current can over time damage the DOUT on the XA2.

Using a diode on over the coil will let the transient current circulate trough the coil instead of going in to the DOUT.

And yes, the older XA2 had a circuit that was more robust that the one in newer, so they could handle this transient better.

But you can still damage those in the old XA2 the same way, so you should still have the diode on the older XA2.