Topology

The Fault Insertion Unit (FIU) section of the OP8900 boards consists of seven relays per differential pair of signals, for a total of 112 relays (7 x16).

Each relay can be controlled individually.

For each group of 7 relays, the possible faults are

• Open-circuit of the pair
• Short-circuit of the two signals of the pair
  
• Two fault injection, with two user-supplied voltage references voltages (VBusA and VBusB), for each signal of the pair.

Embedded Protections

The following protections are implemented:

• In the default state, all relays are open
• All channels are updated simultaneously
• VBusA and VBusB cannot be connected on the same channel at the same time: VBusA and VBusB cannot be shorted
• When the Signal + and Signal - are shorted together, only one other fault is allowed for VBusA or VBusB on that channel pair
• Relays on a channel are always open before closing any other

Even if the power supply on the VBus is limited to 0.1A, a capacitor is present at the output and the peak current can easily >5A before the internal current limit kick in creating permanent damage to the relay.

If a relay is broken in short mode, an RMA can be issued to repair the card. If the customer has access to a technician with valid IPC-610 certification and experience with a rework of through-hole lead-free and no-clean soldering, OPAL-RT authorizes this technician to replace once a faulty relay.

Here is a short recap of the process:

1. Remove the SLSC card out of the SLSC chassis.
2. With a basic multimeter measure the impedance between pin 1 and 4 of all 112 relays. If <100R, the relay needs to be changed.
3. Unsolder the faulty relay. No-clean flux can be used.
4. Solder a new relay: Comus International 3570-1419-054.

Even if some protection is built-in on the output circuit to prevent damage, creating a direct fault to VBus with higher voltage can create permanent damage.