An OT_FAULT was detected because the temperature exceeded the OT_FAULT_LIMIT value. This fault applies to the die temperature on the 2977/2978 devices but is a paged fault on all other SPM devices. The OT/UT warning and fault limits and response are global registers on the 2977/78 and are paged on all other PSM devices.
Possible Causes:
If the device is a LTC2977/78, this fault indicates that high temperature was detected on the internal 2977/78 die
Otherwise, the fault indicates that high temperature was detected on an external temperature sensor on this PSM channel.
OT_FAULT_LIMIT set too low.
External TSENSE pin is floating.
Remedies and Workarounds
Check for floating External TSENSE pins (if applicable) and ground them.
If a VSENSE pin is floating, it is possible that the internal die temp measurement is grossly in error, causing an OT or UT fault or warning.
Other Debugging Tips
For 2977/78 devices, only an internal die temperature is available and therefore the OT/UT warn and fault limits are applied to the measured die temperature. For all other PSM devices, the OT/UT warn and fault limits are paged and applied to each channel’s external TSENSE pin; there are no internal die temp limits for these devices.