A VOUT_UV fault was detected because a voltage less than the VOUT_UV_FAULT_LIMIT was detected on this channel’s VSENSE pin.
Possible Causes:
- VOUT_UV_FAULT_LIMIT set too high.
VOUT_COMMAND setting too low and DAC/servo moved output below VOUT_UV_FAULT_LIMIT.
Regulator feedback resistor value(s) incorrect or assembly issue.
The enable/RUN pin of the device was disabled externally while the channel was ON
The channel dipped under a load after sequencing up properly (after TON_MAX_FAULT_LIMIT)
Remedies and Workarounds
Here are some experiments you can try to narrow things down:
- Lower VOUT_UV_FAULT_LIMIT to see if the problem goes away
- Set the VOUT_UV_FAULT_RESPONSE to 'deglitched off' and increase the deglitch interval until the problem goes away
- Set the VOUT_UV_FAULT_RESPONSE to 'ignore' and see if the system sequences up. Then issue CLEAR_FAULTS to determine whether the problem occurs during startup only or afterward.
Other Debugging Tips
One thing to keep in mind with UV faults are that they can only occur after the device has successfully risen above the VOUT_UV_FAULT_LIMIT within the time budget of TON_MAX_FAULT_LIMIT after the output is enabled. This means that the output did come up initially, and then fell below the VOUT_UV_FAULT limit while the channel was ON. If you have an oscilloscope, perhaps the fastest way to insight is to:
- Trigger the scope on the falling edge of the ALERTB signal, and
- Look at the VOEN and VSENSE at the pins of the IC, and
- VIN for the offending channel (or other relevant signals/channels)
The ALERTB signal will be pulled low by the IC at the time of the fault, indicating the time of the fault.
