A DAC_SATURATED warning was detected because the DAC on this channel reached a maximum or minimum DAC value, and the VDAC pin has reached its limit. The channel may also have faulted off due to an OV or UV.
Possible Causes:
- Floating voltage too far away from VOUT_COMMAND voltage for servo’s compliance range
- DAC servo resistor value too high
- DAC servo resistor missing or cracked
- Regulator feedback resistor value(s) incorrect or assembly issue
- OPERATION register in Margin High or Margin Low state and DAC resistor value is too high
Remedies and Workarounds
Here are some experiments you can try to narrow things down:
- Change DAC mode to disconnected and re-start the channel (if necessary)
- Observe READ_VOUT floating voltage and compare this value with VOUT_COMMAND setting. (Note: VOUT_COMMAND is the target value used by the servo loop)
- Decrease DAC resistor value if the VDAC voltage does not have enough range to servo the output to the VOUT_COMMAND voltage.
- Change the dac_gain to higher setting if the VDAC voltage needs to be greater. If the regulator's feedback voltage is 0.6V or 0.8V, use the lower gain setting (1.38V full scale). For feedback voltages of 1.2V, use the high gain setting (2.65V full scale).
- Generally speaking, DAC resistor values of > 1M ohm will cause DAC_SATURATED warnings.
- Change OPERATION register to 'On' (0x80), avoid Margin High and Margin Low states
Other Debugging Tips
There are a number of scenarios that can contribute to a DAC_SATURATED fault. If you have an oscilloscope, perhaps the fastest way to insight is to:
- Probe the VDAC and VSENSE pins of the IC
- Under typical conditions, the VDAC voltage will be within 100mV of the feedback voltage on a properly working channel, unless channel in margining state
Note: The ALERTB pin might not be asserted if no warnings or faults are detected.
