Below are a few aspects that must be investigated when encountering problems in margining:
Please note that margin on any channel can only be initiated if voltages on all rails have reached their individual POWER_GOOD_ON thresholds
Once margining is initiated the voltages should reach their Margin High/Low values. If they do not, please check if the resistor connected between the DAC/PWM and the feedback node of the power supply is sized correctly. Please refer to the datasheet or the calculator on Margining tab of the GUI.
While selecting the DAC/PWM resistor, make sure that the maximum current output of the DAC/PWM doesn’t exceed 200uA
If a channel shuts down after Margining command is issued, check the following:
a). Ensure that the OV/UV fault limits are beyond the Margin High/Low thresholds. This can be the reason for a shutdown if the Margin Act On Fault has been issued.
b). Make sure to set the DAC/PWM level of the device to be equal to the voltage of the feedback node of the power supply. This level serves as the initial set point for the DAC/PWM to begin margining and setting this value to be too far from the voltage of the feedback node may result in abrupt non-monotonicity in the margined voltage (and may lead to a fault shutdown).
The DAC/PWM level could be calculated from datasheet or by using the calculator on the GUI.