UCD92XX devices have three programmable coefficient banks for each output voltage rail.bank 0x0 is used during soft start and stop,bank 0x1 during normal regulation mode,and bank 0x2 during light load operation. for UCD9222,when to use soft start/stop , light load or normal operation? and how the decide which mode shuold be used.?
First, the controller determines when to use the appropriate compensation bank, Soft Start/Stop during ramp up or ramp down of the rail voltage, Regulation is used once the rail voltage has reached its programmed level, and Light Load during operation when the monitored current falls below a user defined level. Light Load allows phase shedding to be implemented.
Second, the UCD9222 and UCD9244 can only support a single phase per rail so phase shedding at light load is not an option that is supported on these devices and the compensation banks should be grayed out in the Fusion GUI.
Third, it is generally recommended to keep the compensation in the Soft Start/Stop the same as in Regulation with the exception of the Non-Linear Gains which are set to 1.0 (there is a checkbox to set these to 1.0 called Linear Gain or they can be manually set to 1.0). The Auto-Tune feature will perform this automatically.
Note: It is recommended to keep the AFE Gain set too 4x as this is where the controller is factory trimmed for DC accuraccy, using another value may introduce a small DC offset. 4x has been found to work well for all the applications that I have reviewed.
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