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UCD90120A: Question on margin control with the GUI on the UCD90120A

Part Number: UCD90120A

I am using the UCD90120A as a supply control for 6 separate supplies and have margin control on 5 of them.

I have a problem (or a sim-understanding of the margin control). As an example, 2 supplies are set to a nominal 1.2V with a 5% margin value. If I set the Trim/Margining

for both rails to Tri-State and then monitor both supplies, I can use the Margining option in the OPERATION tab to control the voltage as expected:

So far, so good. I then tried to set one of the supplies Margin Mode to Active Trim or Active Duty Cycle. When I turn margin on/off in the OPERATION

tab, the supply left in the Tri-State mode margins up and down, but the supply with either Active Trim or Active Duty Cycle stays at nominal voltage, even with a

duty cycle that should skew the output quite a bit.

Any idea of what I am missing?

Also, a minor complaint with the Monitor. I have a low voltage supply that used open drain, active high enable. The pull-up voltage is around 1.2V. In the monitor, the enable for that pin shows off, even though the supply is on. My guess is the monitor reads the value of that enable pin and seeing it at less than a 3.3V threshold, marks it as off rather than using the fact that that output is set to on. Perhaps a new "LED" coler that indicates the pin is driven but the voltage is below some threshold.

  • Hello

    TRI-STAT, ACTIVE_TRIM and Active Duty Cycle are used when margining function is not enable.

    So when ACTIVE_TRIM is selected, device adjust the rail to its normal voltage.

    When ACTIVE DUTY cycle, is selected, device does not adjust its voltage and keep the fixed duty cycle.

    You may have to turn off the rails and turn rails back on to switch among three states.

    For the 1.2V pull up, the signal is considered low from device point view, that's why the LED is off.

    We will see what we can do on this for the future.

    Regards

    Yihe