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UCC2818A: Large power limit deviation issue

Yoshwa
Expert 4050 points
Part Number: UCC2818A

A large power limit deviation issue has been occurred in Customer’s mass produced power sources.

Product rate of exceeding ±20％ deviation is going up one to two percent.

In some cases, replacing the UCC2818A has largely reduced the deviation late.

What kinds of issues are considered?

Can you estimate the influences of circuit resistor value deviation, IMOUT value, gain constant K and etc.?

I have reviewed the following application note.

 www.tij.co.jp/.../slua196a.pdf

  • 0
    TI__Mastermind 34465 points

    Hello Yoshwa,

    The UCC2818A has a multiplier output pin that sets the current demand level for the power supply.

    The value of this signal effectively sets the power at the applied input voltage.

    The data sheet shows an IMOUT variation of +16.7% to -22% at high line high power and a variation of +15% to -10.7% at low line high power.

    The tolerance of the IMOUT resistor and the current sense resistor will also add to this variation but the major cause of variation is due to the variation in multiplier output  current

    Regards

    John Griffin