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LM5033: LM5033 Vref Pin min spec

Russell Wetherley1
Expert 4255 points
Part Number: LM5033

I have a customer who is using the LM5033 as an isolated bus converter in a design and will be using the REF pin similar to as shown in the application note.  It says in the datasheet however that the minimum current sink is 5mA.  Does this imply that they need to size the pull-up resistor to accommodate this minimum current?  I noticed that Figure 8 in the datasheet shows good reference all the way down to 0mA and the app notes have a relatively large pull-up resistor, 20kohms.  If lower current is ok, why does the datasheet have a minimum value?  Another similar question was asked in the thread below.  If Iref is between 0-5mA, why isn't Vref pulled down?

Thank you very much!

Russell

  • 0
    TI__Intellectual 2910 points

    Hi Russell,

    This spec is meant to indicate the capability of the REF pin to sink current. It does not indicate a current requirement. Basically, the spec is saying that, for any given unit of LM5033 across operating conditions, the maximum current that the REF pin can sink will at least be 5mA. Some would refer to this type of spec as a min(Iref_max). So the device will function with any load lower than this.

    Since this pin can be used as a 2.5-V precision output reference for external circuitry, this spec is important so that designs are not implemented that expect this pin to sink a lot of current.

    I hope this answers your question. If it has, please press the "Verify Answer" button below.

    - Daniel