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REF200: REF200 headroom voltage

Toshio Katsura
Prodigy 20 points
Part Number: REF200
Other Parts Discussed in Thread: LM4041-N

We'd like to provide 100uA currents source using REF200 and DC3.3V power.

Could you tell me headroom voltage spec of REF200?

Our schematic is as follows.

Please let me know it.

Thanks

  • 0
    TI__Mastermind 19370 points

    Hi Toshio,

    The headroom for this device is known as Vcomp on the datasheet. It will be 2.5V to 40V. Will this work for your application?

  • 0 in reply to Marcoo Z
    Prodigy 20 points

    Thank you for your reply.

    My recognition of headroom (Vcomp) is voltage drop from "High"input to "Low" output in REF200. correct?
    I want to know "Low" output voltage using DC3.3V voltage supply to "High"input.
    Vcomp on the datasheet is miminum 2.5V, it's means that "Low" output voltage is 0.8V (3.3V - 2.5V), correct?

  • 0 in reply to Toshio Katsura
    TI__Mastermind 19370 points

    Hi Toshio-san,

    If you connect the REF200 on a 3.3V line with no load, the REF200 will take up all of the 3.3V trying to regulate the current.

    The REF200 is a current source so I would use the "Low" as the minimum headroom so you can calculate the highest load resistance.

    So (3.3V - 2.5V) 0.8V is the highest voltage allowed at 100uA so the biggest load is 8k Ohms.

    If you need just a 100uA current source with the lowest headroom, I would suggest to use a LM4041-N ADJ and the figure on 9.2.6. This diagram shows a current source using the LM4041 which is a 1.2V device so you will have (3.3V - 1.2) 2.1V of head room.