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schottky diode question

Discussion in 'Electronic Basics' started by tempus fugit, Jun 10, 2009.

  1. tempus fugit

    tempus fugit Guest

    Hey all;

    I'm planning on using a MAX4622 CMOS switch in a circuit I'm building. On
    p.7 of the data sheet
    (http://datasheets.maxim-ic.com/en/ds/MAX4621-MAX4623.pdf), it says:

    "If power-supply sequencing is not possible, add two small signal diodes in
    series with the supply pins and a Schottky diode between V+ and VL"

    I've read a bit about Schottky diodes, and I see that there are several
    different types (like with normal diodes I suppose). How do I know what I
    should use for this purpose? Can someone recommend one?

    Thanks
     
  2. tempus fugit

    tempus fugit Guest


    Sorry, I forgot one other question. The datasheet says to sequence V+, then
    Vl, V-, then logic ins. If the V+ was 9v, and Vl was 5v, and I had a power
    supply that went:

    +15vDC =>7809 => 7805, would that be power supply sequencing?

    Thanks again
     
  3. tempus fugit

    tempus fugit Guest


    I'm using it for switching different guitar effects pedals in and out of my
    signal chain. I suppose I don't need 5 ohms, but I have a couple here and
    thought I might as well use them, rather than order other parts.

    Thanks
     
  4. tempus fugit

    tempus fugit Guest

    If the 7809 and 7805 are in series (IOW, output of 7809 feeds input of
    7805), wouldn't there be a delay in between?

    Thanks
     
  5. ehsjr

    ehsjr Guest

    Yes, but the 5V could become available to the circuit
    _before_ the 9V output cap is fully charged.

    Ed
     
  6. tempus fugit

    tempus fugit Guest


    Thanks for that Bill - that's much clearer now. Could you clarify something
    though:
    I assume you mean 7809, not 7905 here?

    So I don't need to worry about the protection diodes? Also, since I'm using
    this device to switch audio signals, I need as close to the supply voltage
    as possible. Would the diodes in series with the supply pin reduce the
    voltage swing by another 0.6v?

    Thanks
     
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