schottky diode question

  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

 

in

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

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tempus fugit wrote:

No. power supply sequencing is when the different power rails are
switched on during powerup with a delay between. Some ICs can become
unstable if all of the rails are applied at once. If you select
regulators with an enable pin (7809, 7805 do not) you can use a simple RC
circuit to delay powerup.

- --
Brendan Gillatt | GPG Key: 0xBF6A0D94
brendan brendangillatt (dot) co (dot) uk
http://www.brendangillatt.co.uk
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then

power

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

 tempus fugit wrote:

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

Ed