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Preferred power supply connections?

Former Member

The schematic I am "capturing" are based on public domain circuits for

audio processing modules in a modular analog synthesizer. There are some

standard power connection schemes which I intend to follow consisting of

+/- 15 Vdc and ground. Typically, the +/- supplies go through a ferrite

bead and a couple of filtering capacitors before hitting the PCB's power

nets.

 

What is the best way to make a power net for the PCB components bcause it

is separated from the power input jack by the ferrite bead? If I connect

the connector pins to the supply +15 and -15 nets, I can't use them on the

PCB. So, what is the best net to use to PCB components to the other side of

the ferrite beads? Should use one of the other available supply nets or

make a unique power net?

 

I have played with different ways to do it, and they seem to work, but as

I'm new at this capture stuff, I'd like to know if there are standard or

preferred ways to accomplish this.

 

This image kind of shows what I mean.

 

Thanks

David

 

 

 

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  • Surprisingly nobody has mentioned EAGLE's gotcha with respect to power

    supplies. EAGLE parts have named power supply pins that automatically

    connect to the net of the same name. Furthermore, on many parts these

    pins are hidden until you use the INVOKE command to bring them into the

    schematic.

     

    It becomes a problem when you try to use an opamp with say pin 4 defined

    as -15V in the part. Add this part into your schematic and that

    (invisible) pin is automatically connect to the net named -15V. If your

    -15V net is called VEE or VSS, no connection. Guess what happens when

    one part has a pin named VCC and another part has a pin named +15V and

    you need to connect both to the same +12V power supply rail...

     

    I don't like these implicit nets at all and I do not use them, but they

    are found all the time in the EAGLE library parts. I believe the newer

    versions of EAGLE may have an option to disable this behavior. ( I still

    use v4 ). Look in the EAGLE help for SUPPLY and POWER directions for

    pins to understand this a little better.

     

    I do use power supply symbols and I also frequently label the nets like

    Olin does. I document all power supply connections in the schematic

    along with their bypass caps, and never use the implicit ones.

     

Reply

  • Surprisingly nobody has mentioned EAGLE's gotcha with respect to power

    supplies. EAGLE parts have named power supply pins that automatically

    connect to the net of the same name. Furthermore, on many parts these

    pins are hidden until you use the INVOKE command to bring them into the

    schematic.

     

    It becomes a problem when you try to use an opamp with say pin 4 defined

    as -15V in the part. Add this part into your schematic and that

    (invisible) pin is automatically connect to the net named -15V. If your

    -15V net is called VEE or VSS, no connection. Guess what happens when

    one part has a pin named VCC and another part has a pin named +15V and

    you need to connect both to the same +12V power supply rail...

     

    I don't like these implicit nets at all and I do not use them, but they

    are found all the time in the EAGLE library parts. I believe the newer

    versions of EAGLE may have an option to disable this behavior. ( I still

    use v4 ). Look in the EAGLE help for SUPPLY and POWER directions for

    pins to understand this a little better.

     

    I do use power supply symbols and I also frequently label the nets like

    Olin does. I document all power supply connections in the schematic

    along with their bypass caps, and never use the implicit ones.

     

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