Package variant with unconnected pins

What part of this question is difficult to understand? I'm assuming it must be, because other questions get answered, but not mine.

On 04/09/2013 09:46 PM, Clifford Heath wrote:

I'm making a symbol for the QFN20 and SSOP24 variants of the SIlicon

Laboratories Si473x famiy devices. Apart from the SSOP having more NC

and earth pins (which I can connect as duplicates), there's an extra pin

(DYBP) on the SSOP which isn't brought out on the QFN. If I add this pin

to the device, I get errors using the QFN package because it isn't

connected.

 

Is it possible to have a pin in a device which is not available in all

package variants? How?

...

What part of this question is difficult to understand? I'm assuming it

must be, because other questions get answered, but not mine.

It's not it's difficult to understand, but more likely that no one has a

good answer to offer.

Just off hand, I'd say that it's not possible to have a pin defined in

the device's symbol, and not have it connected to any pad in the package.

When you say "I get errors" isn't real clear.  Exactly what is the error

message, and when do you get it?  I assume you're getting an error when

you try to add the QFN package to the device, but the QFN package

doesn't have enough pins.

One suggestion I would make is to create a separate device with a new

symbol that doesn't have the DYBP pin defined.  Then adding the QFN to

the new device shouldn't be a problem.  Down side: you now have multiple

Si473x devices.

Alternatively, if the DYBP pin is not needed or should be left

unconnected for proper operation of the IC, you can remove this pin from

the symbol, then add the QFN.  Down side: The DYBP pin is inaccessible

for all packages.

I don't consider these as "good" answers, but merely work-around

suggestions.

HTH

    - Chuck

On 04/09/2013 09:46 PM, Clifford Heath wrote:

I'm making a symbol for the QFN20 and SSOP24 variants of the SIlicon

Laboratories Si473x famiy devices. Apart from the SSOP having more NC

and earth pins (which I can connect as duplicates), there's an extra pin

(DYBP) on the SSOP which isn't brought out on the QFN. If I add this pin

to the device, I get errors using the QFN package because it isn't

connected.

 

Is it possible to have a pin in a device which is not available in all

package variants? How?

...

What part of this question is difficult to understand? I'm assuming it

must be, because other questions get answered, but not mine.

It's not it's difficult to understand, but more likely that no one has a

good answer to offer.

Just off hand, I'd say that it's not possible to have a pin defined in

the device's symbol, and not have it connected to any pad in the package.

When you say "I get errors" isn't real clear.  Exactly what is the error

message, and when do you get it?  I assume you're getting an error when

you try to add the QFN package to the device, but the QFN package

doesn't have enough pins.

One suggestion I would make is to create a separate device with a new

symbol that doesn't have the DYBP pin defined.  Then adding the QFN to

the new device shouldn't be a problem.  Down side: you now have multiple

Si473x devices.

Alternatively, if the DYBP pin is not needed or should be left

unconnected for proper operation of the IC, you can remove this pin from

the symbol, then add the QFN.  Down side: The DYBP pin is inaccessible

for all packages.

I don't consider these as "good" answers, but merely work-around

suggestions.

HTH

    - Chuck