Discussion:
[SI-LIST] 01005 0 ohm resistors in PCIe Gen4 Tx/Rx path
Praveen Kumar
2018-12-05 20:44:01 UTC
Permalink
Hi experts,
Are there any known issues with using 0 ohm resistors in the path of PCIe
Gen4 Tx/Rx signal path.

I couldn’t find frequency characteristics of the resistors from
manufacturer data sheet to see if there is significant insertion loss at
8GHz.

Thanks
Praveen

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Alan Hilton-Nickel
2018-12-05 22:20:01 UTC
Permalink
Hey Praveen,


In the range of functional frequenci= es associated with Gen4 speed
(8-24GHz,depending on what you are looking a= t and why), there is nothing
frequency dependent about a standard SMT resis= tor itself. While the any
material has a dielectric constant and loss tange= nt that will result in FD
characteristics, the 01005 (0201) device is elect= rically too small to be a
large impact on insertion loss or reflective loss= .

That said, it will have some parasitics like package inductance and= pad
capacitance.


Also, you are probably aware that "zero ohm= s" does not exist. A
zero-ohm resistor is a manufacturers term for a ve= ry low resistance,
typically <1 Ohm. Zero-ohm resistors, by that defini= tion, can be as
much as 1 Ohm, or even slightly more. Against your 85 Ohm e= nvironment,
thatis not huge (a fraction of a dB), but something you can ca= lculate.

More importantly, the problem is going to be with the transi= tions. You are
probably routing on an inner layer (stripline), and transiti= oning to the
surface with a via, and possibly back again with another via. = The via
structure will have losses associated with it, those losses (along = with
theparasitics) can be greater than the impact of the resistor itself.=


If you are using zero-ohm resistors as place-holders for dc-blo= cking
capacitors of the same size, then those structural losses should mini= mized
by your design, characterized by simulation and baked into your loss =
budgetalready. I would avoid putting precautionary zero-ohm resistors into=
your design unless they are absolutely necessary.


If you're = still in doubt, the best way to determine your
frequency-dependent characte= ristics is to measure them.


Alan Hilton-Nickel
On December 5, 2018 at 12:44 PM Praveen Kumar
<***@gmail.com[1]>wrot= e:


Hi experts,
Are there any known issues with using 0 ohm re= sistors in the path of PCIe
Gen4 Tx/Rx signal path.

I couldn&#821= 7;t find frequency characteristics of the resistors from
manufacturer da= ta sheet to see if there is significant insertion loss at
8GHz.

T= hanks
Praveen

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http://www.freelists.org/archives/si-list[6]

Ol= d (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.n= et/wb6tpu[7]





Alan = Hilton-Nickel
San Jose, CA =20

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Doug Smith
2018-12-05 22:33:31 UTC
Permalink
Hi Everyone,

A little off topic but I believe there is a health danger to 01005 resistors in the lab. It would not be difficult for them to get in your body by respiration or in the mouth. I think the results would be an early death years later, especially if inhaled. They should never be out in the open in dishes/trays where they can spill out.






Just a thought. Would not want anyone to come down with resistosis or capacitosis (like asbestos) in the coming years.

Doug

On Wed, 5 Dec 2018 14:20:01 -0800 (PST), Alan Hilton-Nickel wrote:


Hey Praveen,


In the range of functional frequenci= es associated with Gen4 speed
(8-24GHz,depending on what you are looking a= t and why), there is nothing
frequency dependent about a standard SMT resis= tor itself. While the any
material has a dielectric constant and loss tange= nt that will result in FD
characteristics, the 01005 (0201) device is elect= rically too small to be a
large impact on insertion loss or reflective loss= .

That said, it will have some parasitics like package inductance and= pad
capacitance.


Also, you are probably aware that "zero ohm= s" does not exist. A
zero-ohm resistor is a manufacturers term for a ve= ry low resistance,
typically <1 Ohm. Zero-ohm resistors, by that defini= tion, can be as
much as 1 Ohm, or even slightly more. Against your 85 Ohm e= nvironment,
thatis not huge (a fraction of a dB), but something you can ca= lculate.

More importantly, the problem is going to be with the transi= tions. You are
probably routing on an inner layer (stripline), and transiti= oning to the
surface with a via, and possibly back again with another via. = The via
structure will have losses associated with it, those losses (along = with
theparasitics) can be greater than the impact of the resistor itself.=


If you are using zero-ohm resistors as place-holders for dc-blo= cking
capacitors of the same size, then those structural losses should mini= mized
by your design, characterized by simulation and baked into your loss =
budgetalready. I would avoid putting precautionary zero-ohm resistors into=
your design unless they are absolutely necessary.


If you're = still in doubt, the best way to determine your
frequency-dependent characte= ristics is to measure them.


Alan Hilton-Nickel
On December 5, 2018 at 12:44 PM Praveen Kumar
<***@gmail.com[1]>wrot= e:


Hi experts,
Are there any known issues with using 0 ohm re= sistors in the path of PCIe
Gen4 Tx/Rx signal path.

I couldn̵= 7;t find frequency characteristics of the resistors from
manufacturer da= ta sheet to see if there is significant insertion loss at
8GHz.

T= hanks
Praveen

----------------------------------------------------------------------------
To unsubscribe from si-list:
si-list-***@freelists.org[2] with 'u= nsubscribe' in the Subject
field

or to administer your membershi= p from a web page, go to:
http://www.freelists.org/webpage/= si-list[3]

For help:
si-list-***@freelists.org[4] with 'help' in the Subject = field


List forum is accessible at:
http://tec= h.groups.yahoo.com/group/si-list[5]

List archives are viewable at: =
http://www.freelists.org/archives/si-list[6]

Ol= d (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.n= et/wb6tpu[7]





Alan = Hilton-Nickel
San Jose, CA =20

--- Links ---
1
2 3D"mailto:s=
3 3D"http://www.freelists.org/webpage/si=
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Grasso, Charles
2018-12-06 15:30:21 UTC
Permalink
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Bil Herd
2018-12-06 17:05:55 UTC
Permalink
Not to mention that you have to now answer the question when you get an MRI:
"Is there a possibility there are small electronic components embedded in
your body".

Bil

-----Original Message-----
From: si-list-***@freelists.org [mailto:si-list-***@freelists.org] On
Behalf Of Doug Smith
Sent: Wednesday, December 05, 2018 5:34 PM
To: ***@hilton-nickel.net; ***@gmail.com; si-list
Subject: [SI-LIST] Re: 01005 0 ohm resistors in PCIe Gen4 Tx/Rx path

Hi Everyone,

A little off topic but I believe there is a health danger to 01005 resistors
in the lab. It would not be difficult for them to get in your body by
respiration or in the mouth. I think the results would be an early death
years later, especially if inhaled. They should never be out in the open in
dishes/trays where they can spill out.






Just a thought. Would not want anyone to come down with resistosis or
capacitosis (like asbestos) in the coming years.

Doug

On Wed, 5 Dec 2018 14:20:01 -0800 (PST), Alan Hilton-Nickel wrote:


Hey Praveen,


In the range of functional frequenci= es associated with Gen4 speed
(8-24GHz,depending on what you are looking a= t and why), there is nothing
frequency dependent about a standard SMT resis= tor itself. While the any
material has a dielectric constant and loss tange= nt that will result in FD
characteristics, the 01005 (0201) device is elect= rically too small to be a
large impact on insertion loss or reflective loss= .

That said, it will have some parasitics like package inductance and= pad
capacitance.


Also, you are probably aware that "zero ohm= s" does not exist. A zero-ohm
resistor is a manufacturers term for a ve= ry low resistance, typically <1
Ohm. Zero-ohm resistors, by that defini= tion, can be as much as 1 Ohm, or
even slightly more. Against your 85 Ohm e= nvironment, thatis not huge (a
fraction of a dB), but something you can ca= lculate.

More importantly, the problem is going to be with the transi= tions. You are
probably routing on an inner layer (stripline), and transiti= oning to the
surface with a via, and possibly back again with another via. = The via
structure will have losses associated with it, those losses (along = with
theparasitics) can be greater than the impact of the resistor itself.=


If you are using zero-ohm resistors as place-holders for dc-blo= cking
capacitors of the same size, then those structural losses should mini= mized
by your design, characterized by simulation and baked into your loss =
budgetalready. I would avoid putting precautionary zero-ohm resistors into=
your design unless they are absolutely necessary.


If you're = still in doubt, the best way to determine your
frequency-dependent characte= ristics is to measure them.


Alan Hilton-Nickel
On December 5, 2018 at 12:44 PM Praveen Kumar
<***@gmail.com[1]>wrot= e:


Hi experts,
Are there any known issues with using 0 ohm re= sistors in the path of PCIe
Gen4 Tx/Rx signal path.

I couldn̵= 7;t find frequency characteristics of the resistors from
manufacturer da= ta sheet to see if there is significant insertion loss at
8GHz.

T= hanks
Praveen

----------------------------------------------------------------------------
To unsubscribe from si-list:
si-list-***@freelists.org[2] with 'u= nsubscribe' in the Subject field

or to administer your membershi= p from a web page, go to:
http://www.freelists.org/webpage/= si-list[3]

For help:
si-list-***@freelists.org[4] with 'help' in the Subject = field


List forum is accessible at:
http://tec= h.groups.yahoo.com/group/si-list[5]

List archives are viewable at: =
http://www.freelists.org/archives/si-list[6]

Ol= d (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.n= et/wb6tpu[7]





Alan = Hilton-Nickel
San Jose, CA =20

--- Links ---
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7 3D"htt=
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Praveen Kumar
2018-12-07 16:07:55 UTC
Permalink
Thanks Alan, Arnee & Scott for the valuable input.
I'm taking care of the transition (added due to the addition of these
resistors) to have minimal impact.
Praveen
Post by Alan Hilton-Nickel
Hey Praveen,
In the range of functional frequencies associated with Gen4 speed
(8-24GHz, depending on what you are looking at and why), there is nothing
frequency dependent about a standard SMT resistor itself. While the any
material has a dielectric constant and loss tangent that will result in FD
characteristics, the 01005 (0201) device is electrically too small to be a
large impact on insertion loss or reflective loss.
That said, it will have some parasitics like package inductance and pad
capacitance.
Also, you are probably aware that "zero ohms" does not exist. A zero-ohm
resistor is a manufacturers term for a very low resistance, typically <1
Ohm. Zero-ohm resistors, by that definition, can be as much as 1 Ohm, or
even slightly more. Against your 85 Ohm environment, that is not huge (a
fraction of a dB), but something you can calculate.
More importantly, the problem is going to be with the transitions. You are
probably routing on an inner layer (stripline), and transitioning to the
surface with a via, and possibly back again with another via. The via
structure will have losses associated with it, those losses (along with the
parasitics) can be greater than the impact of the resistor itself.
If you are using zero-ohm resistors as place-holders for dc-blocking
capacitors of the same size, then those structural losses should minimized
by your design, characterized by simulation and baked into your loss budget
already. I would avoid putting precautionary zero-ohm resistors into your
design unless they are absolutely necessary.
If you're still in doubt, the best way to determine your
frequency-dependent characteristics is to measure them.
Alan Hilton-Nickel
Hi experts,
Are there any known issues with using 0 ohm resistors in the path of PCIe
Gen4 Tx/Rx signal path.
I couldn’t find frequency characteristics of the resistors from
manufacturer data sheet to see if there is significant insertion loss at
8GHz.
Thanks
Praveen
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http://tech.groups.yahoo.com/group/si-list
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Alan Hilton-Nickel
San Jose, CA
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