I'm making a board where I use 0 ohm 1206 bypass resistors which can be DNP'd depending on the options I want to select. I want to make sure a single 1206 resistor can handle the power on the trace but I'm not sure how to calculate that. It would be easy for a typical resistor but since it's a 0 ohm it should technically be able to handle any amount of power but clearly there is some resistance. As I understand it I need to look at the current rating in the datasheet but haven't been able to find a SMT 1206 resistor that can take 10 to 15A continous so perhaps I need to find a different component.

1206 0 Ohm Resistor:
https://www.digikey.com/en/products...?s=N4IgTCBcDaIEoFkDCAxAjGADANgFoBVM5NMQBdAXyA

 

Why didn't you look at the data sheet you referenced?

 

Why didn't you look at the data sheet you referenced?

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Thanks I did, edited my original post.

 

You can get some info here:
https://forum.digikey.com/t/about-zero-ohm-resistor-power-rating/17978
https://www.digikey.com/en/products/detail/yageo/RC1206JR-070RL/729184

 

40A good enough?
https://www.digikey.ca/en/products/detail/isabellenhuette-usa/FMK-Z-R0015-5-0/16836701

 

In theory, the power dissipated in a 0-ohm resistor is 0 watts.
In practice, there is no such thing as a 0-ohm resistor.

 

exactly... so one has to look for a resistor that is not just some "0 Ohm" (that could be anything) but rather specific value low resistance product. and for that one better go for current shunts.

 

You could use a short piece of large (say16Ga) bare, solid copper wire as a zero ohm connection.

 

To gain some insight into the ratings published, take the maximum rated current (2 A.), square that, and multiply by the maximum resistance of 0.05 Ω (50 mΩ) = 200 mW which is a bit less than the dissipation of a typical 1/4 watt thru hole resistor. The 1206 has the added advantage of the copper on the pads at both ends for dissipating the heat. I seriously doubt that it will see anything like that current if one end is connected to a high impedance logic input.

 

what is this circuit for? how did this go from 15A continuous to high impedance logic input?

 

0Ω resistors are usually used for configuration of options. You would not normally try to use a 1206 package for a high current path, that would be....inconceivable!

 

I don't know whether it's valid to compare SM links with through-hole links.
When I used to buy "quarter watt" zero ohm links, there were two different sorts. One was solid metal, and would take a good 5A, the other sort was the same as a metal film resistor - a ceramic tube with a low resistance metal film. That sort acted as a fuse at about 1A.
The moral of the story is that if you find one sort that will take the current, how do you ensure that it isn't swapped at some time for a different type that doesn't.

 

In theory, the power dissipated in a 0-ohm resistor is 0 watts.
In practice, there is no such thing as a 0-ohm resistor.

I want a -1 ohm resistor!

 

I want a -1 ohm resistor!

That is actually possible. I once designed an active motor braking circuit that required a negative resistor for it to work.

 

That is actually possible. I once designed an active motor braking circuit that required a negative resistor for it to work.

?? I could design a circuit which would present a negative resistance over some voltage, current, and frequency range. And I think that tunnel diodes can have a negative dynamic resistance so that decreasing current over a range will cause an increasing voltage drop. But that dissipates power and is not delivering power which a true negative resistor would need to do.

If you could find a thousand (let's say -1 ohm 1206 chip resistors) that would be the beginning of a solution to all of the world's energy problems and would also make batteries obsolete. And, I hesitate to use the word, but I think it would be impossible.

 

I designed a magnetic tape recording system on 8-track cartridge that stored digital information on the tape.
We needed the tape transport to stop instantly when required. The motor control circuit had to present a negative resistance to the transport motor in order to stop the motor instantly. This is in fact similar to regenerative braking, i.e. the circuit had to suck the energy out of the motor.

 

I designed a magnetic tape recording system on 8-track cartridge that stored digital information on the tape.
We needed the tape transport to stop instantly when required. The motor control circuit had to present a negative resistance to the transport motor in order to stop the motor instantly. This is in fact similar to regenerative braking, i.e. the circuit had to suck the energy out of the motor.

I would call that a multi (4 for a typical traction motor) quadrant power supply/motor controller.

https://docs.keysight.com/kkbopen/what-is-a-bipolar-four-quadrant-power-supply-583425137.html

https://www.carotron.com/articles/four-quadrant-motor-control/

Most natural electric event IV curves are non-ohmic and many have negative resistance regions as they involve current flow in plasma.

https://en.wikipedia.org/wiki/Plasm...nductor,a property called negative resistance.