digital bit through 0ohm???

[ljy4468]

Hi everyone?

I've seen TI ADS5500 Evaluation board.(pipeline ADC 14bit 125MS/s)
and all digital output, clk output pass 0-ohm resistor.

why digital signal pass 0-ohm resistor?
what's the effect?

please tell me why.
thanks in advance.

 

[philba]

there is no such thing as 0 ohms. all material has resistance except at superconductor temperatures.

Typically, "0 ohm" resistors are used for several purposes. One is just a jumper to allow creation of a single sided board (or perhaps a fewer layer board). Thompson TV sets are notroious for this. Another use is in a place where a resistor might be used in certain circuit configurations but others the resistor is not needed (and thus 0 ohms is used). It allows a manufacturer to create a single PCB to be used in multiple configurations/products.

 

[Uky]

Very typical during initial layout spins in order to be certain that different configurations can be tried.

If there are high-speed signals involved, the zero Ohm resistors can be replaced with "real" values in order to evaluate different driver impedances in order to minimize signal integrity problems.

 

[IanP]

Try to use the SEARCH function first; it is quite possible that similar topic has been discussed before ..





Regards,
IanP

 

[ljy4468]

Oh thanks!
But I've a question more.
In Analog device's evaluation board(ADC)
there are 22 ohm resistor instead of 0 ohm.....
I want to know more.

thanks

 

[philba]

hard to say exactly but I bet its a current limiter