rpoly2, or rpolyh- when/why is one better than the other?

[krivan]

rpoly2

Hi,

I have to use a resistor of 20kOhm. In the kit I have rpoly1, rpoly2, rpolyh. The colleagues suggested me to use rpoly2 but the rpolyh semms to be a better solution for me.

Does somebody know when/why is one better than the other?

Thx,
K.

 

[kishore2k4]

rhpoly

rhpoly has higher sheet resistance compared to rpoly. It will reduce your area requirement and also the parasitic capacitance associated with it.

 

[krivan]

parasitic capacitor rpolyh

Yes, I know, thanks, but some says that the usage of rpoly2 is more beneficial because it is more precise. However I don't understand why because the uncertainty of the rpolyh is 20%, so as the rpoly2.

So basically the questions is: do I get a resistance around 20kOhm +-20% regardless I use rpoly2, or rpolyh?

 

[littlej_zju]

rpoly2, or rpolyh?

I think, you should make sure which type resistors are for rpoly1 and rpoly2. Usually, P+_rpo_poly has better voltage&temperature coefficient than N+_rpo_poly resistor.
Maybe, rpoly2 is P+_rpo_poly or not?
You'd better check the characterizatin report of voltage/temerature coefficient, mis-match, etc. This report should be provide by foundry.

 

[erikl]

Re: rpoly2, or rpolyh?

... Usually, P+_rpo_poly has better voltage&temperature coefficient than N+_rpo_poly resistor.

This is true for TC (both TC1 & TC2), but not for VC1: here N+poly is better.

@krivan: I think the only disadvantage of rpolyh vs. rpoly2 (if your rpoly2 is P+poly) is the (about 10 times) higher TC1. On the other hand: rpolyh's VC1 is 2..3 orders of magnitude (!) less than that of rpoly2 (again: if your rpoly2 is P+poly).

You'd better check the characterization report of voltage/temperature coefficient, mis-match, etc. This report should be provided by foundry.

This is always true ;-)