Why does this resistor network simulate differently from the physical package?

I am trying to simulate a Bourns 4310R-R2R-104 dual terminator 104 circuit resistor network.

According to the datasheet, the circuit looks like this: When I read the resistance between pin 1 and pin 2 on the physical package I get 200K ohms:  I built an equivalent circuit in Circuit Wizard and measured between the same pins but get a different result: Why is this?

• Your real life measurement seems incorrect, there is no way it should be 200 kohms if that is the correct schematic for this part and you are measuring the correct pins. So I suspect that is not the correct schematic and/or you are measuring the wrong pins. (e.g. could it be a bussed resistor network with 100k resistors and you are measuring between two of the resistors?) – immibis Oct 15 '18 at 23:14
• @immibis I bought the components from Digikey so they should be genuine. I tested pins 1 and 2 on two more components and they measure the same at 200k. – Zhro Oct 15 '18 at 23:17
• If your schematic is correct, the resistance between pins 1 and 2 must be somewhat less than 100K, as R1 in series with all the other resistors in the package are in parallel with R2 – Peter Bennett Oct 15 '18 at 23:19
• Your part number includes "R2R", but the circuit does not look like an R2R ladder. The datasheet linked from mauser and from your question does not seem to be the right one, as it doesn't mention R2R anywhere. Try this datasheet instead maybe?: bourns.com/pdfs/r2r.pdf – Jack B Oct 15 '18 at 23:22
• Your simulation is correct, since it's just 100k in parallel with (100k + 200k/7) giving 56.25k. – Phil G Oct 15 '18 at 23:30

Wrong datasheet

Mouser links to the wrong datasheet. The part number you have looks like ?????-R2R-??? but the datasheet you link covers parts with 101, 102 and 104 as that second group. If you look at this datasheet instead:

https://www.bourns.com/pdfs/r2r.pdf

You will see that you have a SIP package R2R ladder with 100k resistors. If you look at the bottom left schematic in the group of four, you'll see that it does indeed have a resistance of 200K between pin 1 and pin 2.

Ignoring the point about the datasheet being wrong, I'm also at a loss with your schematic - unless you have some of the pins grounded.

Taking the diagram systematically:

you connect across Either end of R2 via pin 1 and pin 2, you also need to include the parallell resistances of: Pin 2 , through R1, R3 and R4 back to Pin 1 Pin 3 , through R1, R5 and R6 back to Pin 1 Pin 4 , through R1, R7 and R8 back to Pin 1 Pin 5 , through R1, R9 and R10 back to Pin 1 Pin 6 , through R1, R11 and R12 back to Pin 1 Pin 7 , through R1, R13 and R14 back to Pin 1 Pin 8 , through R1, R15 and R16 back to Pin 1

Now remembering 1/Rtotal = 1/R1 + 1/R2 etc ... we get

1/Rtotal = 1/100k + 7/300k Rtotal = 30k ohm

So I don't know how the simulator got 56.24 ohms ?