Wanting Clarification/Explanation Regarding Isolated and Bussed Resistor Arrays

Thread Starter

ResistorsHaveResistance

Joined Jul 14, 2022
5
Hello forum,


I just signed up today, and this is my first post here. I'm an amateur solderer and beginner in DIY electronics/theory. I've recently dipped more into the subject due to my newly found interest in Eurorack modular synthesizers. Due to the ridiculous costs involved I've decided to DIY modules whenever I can. This site was actually recommended from another forum mostly focused on Eurorack called ModWiggler. Anyways, here is the predicament at hand:

I'm trying to understand the difference between an "isolated" resistor array and a "bussed" resistor array. My original need for this knowledge is to substitute some oddly stocked 1K resistor arrays (https://www.mouser.com/ProductDetail/Xicon/267-1.0K-RC?qs=YWwvPgWemcQuXs8NypyjgQ== --- https://www.mouser.com/datasheet/2/351/Xicon_09142016_SIP-RC-1201759.pdf) for individual resistors on a DIY build called the Vincursal VCA by Zlob Modular (https://zlobmodular.com/product/vnicursal-vca/ --- https://zlobmodular.com/wp-content/uploads/2021/01/hex_mother6_array21.pdf).


I apologize for my lack of theory understanding. When I have a better learning environment I'd like to sit down and research fundamentals. This site seems adequate for that.

Let me know what you guys know about resistor arrays and any recommendations for substitutions would be much appreciated!​





Thank you for your time,
Ricky
 

BobTPH

Joined Jun 5, 2013
5,458
The datasheet clearly shows the difference. The bussed array has one connection on each resistor connected to a single pin. The isolated array has two distinct pins for each resistor.
 

Thread Starter

ResistorsHaveResistance

Joined Jul 14, 2022
5
The datasheet clearly shows the difference. The bussed array has one connection on each resistor connected to a single pin. The isolated array has two distinct pins for each resistor.
Yes, I see the schematic image on the datasheet, but I still do not have the experience with this kind of things to determine how the 6 pins function. The numbers and symbols near the schematic are a little bit confusing. Sorry if this seems stupid but I think I would benefit from just a dumbed down explanation so I can interpret it better. I suppose I could ask this too: Could I physically break that component to leave 2 pins on and use that single piece as a 1K resistor (hypothetically not practically obviously)?
 

BobTPH

Joined Jun 5, 2013
5,458
Ah, I see your problem now. The datasheet has a text formatting problem.

On each schematic, the 1,2,3, and 4 should be on the four leftmost pins. Then it makes sense.
 

Papabravo

Joined Feb 24, 2006
18,967
Yes, I see the schematic image on the datasheet, but I still do not have the experience with this kind of things to determine how the 6 pins function. The numbers and symbols near the schematic are a little bit confusing. Sorry if this seems stupid but I think I would benefit from just a dumbed down explanation so I can interpret it better. I suppose I could ask this too: Could I physically break that component to leave 2 pins on and use that single piece as a 1K resistor (hypothetically not practically obviously)?
Not very likely. The actual die (slab of semiconductor material) is quite small, maybe 1/10 of the area of the package. The dice (plural of die) are connected to the lead frame with small bonding wires. Your chances of breaking the package and using the part in a different way are somewhere between slim and none.

The reason for the bussed parts is the ability to use the resistors for a "pullup" or "pulldown" application where one side of each resistor is connected to a power rail (power supply voltage) or to ground (reference for voltage measurements). The reason for isolated parts is for applications where you want to connect two nodes in a circuit which can assume any voltage between the power supply rails. You should never contemplate connecting two nodes of a circuit that could potentially be driven to different voltage levels. That would be the road to perdition.
 

Thread Starter

ResistorsHaveResistance

Joined Jul 14, 2022
5
I think I understand then. So an isolated resistor array internally has several separated resistors that function independently from each other, vs a bussed resistor array features a global shared pin and and an additional +- for every resistor. So I think what I'm going to attempt to do then is replace that array with 3 individual through hole resistors that fit within the required specs and form factor. I probably know more about the required sizing for the application but if anyone wants to check the specs and let me know, go for it! I'll post a few alternatives shortly.


Thanks again!
 

MrChips

Joined Oct 2, 2009
26,789
Resistor arrays are meant to be used when you need to reduce board footprint. Using single SMD resistors take care of that problem.

If you prefer to use through-hole leaded components then you might as well stick with individual resistors.
 

Thread Starter

ResistorsHaveResistance

Joined Jul 14, 2022
5
Using SMD resistors is actually a really good idea. I can compare the LS on the array resistor with the standard package size lengths and determine what works best. The build is through hole but I don't see why you couldn't solder SMD onto the through hole pads if your careful.
 

MrChips

Joined Oct 2, 2009
26,789
Using SMD resistors is actually a really good idea. I can compare the LS on the array resistor with the standard package size lengths and determine what works best. The build is through hole but I don't see why you couldn't solder SMD onto the through hole pads if your careful.
I have actually done that a few times myself.
 

Papabravo

Joined Feb 24, 2006
18,967
Using SMD resistors is actually a really good idea. I can compare the LS on the array resistor with the standard package size lengths and determine what works best. The build is through hole but I don't see why you couldn't solder SMD onto the through hole pads if your careful.
I would not recommend putting SMD resistors on through hole pads. You might get bad joints when the solder drops through the hole instead of adhering to the pin and the pad.
 

Ian0

Joined Aug 7, 2020
5,819
Sometimes the resistor arrays have an advantage - although the tolerance might not be brilliant (2%) they are extremely well matched.
 
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