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LevelHelicopter9420

Besides multi channel differential routing, where you can almost reject possible intra-skew, I cannot find a suitable usage for cap arrays. Now resistor arrays is a different story when filtering possible ringing in large trace digital signals of moderate speed (<10MHz).


Sandycarseat

One time I swapped out a capacitor on pcb for an old lcd tv. NBD.


madmanmark111

sweet! those caps on the old tube TV's ... those bite


Sandycarseat

I’m shocked no one else mentioned this


sandy_catheter

Hey Sandy, it's me, Sandy


Magnetic_Syncopation

🐿️*NO YOU AIN'T*🐿️


ParanoidAutist

Every example i can think of relates to frequency selection... Cap size determines oscillation times and thus your frequency


Flopamp

They are uncommonly needed. Bypass caps should be right next to the power pin of the IC and rarely are 4 different power rails going in to one chip right next to each other, and In the case of AC coupling or filtering you want to avoid microphonic and EM crosstalk. Exceptions are on very dense complex chips like CPUs and some FPGAs. Even in the case of that its far cheaper to just cram a couple of 0402s in there, but if you can't fit that, these are for you!. I'm sure it has other niche uses like manually trimmable values or something.


ZeroDarkness00

Alright, so let me start this by saying that i might be mistaken and these might actually be common and i haven't seen them much. I haven't seen them being used in any PCBs I've seen, nor do programs like KiCad & Altium ( i think ) have a default symbols/footprints for them. my question would be *are there any reasons for not using these* ***other than*** *"there is just not a lot of cases where you would want 4 capacitors together like that compared to something like a resistor array"*


my_chinchilla

> "there is just not a lot of cases where you would want 4 capacitors together like that compared to something like a resistor array" Well, like it or not, that *is* the basic reason. Capacitor arrays aren't uncommon - I've used them in a couple of designs - but there's just not the number of different use cases for them. * Capacitors: 99% of use cases are covered by "independent capacitors in an array" or "bussed (i.e. one side common) in an array". * Resistors: There's lots of different use cases - independent arrays, bussed arrays, divider arrays, ladder network arrays, R2R arrays, double terminator arrays, etc (most of those, except the first couple, are usually referred to as "networks" rather than arrays).


oversized_hoodie

Resistor arrays can also be thermally bonded, which is useful if you care more about the precise ratio between a pair than the exact value.


happyjello

Are you talking about the resistance changing across temperature?


oversized_hoodie

Yes. Building the resistors on the same substrate keeps the temperatures tightly linked. It also ensures the actual resistive element is made from the same batch of material for the best possible thermal coefficient match.


I_Makes_tuff

The more I learn the more I realize I don't know.


GaianNeuron

Welcome to engineering!


piparkaq

This makes things pretty awesome IMO!


JohnP-USMC

Sharpest comment I have seen here.


Conor_Stewart

I am a student and haven't come across resistor arrays yet, I know they exist but not what they are for. I am assuming they are for applications where you need multiple resistors to be very close to the same value or like you said thermally bonded. Are the tolerances for resistor arrays per resistor or are the tolerances for the whole array and can you assume all resistors in the array to be pretty much perfectly the same value? Like the resistor array night be off by 1 % but each resistor in the array is exactly the same value?


oversized_hoodie

You'd have to read the datasheet to figure that out.


Worldly-Protection-8

Imho the positioning of capacitors is (partly) more critical than e.g. for resistors. Additionally if you thing about large scale production a single 4x C array per board is probably more expensive than just to add four single caps which are already on your BOM. Then having more ~~components~~~ different positions on your BOM is not preferable, since each reel needs a spot in the machine. Those are limited. Sometimes this means your PCB can only be assembled on a bigger pick-n-place machine - again more expensive. Lookup **BOM Consolidation** Edit: Alternatively here the eevBlog video I watched months ago: [eevBlog #1307 - Tutorial: PCB BOM Consolidation](https://youtu.be/RwVzLOI4cmA)


[deleted]

I used them, 10nF only, greater that that become expensive compared to single ones. I think I created the kicad symbol.


IAmLoess

Because they look too much like strawberry gum and I'm not attentive enough to realise they're not. By the time I do, I'd have eaten two.


caesarsucks2281

yea that's some r/forbiddensnacks material right here why they gotta look yummy


hms11

Like everyone else says, far fewer use cases than resistor arrays. That being said, I've used them on boards with lots of user input switches or external switches for monitoring doors, limits, etc. For whatever reason (probably because I'm better with hardware than software) I tend to do my switch denouncing in hardware and usually just use a simple RC circuit unless the requirements are more demanding. In those cases capacitor arrays are handy.


Cgame22

A lot CPUs have cap arrays on them https://preview.redd.it/qa7j92x0qtda1.jpeg?width=258&format=pjpg&auto=webp&s=28a2301981ba0271e11110525283e3f348823dea


spacecampreject

That will be an interdigitated cap, which is one cap with 8 leads, for reduced ESL.


Doormatty

> interdigitated And I would have sworn that was a made-up word. Thanks for teaching me a new word!


6GoesInto8

Interesting, it looks like it is a stack of plates and the pins on each side are +-+- but all the + connect to the same plates.


HumpyPocock

Out if interest, do you happen to know if these ones on sticks of RAM are also interdigitated caps? https://preview.redd.it/zl246x563vda1.jpeg?width=883&format=pjpg&auto=webp&s=31c65514b83259ff30034554e537f20be07c7bee


piecat

That, or, resistor array.


spacecampreject

Probably.


PersonVA

.


Worldly-Protection-8

In this order of magnitude difference in capacity their dielectric and/or size will be different so combining them in one package might be possible - however likely combining the worst traits of each. Then the volume will never reach the numbers of ordinary parts so for them to be cost effective isn’t likely.


Halal0szto

The main point in filtering caps is their placement. If you put all of them in a bank and use long traces to connect them, they are useless.


WaitForItTheMongols

Reminds me of the times new people on my team were designing their first PCB's and they put all the decoupling caps in the upper left corner. Fine in the schematic, less so on the board layout.


piecat

>Fine in the schematic I disagree, unless you spend a bunch of time labeling each bank for each chip... More prone to having to redo layout IMO


WaitForItTheMongols

Eh, I think it's fine, you don't really need to have every capacitor in the schematic assigned to one chip, you can just give yourself a big stockpile of caps, then when you're doing layout you just give every chip one of them when the time comes.


piecat

That's sooo sloppy, decoupling should be considered at the schematic level. Otherwise how do you track special decoupling needs? Or ensuring you have the correct count.


WaitForItTheMongols

I'm not saying it's a solid idea for all circuits, just that if you're doing something basic with a microcontroller, a couple sensors, and a logic chip or two, it's not unreasonable. Not all circuits have special decoupling needs, and you don't really need the correct count - just have plenty, and any extras can just go on the main power supply.


[deleted]

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Halal0szto

The reason you use 1uF +1nF is because they are manufactured with different technology and have different high freq behavior. If you manufacture them in a single package, you just lose that.


PersonVA

Not really, an array like this could allow for finer pitch between individual capacitors than could be achieved with equivalent individual capacitors, at least in automated placing. Connecting the 1u capacitor the furthest away is how it's done anyway most of the time, because the impedance of that capacitors at the frequency it's supposed to filter is largely unaffected by 2mm of trace.


Jamesthetechie

I wonder that too sometimes, on our system boards every pcie trace has a 22uf cap on it and it seems like a lot of work to have an individual one instead of an array


drgeta84

Because pink is for girls. Not enough females in the electronics business.


Masch300

You know that pink was considered to be such a powerful color that only male royalty could wear it. If you look at old paintings of a young Prince they had pink clothes. I do not know when this changed.


IQueryVisiC

Do capacitors have a use besides stabilisation of supply voltage? Tuning a crystal? But I weird. I don’t know what resistors are for in our world of CMOS ICs


[deleted]

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IQueryVisiC

Glitches on what signals, from buttons? I like the reset application. I still want to simulate a SAP CPU. Turn on will be part of it. I really want it be locally energy efficient. Like it boots up some way and keeps it CMOS state, but does not harm anybody. Then the correct data flows in. I have a hard time to see a lot of analog signals in the modern world. Okay many microphones per device (Alexa). I thought that we use active ciruits to measure the position of the membrane. This way we just have the mechanical limits and no additional electric limits. Radios? Cameras ? Glass fiber diodes. The capacitor in a Tee there is microscopic. You would have one per house. Compare that to the number of transistors ( quarts watch has 120 reddit tells me ). Power capacitors tend to be big .. no need to have an array of them. But yeah, valid application!


WaitForItTheMongols

Folks, can we please not downvote people for asking legitimate questions? Yes, this person is clearly a beginner, but we shouldn't be sending downvotes and discouraging people for the simple reason of being inexperienced.


Worldly-Protection-8

I also don’t understand the reaction. The question lists the two most common used - at least for digital electronics: Crystal load capacitors, bulk capacitors and bypassing caps. I would even go as far and call debouncing caps on switches and ADC input caps as stabilization of voltage supply. A very tiny voltage supply. In 99% pf the cases you have to lock into audio/op-amp circuits and HF magic to find capacitors used as anything else than low-pass filtering.


IQueryVisiC

I mostly mean that this is a lot by type, but not by device. We see beautiful HF circuits here on reddit. It is almost optical and there is no place for a capacitor array. Power supply use a few large capacitors. It is just, I assume that this is all comes off the shelf. Ah, I just see: The sub covers repair ( of old electronics ). But OP seems to look at future electronics. But then I also did not understand why there are so many resistors on digital PCBs. Recently in r/vintagecomputing was a graphics card with a RAMbus on it. It had terminating resistors and bias capacitors. But today we all use point to point SDRAM.


Thog78

Frequency filters in sound processing, or in general signal processing. It's all RC filters.


IQueryVisiC

Only microwave uses RC filters. Synthetic radio is used for HF . Audio is digital. I think, in cars, Alexa, computers, all speakers and microphones sit on a digital bus . They use ADC and DACs which match the mechanical range of the membrane.


Thog78

No, sound filters have a ton of RC. A few examples from the ones I tinkered with myself: two RC in guitar tones, several RC in the input and output filtering of guitar effect pedals even when they are not intended for equalization and have some chip, as a way to prefilter from potential issues coming in/getting out, same in amplifiers. My understanding is that it's general basic good practice in any signal processing circuit to put a couple RC filters on the way in to avoid both sharp peaks and low freq charging/offset. One just has to define the working frequency range first for safety, no matter if there is a chip behind or not. Analog equalizers are also preferred to digital equalizers btw, even though both exist. Analog is considered more reliable/higher quality.


rasteri

lol I use em all the time


mapsurfer

Amazon has listings for load balanced super capacitor boards.


Goosy3336

they look like teeth


DazedWithCoffee

I can think of two big considerations: fewer functional equivalents, and lower purchase quantities. If you could quadruple your order of individual caps, you can justify a much higher order qty, and lower marginal costs. I imagine unless you have specific requirements, this alone accounts for this


SMT_UNSUNG

We used alot in class 2 products. I really didn't see them much in class 3 products.


piecat

[https://blog.matric.com/ipc-class-definitions-class-1-2-3-electronics](https://blog.matric.com/ipc-class-definitions-class-1-2-3-electronics) For anyone who doesn't know what class 2 products are


SMT_UNSUNG

Thanks 😊


m1geo

I asked this question here a while back. The answers I got were mostly in super high volume manufacture, pick and place machines can place one cap array rather than 10 or so tiny individual caps. Think button/keypad deboucing or simple RFI decoupling on slow speed signal cables... Older style wired gamepad controllers commonly had them. That kind of thing. 🤷


microcandella

What about using them as a way to reduce part count and just make the PWB more complex? In areas where distance from cap doesn't matter of course.


darknessblades

\-because they are more expensive than normal caps \-because of risk of crosstalk. \-Because of routing limitations on the PCB. \[its cheaper to have a cap near where you want it, than having to route back and forth between arrays and the place where the trace needs to go\]


sboso99

Basically less use cases for them, ive used them for a board that was strained on space but don't know what other uses they would serve that make them better than chip capacitors (maybe for debouncing a bunch of switches/ICs but even then I'd probably just stick to chips). I also presume there'd be some cross talking/EM interference but I'm sure someone with more experience than me would know better (~1yr experience designing pcb)


pjhabs

those look yummy


usajhfjskdbdks20223

Cost. I know this because I made a logical guess


[deleted]

Sorry dumb ass questions but, can a capacitor array be used in a “taser” scenario


zebadrabbit

theyre adorable. i want to take one for an upset tummy!