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Thread: CS42448 Audio Board BOM Replacements

  1. #1
    Junior Member
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    CS42448 Audio Board BOM Replacements

    Hi,

    I'd like to build Paul's multi-channel board.

    https://oshpark.com/shared_projects/2Yj6rFaW

    Looking at DigiKey shows some of the caps in the BOM are discontinued/unavailable.

    GRM188R71E104KA01D, Murata Electronics North America, 490-1524-1-ND, 7, CAP CER 0.1UF 25V X7R 0603
    CL21A475KOFNNNG, Samsung Electro-Mechanics, 1276-6463-1-ND, 14, CAP CER 4.7UF 16V X5R 0805
    C0805C106K8PACTU, KEMET, 399-4925-1-ND, 7, CAP CER 10UF 10V X5R 0805
    GRM31CD80J107ME39L, Murata Electronics North America, 490-10525-1-ND, 1, CAP CER 100UF 6.3V X6T 1206

    Being new to surface mount, I could use some help choosing suitable replacements.

    Particularly in regard to package and class.

    thanks --

  2. #2
    Senior Member PaulStoffregen's Avatar
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    Digikey's site has an excellent but complex search tool. First you type "capacitor" and then you need to know which category, in this case "Ceramic Capacitors" is the one you want.

    Picking the general category is by far the hardest part, since you might not know why general type you need. If you're not experienced, sometimes the only way is to just keep trying different types until you find the right one. By guessing, you'll eventually figure out is right because it offers the right ranges of specs and the pictures of the parts with the correct specs actually look like the thing you want. For these parts, trust me, "Ceramic Capacitors" is the category you want.

    Then you get a wide (horizontal scroll on any normal screen) list of parameters, for 643,291 products! That's an overwhelming number, but the many options are all meant to help you narrow this list down to just the parts you want.

    The first step is to click the "In Stock" box and then "Apply Filters". Today that cuts it down to only 84,409 products.

    Repeat this for everything you know. For example on that first part, you know it's 0.1uF. Find the "Capacitance" list and scroll down until you find 0.1uF. Click it, and again click "Apply Filters". Now (with today's inventory) that narrows things to only 3,012 products.

    Filtering for X7R temp co trims the list to 1731, and clicking "0603 (1608 Metric)" narrows the list to only 71 products.

    The only spec remaining (from the stuff I put on the list is 25V). With capacitors higher voltage rating is ok, since it's just a maximum before the cap might fail. The list goes up to 50V. If I click 25V, 35V and 50V and again "Apply Filters" the list is now 28 parts. Or if you didn't know this, just click 25V only and odds are good some will exactly match, even though using higher voltage rating would have been ok.

    Many of them are "Digi-reel" which means you pay $7 extra to get them on a reel, which you probably don't need if you're building by hand. Maybe pick the cheapest from that list of 28, or look over the list and pick one at random. Any should work, since they fit all the listed requirements.

    Repeat for each part. It's a bit tedious, but not difficult. Along the way you get to see what many of the buying options are. With a little google work on the choices, you can learn quite a lot about the parts. Or just follow this recipe to find parts that match the required specs.

    If you need more options, maybe read up on what those 3 letter temp co specs mean. Just beware of any that begin with "Y" (meaning a low quality part) or "Z" (meaning a very low quality part - only meant for disposable stuff). Never buy those unless you're sure the low quality is ok for your needs. When the spec begins with "X" you usually have some flexibility when the board won't be used over a wide temperature range. If the spec if NP0 or C0G (meaning the same thing... apparently NP0 is someone's trademark or something) then do not buy a lower quality part.

    There are tons of these little details, but hopefully the process of finding the right category and then narrowing the enormous list to just the parts that match the specs you need is at least understandable. With more knowledge and experience you can find more parts that are acceptable substitutes (like a wider temperature range), but even without that, generally you can use Digikey's excellent search to find a part with the exact same specs.

    Hope this helps?

  3. #3
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    And if you only need a couple of items and do not qualify for free shipping, simply search for and add a Teensy. That is what I usually do.

  4. #4
    I've ordered three boards CS42448 Audio from OSH Park. Now I am ready to order the materials from Digikey. There is one capacitor that is not easily found.
    490-10525-1-ND Capacitor, 100uF, X6T, 1206 has a rated voltage of 6.3V.

    Filtering for dimension, I find 490-7216-1-ND which is almost the same except for the voltage 4V and the temperature coefficient X5R. Will this suffice? I expect the voltage to be 3.3V.

    Otherwise at 6.3V an alternative would become wider from 0.063" to 0.098", for instance 587-4313-1-ND. But then it may not fit on the board.

    P.S. Let's order both of them while I wait for your advice
    Last edited by cow_n_berg; 12-20-2018 at 07:28 PM.

  5. #5
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    I found

    478-8152-1-ND

    CAP TANT 100UF 10% 6.3V 1206

    not sure if 'Molded Tantalum Capacitors' are good for this application

  6. #6
    Senior Member PaulStoffregen's Avatar
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    4V rated is probably fine. Don't have the hardware handy to check, but as I recall that capacitor gets ~2.5 volts (half the 5V analog supply voltage).

    Tantalum is probably fine, as long as the smaller 0.1 uF is ceramic. I used that 100 uF capacitor on the prototype because it's the same (or very similar) as the one we use on Teensy 3.6 for the USB host power output. When I designed this board, draw of larger ceramic capacitors had plenty of those left over from prototyping Teensy 3.6.

  7. #7
    Thank you!

  8. #8
    The codec chip on OSH Park links to CS42448-CQZ. I've found CS42448-DQZ on AliExpress which seems to be exactly the same except for the wider working temperature range. Should DQZ match as well?

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