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An open source layout for LM3886?
An open source layout for LM3886?
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Old 13th January 2021, 01:58 PM   #241
usheral is offline usheral  Canada
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Default Protect BOM

Quote:
Originally Posted by 00940 View Post
@quadfan66: sorry. As the dc protect really isn't that necessary on a lm3886, I've been putting it to the waiting list for too long indeed.

This schematic pretty much tells everything, it's a very simple board. It's a simplified version of the esp 33 board in many ways.

Some comments:
- C1 has to be a bipolar cap, voltage rating can be quite low since it never sees more than about 2V. A 10uF gives decent response.
- Q2-Q3, R6, R7, led1 is just a fault indicator. Not really needed. To be installed or not depending on what you want.
- all diodes are 1n4148. All resistors can be 1/2W.
- the optocoupler can also be the APV1121S
- D5 is a big TVS. Its working voltage must be a bit higher than your PS rails.
- with the version posted earlier, you have to be extra careful no to short the output lead to the binding post. Distances are a bit too small. I attach a new version of the board fixing that.
I'm putting together a Mouser BOM for the protect, and am stalled at D5. The TVS Schottky diodes that I've looked at so far are all surface mount. The eagle file has P2-15 as the package designation, I can find little or no information as to what a P2-15 package is. Do you have a part number from any supplier that I can compare?

Thanks,

Adam

When (if?) I get a BOM together for this, I'll post it. Thanks to NealJ (and 00940, obviously) for their published BOMs for the other boards.
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Old 13th January 2021, 02:59 PM   #242
00940 is offline 00940  Belgium
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It's a TVS from the P6KE serie, DO-15/DO-204AC package.

edit: take note of post 227 for the PSU BOM.
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Old 13th January 2021, 06:00 PM   #243
usheral is offline usheral  Canada
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Default D5

Thanks!

I'm going to use P6KE100A-T for the D5 (unless I've misunderstood you).

I think 227 is where I got the PSU BOM, but I"ll double check. Both NealJ's amplifier BOM and the PSU BOM uploaded and processed no problem with Mouser Canada.

Once again, I really appreciate the effort that has gone into this project to date!
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Old 13th January 2021, 06:29 PM   #244
00940 is offline 00940  Belgium
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I found my original order : STMicroelectronics P6KE47CA

It's the bidirectionnal version. With 47v, it's good enough for typical psu rails for chip amps.
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Old Yesterday, 08:57 AM   #245
Zbasse is offline Zbasse
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I'm wondering if two of these can be bridged for more output power. Is this even possible?
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Old Yesterday, 09:28 AM   #246
00940 is offline 00940  Belgium
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Yes. But...

My rule of thumb to keep lm3886 happy is : about +/-28Vdc rails into a 4R load, +/-35Vdc rails into a 8R load. Bridging "halves" the load, paralleling "doubles" it. Combine at will.

It's easier to bridge (you only need an inverter stage in front of one amp) than to parallel (you need to match accurately the gain setting resistors and add a low value load sharing resistor).
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