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Old 5th November 2005, 01:39 AM   #1
nuppe is offline nuppe  Sweden
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Default digital preamp problems

Hi!

I'm thinking of building a small digital control "preamp" from scratch, but there are some issues i'm trying to figure out before i go ahead.

My main concern is that the micro i chose is a little short on i/o, so i need some series to parallell converters. Also i might run in to level problems, the micro is 3.3v and some of the other chips are 5v. The main reason i chose the micro (at89c5131) is that it is programmable directly via the integrated USB, no external programmer needed.

So my questions are:

1. Is the allegro a6810 suitable to drive relays?

My relays require about 0,03 A at 4,5 v and the a6810 should be able to source 40 mA according to the datasheet, but i can't see any spec for minimum output voltage, just max 60 v... Datasheet is available here . It seems perfect, as it would also handle the serial to parallell conversion. Are there other similar devices that would do if it doesn't?

2. Will there be logic level problems?
The a6810 can handle 3.3v levels, but what about the pga4311? The datasheet mentions something about "high-level input voltage" as minimum +2V, does this mean it will react to digital signals at 2v and up?

3. Do standard lcd (or oled) controllers accept 3.3v levels?
I'm going to add a display so that i can set relative levels between high/low/mid channels and view overall volume level.

If you're curious, the crossover will be based on this Rane design , but with fixed resistors on a small interchangeable connector/board. It might look as i'm in over my head, and yes, i expect this will take a long time to finish, but i like a challenge...

Any comments or bashings are welcome, all input is appreciated.
(forgive the crude paint drawing, it's just a quick sketch)

/Andreas
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Old 5th November 2005, 10:45 AM   #2
seoman is offline seoman  Netherlands
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Why don't you use the 5v version of this atmel chip?
and there are 64, 52 pin versions available.

So skip a lot of problems by chosing the AT89C5131A-M

AT89C5131A-RDTIM 32 2.7 to 5.5V Industrial VQFP64 Tray
AT89C5131A-PUTIM 32 2.7 to 5.5V Industrial QFN32 Tray
AT89C5131A-S3SIM 32 2.7 to 5.5V Industrial PLCC52 Stick
AT89C5130A-RDTUM 16 2.7 to 5.5V Industrial & Green VQFP64

Regards, simon
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Old 5th November 2005, 10:10 PM   #3
nuppe is offline nuppe  Sweden
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Quote:
Originally posted by seoman
Why don't you use the 5v version of this atmel chip?
and there are 64, 52 pin versions available.

So skip a lot of problems by chosing the AT89C5131A-M

AT89C5131A-RDTIM 32 2.7 to 5.5V Industrial VQFP64 Tray
AT89C5131A-PUTIM 32 2.7 to 5.5V Industrial QFN32 Tray
AT89C5131A-S3SIM 32 2.7 to 5.5V Industrial PLCC52 Stick
AT89C5130A-RDTUM 16 2.7 to 5.5V Industrial & Green VQFP64

Regards, simon

I would love to, but i have not been able to find it in sweden. ELFA (the only large swedish electronics distributor i know of) has very poor selection in my opinion (in other areas as well). The only version i've seen is the (outdated!) 28 pin AT89C5131-TISIL. Any swedes out there who know of a better supplier? Or any supplier at all that stock better versions of these?

I've searched farnell and rs components, but no go. Btw, their web sites are a pain to use...

/Andreas
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Old 6th November 2005, 10:56 AM   #4
seoman is offline seoman  Netherlands
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Have you tried requesting a sample from Atmel directly?

http://www.atmel.com/forms/Samples.asp?family_id=655
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Old 6th November 2005, 12:09 PM   #5
nuppe is offline nuppe  Sweden
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Thanks a lot for the link Simon!
I've been to Atmels site several times, but i somehow overlooked that they offer samples...

I searched a little more and found that digi-key stocks many atmel chips, but ordering from the US for just a couple of chips doesn't feel very tempting. I think i'll go for samples.

Thanks again!

/Andreas
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