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Manust
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Hello!

Postby Manust » Wed Mar 30, 2011 8:19 am

Hey!

I'm Manuel, from Germany.
I'm working on my Master Thesis in the laboratory for digital techniques and microcomputertechnology. My masters project is a High End USB Streaming Device with several In/Output options combined with a High End Class-D Amp. After a while researching i decided to go with xmos devices for the USB streaming part.
So I'm new to xmos and after reading datasheets over datasheets i guess working with these controllers will be great.
I already made my first schematics which i will post in the relevant forum.

Greetings,
Manuel
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TonyD
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Postby TonyD » Wed Mar 30, 2011 9:00 am

Hi Manuel

Welcome to the Xcore Exchange

Your USB streaming project sounds very interesting and a very good match for the Xmos processors.

If you want, you can add your design files to the projects section of the forum.
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Postby jason » Wed Mar 30, 2011 9:09 am

Indeed, pretty much what TonyD said - welcome to XCore.com!
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Postby ale500 » Wed Mar 30, 2011 10:12 am

Hei Manuel ! Welcome !.

Also from Germany ? Great !.

High-end class D... are you going with a discrete solution or are you going for instance with one of TI's class-D amplifiers ? I have used a couple of them... they are incredibly small for the power !
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Manust
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Postby Manust » Wed Mar 30, 2011 10:58 am

Hey

The Class-D Amp was a discrete Solution. I Also built an amp using TAS5630 from TI. They are great in their size but THD ratings were to high for this particular project.
My discrete Amp is based on the IRS20957 Gate Driver combined with IRF6645 Directfets. The results in THD and the sound are great. The PCB is sized 90mmx90mm with 2x120W or 1x240W output power. THD Ratings are below 0,01%.
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Postby Woody » Wed Mar 30, 2011 1:35 pm

Hi Manuel and welcome,

Have you seen that there is a classD application example on xmos.com (https://www.xmos.com/applications)?

It's an open loop implementation, and there is some documentation on a low cost example implementation of this code on the site too (https://www.xmos.com/support/documentation#applications).

I'm happy to discuss it if you want more details.

Cheers,

Woody
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Postby Heater » Wed Mar 30, 2011 1:52 pm

Manust,

Welcome.

Any chance you might post your discrete class D amp somewhere?
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Postby ale500 » Wed Mar 30, 2011 2:09 pm

Heater:

Just look at the datasheet of the IRS2092 for the source. Sure he did some thinkering with it but as a starting point looks quite interesting. Sadly it has an analog input... I was looking for one with PWM input... the IRS20957 is what I was looking for... nice.
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Postby Heater » Wed Mar 30, 2011 5:01 pm

IRS2092 looks very interesting. I'm obviously a bit out of touch with these things.

IRS20957 is more what we need to drive from an XMOS. Anyone know what audio bandwidth we get out of them? There's not much to go on in the data sheet.

What I would like is a XMOS board with stereo SPDIF and/or USB in and 6 times PWM out into something like IRS20957.
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Manust
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Postby Manust » Wed Mar 30, 2011 9:30 pm

The ClassD Implementation on an XMOS Device sounds very interesting. Im going to talk about this topic with my professor on our next meeting.

I'm sorry but i'm not allowed to provide the schematics of my particular Class-D Amp, but there's an IRF Reference Design called IRAUDAMP4A on which principle the design is based on. These amps still have an analog input and a self oscillating design, but the IRS20957 can also be used in an open loop design with direct PWM input. Also integrated current sensing is great to protect speakers. I can't say a lot about bandwidth since my design got an LPF with a corner frequency of about 30kHz to attenuate the switching frequency of about 400kHz which proved to be the best frequency in my design.

I Also used IRS2092. THD ratings are a bit lower than with my IRS20957 design but still below 0,01%. For analog solutions i would really suggest these chips, since they are lot easier to handle in analog designs and the pwm modulator is integrated.

For Power Stage Mosfets i would suggest IRFI4019 or IRFI4212 TO-220 half bridge mosfets. Those are double N-Channel Mosfets with good power ratings and the price is also great. IRF6645 Directfet Mosfets showed the best results, but the handling of this package is hard and cooling solutions will be more expensive than cooling for TO-220.

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