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Class D Switching Power Amplifiers and Power D/A conversion

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Old 30th August 2006, 07:12 AM   #1
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Default New Chip Junk

I never heard of them before today

http://www.freescale.com/files/wirel...r%20channel%22
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Old 30th August 2006, 09:40 AM   #2
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You've never heard of the chip or freescale?
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Old 30th August 2006, 11:01 AM   #3
BWRX is offline BWRX  United States
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Yes, Freescale is not new, but their entry into class d is.

Digital feedback? C'mon, that's almost as bad as the class T claim.

Still looks intersting though.
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Old 30th August 2006, 11:15 AM   #4
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Nah, the class T claim is probably worse. This monster actually sounds like it "might" be digital in some..arguable way.

"As seen in Figure 2 below, the FSA95601 controller feedback system compares the output of the switching power stage with an internally generated ideal PWM signal for the corresponding channel to identify errors. The resulting error is converted into the digital domain by an A/D converter. Compensation for the digitized error component is mixed with the original PWM signal to make any necessary corrections for timing or amplitude errors.
Figure 2. High-Performance Digital Feedback
Freescale’s 4 Symphony™ Class D Digital Amplifier Solution Freescale Semiconductor"

Who knows, might be interesting for a cheap mid-fi PC theater thing
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Old 30th August 2006, 12:42 PM   #5
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Quote:
New Chip Junk
One mans trash is another mans treasure!

Or, to put it another way.... One accomplished class-d amp builders trash is another not so accomplished class-d enthusiasts treasure.
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Old 30th August 2006, 12:44 PM   #6
BWRX is offline BWRX  United States
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Well in that diagram they're taking feedback pre-output filter which is analog, subtracting it from their ideal "digital" PWM signal, then running that through an A/D converter.

Why would you need to run a digital signal through an ADC?

It may sound really good but that doesn't mean their marketing department can get away scot free
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Old 30th August 2006, 12:49 PM   #7
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To quantize the error for some retarded reason? Beats me.... like I said it's arguable Either way I think it sucks. Hence the mid-fi at best.. I like the connectivity options though.
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Old 30th August 2006, 03:46 PM   #8
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BTW, it's similar to Bruno's US6803816 B2
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Old 30th August 2006, 10:06 PM   #9
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Quote:
Originally posted by BWRX
Well in that diagram they're taking feedback pre-output filter which is analog, subtracting it from their ideal "digital" PWM signal, then running that through an A/D converter.
I'm missing something there, too. Is there something wrong/missing in that diagram, or do I just not see it?
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Old 30th August 2006, 10:23 PM   #10
BWRX is offline BWRX  United States
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They're basically using the terms digital and switch-mode interchangeably. Their "ideal digital PWM signal" is not digital but analog. The ideal PWM signal is generated from the processed PCM signal, and will have error depending on how many bits are used in the conversion.

The diagram in Fig 2 is a little different than the one in Fig 1 which shows how the signal is really routed. Fig 2 is misleading because the digital PWM correction stage does not directly drive the output stage. Rather, it is fed back to the PWM generator.
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