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Class D Switching Power Amplifiers and Power D/A conversion

TAS5825M based amp
TAS5825M based amp
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Old 10th March 2019, 10:36 PM   #1
aurel32 is offline aurel32  France
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Default TAS5825M based amp

I was looking at power amp chips at TI, and noticed about the TAS5825M chip. It's a class D amp with I2S input, able to provide 2x30W in 8 ohms with a decent THD. Not that powerful, but that should be enough for a small appartement. It seems to be a relatively new chip, but is already available on a few distributors.

The only downside is that it comes in a VQFN32 package, not that DIY friendly. Also it needs to dissipate 6W at full 2x30W load, not sure it's easy to do in the PCB.

Has anybody tried that chip and can provide some feedback?
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Old 11th March 2019, 01:40 PM   #2
lutkeveld is offline lutkeveld
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I have provided a free evaluation design on the E2E forum:
[Resolved] TAS5825M: Free TAS5825M breakout board design - Audio forum - Audio - TI E2E Community

Its a great chip. My experiences so far:
-Running it filterless or with FB output filter almost doubles quiescent current, so not really desirable
-Very easy to use both in hardware and software implementation
-The chip cant thermally handle sine waves with high power output, but with music its just fine.

The most powerful feature is the DSP, but you need the TI EVM and GUI to export DSP files. I reverse-engineered the register map, which allows for people to write a tool to program the DSP stand-alone. However, a lot of work is needed to write the software in Java, which I am not very familiar with.
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Old 13th March 2019, 04:50 PM   #3
aurel32 is offline aurel32  France
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Quote:
Originally Posted by lutkeveld View Post
I have provided a free evaluation design on the E2E forum:
[Resolved] TAS5825M: Free TAS5825M breakout board design - Audio forum - Audio - TI E2E Community

Its a great chip. My experiences so far:
-Running it filterless or with FB output filter almost doubles quiescent current, so not really desirable
-Very easy to use both in hardware and software implementation
-The chip cant thermally handle sine waves with high power output, but with music its just fine.
Thanks for the feedback. I wonder if it is possible to add a small heatsink over the chip. It's very thin, so it might prevent placing decoupling capacitor very close to the chip.

Quote:
The most powerful feature is the DSP, but you need the TI EVM and GUI to export DSP files. I reverse-engineered the register map, which allows for people to write a tool to program the DSP stand-alone. However, a lot of work is needed to write the software in Java, which I am not very familiar with.
It's nice that you have been able to reverse engineer the register map as the TI software is not available to hobbyists (they want a real company name). Is it the same DSP that can be found for example in the PCM5242?
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Old 13th March 2019, 06:48 PM   #4
lutkeveld is offline lutkeveld
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The DSP is meant to be cooled by the pcb. Besides making sure that there is a good connection to a big groundplane, there is not much you can do. A heatsink on top of the poorly conducting case does not do much.

The DSP is indeed pretty similar to the PCM5242

The biggest problem with the TI software is that it requires the PurePath motherboard and the specific EVM of the amplifier, costing around 350 euro. Besides that its amazing software. Performs and looks very well.

TI releases some of the maps, but not for the DSP setting I wanted to use (1.1 mode).
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Old 25th March 2019, 08:07 AM   #5
Firerunning is offline Firerunning  China
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Quote:
Originally Posted by lutkeveld View Post
The DSP is meant to be cooled by the pcb. Besides making sure that there is a good connection to a big groundplane, there is not much you can do. A heatsink on top of the poorly conducting case does not do much.

The DSP is indeed pretty similar to the PCM5242

The biggest problem with the TI software is that it requires the PurePath motherboard and the specific EVM of the amplifier, costing around 350 euro. Besides that its amazing software. Performs and looks very well.

TI releases some of the maps, but not for the DSP setting I wanted to use (1.1 mode).
I tried to configure this amplifier via MCU, but it doesn't work. Maybe some necessary registers are not listed in the datasheet? So what should I do to configure it without PPC3 and EVM broad?
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Old 25th March 2019, 08:58 AM   #6
lutkeveld is offline lutkeveld
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Some of the preconfigured DSP settings (flows) are documented by TI, others have to be reverse engineered by changing settings in PurePathConsole and looking at the register writes.

I can help if you tell me what exactly you want to do and what you have tried.
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Old 25th March 2019, 04:28 PM   #7
Firerunning is offline Firerunning  China
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Quote:
Originally Posted by lutkeveld View Post
I can help if you tell me what exactly you want to do and what you have tried.
I tried to configure the register following this cfg file but I didn't write the DSP register. My input sample rate is 176.4/192kHz, I wonder if the input sample rate is too high. I want to configure it to Process Flow 8 (Housekeeping, 2.0) with Hybrid Mode and only SRC function is needed.
Attached Files
File Type: txt TAS5825_PPC3_Example_Before Rework.txt (47.0 KB, 10 views)
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Old 25th March 2019, 06:30 PM   #8
lutkeveld is offline lutkeveld
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Please upload all your code, including the functions you use to write to the amplifier.
And also which micro are you using?

You have the EVM and motherboard I assume? Export the DSP config as a header file, include the header file and write an external function that can write the settings the amp with I2C.

If you set burst = 0 during export to header file your header file will contain some examples on how to write the functions needed to transfer the settings and after that a big array, which contains the registers and their values. Then you can write a big for-loop that sets all registers to their correct value. You can also set burst = 120 but then the function to write it via I2C becomes a little bit more complex, but you will save some memory.

Also do not forget to set it to play mode (register 0x03 set to 0x03). The chip should work by default (no DSP loaded) when you give it an I2S signal.
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Old 25th March 2019, 07:06 PM   #9
JMF11 is online now JMF11  France
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Quote:
Originally Posted by lutkeveld View Post
I have provided a free evaluation design on the E2E forum:
[Resolved] TAS5825M: Free TAS5825M breakout board design - Audio forum - Audio - TI E2E Community

...
The most powerful feature is the DSP, but you need the TI EVM and GUI to export DSP files. I reverse-engineered the register map, which allows for people to write a tool to program the DSP stand-alone. However, a lot of work is needed to write the software in Java, which I am not very familiar with.

Hello, How is the TI EVM required to export the DSP files ? I'm working (slowly) on a TAS 3251 project, and in my understanding, the PPC3 soft can generate the codes to load in the DSP, and those can be loaded by any microcontroller through I2C.


Is it wrong ?


Best regards,


JM
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Old 25th March 2019, 08:05 PM   #10
lutkeveld is offline lutkeveld
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The register maps are sometimes given, like can be seen here:
http://www.ti.com/lit/an/slaa786a/slaa786a.pdf

In PPC3 you can tune the DSP settings to your liking and dump the registers (header file) which can be used by a microcontroller to load these settings into the chip on a stand-alone custom PCB.

In theory you can set up your own DSP setings but its way more complicated than with the motherboard/EVM/PPC3 combo.
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