Looking for class-d chips with digital inputs (i2s), hardware control (no external µC) and some power (>100W) i found the automotive amplifiers from ST Microelektronicś:
Class D Audio Power Amplifiers - Digital Input Audio Amps - STMicroelectronics
The info brief looks promising
- SNR and dynamic range are excellent
- the feedback loop includes the output filters
- i2s input
- plenty of output power
- can be operated without external µC
- but give a lot of goodies with i2c control, ie. live impedance monitoring
- ...
Did anyone used one of these chips? I could not find any reference schematics or application notes - asked ST's support - but got no answer until now.
Class D Audio Power Amplifiers - Digital Input Audio Amps - STMicroelectronics
The info brief looks promising
- SNR and dynamic range are excellent
- the feedback loop includes the output filters
- i2s input
- plenty of output power
- can be operated without external µC
- but give a lot of goodies with i2c control, ie. live impedance monitoring
- ...
Did anyone used one of these chips? I could not find any reference schematics or application notes - asked ST's support - but got no answer until now.
It seems the chips are under development, maybe looking for inspiration and potential customers. The claims in the ads sound quite familiar, coming from some engineering department, maybe not theirs.
In some cases the marketing department leads the documentation department, and the documentation department leads the engineering department.
How can some other department lead the engineering department? They hire "half engineers" and control them through the other half. Consumer market.
In some cases the marketing department leads the documentation department, and the documentation department leads the engineering department.
How can some other department lead the engineering department? They hire "half engineers" and control them through the other half. Consumer market.
The FDA2100LV and FDA4100LV were announced several years ago and those videos made them look like an exciting product. The on-board voltage boost and LC filter inside the feedback loop provided a lot of clean power. But I kept checking stock levels at ST distributors to see if they had shown up and didn't see any product available for several years and forgot about them. However, now both Digikey and Mouser have them listed as non-stocked items, and Future Electronics has 395 of the FDA2100LV in stock (for $7.76). So it looks like it is a real product, but one that might be hard to obtain if you aren't a major customer.
Integrating too many functions in the same chip can result in a high-production-cost IC that competes in sales with other low-production-cost ICs of same brand. Production cost is highly dependent on the production volume needed. Chips too function-specific can turn into a commercial fail, or there is the risk of someone else copying the concept for a few cents less and "stealing" the customer (something impossible for more standard chips, where customers are thousands).
The usage of separate, more standard, chips, for DC-DC boost, DAC, and class D amplifier, can result in similar bill-of-materials cost as with the $8 chip integrating all 3 functions.
A brand that manufactures more than a type of product can benefit from buying the same generic chips for several products in higher volume, at a lower price per unit. These chips from ST seem like custom-made for a brand that sells only a particular type of product.
Maybe ST "chased its tail"? This is approximately what happens when the human brain gets overloaded by redundant computations.
The usage of separate, more standard, chips, for DC-DC boost, DAC, and class D amplifier, can result in similar bill-of-materials cost as with the $8 chip integrating all 3 functions.
A brand that manufactures more than a type of product can benefit from buying the same generic chips for several products in higher volume, at a lower price per unit. These chips from ST seem like custom-made for a brand that sells only a particular type of product.
Maybe ST "chased its tail"? This is approximately what happens when the human brain gets overloaded by redundant computations.
wtf
Looks like good sounding powered speakers are not sufficient "hitec" - we need to build motor sound emulators to get ST's attention
It's not about "hitec"--it's just a business decision. ST is an $8B company, and they got where they are by making good alliances with large customers. For example, ST was the foundry for both Tripath and Apogee, and while both companies were selling chips ST was content to provide the enabling semiconductor technology and manufacturing capability. Once those companies "passed away", ST was able to sell the Apogee devices under their own part numbers. So who knows--maybe some agreement will expire and these devices (and detailed data sheets) will become more readily available.
BTW, the first articles on the FDA2100LV and FDA4100LV showed up back in 2013 and by 2014 there were articles in EDN and other trade magazines about the chip's potential for reducing the BOM for head units in car radios. Several of the articles in 2014 said the chip was available immediately, so this chip has probably been on the market for close to 4 years.
There are a number of other good class D chips that have either not been available to hobbyists or else the vendor does not make detailed design information easily available. The Zetec devices that were used in the NAD products had similar "data brief" teasers that did not have any substantial application information. Sanyo had an interesting series (STK-428) that was fairly well hidden from general view. Neofidelity might have the largest installed base of class-D chips (LCD TV's), but the information posted on their website is sparse. Rohm also has some interesting class-D chips with digital inputs, and they have lots of useful information on their website, but finding stock on their chips was difficult. I don't know what happened to Plusis, but they had some nice digital input class D amps with embedded DSP. The bottom line is that there is a lot of interesting technology that could be used in the DIY audio community that simply isn't available to us, and that is always going to be the case.
I'd also be concerned about reliability too. Containing too many power applications within the single package could lead to issues there. Of course with enough protection features it should be fine, but it could cause problems.
From an automotive point of view, combining a boost converter with a digital input class D amplifier, is a fairly good idea and as far as I can see ST also offer parts without the boost converter too. Now if they'd only add in a DSP to complement the DAC
Now if they'd only add in a DSP to complement the DAC
For me the opposite - i dont want the fancy stuff - fixed signal, processing, step up converter, i2c control, impedance monitoring, ... - just high quality i2s to PWM conversion with some power.
The STA350BW has not enough power, the STA328 needs a external µC, and both dont give the soundquality promised here ...
Sometimes simplicity is called for - for example I'd like there to be a basic analogue input version of these ST class D amplifiers too. Of course that is only if they have the kind of performance I hope that they have (TPA32xx rivals).
But most of the other time I welcome additional features. If you take your high quality i2s > power amplifier, with post filter feedback, adding in a DSP, i2c control and impedance monitoring doesn't usually mean sacrificing the basic functionality. These are usually things that are put there on a 'use them if you want them' basis. A decent number of these types of thing work with a basic default set-up, with all the extra features bypassed, meaning you can hard-wire them and don't need a uC.
Still, most of my stuff uses a uC, even my 6 channel TPA3251 amp uses one. If a DSP was included in one of these ST devices then you could implement an active crossover + power stage, all in one chip, needing only a source. As they are now you'd need a separate processor for full functionality and most car systems, at least these days and where these chips are being targeted, have DSP processing somewhere.
You are right - additionally features are not generally wrong - as long we are not forced to use them. Thats why im interested in these chips - you can use the advanced features if you want - but you dont need to.
In my case - some not so usual signal processing is the target of experiments - so there is a dsp board anyway - and extra µC control would give nothing but burden.
In my case - some not so usual signal processing is the target of experiments - so there is a dsp board anyway - and extra µC control would give nothing but burden.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.