Which is best boosted Class-D amplifier

Glenn,

The main differences between the parts is the boost circuit and the feature set.

• Boost Differences impact the output power; however all parts appear to meet your 2.5W requirement.
  • MAX98380 is using a capacitive based charge pump to create a boosted rail that is approx. 3*VBAT
  • MAX98390 is using an inductive boost circuit and creates a boosted rail that is programmable to voltages between 6.5V and 10V.
  • SSM4567 also has a capacitive boost that creates a 5.1V power rail for the class-D.

All parts have a dynamic range > 100dB with very low noise floor and better than 0.1% THD over frequency and power.  So, the class-D performance is fairly similar.

The MAX98380 has the lowest quiescent power at 10mW.

This is a broad overview of the main similarities and differences.  Perhaps the required feature set will help drive the decision. What other features or requirements might you have?

Mike

I think it will come down to a choice between the two MAX parts. Can you quickly tell me which can deliver 3W of power to the speaker with lower THD+N? What is the quiescent power of the MAX98390? Which of the MAX parts are easier to deal with from an EMC perspective? My guess is that the charge pump is simpler.

Glen,

In general, the MAX98390 has more features and higher pin count.

The MAX93090 uses between 16mA and 20mA depending on the exact feature set enabled and power supply levels, but in general, it will have a higher quiescent current than the MAX98380.

At 3W both parts have THD+N that vary between -60dB and -80dB.  The exact THD+N varies with load and supply voltage.  Here are a few plots for quick comparison.

MAX98380 – The THD can be further improved from this if needed with more/larger flying caps on the charge pump. (see DS for more info)

MAX98390

For more thorough data, the datasheets are well written with more plots of THD.

MAX98380.pdf (analog.com)

MAX98390.pdf (analog.com)

Both parts meet EN55022B electromagnetic interference (EMI) regulation standards without the addition of an LC filter for typical applications.  If the class-D output were to be driven down several inches of non-shielded wire, then output filter would be necessary.

While I think both parts are straightforward to implement into audio solutions, the MAX98380 is a somewhat simpler part and has fewer pins.  I don’t have access to pricing information, but I’d suspect that the MAX98380 is cheaper as it does not include the voltage and current sense ADCs.

Mike

Thanks for being generous with your time, Mike. It looks like the MAX98380 is only available in a 0.35mm-pitch package, which is a bit more difficult to lay out than the 0.5mm-pitch MAX98390, but depending on the cost-savings, might be worth the aggravation. I can't find pricing on the '380 anywhere -- not even on aggregators like Octopart. Digikey doesn't even list it. Is it a real, shipping part?

Glen,

The MAX98380 is definitely a real part and is currently shipping in volume.  I'm aware of a large customers using this in volume.

I have someone looking into the missing pricing on our website.  This is believed to be a linking error within our website, and it may take a few weeks to be properly updated.

DigiKey should be stocking our parts in general and that one specifically.  It isn't completely clear why they don't currently show the part for sale, but if you request the part, my understanding is that will trigger a purchase of MAX98380 and would permanently add that to DigiKey's offering.

Is there any EVM that I can order somewhere? Again, like the amp itself, I can't find an EVM anywhere.

Hello Glenn,

Here is a link to the eval board on our web site:

MAX98380EVSYS Evaluation Board | Analog Devices

There is a "Buy" button.

Mike who replied to you and is the expert on these parts is on the west coast. I am on the east coast and work with the DSPs not the amps so I can mention this where Mike is too humble. 

The former Maxim crew out on the west coast of which Mike is one of them are some of the smartest people I have met. They have forgotten more than I know! They layout the bumps (pins) on these parts in a very smart way. They call it a "TipTop" design. This is where for virtually all the applications they set it up so you will not need to use vias in a pad! this will significantly save you on PCB design and build costs! Things like the reset pin and address pins are setup to have ground and power next to them so a simple trace can connect the pin. The rest of the pins can all be connected from the outside edge of the part thereby not requiring a via in a pad!

It really is brilliance in its simplicity. So study your needs and I think you will find you will not require a via in a pad and it will only be the small geometry of the pad itself that increases the cost. 

Dave T

(Mike will be mad at me that I was bragging about him) 

My layout guy was just commenting on this. He had a look at the bump layout and realized he wouldn't have to do much via-in-pad (or even any at all), just the usual escape routing. So this is good news! While I have you here, I tried to order the eval kit and it will not let me purchase without a quote. I followed the various instructions for getting a quote and ended up in a dead end: "The request failed as the service is temporarily unavailable. Please try again later." I have the feeling the same thing will happen later. Please advise if you can.

Glenn,

The pricing should be published, and the part should be stocked at Digi Key.  I've escalated this issue within our business unit.

Additionally, I'm looking at how to get an MAX98380EVSYS to you.

Mike

Mike, it would be absolutely magnificent if you could get me an eval kit! I'm quite eager to validate my proposed design and the quicker I can do this, the better.