Attention Neil Davis and others - new Class D amp ICs from IR

[charlielaub]

Wow, these look interesting! New to me, at least.

• Integrated PWM driver and MOSFET output stage in a single package.
• Operation can be with OR WITHOUT heatsink.
• Power rating between 35 and 160W depending on configuration.
• Dual channel chips!

International Rectifier IR43xx Class D Audio Amplifiers

-Charlie

[envisionelec]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

Great. Thank you.

[neildavis]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

Wow, these look interesting! New to me, at least.

-Charlie

They've been out for while now. I bought 4 of them last August, and I finally got around to making a board with them. The board is partially assembled now, but I've got to finish assembling and develop a lot of code before I can evaluate it.

The board has two single-ended amps plus another pair of IR4301's that can be bridged. It uses an ADAU1701 for the active crossover, so the board can be used for stereo, 2.1, 3-way or 4-way. And I added a DAC to the ADAU1701 digital outputs for driving external sub amps (two channels). And there is a connector for a 3x16 LCD display. So if I can get it to work, it should be a rather cool design.

Charlie--I had to clean up my assembly area to start on this, and finally got around to upgrading those miniDSP controller boards (had to cut off the old CPU and put on a new one). So I'm a lot closer to sending you one. But I've got to send you some software to control it from Excel--I'm still working on that. Had grandkids for a week and will be working on my wife's Mini this weekend, so things have been slow. Of course, laying out this board took some time...

[envisionelec]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

Of course, laying out this board took some time...

That's because you still use PCB Depressed. :o

[SirNickity]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

It's pretty nice software.. no bells and whistles, but for plain vanilla board design, it's perfectly capable and doesn't fight against you. On the other hand, I just put in an order for 4 boards. $300. :eek: I suppose if I didn't absolutely have to order solder mask and silkscreening....

[neildavis]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

That's because you still use PCB Depressed. :o

Well, yes and no. I started out using Autotrax Design Express (DEX). Autotrax was started by an Altium expatriot (Iliya Kovac), and it has finally evolved to where it is a credible product. This was going to be my first DEX project, and I actually built a number of library components. But I had already done the CPU/LCD and ADAU1701 circuitry for other projects in ExpressPCB, and I needed to come up with a Christmas present from my mom, so I went with what I already had and was familiar with. I was able to reuse pieces from other ExpressPCB schematics and PCB's and put this together fairly fast so I could use her credit card for the PCB purchase. But I swear, it's my last ExpressPCB project. ExpressPCB is an OK program for throw-away designs, but obviously, it locks you into their proprietary formats. I expected to have some "issues" with this layout because of the nature of class D amps, so in this case it didn't bother me that this design was a "throw-away".

There are a couple of challenges in this board that make it "high-risk". The first is the use of a common clock. I'm using a frequency-synthesis chip to generate a common clock for all of the chips, but it still looks like the IR4301 varies the clock about this center frequency. What that will do to my power supply and grounds under heavy loads is TBD. This may be the reason IR doesn't show any reference amps for the IR4301 that are bridged, but I guess I'll find out. Another unknown is the thermal design. I think I came up with two novel ways to remove heat, and I'll have to do some testing to see how they work. And, of course, there always seem to be layout issues with class D amps. I have separate analog and output groud planes, but IR uses some heavy B- planes, and my design doesn't. So we'll see. I wanted this board as a Christmas present so I can learn more about these amps, and ExpressPCB just made more sense at the time.

[envisionelec]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

It's pretty nice software.. no bells and whistles, but for plain vanilla board design, it's perfectly capable and doesn't fight against you. On the other hand, I just put in an order for 4 boards. $300. :eek: I suppose if I didn't absolutely have to order solder mask and silkscreening....

I pay, on average, $95 for 6 boards. Mask+silk both sides for a 2 layer board. 4 layers is about $135 for 6 or fewer.

That is just one of the reasons I don't use PCB Express. The other is terrible looking routing. With apologies to Neil, I have a particular "skin crawl" when I see non-orthogonal lines at which PCB-E is especially good. Every board I design is treated as though it could be a production run so it looks like a production board. If it works first time, then it saves a few hundred in NRE. If it doesn't, then it's easier to trace.

[envisionelec]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

Well, yes and no. I started out using Autotrax Design Express (DEX). Autotrax was started by an Altium expatriot (Iliya Kovac), and it has finally evolved to where it is a credible product. This was going to be my first DEX project, and I actually built a number of library components. But I had already done the CPU/LCD and ADAU1701 circuitry for other projects in ExpressPCB, and I needed to come up with a Christmas present from my mom, so I went with what I already had and was familiar with. I was able to reuse pieces from other ExpressPCB schematics and PCB's and put this together fairly fast so I could use her credit card for the PCB purchase. But I swear, it's my last ExpressPCB project. ExpressPCB is an OK program for throw-away designs, but obviously, it locks you into their proprietary formats. I expected to have some "issues" with this layout because of the nature of class D amps, so in this case it didn't bother me that this design was a "throw-away".

There are a couple of challenges in this board that make it "high-risk". The first is the use of a common clock. I'm using a frequency-synthesis chip to generate a common clock for all of the chips, but it still looks like the IR4301 varies the clock about this center frequency. What that will do to my power supply and grounds under heavy loads is TBD. This may be the reason IR doesn't show any reference amps for the IR4301 that are bridged, but I guess I'll find out. Another unknown is the thermal design. I think I came up with two novel ways to remove heat, and I'll have to do some testing to see how they work. And, of course, there always seem to be layout issues with class D amps. I have separate analog and output groud planes, but IR uses some heavy B- planes, and my design doesn't. So we'll see. I wanted this board as a Christmas present so I can learn more about these amps, and ExpressPCB just made more sense at the time.

Neil, I'm just busting your chops. I know a lot of people use them and they work fine. My biggest problem with them is they have (at the time I tried them) no appreciable DRC and it will let you make non-compliant boards.

I haven't heard about Autotrax in many years...

I think you're going to see some problems with those small B+ and B- traces. This is the type of amp that really needs a 4 layer board with large planes for those rails. When I did that in the (rhymes with) Squirt-Yoo amps, it really cleaned up the over/undershoot on the rails over the sample I was given. And that's the way I test it - square wave signal into the amp and DIY current probes (CT style) on B+/B-. I monitor the resistive-loaded output with a ($$) differential scope probe. I also monitor current on the ground connection at the chip, the speaker connection and at the feedback node(s). Once I'm satisfied with the layout, then I perform all the calcs to get the correct bypass caps in place.

Your novel heatsink looks like a set of three Faston tabs? If it is, then jumper the power right through them. You're welcome. :D

[SirNickity]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

Where do you have yours made? I know PCBE will allow you to get the Gerber files from past orders. And like you -- even though it'll never happen in my case -- I try to design my boards as if they were going to be sold and scrutinized by scores of end-users with experience in PCB design. I'm also about 1.5 years into PCB design, so I probably make tons of newbie mistakes that would have experienced designers sighing. ;-)

If I ever duplicate this last project, I will probably try to have the boards made elsewhere. The per-board cost isn't very high, but the $245 setup fee hurts. It could've been cheaper, but I was 0.6 sq. in. above their 21 sq. in. cutoff for the prototype service. I stopped trying to squeeze it down any further, and just tossed another board in that I wanted to have made anyway.

If you're feeling charitable, have a glance. I could use constructive criticism. (Hoping this isn't too much of a thread jack.)

PSU board (linear plus regulated split rail and switched 5v rail) and preamp/crossover/inactivity detector control board.

LM3886/1875 bi-amp, and some incidental stuff for testing and pin size reference.

[envisionelec]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

Where do you have yours made? I know PCBE will allow you to get the Gerber files from past orders. And like you -- even though it'll never happen in my case -- I try to design my boards as if they were going to be sold and scrutinized by scores of end-users with experience in PCB design. I'm also about 1.5 years into PCB design, so I probably make tons of newbie mistakes that would have experienced designers sighing. ;-)

If I ever duplicate this last project, I will probably try to have the boards made elsewhere. The per-board cost isn't very high, but the $245 setup fee hurts. It could've been cheaper, but I was 0.6 sq. in. above their 21 sq. in. cutoff for the prototype service. I stopped trying to squeeze it down any further, and just tossed another board in that I wanted to have made anyway.

If you're feeling charitable, have a glance. I could use constructive criticism. (Hoping this isn't too much of a thread jack.)

PSU board (linear plus regulated split rail and switched 5v rail) and preamp/crossover/inactivity detector control board.
[ATTACH=CONFIG]32313[/ATTACH]
LM3886/1875 bi-amp, and some incidental stuff for testing and pin size reference.
[ATTACH=CONFIG]32314[/ATTACH]

I've been using www.myropcb.com for the past 8 years. Their prices have risen substantially, but are still 50-60% of stateside folks. AND, the quality is fantastic. I can't say the same for many USA-sourced boards.

It looks really good. The node at R3 and R10 on the amp board should be separated into two separate paths back to source GND for reduced crosstalk. Very nice grounding, otherwise. I rarely see good star grounds. I think you're a natural.

I've never seen PCB express look so good...

[Pete Schumacher]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

It doesn't look like MyroPCB offers software like PCB Express. What do you use for schematic capture/PCB layout software?

[neildavis]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

Your novel heatsink looks like a set of three Faston tabs?

Well, that's one of the tricks I used to remove heat...I thought they made nice little heatsinks. But the method that will probably be a lot more effective goes on the back of the board. Trade secret for now.

As I said, this board is for learning. It's got a number of chips that I've never used before and will require a fair amount of control code in the micro. There's lots to go wrong and lots to learn. A couple of things I wanted to try never made it, though--such as the DC output detection and some additional inputs. I was going to do the DC detection (along with over/under voltage) with the micro but running the traces across the board was going to be too hard.

The amp circuits are loosely based on the IRAUDAMP12, but the layout is totally experimental. Lots of parts changes along the way, as well. I'm hoping it will lead to a nice product but I expect at least another design iteration before it's ready for final boards.

[alexdidonato]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

Well, yes and no. I started out using Autotrax Design Express (DEX). Autotrax was started by an Altium expatriot (Iliya Kovac), and it has finally evolved to where it is a credible product. This was going to be my first DEX project, and I actually built a number of library components. But I had already done the CPU/LCD and ADAU1701 circuitry for other projects in ExpressPCB, and I needed to come up with a Christmas present from my mom, so I went with what I already had and was familiar with. I was able to reuse pieces from other ExpressPCB schematics and PCB's and put this together fairly fast so I could use her credit card for the PCB purchase. But I swear, it's my last ExpressPCB project. ExpressPCB is an OK program for throw-away designs, but obviously, it locks you into their proprietary formats. I expected to have some "issues" with this layout because of the nature of class D amps, so in this case it didn't bother me that this design was a "throw-away".

There are a couple of challenges in this board that make it "high-risk". The first is the use of a common clock. I'm using a frequency-synthesis chip to generate a common clock for all of the chips, but it still looks like the IR4301 varies the clock about this center frequency. What that will do to my power supply and grounds under heavy loads is TBD. This may be the reason IR doesn't show any reference amps for the IR4301 that are bridged, but I guess I'll find out. Another unknown is the thermal design. I think I came up with two novel ways to remove heat, and I'll have to do some testing to see how they work. And, of course, there always seem to be layout issues with class D amps. I have separate analog and output groud planes, but IR uses some heavy B- planes, and my design doesn't. So we'll see. I wanted this board as a Christmas present so I can learn more about these amps, and ExpressPCB just made more sense at the time.

IRAUDAMP19 is 2xIR4301 and they can be bridged.
http://www.irf.com/technical-info/re...iraudamp19.pdf

I have my concerns about any self-oscillating amps in close proximity on the same power and ground planes. The Tripath design, specifically TC2001, separated the PWM frequency of the two channels by a certain amount of frequency so they didn't easily interact, i.e. create IMD. I should mention I also prefer to use full-bridge over half bridge.

I too use PCBexpress for my personal or throw away designs, cheap and like you said it doesn't fight back.

[SirNickity]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

I've been using www.myropcb.com for the past 8 years. Their prices have risen substantially, but are still 50-60% of stateside folks. AND, the quality is fantastic. I can't say the same for many USA-sourced boards.

It looks really good. The node at R3 and R10 on the amp board should be separated into two separate paths back to source GND for reduced crosstalk. Very nice grounding, otherwise. I rarely see good star grounds. I think you're a natural.

I've never seen PCB express look so good...

Thanks so much for the feedback, it's really appreciated. I didn't quite expect to get an A on this assignment. ;-) That R3-R10 link makes me laugh. I hesitated to combine them at R10 on principle, then shrugged it off. I guess I should've listened to my instincts. But hey, if that's the standout criticism, I'll take it!

I'll post the complete design (schematics and BOM and whatnot) on my Active Microbe thread once I've had a chance to build and test it for functionality. I don't expect anyone will want to duplicate it for reasons of cost alone, but it still might be an interesting gawk for other electronics hobbyists. This was certainly an educational labor of love rather than an economical choice.

[envisionelec]

Re: Attention Neil Davis and others - new Class D amp ICs from IR

It doesn't look like MyroPCB offers software like PCB Express. What do you use for schematic capture/PCB layout software?

Myro is just a job shop.

I used Eagle for 10 years starting with version 3.xx. I finished with them at 6.1. They've not made enough improvements since their sell out to Element 14. I use Altium Designer 10 almost exclusively now. I can also use OrCAD, but don't prefer it.