LME49810 - a new cousin for LM4702

[glennb]

Hi chip heads,

LME49810 is a new audio power amp driver chip which appears in National Semiconductor's latest Analog Product Guide (2Q2007), available at http://www.national.com/whatsnew/fil...t_selguide.pdf (88 pages, 1.7MB)

The product folder is at http://www.national.com/pf/LM/LME49810.html and the PDF data sheet (22 pages) can be downloaded from there.

Its been briefly mentioned in the LM4702 thread http://www.diyaudio.com/forums/showt...postid=1222529 but I thought a new thread should be started.

The LME49810 is a 'single' cousin of the 'dual' LM4702, although its output current is about ten times that of the LM4702 and new features have been added like soft clamping and dedicated bias pins for the Vbe multiplier. The power supply rails are up to +/- 100V, slew up to 50 V/uS.

My samples have just gone into 'shipped' status from Singapore, so the first prototype amp is not far away....

[glennb]

About 10 minutes after that post the nice UPS guy knocked on the front door. Ripping into the package and pulling out the camera....

The LME49810 is in the middle, with a ruler for scale. It is flanked by a LM4702 and LM4780 also for scale. It has tiny pins like the LM4780, but at least they don't have to pass the full speaker output current! 2mm pin spacing on the left and 4mm pin spacing on the right.

[sayang001]

My samples are due to arrive today as well. Will start some testing with TIP142 & TIP147 first, mainly following the shematic in the datasheet.

Next step would be a Sziklai Output like the C200 from ampslab here:

http://www.ampslab.com/c200cfp.htm

Of course I'm open for other suggestions.

[Nordic]

National wanyed $56 to ship the samples... madness!, I'll just wait for a local retailer to stock these.

[Russ White]

Yes, I too have taken notice of this chip. I would say it is much better suited for a FET amp than the 4702 is. And I have my samples and will be testing that scenario with IRFP240 and IRFP9240 very soon.

The bias arrangement and Baker clamp, which basically helps keep the amp stable into clipping if I understand correctly, make this chip much more robust than the 4702. I just want to see how it sounds first, and the MOSFET arrangement here could not be simpler.

Here is a brief explanation of a Baker Clamp from on old TI doc:

What is the function of a Baker Clamp?
The collector current of the power transistor in a switching regulator is proportional to variable output load current. Normally, with bipolar transistors the fixed base drive current is optimized for a maximum output load current. This can result in unacceptably large storage time at light load, because the transistor will be driven into deep saturation. The baker clamp prevents deep transistor saturation by providing a path for excessive base drive current. Many applications, such as flyback and forward converters, are utilizing this technique. The baker clamp diode must have a fast reverse recovery time.

Cheers!
Russ

[alexcd]

I expect big things from you guys with this chip.

[dfdye]

I'm not ready to ditch the 4702 yet, but it certainly seems this chip will do everything the 4702 would and then some. I do wonder what the price point will be.

[glennb]

I've put up a web page for this chip at http://home.pacific.net.au/~gnb/audio/lme49810.html, to sit along-side my pages for the LM4702 and LM4780. More information will be added as experimentation with the chip proceeds. Feel free to send me comments, corrections, ideas.

The LM4702 would still be preferred for lower power stereo amps, but for high power mono blocks the LME49810 looks better.

[Russ White]

I am not sure I can find a good reason to prefer the LM4702 for any application..... Honestly.

[dfdye]

price?? do we know what they are charging for this thing yet?