Lm4702

[Mike Gergen]

Anybody investigate this part yet?

[Gcollier]

Hmm...this one looks interesting. I ordered a couple of samples. It would give me an excuse to use up all of the thransformers I have that put out too much voltage for a gainclone. If you want to work togeteher on a board design let me know.

G.

[Mark St. Denis]

Were is everyboby. LM4702 looks like a gold mine. Why are the blogs so quite? Were are the prototyping tools?

Mark
Las Vegas, Nevada

[dfdye]

Search = goldmine!

http://www.diyaudio.com/forums/showt...854#post750854

If you are interested in getting a prototype board to help those investigations along, there is even a group buy for some boards active!

http://www.diyaudio.com/forums/showt...724#post898724

[Mark St. Denis]

Hello,

I am a beginner at this so I hope this question helps.
National Semiconductor has a "Build It" page at www.national.com/appinfo/power/webbench/buildit/ with a "contact us" click that is subdivided into sales, technical and others. Does anyone know how user friendly NS "Build It" and "contact technical" is? Perhaps NS is wiiling to give good technical advice to diyaudio members via postings, since they have complete development enviroments for other audio amplifiers, yet not for LM4702.

Mark St. Denis

[Mark St. Denis]

Hello,

In June 2004 NS made Application Note 1192 by John De Celles and Troy Huebner AN-1192.pdf in reference to LM3886 at Analog University www.national.com/AU/design/0,4706,6_0_,00.html. In this note power dissipation is discussed on page 10 figure 11 by FFT's on Noise Floor Tests with log-scale noise floor and then concluding as quoted "as showen in figure 12 noise level is quite low and influence of the power supply is relativility small" while using note 7.2.3 typically unregulated bi-polar 385VA torodial transformer, therein showing the coupling effect to any 60Hz power line signal or other 60 Hz vibe to be minimum. Were are the FFT Noise Floor Tests for LM4702? In all the LM4702 discussions, I guess it is just assumed, that any power supply will suffice, with no interference to some peoples favorite base frequencies DC to 200Hz.

Mark

[Bazukaz]

Still , as i understand , the IC does not protect output transistors at all ?

[veteran]

Originally posted by Bazukaz
Still , as i understand , the IC does not protect output transistors at all ?

Yes, You are right. There is only thermal shutdown and current protection for LM4702 output.

[Mark St. Denis]

Hi Bazukas,

I think I see what you mean? (1) In 1993 John De Celles per AN-898.pdf says approximate quote "Overture Serries possesses unique protection system that should save designers costs ... these SPiKE advantages are generally only in high end and discrete amplifiers ... this type of protection usually requires costly zeners or fast recovery Schottky diodes" and then (2) In 1994 John De Celles per AN1192.pdf says approximate quote at section 4.2 "go through worst case power dissipation senarios which implies sinusoids will be used with unregulated power supplies ... and then onto section 4.3 bridged if two individual IC's are used then total power dissipation is divided by each IC" or Pdmax = Vcctot squared vs. Pdmax = Vbtl. I like bridged IC's
anyway, so the point that NS in some manner watered down their own SPike dynamic, that is O.K. by me. Sinusoids in unregulated power supplies, no problem. I hope I got your topic point, at least in partial reply.

Mark

[Mark St. Denis]

Hello,

By this time, everyone can know that Application Note 1490 by National was released in May 2006 showing completed prototype of LM 4702 at www.national.com/an/AN/AN-1490.pdf#page=7 and this is good timing for their Knowledge Base.

Mark