Need help on this TDA7293 schematic

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m2003br

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Joined 2004
Mike,
please think about:
If the maximum allowed is 50V, this is for a "real world" worst overvoltage condition of AC line. for a nominal AC line, the projectist may have choose about 10% less. But, this is a unloaded condition. A tipical consumer power supply have high internal resistance, possibly dropping to less than 35V fully loaded. this manner, you have high instantaneous peak, but lower RMS power output. This form a natural mechanism for protection of IC.
Now, if you intend to feed the IC with a good regulated power supply, don't go above +- 40V for 8 ohms and +- 29V for 4 ohms, as stated in TDA7293 datasheet.
 
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MikeTuriel

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Joined 2004
cytlabs.com
You might have reason, but I started the test with tensions of 50+50 v after 45+45 v and finally with 40+40 v with loads of 8 ohms. The power supply had 30000uf 30000uf. My experience with the TDA7293 was very bad, always be burned. :whazzat:

I liked the specifications of the TDA7293, that is why I made development, in testing works well, but then in the field, burned.

Previously I had worked with the LM3886 with 40 +40 v tensions and never burned me. Regards.
 
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ilimzn

Member
Joined 2005
MikeTuriel, I suggest you reda the WHOLE spec sheetm, including the part where maximum voltages of various input pins are given WRT power supplies, and you wills ee that the +- supply must be reduced unless you insure that at startup all the supplies track and none comes up before the other, violating the part of the specs I have just mentioned. The specs are actually circumvent about a few things. For instance, the substrate voltage trick with separate power supplyes for front end is not mentioned, but implemented in the class G design by default, since the mentioned diodes are needed for class G operation. Also, only an older version datasheet for the 7294 contains a simplified internal schematic, which can show you how a separate power supply for the fornt end can remove the need for output strage bootstrapping.
I have used a ton of TDA7294 and 93, and burned only one when a separate front end supply failed short so the diode insuring substrate voltage burned. This also brings me to the question that your ICs could be fake (lower voltage models re-marked). This has happened with LMxxxx power amps in the past, and older TDA parts as well.
Dozens of manufacturers use the TDA729x series and with great success, so why do they not have your problems?
 
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