Class D power amplifier (25/50 watts) based on the MAX9709 chip. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers
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We continue the review of class power amplifiers D integrated circuits from various manufacturers. This time we will survey (surround?) a microcircuit MAX9709produced by a corporation MAXIM.
Despite the relatively small output power indicated in the title of the article, it has one indisputable advantage - acoustics can be connected directly to the microcircuit terminals - no additional inductors are required - as they say - everything is included.
The chip has built-in overload protection, output current limiter, "boom bang" suppression when power is turned on and off. It is also possible to program the gain and the amplifier cut-off temperature.
The main drawback, in my opinion, is the nightmare packages in which the microcircuit is produced - this is either a 56-pin TQFN or a 64-pin TQFP. By the way, keep in mind that the pin numbering on the diagrams is given just for the latter.
Let's look at the diagrams.
Turning on the chip in stereo mode:
And in mono mode:
As you can see, the microcircuit is connected to two power sources - 22 V for the analog part and 5-12 V for the digital one. If it is assumed that the microcircuit will be powered by 12 volts, then the power supply leads can be combined. Otherwise, it is enough to connect any integrated stabilizer - KREN or LM - to the power supply of the analog part.
As for heat removal from microcircuits, the manufacturer offers two methods.
The first is the manufacture of a double-sided board, on both sides of which two multi-, for example, 6-gons are etched one above the other. Both, of course, are arranged so as to get under the belly of the microcircuit and are connected either with metallized holes in several places - the more, the better, or simply with wire jumpers, but also - the better, the more. Thus, the microcircuit is located on top of one of the polygons, and the opposite one is connected to some of the largest and thickest tracks on the board.
Or, the second option - the usual heat sink on top of the microcircuit - is not the largest. There is an idea to put it on hot glue - cheap and cheerful.
I don’t give a plate with elements - it is obscenely small.
Publication: radiokot.ru
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