Continue review of power amplifiers class-D integrated circuits from different manufacturers. This time we will look at the chip MAX9709 produced by the Corporation MAXIM.
Despite the relatively small power output, it has one distinct advantage - speaker system can be connected directly to the pins of the chip - no additional inductors are not required - as they say - everything is included.

The chip's main characteristics are the following:Voltage, V 10...22
Supply current (no signal), 20 mA


Maximum output power:stereo mode(KG=10%) 29
in mono mode(KG=10%) 50


The "normal" output power, W:in stereo(KG=0.1%) 12
in mono mode(KG=0.09%) 22
Signal/noise ratio (a weighted), % 96
Efficiency (max.), % 87


The chip has built-in overload protection, the limiter output current suppression "boom-boom" when turning on and off the power. Also has a programmable gain, and temperature turning the amplifier off.
The main drawback, in my opinion is a horrible case in which the chip is available is either a 56-pin TQFN or 64-lead TQFP. By the way, note that the pin numbering on the schemes given for the latter.
Looking scheme.
The inclusion of the chip in stereo:
Power amplifier class d (25/50 watts)

And in mono:


As can be seen, the chip is connected to two power sources - 22 - for the analog part and 5-12 In for digital. If it is assumed that the chip will be powered by a 12 volt, terminals for supplying power can be combined. Otherwise, enough to power the analog section to connect any integral stabilizer - ROLL or LM.
As for removing heat from the chip - manufacturer provides two ways.
The first is the manufacture of double-sided PCB, on both sides of which mytravelguide two a lot is, well, for example, 6-gon one above the other. Both, of course, arranged so as to fall under the belly of the chip and are connected either metallized holes in a few places - the more the better, or just wire links, but also - even more. Thus, the chip is located on top of one of the polygons, and the opposite connected with some of the biggest and a thick carpet on the Board.
Or, the second option is a conventional heat sink on top of the chip - not the biggest. Has the idea to put him on the hot-melt adhesive - cheap and cheerful.

Add comment

Menu

Service manuals

Copyright © 2018 Electrical circuits.