[R-390] class d amplifiers

[John Wendler]

I worked with a ti class d amp about 4 years ago for a UHF radio product.

I cannot speak to the HF noise generated by the chip you identify, but I
would certainly put any class d amp in a good shield with feed through
filters as a precaution.  Just because it meets FCC does not mean it won't
cause you heartburn in proximity to your antenna.

Several of the reviews mention white noise when the volume is down - I
might call apps engineers at several different class d manufacturers to see
if that is characteristic of the class d or whether their product is
better.  Analog Devices and TI come to mind.  You would need to buy one of
their eval boards if you are unable to work with SMT - many of those chips
heatsink through a ground paddle in the bottom of the chip.

The biggest problem I had was trying to measure the output with an
oscilloscope.  The output on my chip was full differential; hooking the
ground lead to the chip blew the chip out.  This chip is similar.

You have to use a differential probe or two probes with your scope channels
in a differencing configuration.  You cannot use a speaker where one
terminal is grounded.