Hi all
I have an unwanted amount of the switch waveform (square wave) appearing on the output using a very standard TPS54227 design (15V - 1.9V).
The waveform looks extremely similar to figure 13 in the datasheet, p14 - www.ti.com/.../tps54227.pdf
Except that the square pulses are large enough at about 40mV to be worrisome, regardless of load.
In my experience of sync buck circuit theory and from checking simulations it is not caused by current flow in the circuit, even if a ground was bad or solder joint was dry - the filter would still lead to the textbook capacitor ripple shape.
This leads me to blame either
a) layout - i followed the layout guidelines quite closely but may have tried to miniaturize a bit too much
b) measurement technique - we are measuring using a tight loop with gnd spring - but might be a fairly cheap probe.
Thankful if you have any similar experiences/advice.
-Cal