I am designing a buck converter with an LM5117 and an external gate driver.
I measure the following waveforms : In green the gate command of the low side FET, in red the CM output (not filtered and not loaded), in blue the signal on the 33 mOhm sense resistor measuring output inductor current and in yellow, the inductor current (0.5 A/div). The signal on the sense resistor is what is expected going from approximately -50 mV to -25 mV for 1.4 A to 0.7 A inductor current when the low side switch is on. However, the output level on the CM output is not what I would have expected it to be because the datasheet gives a typical CS to CM gain of 20.5 V/V. I measure only 50 mV.
Maybe my part is broken however everything else seems to work fine (except at DC > 90%, however this could be another problem). Did I miss something?
Edit : The CS input is not filtered
