Hi all, I'm using this device to produce a 24V rail at 35 mA max (variable load from about 10 to 35 mA) from two series Lithium cells, so about 6 to 8.5V input.
I'm using the X version, so 1.6 MHz switching. Under most conditions of input voltage and load, the device runs in discontinuous mode which imposes a large ripple on the output voltage at around 800 Hz but this changes depending on load and input voltage. It seems as though the control system is unstable, the output ripple goes above and below the set value.
I note in the data sheet, the Y version seems to be recommended for "high voltage" operation, unfortunately I cant get these at the moment, they're on long delivery. I note the data sheet says 16V output and higher... does this mean it's unreliable above 16Vdc output?
I've tried different inductor values from 10 uH to 47 uH, all much higher sat current than needed, and tried different caps on the output from 100n to 40uF as 4 off 0805 10u, but the oscillation is always there.
Any thoughts on what could be wrong? As far as I tell the device is not getting hot and going into thermal shutdown and it's on a groundplane board. I tried one of these before several years ago and couldn't get it to work properly.