Giannis_TDM
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- Apr 27, 2019
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Hey, so after replacing the SDX on my 462 build, wasn't broken or anything, I just wanted the reverse pol protection my driver offers, I run some quick tests to see how my driver holds up to a favourite of the community, Results are, Well, See for yourself!
That's the output voltage waveform of the SDX at a 1,7A set, 46mv p-p is not too bad all things considered,
Here is a small write up of my other observations: to start off, what surprised me was the switching freq, The inductor on board is labelled as 220nH so I expected, With that in mind the switching freq to be in excess of a mhz, but Its actually around 330khz, the output cap reads about 10uF which seems kind of small considering the switching frequency, the 50mv p-p at the 1.7A set current is kind of meh all things considered, I would expect it to be 200+mv at its full 4.5A spec but I can at least note down, with a low ish sampling speed (1NPLC, Keithley DMM6500) so can't completely judge based of that but it holds current decently, peak to peak current ripple was indicated around the 2mA p-p mark.
And for the sake of completion, a picture of the 3A buck capture at the same 1.7A that went into the build
(used channel 3 so it would be in a different color)
finally, because I thought it would look cool, the 2 overlaying
MarioMaster on laser discord, where I first posted my limited testing, wanted to see a proper current ripple measurement be performed for both and I could not agree more.
mine to start off same 1.7A set,
blue trace v ripple
purple trace current ripple as measured across the 57.53mΩ shunt, the formula for calculating the current ripple is just simple ohm's law, take that 8mv p-p drop and divide it by the resistance, 8/57.53 =0.13905mA current ripple
Now,
SXD v6, blue trace v ripple
purple trace current ripple as measured across the 144.37mΩ shunt, the formula for calculating the current ripple is just simple ohm's law, take that 41.8mv p-p drop and divide it by the resistance, 41.8/144.37 =0.28953mA current ripple
Note: The voltage ripple is higher for both due to the setup required (extensions cables from the shunt) inducing several parasitics into the feedback loop, under normal operation the voltage ripple will be as shown in the first 2 images and better.
That's the output voltage waveform of the SDX at a 1,7A set, 46mv p-p is not too bad all things considered,
Here is a small write up of my other observations: to start off, what surprised me was the switching freq, The inductor on board is labelled as 220nH so I expected, With that in mind the switching freq to be in excess of a mhz, but Its actually around 330khz, the output cap reads about 10uF which seems kind of small considering the switching frequency, the 50mv p-p at the 1.7A set current is kind of meh all things considered, I would expect it to be 200+mv at its full 4.5A spec but I can at least note down, with a low ish sampling speed (1NPLC, Keithley DMM6500) so can't completely judge based of that but it holds current decently, peak to peak current ripple was indicated around the 2mA p-p mark.
And for the sake of completion, a picture of the 3A buck capture at the same 1.7A that went into the build
(used channel 3 so it would be in a different color)
finally, because I thought it would look cool, the 2 overlaying
MarioMaster on laser discord, where I first posted my limited testing, wanted to see a proper current ripple measurement be performed for both and I could not agree more.
mine to start off same 1.7A set,
blue trace v ripple
purple trace current ripple as measured across the 57.53mΩ shunt, the formula for calculating the current ripple is just simple ohm's law, take that 8mv p-p drop and divide it by the resistance, 8/57.53 =0.13905mA current ripple
Now,
SXD v6, blue trace v ripple
purple trace current ripple as measured across the 144.37mΩ shunt, the formula for calculating the current ripple is just simple ohm's law, take that 41.8mv p-p drop and divide it by the resistance, 41.8/144.37 =0.28953mA current ripple
Note: The voltage ripple is higher for both due to the setup required (extensions cables from the shunt) inducing several parasitics into the feedback loop, under normal operation the voltage ripple will be as shown in the first 2 images and better.
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