Ripple Measurements
In the following table you will find the ripple levels that we measured on the main rails of ST50F-P. According to ATX specification the limits are 120 mV (+12V) and 50 mV (5V & 3.3V).
Ripple Measurements |
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Test | 12 V | 5 V | 3.3 V | Pass/Fail |
20% Load | 13.2 mV | 10.2 mV | 6.4 mV | Pass |
40% Load | 18.8 mV | 12.2 mV | 7.0 mV | Pass |
50% Load | 21.6 mV | 14.2 mV | 7.8 mV | Pass |
60% Load | 30.2 mV | 17.8 mV | 8.6 mV | Pass |
80% Load | 37.6 mV | 20.6 mV | 11.8 mV | Pass |
100% Load | 49.4 mV | 25.8 mV | 14.2 mV | Pass |
Crossload 1 | 15.2 mV | 16.8 mV | 10.8 mV | Pass |
Crossload 2 | 44.8 mV | 23.8 mV | 12.8 mV | Pass |
Ripple/noise suppression in general terms is fairly good. The best performer was 3.3V with 14.2 mV ripple at worst case. The +12V rail follows and 5V comes in the last place with maximum ripple reaching the middle of the limit.
Ripple at Full Load
In the following oscilloscope screenshots you can see the AC ripple and noise that the main rails registered (+12V, 5V, 3.3V). The bigger the fluctuations on the oscilloscope's screen the bigger the ripple/noise. We set 0.01 V/Div (each vertical division/box equals to 0.01V) as standard but sometimes we are forced to use 0.02 V/Div, meaning that the fluctuations will look smaller but actually this wont be the case.
Ripple at Crossload 2
As above the order of images is +12V, 5V and 3.3V.