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Ripple Measurements
To learn how we measure ripple, please click here.
The following table includes the ripple levels we measured on the ST85F-PT's rails. The limits, according to the ATX specification, are 120 mV (+12V) and 50 mV (5V, 3.3V and 5VSB).
| Test | 12V | 5V | 3.3V | 5VSB | Pass/Fail |
|---|---|---|---|---|---|
| 10% Load | 6.5 mV | 8.6 mV | 6.8 mV | 5.1 mV | Pass |
| 20% Load | 7.4 mV | 10.2 mV | 7.0 mV | 7.2 mV | Pass |
| 30% Load | 8.9 mV | 11.6 mV | 8.2 mV | 8.8 mV | Pass |
| 40% Load | 10.6 mV | 14.8 mV | 10.0 mV | 12.0 mV | Pass |
| 50% Load | 12.6 mV | 16.8 mV | 11.6 mV | 14.1 mV | Pass |
| 60% Load | 14.8 mV | 17.7 mV | 13.3 mV | 14.0 mV | Pass |
| 70% Load | 18.7 mV | 18.2 mV | 15.1 mV | 17.4 mV | Pass |
| 80% Load | 23.7 mV | 18.6 mV | 17.3 mV | 18.2 mV | Pass |
| 90% Load | 29.0 mV | 18.3 mV | 16.7 mV | 20.6 mV | Pass |
| 100% Load | 34.9 mV | 22.0 mV | 21.2 mV | 25.2 mV | Pass |
| 110% Load | 48.6 mV | 36.5 mV | 34.8 mV | 42.2 mV | Pass |
| Cross-Load 1 | 8.3 mV | 10.5 mV | 10.2 mV | 8.1 mV | Pass |
| Cross-Load 2 | 34.8 mV | 22.0 mV | 19.9 mV | 24.2 mV | Pass |
Ripple suppression at +12V isn't the best we've seen, but it's good enough. You have to push the PSU beyond its rated limits to see over 40 mV ripple on this rail. On the minor rails, ripple is quite low, and the 5VSB rail delivers clean output even under full load.
Ripple Oscilloscope Screenshots
The following oscilloscope screenshots illustrate the AC ripple and noise registered on the main rails (+12V, 5V, 3.3V and 5VSB). The bigger the fluctuations on the screen, the bigger the ripple/noise. We set 0.01 V/Div (each vertical division/box equals 0.01 V) as the standard for all measurements.
