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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 ST45SF's rails. The limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V and 5VSB).

10% Load13.3mV10.8mV17.0mV7.7mVPass
20% Load21.4mV13.8mV18.7mV10.0mVPass
30% Load17.5mV16.0mV21.3mV11.5mVPass
40% Load20.2mV17.4mV25.0mV13.4mVPass
50% Load24.9mV19.8mV26.0mV14.2mVPass
60% Load26.8mV21.1mV24.9mV17.3mVPass
70% Load29.6mV23.6mV28.6mV19.7mVPass
80% Load35.6mV25.6mV36.7mV23.9mVPass
90% Load41.3mV28.1mV41.4mV25.1mVPass
100% Load50.2mV32.7mV40.8mV29.7mVPass
110% Load60.3mV32.7mV42.5mV31.1mVPass
Cross-Load 123.7mV33.2mV37.5mV29.3mVPass
Cross-Load 251.8mV18.8mV32.6mV11.9mVPass

Ripple suppression is decent on every rail except 3.3V, where it exceeds 40mV under full load. To be fair, we did tax this small PSU with an almost-46°C operating temperature during the full load and overload tests.

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 0.01V) as the standard for all measurements.

Ripple At Full Load

Ripple At 110-Percent Load

Ripple At Cross-Load 1

Ripple At Cross-Load 2

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Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.