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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).

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Test	12V	5V	3.3V	5VSB	Pass/Fail
10% Load	13.3mV	10.8mV	17.0mV	7.7mV	Pass
20% Load	21.4mV	13.8mV	18.7mV	10.0mV	Pass
30% Load	17.5mV	16.0mV	21.3mV	11.5mV	Pass
40% Load	20.2mV	17.4mV	25.0mV	13.4mV	Pass
50% Load	24.9mV	19.8mV	26.0mV	14.2mV	Pass
60% Load	26.8mV	21.1mV	24.9mV	17.3mV	Pass
70% Load	29.6mV	23.6mV	28.6mV	19.7mV	Pass
80% Load	35.6mV	25.6mV	36.7mV	23.9mV	Pass
90% Load	41.3mV	28.1mV	41.4mV	25.1mV	Pass
100% Load	50.2mV	32.7mV	40.8mV	29.7mV	Pass
110% Load	60.3mV	32.7mV	42.5mV	31.1mV	Pass
Cross-Load 1	23.7mV	33.2mV	37.5mV	29.3mV	Pass
Cross-Load 2	51.8mV	18.8mV	32.6mV	11.9mV	Pass

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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.