SSI America EPS2U Ripple / Noise, Timing Requirements, Ripple and Noise, Output Voltage Timing

SSI

EPS2U Power Supply Design Guide, V2.1

6.8Ripple / Noise

STATUS

Required

The maximum allowed ripple/noise output of the power supply is defined in Table 22. This is measured over a bandwidth of 0 Hz to 20 MHz at the power supply output connectors. A 10 µF tantalum capacitor in parallel with a

0.1µF ceramic capacitor are placed at the point of measurement.

Table 22: Ripple and Noise

+3.3 V	+5 V	+12 V	-12 V	+5 VSB
50 mVp-p	50 mVp-p	120 mVp-p	120 mVp-p	50 mVp-p

6.9Timing Requirements

STATUS

Required

These are the timing requirements for the power supply operation. The output voltages must rise from 10% to within regulation limits (Tvout_rise) within 5 to 70 ms. The +3.3 V, +5 V and +12 V output voltages should start to rise at about the same time. All outputs must rise monotonically. The +5 V output needs to be greater than the +3.3 V output during any point of the voltage rise. The +5V output must never be greater than the +3.3V output by more than 2.25 V. Each output voltage shall reach regulation within 50 ms (Tvout_on) of each other during turn on of the power supply. Each output voltage shall fall out of regulation within 400 ms (Tvout_off) of each other during turn off. Figure 2 and Figure 3 show the turn ON and turn OFF timing requirements. In Figure 3, the timing is shown with both AC and PSON# controlling the ON/OFF of the power supply.

Table 23: Output Voltage Timing

Item	Description	MIN	MAX	Units
Tvout_rise	Output voltage rise time from each main output.	5	70	ms
Tvout_on	All main outputs must be within regulation of each		50	ms
	other within this time.
Tvout_off	All main outputs must leave regulation within this		400	ms
	time.

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