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EPS2U Power Supply Design Guide, V2.1
6.8 Ripple / 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
0.1 µF 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
6.9 Timing Requirements
STATUS
Required
These are the timing requirements for the power supply operation. The output voltages must rise from 10% to
within regulation limits (T
vout_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 (T
vout_on
) of each other during turn
on of the power supply. Each output voltage shall fall out of regulation within 400 ms (T
vout_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
T
vout_rise
Output voltage rise time from each main output. 5 70 ms
T
vout_on
All main outputs must be within regulation of each
other within this time.
50 ms
T
vout_off
All main outputs must leave regulation within this
time.
400 ms
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