9
The +3.3VDC, +5VDC and +12V outputs will see transients up to 50% of the maximum
output current. \ The transient slew rate will be 2.5 A/ms. The power supply should be
stable under all transient conditions from any steady state load, and the over/undershoot
should be within the regulation band stated in Section 3.2.1.
3.3.5
+5VDC/+3.3VDC Power Sequencing
The +5VDC output level must be equal to or greater than the +3.3VDC output at all times
during power-up and normal operation. The time between the +5VDC output reaching its
minimum in-regulation level and +3.3VDC reaching its minimum in-regulation level
must be less than or equal to 20msec.
3.3.6
Voltage Hold-up Time
The power supply shall maintain output regulation per Section 3.2.1 despite a loss of
input power at the nominal range (Low = 115Vac, 60 Hz or 230Vac, 50 Hz) at
maximum continuous output load as applicable for a typical of 17 ms.
3.4
Timing / Housekeeping / Control
Figure 1: Power Supply Timing
Notes:
a. T2 is defined in Section 3.4.5
b. T3, T4, and T5 are defined in Table 7
3.4.1 PWR_OK
PWR_OK is a "power good" signal. It is asserted high by the power supply to indicate
that the +5VDC and +3.3VDC outputs are above the undervoltage thresholds listed in
Section 3.2.1 and that sufficient mains energy is stored by the converter to guarantee
continuous power operation within specification for at least the duration specified in
Section 3.3.6. Conversely, PWR_OK should be deasserted to a low state when either the
+5VDC or the +3.3VDC output voltages falls below the undervoltage threshold, or when
mains power has been removed for a time sufficiently long such that power supply
operation cannot be guaranteed beyond the hold-up time. The electrical and timing
characteristics of the PWR_OK signal are given in Table 7 and in Figure 1.
Table 7: PWR_OK Signal Characteristics
