Intel ATX12V - Manual (Page 26)

ATX12V Power Supply Design Guide
Version 2.0
26
3.4. Output Protection
3.4.1. Over-voltage Protection
The over-voltage sense circuitry and reference shall reside in packages that are separate and
distinct from the regulator control circuitry and reference. No single point fault shall be
able to cause a sustained over-voltage condition on any or all outputs. The supply shall
provide latch-mode over-voltage protection as defined in Table 15.
Table 15. Overvoltage Protection
Output Min. Nom. Max. Unit
+12 V1DC & +12V2DC 13.4 15.0 15.6 Volts
+5 VDC 5.74 6.3 7.0 Volts
+3.3 VDC 3.76 4.2 4.3 Volts
3.4.2. Short-circuit Protection
An output short circuit is defined as any output impedance of less than 0.1 ohms. The
power supply shall shut down and latch off for shorting the +3.3 VDC, +5 VDC, or
+12 VDC rails to return or any other rail. The +12 V1DC and +12V2DC should have
separate short circuit and overload protection. Shorts between main output rails and +5
VSB shall not cause any damage to the power supply. The power supply shall either shut
down and latch off or fold back for shorting the negative rails. +5 VSB must be capable of
being shorted indefinitely, but when the short is removed, the power supply shall recover
automatically or by cycling PS_ON#. The power supply shall be capable of withstanding a
continuous short-circuit to the output without damage or overstress to the unit (for
example, to components, PCB traces, connectors) under the input conditions specified in
Section 3.1. The maximum short-circuit energy in any output shall not exceed 240 VA, per
IEC 60950 requirements.
3.4.3. No-load Operation
No damage or hazardous condition should occur with all the DC output connectors
disconnected from the load. The power supply may latch into the shutdown state.
3.4.4. Over-current Protection
Overload currents applied to each tested output rail will cause the output to trip before
reaching or exceeding 240 VA. For testing purposes, the overload currents should be
ramped at a minimum rate of 10 A/s starting from full load.