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EPS2U Power Supply Design Guide, V2.1
Table 26: Over Current Protection
Common Plane Split Plane
Voltage Over Current Limit (Iout limit) Over Current Limit (Iout limit)
+3.3 V 110% minimum; 150% maximum 110% minimum; 150% maximum
+5 V 110% minimum; 150% maximum 110% minimum; 150% maximum
+12V1 18A minimum; 20A maximum; 22A peak
1
15A minimum; 20A maximum
+12V2 Peak current minimum; 20A maximum Peak current minimum; 20A maximum
+12V3 Peak current minimum; 20A maximum (550W only) Peak current minimum; 20A maximum
+12V4 N/A Peak current minimum; 20A maximum
1. +12V1 peak currents shall be maintained for a minimum of 500msec. The maximum duration of the peak current exceeding
the 240VA limit should be limited to meet safety regulations. A maximum duration of 1 second is recommended.
7.3 Over Voltage Protection
STATUS
Required
The power supply over voltage protection shall be locally sensed. The power supply shall shutdown and latch off
after an over voltage condition occurs. This latch shall be cleared by toggling the PSON
#
signal or by an AC
power interruption. Table 27 contains the over voltage limits. The values are measured at the output of the
power supply’s connectors. The voltage shall never exceed the maximum levels when measured at the power
pins of the power supply connector during any single point of fail. The voltage shall never trip any lower than the
minimum levels when measured at the power pins of the power supply connector.
Table 27: Over Voltage Limits
Output Voltage MIN (V) MAX (V)
+3.3 V 3.9 4.5
+5 V 5.7 6.5
+12V1,2,3 13.3 14.5
-12 V -13.3 -14.5
+5 VSB 5.7 6.5
7.4 Over Temperature Protection
STATUS
Recommended
The power supply will be protected against over temperature conditions caused by loss of fan cooling or
excessive ambient temperature. In an OTP condition the PSU will shutdown. When the power supply
temperature drops to within specified limits, the power supply shall restore power automatically. The OTP circuit
must have built in hysteresis such that the power supply will not oscillate on and off due to temperature recovering
condition. The OTP trip level shall have a minimum of 4 °C of ambient temperature hysteresis.
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