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CP3923 User Guide
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6.1.3.3
Tolerance
The tolerance of the voltage lines is described in the CompactPCI specification (PICMG 2.0). The recommended measure-
ment point for the voltage is the CompactPCI connector on the switch.
The following table provides information regarding the required characteristics for each board input voltage.
The output voltage overshoot generated during the application (load changes) or during the removal of the input voltage
must be less than 5% of the nominal value. No voltage of reverse polarity may be present on any output during turn-on or
turn-off.
6.1.3.4
Regulation
The power supply shall be unconditionally stable under line, load, unload and transient load conditions including capaci-
tive loads. The operation of the power supply must be consistent even without the minimum load on all output lines.
Table 6-2:
Input Voltage Characteristics
Voltage
Nominal Value
Tolerance
Maxi. Ripple (p-p)
Remarks
5 V
+5.0 VDC
+5%/-3%
50 mV
Main Voltage
3.3 V
+3.3 VDC
+5%/-3%
50 mV
-
VI/O (PCI) Voltage
+3.3 VDC or +5 VDC
+5%/-3%
50 mV
-
GND
Ground, not directly connected to potential earth (PE)
WARNING
All of the input voltages must be functionally coupled to each other so
that if one input voltage fails, the other input voltages must be regu-
lated proportionately to the failed voltage. For example, if the +5V
begins to decrease, +3.3V must decrease accordingly. This is required
in order to preclude cross currents within the CP3923.
Failure to comply with above may result in damage to the board or
improper system operation.
Note...
If the main power input is switched off, the supply voltages will not go to 0V
instantly. It will take a couple of seconds until the capacitors are discharged. If the
voltage rises again before it has gone below a certain level, the circuits may enter a
latch-up state where even a hard RESET will not help any more. The system must be
switched off for at least 3 seconds before it may be switched on again. If problems
still occur, turn off the main power for 30 seconds before turning it on again.
