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Installation Requirements
4-8 C141-E235
4.2 Power Supply Requirements
(1) Allowable input voltage and current
The power supply input voltage measured at the power supply connector pin of the HDD (receiving
end) must satisfy the requirement given in Subsection 2.1.3. (For other requirements, see Items (4)
below.)
(2) Current waveform (reference)
Figure 4.7 shows the waveform of +12 VDC.
MAW3300FC
Current (500mA/div)
Time (2 sec/div)
MAW3147FC
Current (500mA/div)
Time (2 sec/div)
MAW3073FC
Current (500mA/div)
Time (2 sec/div)
Figure 4.7 Current waveform (+12 VDC)
(3) Power on/off sequence
The order of the power on/off sequence of +5 VDC and +12 VDC, supplied to the HDD, does not
matter.
(4) Sequential starting of spindle motors
After power is turned on to the HDD, a large amount of current flows in the +12 VDC line when the
spindle motor rotation starts. Therefore, if more than one HDD is used, the spindle motors should be
started sequentially using one of the following procedures to prevent overload of the power supply
unit.
a) Issue START/STOP commands at more than 12-second intervals to start the spindle motors. For
details of this command specification, refer to Fibre Channel Interface Specifications.
b) Turn on the +12 VDC power in the power supply unit at 12-second intervals or more to start the
spindle motors sequentially.