4.2 Power Supply Requirements
4.2Power Supply Requirements
(1)Allowable input voltage and current
The power supply input voltage measured at the power supply connector pin of the HDDs (receiving end) must satisfy the requirement given in Subsection 2.1.3. (For other requirements, see Items (4) and (5) below.)
(2)Current waveform (reference)
Figure 4.7 shows the spin-up current waveform of +12V DC.
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Current (500mA/div) |
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Figure 4.7 Current waveform (+12V DC)
(3) Power on/off sequence
The order of the power on/off sequence of +5V DC and +12V DC, supplied to the HDDs, does not matter.
(4) Sequential starting of spindle motors
After power is turned on to the HDDs, a large amount of current flows in the +12V DC 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) Control the sending of the NOTIFY (ENABLE SPINUP) primitive so that the spindle motors of individual disk drives are started in intervals of 12 seconds or more.
b) Turn on the +12V DC power in the power supply unit at intervals of 12 seconds or more to start the spindle motors sequentially.
