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4.2 Power Supply Requirements
C141-E252 49
Figure 4.7 shows the Max Seek current waveform of+5V DC and +12V DC.
Time (2 sec/div) Time (2 sec/div) Time (2 sec/div)
Time (2 sec/div) Time (2 sec/div) Time (2 sec/div)
Figure 4.7 Current waveform (Max seek)
(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 HDD 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.