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4.2 Power Supply Requirements
C141-E219 4-7
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 +12V DC.
MAV2073RC
Current (500mA/div)
Time (2 sec/div)
MAV2036RC
Current (500mA/div)
Time (2 sec/div)
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 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 +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 more than 12-second intervals to start
the spindle motors sequentially.