Seagate Cheetah 18FC ST118202FC, Product Manual

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Cheetah 18FC Product Manual, Rev. C 19
6.0 Physical/electrical specifications
This section provides information relating to the physical and electrical characteristics of the drive.
6.1 AC power requirements
None.
6.2 DC power requirements
The voltage and current requirements for a single drive are shown below. On-board +3.3V current is derived
entirely from the +5V supply. Values indicated apply at the drive connector. Parameters, others than spindle
start, are measured after a 10-minute warm-up.
[1] Measured with average reading DC ammeter. Instant12V current peaks will exceed these val-
ues.
[2] A –10% tolerance is allowed during initial spindle start but must return to
±
5% before reaching 10,000
RPM. The
±
5% must be maintained after the drive signifies that its power-up sequence has been com-
pleted and that the drive is able to accept selection by the host initiator.
[3] See +12V current profile in Figure 3.
[4] This condition occurs when the Motor Start option is enabled and the drive has not yet received a Start
Motor command.
[5] See paragraph 6.2.1, “Conducted noise immunity.” Specified voltage tolerance includes ripple, noise, and
transient response.
[6] At power up, the motor current regulator limits the 12 volt current to an average value of less than 2.1
amperes, although instantaneous peaks may exceed this value. These peaks should measure 5 msec
duration or less.
[7] Operating condition is defined as a third stroke seek at OD and Read One track. Command issued every
42 msec.
[8] During idle, the heads are relocated every 60 seconds to a random location within the band from track 0 to
one-fourth of maximum track. This will result in a random variation in the +12 volt idle current of 0.0152
Amperes (0.182 Watts).
General DC power requirement notes.
1. Minimum current loading for each supply voltage is not less than 2% of the maximum operating current
shown.
2. The +5V and +12V supplies should employ separate ground returns.
3. Where power is provided to multiple drives from a common supply, careful consideration for individual drive
power requirements should be noted. Where multiple units are powered on simultaneously, the peak start-
ing current must be available to each device.
Table 1: DC power requirements
ST118202FC
Voltage regulation Notes [5]
+5V
±5%
(Amps) +12V
±5%[2]
(Amps)
Avg idle current [1] [8] 0.70 1.25
Max start current (peak DC) [3] [6] 0.76 3.2
Delayed motor start (max) [1] [4] 0.72 0.57
Operating current:
Typical [1] [7] 0.76 1.39
Maximum [1] 0.80 1.41
Max (peak) 1.04 2.91