Fujitsu MBA3073NC, MBA3073NP, MBA3300NP, MBA3147NC, MBA3300NC Delay time of spindle motor starting

(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 by the following procedures to prevent overload of the power supply unit. Regarding how to set a spindle motor start control mode, see Subsection 5.3.2.

For the NP model drives, the spindle motors should be started sequentially using of the following procedures.

a)Issue START/STOP commands at more than 12-second intervals to start the spindle motors. For details of this command specification, refer to Subsection 3.1.10 “START/STOP UNIT (1B)” of the SCSI Logical Interface Specifications.

b)Turn on the +12V DC power in the power supply unit at 12-second intervals or more to start the spindle motors sequentially.

For the NC model drives, the spindle motors should be started after a delay of 12 seconds times [SCSI ID] by setting CN1-38 pin to open and CN1-78 pin to short.

SCSI ID	Delay time of spindle motor starting
0	0
1	12 s
2	24 s
.	.
15	180 s

(5)Power supply to SCSI terminating resistor

If power for the terminating resistor is supplied from the HDD to other SCSI devices through the SCSI bus, the current-carrying capacity of the +5 VDC power supply line to the HDD must be designed with considering of an increase of up to 200 mA.

A method of power supply to the terminating resistor is selected with a setting terminal on the HDD (NP model only). See Subsection 5.3.2 for this selection.

For the electrical condition of supplying power to the terminating resistor, refer to Section 1.4 “Electrical Requirements” of the SCSI Physical Interface Specifications.

(6)Noise filter

To eliminate AC line noise, a noise filter should be installed at the AC input terminal on the HDD power supply unit. The specification of this noise filter is as follows:

•Attenuation: 40 dB or more at 10 MHz

•Circuit construction: T-configuration as shown in Figure 4.12 is recommended.

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