Seagate ST118202LC, Product Manual

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Cheetah 18 Product Manual, Rev. B 21
6.3 Power dissipation
For drives using single-ended interface circuits, typical operating random read power dissipation is 18.7 watts
(64 BTUs per hour) of DC power average at nominal voltages. Typical power dissipation under idle conditions
is 15.4 watts (52.7 BTUs per hour).
For drives using low voltage differential interface circuits, typical operating random read power dissipation is
19.1 watts (65.3 BTUs per hour) of DC power average at nominal voltages. Typical power dissipation under idle
conditions is 15.5 watts (53 BTUs per hour).
6.4 Environmental limits
Temperature and humidity values experienced by the drive must be such that condensation does not occur on
any drive part. Altitude and atmospheric pressure specifications are referenced to a standard day at 58.7°F
(14.8°C). Maximum wet bulb temperature is 82°F (28°C).
6.4.1 Temperature
a. Operating
With cooling designed to maintain the case temperatures of Table 3, the drive meets all specifications over
a 41°F to 122°F (5°C to 50°C) drive ambient temperature range with a maximum temperature gradient of
36°F (20°C) per hour. The enclosure for the drive should be designed such that the temperatures at the
locations specified in Table 3 are not exceeded. Air flow may be needed to achieve these temperature val-
ues (see Section 8.3 and 8.3.1). Operation at case temperatures above these values may adversely affect
the drives ability to meet specifications.
The MTBF specification for the drive is based on operating in an environment that ensures that the case
temperatures specified in Table 3 are not exceeded. Occasional excursions to drive ambient temperatures
of 122°F (50°C) or 41°F (5°C) may occur without impact to specified MTBF. Air flow may be needed to
achieve these temperatures (see Section 8.3.1). Continual or sustained operation at case temperatures
above these values may degrade MTBF.
To confirm that the required cooling for the Cheetah electronics and HDA is provided, place the drive in its
final mechanical configuration, perform random write/read operations. After the temperatures stabilize,
measure the case temperature of the components listed in Table 3 (see note [2]).
The maximum allowable HDA case temperature is 60°C. Operation of the drive at the maximum case tem-
perature is intended for short time periods only. Continuous operation at the elevated temperatures will
reduce product reliability.
Table 3: PCBA and HDA temperatures
Note.
[1] Section 8.3.1 describes the air-flow patterns used when generating the 1 million hours MTBF guide-
lines in column 2. Air flow was opposite that shown in Section 8.3.1. Local air velocity was 0.74 m/sec
(145 lfpm). Inlet air temperature to the drive was 77°F (25°C), plus 9°F (5°C) temperature rise in the
test enclosure 86°F/30°C ambient local to the drive).
[2] Measure HDA temp at point labeled “HDA” on Figure 4.
[3] PCB mounted integrated circuit case.
Items in
Figure 4
Maximum allowable
case temperature (
° C)
operating
Maximum allowable
case [3] temperatures (°C)
to meet MTBF spec.
HDA [2] 60 45
U12 80 60
U1 68 48
U5 76 56
U14 71 51