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Seagate Enterprise Capacity 2.5 HDD v3 SAS Product Manual, Rev. D 53
11.4.6 SAS transmitters and receivers
A typical SAS differential copper transmitter and receiver pair is shown in Figure 13. The receiver is AC coupling to eliminate ground shift
noise.
Figure 13. SAS transmitters and receivers
11.4.7 Power
The drive receives power (+5 volts and +12 volts) through the SAS device connector.
Three +12 volt pins provide power to the drive, 2 short and 1 long. The current return for the +12 volt power supply is through the common
ground pins. The supply current and return current must be distributed as evenly as possible among the pins.
Three +5 volt pins provide power to the drive, 2 short and 1 long. The current return for the +5 volt power supply is through the common
ground pins. The supply current and return current must be distributed as evenly as possible among the pins.
Current to the drive through the long power pins may be limited by the system to reduce inrush current to the drive during hot plugging.
11.5 Signal characteristics
This section describes the electrical signal characteristics of the drive’s input and output signals. See Section 11.4.5 for signal type and
signal name information.
11.5.1 Ready LED Out
The Ready LED Out signal is driven by the drive as indicated in the table below.
Table 12 Ready LED Out conditions
Normal command activity LED status
Ready LED Meaning bit mode page 19h
01
Spun down and no activity
Off Off
Spun down and activity (command executing)
On On
Spun up and no activity
On Off
Spun up and activity (command executing)
Off On
Spinning up or down
Blinks steadily
(50% on and 50% off, 0.5 seconds on and off for 0.5 seconds)
Format in progress, each cylinder change
Toggles on/off