Grounding; Figure 14. St410800 Configuration Select Header Specification - Seagate Elite 9 Product Manual

Elite 9 Product Manual, Rev. C
10.2.1.2
10.2.1.3
10.3
Termination
The reference index signal (SSREF+) is terminated with a 2.21K ohm
resistor. Each drive has a spindle sync terminator resistor located on the
main PCB. The spindle sync terminator resistor is not removable and is
always in the circuit. A diode prevents current from backfeeding.
Physical interface
The dimensions of the J4A connector mounted on the main PCB to
interconnect the drives are shown in Figure 14. It is a 24-pin, 12-jumper
position gold header type connector; however, pins 13, 14, 21, and 22 are not
installed. Only pins 23 and 24 are used for connecting the reference index
signal cable, as shown in Figure 12. Pin 23 is ground, and pin 24 is SSREF+.
.079
(2 mm)

Figure 14. ST410800 configuration select header specification

Grounding

Signal ground (PCB) and HDA ground are connected together in the Elite 9
family drives—do not separate this connection. Maximizing the conductive
contact area between HDA ground and system ground may reduce radiated
emissions. If you do not want the system chassis to be connected to the HDA/
PCB ground, you must provide a nonconductive (electrically isolating)
method of mounting the drive in the host equipment; however, this may
increase radiated emissions and is the system designer's responsibility.
.945
(24 mm)
.079 (2 mm)
J4A
.866
(22 mm)
43