Seagate Cheetah 73 ST173404LC, Product Manual

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54 Cheetah 73 Product Manual, Rev. D
To minimize discontinuances and signal reflections, cables of different impedances should not be used in the
same bus. Implementations may require trade-offs in shielding effectiveness, cable length, number of loads
and spacing, transfer rates, and cost to achieve satisfactory system operation. If shielded and unshielded
cables are mixed within the same SCSI bus, the effect of impedance mismatch must be carefully considered.
Proper impedance matching is especially important in order to maintain adequate margin at FAST-20, FAST-40,
and FAST-80 SCSI transfer rates.
Note. For LVD operation, twisted pair cables are recommended. For LVD Fast-40 operation, twisted pair
cables are strongly recommended. For Fast-80 operation, twisted pair cables are required.
ST173404LC/LCV:
The 80-pin connector option is intended for use on drives that plug directly into backplane connector in the host
equipment. In such installations, all backplane wiring segments are subject to the electromagnetic concepts
presented in Standard T10/1302D, section 6. For LC/LCV model drives, installations with connectors on cables
are not recommended.
9.6.4 Mating connectors
Part numbers for the different type connectors that mate with the various Cheetah 73 I/O connectors are given
in the sections following.
9.6.4.1 Mating connectors for LW/LWV drives
The nonshielded cable connector shall be a 68 conductor connector consisting of two rows of 34 male contacts
with adjacent contacts 0.050 inch (1.27 mm) apart.
Recommended mating flat cable connector part numbers are:
[1] See Figure 18.
The drive device connector is a nonshielded 68 conductor connector consisting of two rows of 34 female pins
with adjacent pins 50 mils apart. The connector is keyed by means of its shape (see Figure 19).
9.6.4.2 Mating connectors for LC and LCV model drives
The nonshielded connector shall be an 80-conductor connector consisting of two rows of 40 contacts with adja-
cent contacts 50 (1.27 mm) mils apart (see Figure 20). I/O connection using a cable is not recommended. The
length and size of the host equipment DC power carrying conductors from the DC power source to the host
equipment 80-pin disk drive interface connector(s) should be strictly designed according to proper power trans-
mission design concepts. No possibility for the equipment user to attach an 80-pin cable/connector should be
allowed, since the length of the DC power carrying conductors could not be controlled and therefore could
become too long for safe power transmission to the drive. Daisy-chain 80-conductor cables should especially
not be allowed, since the power-carrying conductors on the 80-conductor interface were not intended to sup-
port a series of drives.
To insure that both drive connector and host equipment mating connector mate properly, both drive connector
and host equipment mating connector must meet the provisions of “SFF-8046 Specification for 80-pin connec-
tor for SCSI Disk Drives.”
Amp Model 786096-7 Female, 68-pin, panel mount
Amp Model 786090-7 Female, 68-pin, cable mount
Amp Model 749925-5 (50 mil conductor centers, 28 or 30 AWG wire)
Use two, 34 conductor, 50 mil center flat cable with this connector.
This type connector can only be used on cable ends. [1]
Amp Model 88-5870-294-5 W/O Strain Relief (25 mil conductor centers, 30 AWG wire).
Use either on cable ends or in cable middle section for daisy-chain
installations [1].
Amp Model 1-480420-0 Power connector 4 circuit housing
Berg 69307-012 12-position, 2 x 6, 2 mm receptacle housing