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Texas Instruments has introduced the industry's first nine-channel single-ended SCSI (Small Computer System Interface) transceiver integrated with active termination.
The new device reduces noise associated with high-speed SCSI single-ended parallel data buses to provide more accurate and reliable data communication.
SCSI is a high-speed, daisy-chained I/O bus typically used in computer systems to connect peripheral devices to the system's CPU. When designers increase the speed of SCSI I/O subsystems, noise and termination line effects also can increase, thus exceeding noise margins and corrupting data carried on the bus.
"This new device from TI combines a full set of analog solutions in an 'analog-friendly' semiconductor process," said Kevin Gingerich, strategic marketing manager at TI.
Designated the SN75LBC968, the transceiver features low capacitance of only 13.5 picoFarads (pF), well within the SCSI specification's limit of 25 pF per node on the bus. High node capacitance decreases the signal amplitude and chance of data errors on the SCSI bus.
In addition, the driver outputs of the 'LBC968 have active signal negation, which improves the negation signal strength on heavily loaded buses.
The 'LBC968 limits a transmission line's slew rate to minimize noise coupling or cross-talk interference from adjacent lines. The accurate input voltage threshold levels and wide hysteresis of the receivers provide large noise margins and a noise filter that rejects all noise pulses shorter than 5 ns.
The controller-side I/Os of the 'LBC968 are compatible with low-voltage 3.3-V logic, providing an effective bridge for designers upgrading a computer system to low-voltage logic using the 5-V SCSI bus as the I/O subsystem. The device's integrated current-mode termination provides the highest level of termination current to the bus allowed by the specification.
The SN75LB968 supports the SCSI standard of 10 million data transfers per second. Each of the nine identical channels on the device conform to the requirements of SCSI-2 (ANSI X3.131- 1994) and the proposed SCSI-3 specs.
For increased bus data reliability and performance up to 25 meters, TI offers the SN75LBC976 Differential SCSI Nine-Channel Transceiver.
Both devices are available now Texas Instruments and authorized distributors . They are packaged in the space-saving 56-pin SSOP, fabricated with TI's LinBiCMOS process, which assures low power consumption and low voltage.
The SN75LB968 has a suggested 1,000-piece resale price of $8.40. The 'LBC976 is available for $13.40.
January 1995, vol. 12, no.1