The UCC5614 provides 9 lines of active termination for a SCSI (Small
Computer Systems Interface) parallel bus. The SCSI standard recommends active termination at both ends of the cable.
The UCC5614 is ideal for high performance 3.3V SCSI systems. The key
features contributing to such low operating voltage are the 0.1V drop out
regulator and the 2.7V reference. The reduced reference voltage was
necessary to accommodate the lower termi nation current dictated in the
SCSI-3 specification. During disconnect the supply current is typically
only 0.5µA, which makes the IC attractive for battery powered systems.
The UCC5614 is designed with an ultra low channel capacitance of
1.8pF, which eliminates effects on signal integri ty from disconnected terminators at interim points on the bus.
The UCC5614 can be programmed for either a 110 ohm or 2.5k ohm termination. The 110 ohm termination is used for standard SCSI bus lengths
and the 2.5k ohm terminati on is typically used in short bus applications.
When driving the TTL compatible DISCNCT pin directly, the 110 ohm termination is con nected when the DISCNCT pin is driven low, and disconnected when driven high. When the DISCNCT pin is driven through an
impedance between 80k and 150k, the 2.5k ohm termination is connected when the DISCNCT pin is driven low, and disconnected when
driven high.
UCC5614
9-Line 3-5 Volt Low Cap ac ita nc e SCSI Activ e Termin at or
FEATURES DESCRIPTI ON
BLOCK DIAGRAM
Circuit Design Patented
• Complies with SCSI, SCSI-2 and
SCSI-3 Standards
• 2.7V to 7V Operation
• 1.8pF Channel Capacitance during
Disconnect
• 0.5µA Supply Current in Disconnect
Mode
• 110 Ohm/2.5k Programmable
Termination
• Completely Meets SCSI Hot Plugging
• -400mA Sourcing Current for
Termination
• +400mA Sinking Current for Active
Negation Drivers
• Trimmed Termination Current to 4 %
• Trimmed Impedance to 7%
• Current Limit and Thermal Shutdown
Protectio n
continue d
12/94
UDG-94029-1
UCC5614
The power amplifier output stage allows the UCC5614 to
source full termination current and sink active negation
current when all termination lines are actively negated.
The UCC5614 is pin for pin compatible with Unitrode’s
other 9 line SCSI terminators, allowing lower capacitance
and lower voltage upgrades to existing systems. The
UCC5614, as with all Unitrode terminators, is completely
hot pluggable and appears as high impedance at the terminating channels with V
TRMPWR = 0V or open.
Internal circuit trimming is utilized, first to trim the 110
ohm termination impedance to a 7% tolerance, and then
most importantly, to trim the output current to a 4% tolerance, as close to the max SCSI-3 spec as possible,
which maximizes noise margin in fast SCSI operation.
Other features include thermal shutdown and current
limit.
This device is offered in low thermal resistance versions
of the industry standard 16 pin narrow body SOIC, 16 pin
ZIP (Zig-Zag In Line package), 24 pin TSSOP and 28 pin
PLCC.
ABSOLUTE MAXIMUM RATINGS
Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V
Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +7V
Regulator Output Curren t. . . . . . . . . . . . . . . . . . . . . . . . . . 0.6A
Storage Temperature . . . . . . . . . . . . . . . . . . . −−65°C to +150°C
Operating Tem pe ratur e . . . . . . . . . . . . . . . . . −−55°C to +150°C
Lead Temperat ure (Solde ring, 10 Sec .). . . . . . . . . . . . . +300°C
RECOMMENDED OPERATING CONDITIONS
Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . 2.7V to 5.25V
Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +5V
Disconnect Input Voltage . . . . . . . . . . . . . . . . . . 0V to Termpwr
Description Continued
Unless otherwise specified all volta ges ar e with respect to
Ground. Cur rents are positive into, negative out of the specified terminal.
Consult Packaging Sectio n of Unitr ode Int egr at ed Circ uits databook for thermal limitations and con sider at ions of pack ages .
CONNECTION DIAG RAMS
DIL-16 (Top View )
N or J Package
ZIP-16 (Top View)
Z Package
Note: Drawings are not to scale.
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