UCC5614 9-Line 3-5 Volt Low Capacitance SCSI Active Terminator FEATURES DESCRIPTION • Complies with SCSI, SCSI-2 and SCSI-3 Standards • 2.7V to 7V Operation 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. • 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 Protection 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 termination 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 integrity 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 termination is typically used in short bus applications. When driving the TTL compatible DISCNCT pin directly, the 110 ohm termination is connected 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. continued BLOCK DIAGRAM UDG-94029-1 Circuit Design Patented 12/94 UCC5614 Description Continued 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. 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. 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 VTRMPWR = 0V or open. 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. Internal circuit trimming is utilized, first to trim the 110 ohm termination impedance to a 7% tolerance, and then ABSOLUTE MAXIMUM RATINGS RECOMMENDED OPERATING CONDITIONS Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +7V Regulator Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . 0.6A Storage Temperature . . . . . . . . . . . . . . . . . . . −65°C to +150°C Operating Temperature . . . . . . . . . . . . . . . . . −55°C to +150°C Lead Temperature (Soldering, 10 Sec.) . . . . . . . . . . . . . +300°C Unless otherwise specified all voltages are with respect to Ground. Currents are positive into, negative out of the specified terminal. Consult Packaging Section of Unitrode Integrated Circuits databook for thermal limitations and considerations of packages. Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . 2.7V to 5.25V Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +5V Disconnect Input Voltage . . . . . . . . . . . . . . . . . . 0V to Termpwr CONNECTION DIAGRAMS DIL-16 (Top View) N or J Package ZIP-16 (Top View) Z Package Note: Drawings are not to scale. 2 UCC5614 CONNECTION DIAGRAMS (cont.) SOIC-16 (Top View) DP Package TSSOP-24 (Top View) PWP Package * DP package pin 5 serves as signal ground; pins 4, 12, 13 serve as heatsink/ground. * PWP package pin 5 serves as signal ground; pins 6, 7, 8, 9, 17, 18, 19, and 20 serve as heatsink/ground. Note: Drawings are not to scale. ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = 0°C to 70°C. TRMPWR = 3.3V, DISCNCT = 0V, RDISCNCT= 0 ohms. TA = TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS All termination lines = Open 1 2 mA All termination lines = 0.2V 210 218 mA 0.5 5 µA Supply Current Section Termpwr Supply Current Power Down Mode DISCNCT = Termpwr Output Section (110 ohms - Terminator Lines) Terminator Impedance Output High Voltage Max Output Current (Note 1) VLINE = 0.2V TJ = 25°C VLINE = 0.2V VLINE = 0.2V, TRMPWR = 3V TJ = 25°C (Note 1) VLINE = 0.2V, TRMPWR = 3V (Note 1) 102.3 110 2.5 2.7 117.7 Ohms 3.0 V −22.1 −23 −24 mA −21 −23 −24 mA −20.2 −23 −24 mA −19 −23 −24 mA Output Leakage DISCNCT = 2.4V, TRMPWR = 0V to 5.25V 10 −22.4 400 mA nA Output Capacitance DISCNCT = 2.4V (Note 2) (DP Package) 1.8 2.5 pF VLINE = 0.5V Output Section (2.5k ohms - Terminator Lines) (RDISCNCT = 80k ohms) Terminator Impedance Output High Voltage Max Output Current Output Leakage Output Capacitance 2 2.5 3 kΩ 2.5 2.7 3.0 V VLINE = 0.2V −0.7 −1 −1.4 mA VLINE = 0.2V, TRMPWR = 3V (Note 1) −0.6 −1 −1.5 mA 10 1.8 400 2.5 nA pF 2.7 3.0 V 0.1 0.2 V −400 −800 mA TRMPWR = 3V (Note 1) DISCNCT = 2.4V, TRMPWR = 0 to 5.25V DISCNCT = 2.4V (Note 2) (DP Package) Regulator Section Regulator Output Voltage 5.25V > TRMPWR > 3V Drop Out Voltage All Termination Lines = 0.2V Short Circuit Current VREG = 0V 2.5 −200 3 UCC5614 ELECTRICAL CHARACTERISTICS (cont.) Unless otherwise stated, these specifications apply for TA = 0°C to 70°C. TRMPWR = 3.3V, DISCNCT = 0V, RDISCNCT= 0 ohms. TA = TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS 200 800 mA °C Regulator Section (cont.) Sinking Current Capability VREG = 3V Thermal Shutdown (Note 2) 400 170 Thermal Shutdown Hysteresis (Note 2) 10 °C Disconnect Section Disconnect Threshold RDISCNCT = 0 & 80k 0.8 Input Current DISCNCT = 0V Note 1: Measuring each termination line while other 8 are low (0.2V). Note 2: Guaranteed by design. Not 100% tested in production. APPLICATION INFORMATION Figure 1: Typical SCSI Bus Configurations Utilizing 2 UCC5614 Devices Figure 2: Typical Wide SCSI Bus Configurations Utilizing 3 UCC5614 Devices. UNITRODE INTEGRATED CIRCUITS 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. 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