UCC5611 18-Line 3-5 Volt SCSI Active Terminator, Reverse Disconnect FEATURES DESCRIPTION • Complies with SCSI, SCSI-2, SCSI-3 and FAST-20 (Ultra) Standards • 2.75V to 7V Operation The UCC5611 provides 18 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 segment. • 1.8pF Channel Capacitance during Disconnect • 1µA Supply Current in Disconnect Mode • 110 Ohm/2.5k Programmable Termination • Completely Meets SCSI Hot Plugging • −650mA 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 UCC5611 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 2.75V 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 1µA, which makes the IC attractive for battery powered systems. The UCC5611 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 UCC5611 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 high, and disconnected when low. 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 high, and disconnected when driven low. continued BLOCK DIAGRAM UDG-94131-1 Circuit Design Patented 3/97 UCC5611 Description Continued The power amplifier output stage allows the UCC5611 to source full termination current and sink active negation current when all termination lines are actively negated. 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-20 SCSI operation. The UCC5611 is pin for pin compatible with Unitrode’s other 18 line SCSI terminators, except that DISCNCT is now active low, allowing lower capacitance and lower voltage upgrades to existing systems. The UCC5611, 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 28 pin wide body SOIC, 24 pin wide body DIP and 28 pin PLCC. Internal circuit trimming is utilized, first to trim the 110 ABSOLUTE MAXIMUM RATINGS CONNECTION DIAGRAMS Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +7V Regulator Output Current . . . . . . . . . . . . . . . . . . Self-regulating 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. PLCC-28 (Top View) QP Package RECOMMENDED OPERATING CONDITIONS Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . 2.75V to 5.25V Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +5V Disconnect Input Voltage . . . . . . . . . . . . . . . . . . 0V to Termpwr * QP package pins 12 - 18 serve as both heatsink and signal ground. DIL-24 (Top View) N or J Package SOIC-28 (Top View) DWP Package * DWP package pin 28 serves as signal ground; pins 7, 8, 9, 20, 21, 22 serve as heatsink/ground. Note: Drawings are not to scale. 2 UCC5611 ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = 0°C to 70°C. TRMPWR = 3.3V, DISCNCT = 3.3V, RDISCNCT = 0 ohms. TA = TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS Supply Current Section Termpwr Supply Current Power Down Mode All termination lines = Open 1 2 mA All termination lines = 0.2V 415 435 mA DISCNCT = 0V 0.5 5 µA Output Section (110 ohms - Terminator Lines) Terminator Impedance (Note 4) 102.3 110 117.7 Ohms Output High Voltage TRMPWR = 3V (Note 1) 2.5 2.7 3.0 V Max Output Current VLINE = 0.2V, TJ = 25°C −22.1 −23 −24 mA −21 −23 −24 mA VLINE = 0.2V VLINE = 0.2V, TRMPWR = 3V, TJ = 25°C (Note 1) VLINE = 0.2V, TRMPWR = 3V (Note 1) −20.2 −23 −24 mA −19 −23 −24 mA −22.4 mA Output Leakage DISCNCT = 0V, TRMPWR = 0V to 5.25V 10 400 nA Output Capacitance DISCNCT = 0V, DWP Package (Note 2, 3) 1.8 2.5 pF 2 2.5 3 kΩ VLINE = 0.5V Output Section (2.5k ohms - Terminator Lines) (RDISCNCT = 80k ohms) Terminator Impedance Output High Voltage TRMPWR = 3V (Note 1) 2.5 2.7 3.0 V Max Output Current VLINE = 0.2V −0.7 −1 −1.4 mA VLINE = 0.2V, TRMPWR = 3V (Note 1) −0.6 −1 −1.5 mA Output Leakage DISCNCT = 0V, TRMPWR = 0 to 5.25V 10 400 nA Output Capacitance DISCNCT = 0V, DWP Package (Note 2, 3) 1.8 2.5 pF Regulator Section Regulator Output Voltage 5.25V > TRMPWR > 3V Drop Out Voltage All Termination Lines = 0.2V 2.5 2.7 3.0 V 0.1 0.2 V Short Circuit Current VREG = 0V Sinking Current Capability VREG = 3V −450 −650 −800 mA 200 400 800 mA Thermal Shutdown (Note 2) 170 °C Thermal Shutdown Hysteresis (Note 2) 10 °C Disconnect Section Disconnect Threshold RDISCNCT = 0 & 80k Input Current DISCNCT = 3.3V Note 1: Note 2: Note 3: Note 4: 0.8 Measuring each termination line while other 17 are low (0.2V). Guaranteed by design. Not 100% tested in production. Output Capacitance is measured at 0.5V. Tested by measuring IOUT with VOUT = 0.2V and VOUT = VREG - 0.1V then calculating the impedance. 3 1.5 2.0 V 30 50 µA UCC5611 APPLICATION INFORMATION UDG-94132 Figure 1: Typical SCSI Bus Configurations Utilizing A UCC5611 Device UNITRODE CORPORATION 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. (603) 424-2410 • FAX (603) 424-3460 4 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. 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