UC5602 SCSI Active Terminator FEATURES DESCRIPTION • Complies with SCSI, SCSI-2 Standards • 10pF Channel Capacitance During Disconnect • The UC5602 is a pin compatible version of its predecessor, the UC5601, and is targeted for high volume applications which require active termination, but not the high performance of the UC5601. The major differences are relaxed output current and termination tolerances, and the absence of low side clamps. Active Termination for 18 Lines • Logic Command Disconnects all Termination Lines • Low Supply Current in Disconnect Mode • Trimmed Regulator for Accurate Termination Current • Current Limit and Thermal Shutdown Protection • 110 Ohm Termination • Meets SCSI Hot Plugging The UC5602 provides 18 lines of active termination for a SCSI (Small Computer Systems Interface) parallel bus. The SCSI-2 standard recommends active termination at both ends of the cable segment, and SCSI-3 will make it a requirement. The UC5602 provides a disconnect feature which, when opened or driven high, will disconnect all terminating resistors, and disables the regulator; greatly reducing standby power. The output channels remain high impedance even without Termpwr applied. Internal circuit trimming is utilized, first to trim the impedance to a 7% tolerance; and then most importantly, to trim the output current 7% tolerance, as close to the max SCSI as possible, which maximizes noise margin in fast SCSI operation. Other features include thermal shutdown, current limit, and 40mA of active negation sink current capability. This device is offered in low thermal resistance versions of the industry standard 28 pin wide body SOIC and PLCC, as well as a 24 pin DIL plastic package. BLOCK DIAGRAM UDG-94052 10/94 Circuit Design Patented UC5602 ABSOLUTE MAXIMUM RATINGS CONNECTION DIAGRAMS Termpwr Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +7V Regulator Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5A 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4.0V to 5.25V Signal Line Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +3V Disconnect Input Voltage . . . . . . . . . . . . . . . . . . 0V to Termpwr * QP package pins 12 - 18 serve as both heatsink and signal ground. SOIC-28 (Top View) DWP Package DIL-24 (Top View) N 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 UC5602 ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = 0°C to 70°C. TRMPWR = 4.75V, DISCNCT = 0V. TA = TJ. PARAMETER Supply Current Section Termpwr Supply Current TEST CONDITIONS MIN All termination lines = Open All termination lines = 0.5V Power Down Mode DISCNCT = Open Output Section (Termination Lines) Termination Impedance ∆ILINE = -5mA to -15mA Output High Voltage Max Output Current Max Output Current Output Leakage Output Capacitance Regulator Section Regulator Output Voltage Line Regulation Load Regulation Drop Out Voltage Short Circuit Current Sinking Current Capability Thermal Shutdown Disconnect Section Disconnect Threshold Threshold Hysteresis Input Current TJ = 25°C 0°C < TJ < 70°C VTRMPWR = 4V (Note 1) TJ = 25°C 0°C < TJ < 70°C VLINE = 0.5V TJ = 25°C 0°C < TJ < 70°C VLINE = 0.5V, TRMPWR = 4V (Note 1) TJ = 25°C 0°C < TJ < 70°C TRMPWR = 0V to 5.25V VLINE = 0 to 4V REG = 0V VLINE = 5.25V DISCNCT = 4V TRMPWR = 0V to 5.25V, REG = Open VLINE = 0V to 5.25V DISCNCT = Open (Note 2) 102 97 2.6 2.55 -19.5 -18.5 -18.0 -17.0 TJ = 25°C 0°C < TJ < 70°C 2.7 2.55 TRMPWR = 4V to 6V IREG = 0 to -400mA All Termination Lines = 0.5V VREG = 0V VREG = 3.5V MAX UNITS 20 400 100 29 435 150 mA mA µA 110 10 118 129 3.1 3.2 -22.4 -22.4 -22.4 -22.4 400 100 400 Ω Ω V V mA mA mA mA nA µA nA 10 13 pF 2.9 3.1 3.2 20 50 1.2 -850 V V mV mV V mA mA °C 1.7 V mV µA 2.9 -21.4 -21.5 10 -450 20 1.1 DISCNCT = 0V TYP 10 20 1.0 -650 40 170 1.4 100 150 200 Note 1: Measuring each termination line while other 17 are low (0.5V). Note 2: Guaranteed by design. Not 100% tested in production. THERMAL DATA DWP package: (see packaging section of UICC data book for more details on thermal performance) Thermal Resistance Junction to Leads, θjL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18°C/W Thermal Resistance Junction to Ambient, θja . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33°-43°C/W N package: Thermal Resistance Junction to Leads, θjL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50°C/W Thermal Resistance Junction to Ambient, θja . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95°-105°C/W QP package: Thermal Resistance Junction to Leads, θjL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15°C/W Thermal Resistance Junction to Ambient, θja . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30°-40°C/W Note: The above numbers for θjL are maximums for the limiting thermal resistance of the package in a standard mounting configuration. The θja numbers are meant to be guidelines for the thermal performance of the device/pc-board system. All of the above numbers assume no ambient airflow. 3 UC5602 UDG-94053 Typical SCSI Bus Configuration Using the UC5602 A Look at the Response of a SCSI-2 Cable Figure 1 shows a single line of a SCSI cable. The driver is an open colletor type which when asserted pulls low, and when negated the termination resistance serves as the pull-up. Figure 2 shows a worst case scenario of mid cable deassertion with a close proximity receiver. The voltage VSTEP is defined as: VSTEP = VOL +IO Z0 VOL = IO = Z0 = Driver Output Low Voltage Current from Receiving Terminator Cable Characteristic Impedance IO = UDG-94054 Figure 1. A Single Line of a SCSI Cable VREG − VOL 110 In the pursuit of higher data rates, sampling could occur during this step portion, therefore it is important to ensure that the step is as high as possible to get the most noise margin. For this reason the UC5602 is trimmed so that the output current (IO) is as close as possible to the SCSI max current spec of 22.4mA. The Termination impedance is initially trimmed on the IC to 110 ohms typical, then the regulator voltage is trimmed for the highest output current to within 22.4mA. UDG-94055 Figure 2. A Typical Response of a SCSI Cable 4 UC5602 Max Output Current vs. Temperature VREF vs. Temperature VREF vs. VIN Output Impedance vs. Temperature UNITRODE INTEGRATED CIRCUITS 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. (603) 424-2410 • FAX (603) 424 3460 5 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. 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