UCC5638 Multimode SCSI 15 Line Terminator FEATURES DESCRIPTION • Auto Selection Single Ended (SE) or Low Voltage Differential (LVD) Termination The UCC5638 Multimode SCSI Terminator provides a smooth transition into the next generation of the SCSI Parallel Interface (SPI-2). It automatically senses the bus, via DIFFB, and switches the termination to either single ended (SE) or low voltage differential (LVD) SCSI, dependent on which type of devices are connected to the bus. The UCC5638 can not be used on a HVD, EIA485, differential SCSI bus. If the UCC5638 detects a HVD SCSI device, it switches to a high impedance state. • Meets SCSI-1, SCSI-2, SCSI-3, SPI, Ultra (Fast-20), Ultra2 (SPI-2 LVD SCSI) and Ultra3/Ultra160 Standards • 2.7V to 5.25V Operation • Differential Failsafe Bias • Thermal packaging for low junction temperature and better MTBF. The Multimode terminator contains all functions required to terminate and auto detect and switch modes for SPI-2 bus architectures. Single Ended and Differential impedances and currents are trimmed for maximum effectiveness. Fail Safe biasing is provided to insure signal integrity. Device/Bus type detection circuitry is integrated into the terminator to provide automatic switching of termination between single ended and LVD SCSI and a high impedance for HVD SCSI. The multimode function provides all the performance analog functions necessary to implement SPI-2 termination in a single monolithic device. The UCC5638 is offered in a 48 pin LQFP package for a temperature range of 0°C to 70°C. BLOCK DIAGRAM (NOISE LOAD) HIGH POWER DIFFERENTIAL 2.15V DIFFB REF 1.3V LOW VOLTAGE DIFFERENTIAL 34 0.6V 1.3V DIFFSEN 12 L1– 11 L1+ 2 L15– 1 L15+ –15mA ≤ ISOURCE ≤ –5mA 50µA ≤ ISINK ≤ 200µA SINGLE ENDED 110 REF 2.7V SOURCE/SINK REGULATOR 124 56mV 52.5 – + REF 1.25V 56mV 52.5 + – ALL SWITCHES MODE UP SE DOWN LVD OPEN DISCNCT 10µA SE GND SWITCH 110 124 DISCNCT 36 56mV 52.5 – + 56mV + – TRMPWR 35 3 52.5 SE GND SWITCH 27 HS/GND HS/GND 4-9 28-33 GND 10 REG 4.7µF . UDG-98063 SLUS271A - FEBRUARY 2000 UCC5638 CONNECTION DIAGRAMS ABSOLUTE MAXIMUM RATINGS TRMPWR Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6V Signal Line Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to 5V Package Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2W Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . . –55°C to +150°C Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C Recommended Operating Conditions . . . . . . . . . 2.7V to 5.25V (TOP VIEW) FQP Package HS/GND HS/GND HS/GND HS/GND HS/GND HS/GND REG Currents are positive into negative out of the specified terminal. Note: Consult Packaging Section of Databook for thermal limitations and considerations of package. L1+ TRMPWR L15– L1– L15+ 12 11 RECOMMENDED OPERATING CONDITIONS TRMPWR Voltage . . . . . . . . . . . . . . . . . . . . . . . . 2.7V to 5.25V Temperature Ranges . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C 10 9 8 7 6 5 4 2 3 1 L2+ 13 48 L14– L2– 14 47 L14+ L3+ 15 46 L13– L3– 16 45 L13+ L4+ 17 44 L12– L4– 18 43 L12+ L5+ 19 42 L11– L5– 20 41 L11+ L6+ 21 40 L10– L6– 22 39 L10+ L7+ 23 38 L9– L7– 24 25 26 37 L9+ 27 28 29 30 31 32 33 34 35 36 DISCNCT L8+ L8– GND HS/GND DIFFSENS HS/GND HS/GND HS/GND DIFFB HS/GND HS/GND ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = TJ = 0°C to 70°C, TRMPWR = 3.3V. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS TRMPWR Supply Current Section TRMPWR Supply Current LVD SCSI Mode 20 25 mA SE SCSI Mode 1.6 10 mA Disabled Terminator 250 400 A Regulator Section 1.25V Regulator LVD SCSI Mode 1.15 1.25 1.35 V 1.25V Regulator Source Current VREG= 0V –375 –700 –1000 mA 1.25V Regulator Sink Current VREG= 3.3V 170 300 700 mA 1.3V Regulator Diff Sense 1.2 1.3 1.4 V 1.3V Regulator Source Current VREG= 0V –15 –5 mA 1.3V Regulator Sink Current VREG= 3.3V 50 2.7V Regulator SE SCSI Mode 2.5 2.7 200 3.0 V A 2.7V Regulator Source Current VREG= 0V –375 –700 –1000 mA 2.7V Regulator Sink Curren VREG= 3.3V 170 300 700 mA 100 105 110 110 150 Differential Termination Section Differential Impedance Common Mode Impedence (Note 2) Differential Bias Voltage 100 Common Mode Bias Output Capacitance 1.15 Single Ended Measurement to Ground (Note 1) 2 165 125 1.25 mV 1.35 V 3 pF UCC5638 ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = TJ = 0°C to 70°C, TRMPWR = 3.3V. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS 102.3 110 117.7 Signal Level 0.2V, All Lines Low –21 –24 –25.4 mA Signal Level 0.5V –18 –22.4 mA 400 nA 3 pF Single Ended Termination Section Impedance Termination Current Z = (VLX − 0 . 2V ) ILX , (Note 3) Output Leakage Output Capacitance Single Ended Measurement to Ground (Note 1) Single Ended GND SE Impedance I= 10mA 20 60 Disconnect and Diff Buffer Input Section DISCNCT Threshold 0.8 DISCNCT Input Current 2.0 10 Diff Buffer Single Ended to LVD Threshold 30 V A 0.5 0.7 V Diff Buffer LVD to HPD Threshold 1.9 2.4 V DIFFB Input Current –10 10 A Note 1: Guaranteed by design. Not 100% tested in production. Note 2: Line+ (positive) tied to Line– (negative); 1. 2V [I(VCM max) – I(VCM min)] Note 3: VLX= Output voltage for each terminator minus output pin (L1– through L15–) with each pin unloaded. ILX = Output current for each terminator minus output pin (L1– through L15–) with the minus output pin forced to 0.2V. PIN DESCRIPTIONS DIFFB: Diff sense filter pin should be connected at a 0.1 F capacitor. LINEn–: Signal line active line for single ended or negative line in differential applications for the SCSI bus. DIFFSENS: The SCSI bus Diff Sense line to detect what types of devices are connected to the SCSI bus. LINEn+: Ground line for single ended or positive line for differential applications for the SCSI bus. DISCNCT: Disconnect pin shuts down the terminator when it is not at the end of the bus. The disconnect pin low enables the terminator. REG: Regulator bypass pin, must be connected to a F capacitor. TRMPWR: VIN 2.7V to 5.25V supply, bypass near the terminator with a 4.7 µF capacitor to ground. Note: In Disconnect Mode, the comparitor set powers down for low idle current. 3 UCC5638 APPLICATION INFORMATION The UCC5638 is a Multi-mode active terminator with selectable single ended (SE) and low voltage differential (LVD) SCSI termination integrated into a monolithic component. Mode selection is accomplished with the “diff sense" signal. and 4 mil spacing between the runs within a pair, and a minimum of 8 mil spacing to the next pair. This spacing between the pairs reduces potential crosstalk. Beware of feed-throughs and each through hole connection adds a lot of capacitance. Standard power and ground plane spacing yields about 1pF to each plane. Each feedthrough will add about 2.5pF to 3.5pF. Enlarging the clearance holes on both power and ground planes can reduce the capacitance and opening up the power and ground planes under the connector can reduce the capacitance for through hole connector applications. Microstrip technology is normally too low of impedance and should not be used. It is designed for 50 rather than 120 differential systems. The diff sense signal is a three level signal, which is driven at each end of the bus by one active terminator. An LVD SCSI or multi-mode terminator drives the diff sense line to 1.3 V. If diff sense is at 1.3 V, then bus is in LVD SCSI mode. If a single ended SCSI device is plugged into the bus, the diff sense line is shorted to ground. With diff sense shorted to ground, the terminator changes to single ended mode to accommodate the SE device. If an HVD SCSI device is plugged in to the bus, the diff sense line is pulled high and the terminator shuts down. Capacitance balance is critical for Ultra2 and Ultra3/Ultra160. The balance capacitance standard is 0.5pF per line with the balance between pairs of 2pF. The components are designed with very tight balance, typically 0.1pF between pins in a pair and 0.3pF between pairs. Layout balance is critical, feed-throughs and etch length must be balanced, preferably no feed-throughs would be used. Capacitance for devices should be measured in the typical application, material and components above and below the circuit board effect the capacitance. The diff sense line is driven and monitored by the terminator through a 50Hz noise filter at the DIFFB input pin. A set of comparators, that allow for ground shifts, determine the bus status as follows. Any diff sense signal below 0.5V indicates single ended, between 0.7V and 1.9V is LVD SCSI and above 2.2V is HVD SCSI. In the single ended mode, a multi-mode terminator has a 110 terminating resistor connected to a 2.7V termination voltage regulator. The 2.7V regulator is used on all Unitrode terminators designed for 3.3V systems. This requires the terminator to operate in specification down to 2.7V TRMPWR voltage to allow for the 3.3V supply tolerance, an unidirectional fusing device and cable drop. At each L+ pin, a ground driver drives the pin to ground, while in single ended mode. The ground driver is specially designed so it will not effect the capacitive balance of the bus when the device is in LVD SCSI or disconnect mode. The device requirements call for 0.5pF balance on the lines of a differential pair. The terminator capacitance has to be a small part of the capacitance imbalance. Multi-mode terminators need to consider power dissipation; the UCC5638 is offered in a power package with heat sink ground pins. These heat sink/ground pins are directly connected to the die mount paddle under the die and conduct heat from the die to reduce the junction temperature. These pins need to be connected to etch area or a feed-through per pin connecting to the ground plane layer on a multi-layer board. In 3.3V TRMPWR systems, the UCC3912 should be used to replace the fuse and diode. This reduces the voltage drop, allowing for cable drop to the far end terminator. 3.3V battery systems normally have a 10% tolerance. The UCC3912 is 150mV drop under LVD SCSI loads, allowing 150mV drop in the cable system. All Unitrode LVD SCSI and multi-mode terminators are designed for 3.3V systems, operating down to 2.7V. Layout is very critical for Ultra2 and Ultra3/Ultra160 systems. Multi-layer boards need to adhere to the 120 impedance standard, including connector and feed-through. This is normally done on the outer layers with 4 mil etch 4 UCC5638 TYPICAL APPLICATION TERMPWR 3 L1+ L1+ L1– L1– TRMPWR TRMPWR CONTROL LINES (9) L9+ L9+ L9– L9– L10+ L10+ L10– L10– 3 TRMPWR 4 BITS OF THE HIGH BYTE L15+ L15+ L15– L15– 36 DISCNCT DISCNCT 36 DIFFSENSE 35 REG DIFF B 10 34 35 DIFFSENSE 20k 4.7µF . 0.1µF . DIFF B REG 34 10 20k 0.1µF . 270k 4.7µF 4.7µF . 4.7µF L1+ L1+ L1– DATA LINES (15) 3 L1– HIGH BYTE 4 BITS PLUS PARITY DATA LINES (15) L5+ L5+ L5– L5– TRMPWR TRMPWR L6+ L6+ L6– L6– 3 LOW BYTE 8+ PARITY 36 DISCNCT L14+ L14+ L14– L14– DISCNCT 36 REG DIFF B DIFF B REG 10 34 34 10 4.7µF . 4.7µF SCSI CONTROLLER DIFFSENS UDG-98064 Note: A 220k resistor is added to ground to insure the transceivers will come up in single-ended mode when no terminator is enabled. The controller DIFFSENS ties to the DIFFB pin on the terminators, only one RC network should be on a device. UNITRODE CORPORATION 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. (603) 424-2410 • FAX (603) 424-3460 5