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| UCC5638 Multimode SCSI 15 Line Terminator FEATURES * Auto Selection Single Ended (SE) or Low Voltage Differential (LVD) Termination * 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. DESCRIPTION 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. 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 0C to 70C. BLOCK DIAGRAM (NOISE LOAD) 2.15V DIFFB 34 0.6V HIGH POWER DIFFERENTIAL LOW VOLTAGE DIFFERENTIAL SINGLE ENDED 110 SOURCE/SINK REGULATOR 124 REF 1.25V ALL SWITCHES MODE UP SE DOWN LVD OPEN DISCNCT 56mV -+ 56mV +- SE GND SWITCH 110 124 52.5 11 L1+ 52.5 12 L1- REF 1.3V -15mA ISOURCE -5mA 50A ISINK 200A 1.3V 35 DIFFSEN REF 2.7V 10A DISCNCT 36 56mV -+ 56mV +- 52.5 2 52.5 1 L15+ L15- TRMPWR 3 SE GND SWITCH HS/GND 27 GND 4-9 HS/GND 28-33 10 REG 4.7F . UDG-98063 SLUS271A - FEBRUARY 2000 UCC5638 ABSOLUTE MAXIMUM RATINGS TRMPWR Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6V Signal Line Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to 5V Package Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2W Storage Temperature . . . . . . . . . . . . . . . . . . . -65C to +150C Junction Temperature . . . . . . . . . . . . . . . . . . . -55C to +150C Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300C Recommended Operating Conditions . . . . . . . . . 2.7V to 5.25V CONNECTION DIAGRAMS (TOP VIEW) FQP Package HS/GND HS/GND HS/GND REG L1+ L1- HS/GND HS/GND HS/GND TRMPWR L15- L15+ Currents are positive into negative out of the specified terminal. Note: Consult Packaging Section of Databook for thermal limitations and considerations of package. 12 11 L2+ L2- L3+ 13 14 15 16 17 18 19 20 21 22 23 24 25 26 10 9 8 7 6 5 4 3 2 1 48 47 46 45 44 43 42 41 40 39 38 37 L14- L14+ L13- L13+ L12- L12+ L11- L11+ L10- L10+ L9- L9+ RECOMMENDED OPERATING CONDITIONS TRMPWR Voltage . . . . . . . . . . . . . . . . . . . . . . . . 2.7V to 5.25V Temperature Ranges . . . . . . . . . . . . . . . . . . . . . . 0C to +70C L3- L4+ L4- L5+ L5- L6+ L6- L7+ L7- 27 28 29 30 31 32 33 34 35 36 L8+ L8- GND HS/GND HS/GND HS/GND DISCNCT DIFFSENS DIFFB HS/GND HS/GND HS/GND ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = TJ = 0C to 70C, TRMPWR = 3.3V. PARAMETER TRMPWR Supply Current Section TRMPWR Supply Current LVD SCSI Mode SE SCSI Mode Disabled Terminator Regulator Section 1.25V Regulator 1.25V Regulator Source Current 1.25V Regulator Sink Current 1.3V Regulator 1.3V Regulator Source Current 1.3V Regulator Sink Current 2.7V Regulator 2.7V Regulator Source Current 2.7V Regulator Sink Curren Differential Termination Section Differential Impedance Common Mode Impedence Differential Bias Voltage Common Mode Bias Output Capacitance Single Ended Measurement to Ground (Note 1) (Note 2) 100 110 100 1.15 1.25 105 150 110 165 125 1.35 3 mV V pF LVD SCSI Mode VREG= 0V VREG= 3.3V Diff Sense VREG= 0V VREG= 3.3V SE SCSI Mode VREG= 0V VREG= 3.3V 1.15 -375 170 1.2 -15 50 2.5 -375 170 2.7 -700 300 1.25 -700 300 1.3 1.35 -1000 700 1.4 -5 200 3.0 -1000 700 V mA mA V mA A V mA mA 20 1.6 250 25 10 400 mA mA A TEST CONDITIONS MIN TYP MAX UNITS 2 UCC5638 ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = TJ = 0C to 70C, TRMPWR = 3.3V. PARAMETER Single Ended Termination Section Impedance TEST CONDITIONS MIN 102.3 TYP 110 MAX UNITS 117.7 Z= (VLX - 0 . 2V ) ILX , (Note 3) -21 -18 -24 -25.4 -22.4 400 3 20 0.8 10 0.5 1.9 -10 60 2.0 30 0.7 2.4 10 V A V V A mA mA nA pF Termination Current Output Leakage Output Capacitance Single Ended GND SE Impedance Disconnect and Diff Buffer Input Section DISCNCT Threshold DISCNCT Input Current Diff Buffer Single Ended to LVD Threshold Diff Buffer LVD to HPD Threshold DIFFB Input Current Signal Level 0.2V, All Lines Low Signal Level 0.5V Single Ended Measurement to Ground (Note 1) I= 10mA Note 1: Guaranteed by design. Not 100% tested in production. Note 2: Line+ (positive) tied to Line- (negative); [I(VCM max) - I(VCM min)] 1. 2V 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. DIFFSENS: The SCSI bus Diff Sense line to detect what types of devices are connected to 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. Note: In Disconnect Mode, the comparitor set powers down for low idle current. LINEn-: Signal line active line for single ended or negative line in differential applications for the SCSI bus. LINEn+: Ground line for single ended or positive line for differential applications for the SCSI bus. 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 F capacitor to ground. 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. 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. 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. 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 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. 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. 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. 4 UCC5638 TYPICAL APPLICATION L1+ TERMPWR 3 TRMPWR L9+ L9- L1- CONTROL LINES (9) L9+ L9- L1+ L1- TRMPWR 3 TRMPWR L10+ L10- 4 BITS OF THE HIGH BYTE L15+ L15- 36 DISCNCT DIFFSENSE 35 REG 10 DIFF B 34 20k 0.1F . 20k L10+ L10- L15+ L15- DISCNCT 36 35 DIFFSENSE DIFF B 34 REG 10 4.7F . 270k 0.1F . 4.7F 4.7F . 4.7F L1+ L1- DATA LINES (15) L5+ L5- HIGH BYTE 4 BITS PLUS PARITY L5+ L5- L1+ L1- DATA LINES (15) 3 TRMPWR L6+ L6- LOW BYTE 8+ PARITY L14+ L14+ L14- L6+ L6- TRMPWR 3 36 DISCNCT L14- DISCNCT 36 REG 10 DIFF B 34 DIFF B 34 REG 10 4.7F . 4.7F 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 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 acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. Customers are responsible for their applications using TI components. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI's publication of information regarding any third party's products or services does not constitute TI's approval, warranty or endorsement thereof. Copyright (c) 2000, Texas Instruments Incorporated |
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