DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator www.maxim-ic.com GENERAL DESCRIPTION FEATURES The DS2125 Ultra3 LVD/SE SCSI terminator is both a low-voltage differential (LVD) and single-ended (SE) terminator. The multimode operation enables the designer to implement LVD in current products while allowing the end user SE backward compatibility with legacy devices. If the device is connected in an LVD-only bus, the DS2125 uses LVD termination. If any SE devices are connected to the bus, the DS2125 uses SE termination, which is accomplished automatically inside the part by sensing the voltage on the SCSI bus DIFFSENS line. § § § § § § § § For the LVD termination, the DS2125 integrates two current sources with 15 precision resistor strings. For the SE termination, one regulator and 15 precision 110W resistors are used. Two DS2125 terminators are needed for a wide SCSI bus. Fully Compliant with Ultra3 SCSI Provides Multimode Low-Voltage Differential/Single-Ended (LVD/SE) Termination for 15 Signal Line Pairs Auto-Selection of LVD or SE Termination 5% Tolerance on SE and LVD Termination Resistance Low 3pF Power-Down Capacitance On-Board Thermal-Shutdown Circuitry SCSI Bus Hot-Plug Compatible Fully Supports Actively Negated SE SCSI Signals PIN CONFIGURATION TOP VIEW HS_GND HS_GND HS_GND VREF R1P R1N APPLICATIONS Raid Systems SCSI Host Bus Adapter (HBA) Cards Servers SCSI Cables Network Attached Storage (NAS) Storage Area Networks (SANs) ORDERING INFORMATION PART DS2125 TEMP RANGE 0°C to +70°C PIN-PACKAGE 48 LQFP HS_GND HS_GND HS_GND TPWR R15N R15P R2P 12 13 R2N 14 R3P 15 R3N 16 R4P 17 R4N 11 10 9 8 7 6 5 4 3 2 1 48 R14N 47 R14P 46 R13N 45 R13P 44 R12N 18 43 R12P R5P 19 42 R11N R5N 20 41 R11P R6P 21 40 R10N R6N 22 39 R10P R7P 23 38 R9N R7N 24 37 36 R9P Dallas Semiconductor DS2125 25 26 27 28 29 30 31 32 R8P R8N GND HS_GND HS_GND HS_GND 33 34 35 ISO DIFFSENSE DIFF_CAP HS_GND HS_GND HS_GND LQFP Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata. 1 of 7 REV: 052604 DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator ABSOLUTE MAXIMUM RATINGS VREF, ISO, GND, DIFFSENSE, DIFF_CAP, TPWR, RxP, RxN (x = 1 . . . 15) VREF Continuous Output Current Continuous Power Dissipation (TA = +70°C), 48-Pin LQFP Operating Temperature Range Junction Temperature Storage Temperature Range Lead Temperature (soldering, 10s) -0.3V, +6.0V ±200mA 2W 0°C to +70°C +150°C -65°C to +160°C +300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (TPWR = 3.3V, TA = 0°C to +70°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS TPWR Operating Supply LVD VTPWR Range SE TPWR SUPPLY CURRENT ITPWR_LVD LVD SCSI mode TPWR Supply Current ITPWR_SE SE SCSI mode (All Lines Open) ISO mode (terminators disabled) ITPWR_ISO LVD TERMINATION (Applies to each line pair, 1 to 15 in LVD mode) Differential-Mode RDM Termination Resistance Common-Mode RP and RN shorted together RCM Termination Resistance Differential-Mode Bias VDM All lines open Common-Mode Bias VCM RP and RN shorted together SE TERMINATION (Applies to SE terminators, 1 to 15 in SE mode) RSE = (VLx - 0.2) / ILx, where VLx = voltage at terminator Single-Ended Mode RSE pin with pin unloaded and Termination Resistance ILx = current for each terminator pin with the pin forced to 0.2V (Note 2) Termination Current Signal level at 0.2V, all lines low ISE (Note 2) Signal level at 0.5V SE Voltage Reference VREF Pin Leakage (Note 2) TYP MAX 5.5 5.5 UNITS 32 10 750 mA mA mA 100 110 W 110 165 W 20 1.6 250 VREF unloaded; vary TPWR from 2.7V to 5.5V 2.85V Regulator (Note 2) V 100 1.15 1.25 125 1.35 mV V 104.5 110 115.5 W -21.0 -18.0 -24 -25.4 -22.4 mA 2.7 2.85 3.0 V 400 nA 60 W 3 pF With ISO high Single-Ended GND RGND Resistance TERMINATOR PIN CAPACITANCE Terminator Pin CIN Capacitance VREF REGULATOR 1.25V Regulator Output VREF_LVD Voltage 1.25V Regulator ShortISOURCE Circuit Source Current 1.25V Regulator ShortISINK Circuit Sink Current 1.25V Regulator Line Regulation 2.85V Regulator ShortCircuit Source Current 2.85V Regulator ShortCircuit Sink Current MIN 2.7 4.0 Measured at RP pins, I = 10mA 20 With ISO high (Note 1) 1.15 1.25 1.35 V VREF = 0V -375 -700 -1000 mA VREF = 3.3V 170 300 700 mA 1.0 2.5 % 2.7 2.85 3.0 V VREF = 0V (Note 2) -375 -700 -1000 mA VREF = 3.3V (Note 2) 170 300 700 mA 2 of 7 DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator ELECTRICAL CHARACTERISTICS (continued) (TPWR = 3.3V, TA = 0°C to +70°C, unless otherwise noted.) PARAMETER VREF REGULATOR 2.85V Regulator Line Regulation DIFFSENS OUTPUT DIFFSENS Driver Output Voltage DIFFSENS Driver Source Current DIFFSENS Driver Sink Current DIFFSENS Leakage (Note 3) SYMBOL CONDITIONS MIN VREF unloaded; vary TPWR from 4.0V to 5.5V TYP MAX UNITS 1.0 2.5 % VDSO -5mA £ IDFFSENS £ 50mA 1.2 1.4 V IDSH VDIFFSENS = 0V -15 -5 mA IDSL VDIFFSENS = 3.3V 100 200 mA -3 +1 1 3 ILEAK, LOW ILEAK, HIGH THERMAL SHUTDOWN Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis MODE CHANGE DELAY/FILTER Mode Change Delay tDELAY LOGICAL SIGNALS (ISO) Input Low Voltage VIL With ISO high, |VDIFFSENS| = 0.3V With ISO high, |VDIFFSENS - VTPWR| = 0.3V mA For increasing temperature (Note 1) 150 °C (Note 1) 10 °C 0.66 1.25 -0.3 2 2.00 ms +0.8 TPWR + 0.3 V Input High Voltage VIH V Input Current DIFF_CAP Input Current DIFF_CAP SE Operating Range DIFF_CAP LVD Operating Range DIFF_CAP HVD Operating Range IIL VCC = 3.3V -30 IL VIL = -0.3V -1 +1 mA VSEOR -0.3 +0.5 V VLVDOR 0.7 1.9 V VHVDOR 2.4 VTPWR + 0.3 V mA -10 Note 1: Guaranteed by design. Note 2: TPWR = 4.0V. Note 3: Room temperature only. PIN DESCRIPTION PIN 1, 2, 11–26, 37–48 NAME RxP, RxN FUNCTION Signal Termination. Connect to SCSI bus signal lines. Termination Power. Connect to the SCSI TERMPWR line and decouple with a 2.2mF capacitor. 3 TPWR 4–9, 28–33 HS_GND 10 VREF Reference Voltage. 2.85V reference in SE mode and 1.25V reference in LVD mode; must be decoupled with a 4.7mF capacitor. 27 GND Ground. Signal ground, 0V. 34 DIFF_CAP 35 DIFFSENSE 36 ISO Heat-Sink Ground. Internally connected to the mounting pad. This should be grounded. DIFFSENSE Capacitor. Connect a 0.1mF capacitor for the DIFFSENSE filter. Input to detect the type of device (differential or single-ended) on the SCSI bus. DIFFSENSE. Output to drive the SCSI bus DIFFSENS line. Isolation. When pulled high, the DS2125 isolates its bus pins (RxN, RxP) from the SCSI bus. 3 of 7 DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator Figure 1. Block Diagram ISO DIFFSENSE THERMALSHUTDOWN CIRCUITRY SE DIFFENSE CIRCUITRY DIFF_CAP CONTROL LOGIC LVD HVD VREF VREF + - 10W 10W BANDGAP 1.25V + - R1N R15N Dallas Semiconductor DS2125 R1P R15P + - SE GND DRIVER 4 of 7 DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator Figure 2. SCSI Bus Configuration TERMPWR TERMPWR TPWR TPWR ISO ISO CONTROL LINES (15) VREF DIFFSENS DIFF_CAP 4.7mF DIFFSENSE 20kW DIFFSENS 20kW 0.1mF DIFF_CAP 0.1mF VREF 4.7mF TPWR TPWR ISO ISO CONTROL LINES (15) VREF DIFFSENS DIFFSENS DIFF_CAP DIFF_CAP 4.7mF VREF 4.7mF Note: The following terms are used throughout this data sheet: DIFFSENS: Refers to the SCSI bus signal. DIFFSENSE: Refers to the DS2125 pin name and internal circuitry capable of driving the DIFFSENS line. DIFF_CAP: Refers to the DS2125 pin name and internal circuitry relating to monitoring the DIFFSENS line. DETAILED DESCRIPTION The DS2125 combines LVD and SE termination with DIFFSENSE sourcing and detection. A bandgap reference is fed into two amplifiers, which creates a 1.25V reference voltage and a 2.85V reference voltage. The control logic determines which of these references are applied to the termination resistors. If the SCSI bus is in LVD mode, the 1.25V reference is used. If the SCSI bus is in SE mode, the 2.85V reference is used. That same control logic switches in/out parallel resistors to change the total termination resistance accordingly. Finally, in SE mode the Rp pins are switched to ground. The DIFFSENSE circuitry decodes trinary logic. There is one of three voltages on the SCSI control line called DIFFSENS. Two comparators and a NAND gate determine if the voltage is below 0.6V, above 2.15V, or in between, which indicates the mode of the bus as SE, HVD, or LVD, respectively. 5 of 7 DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator The DS2125’s DIFF_CAP pin monitors the DIFFSENS line to determine the device’s proper operating mode. The DIFFSENSE pin can also drive the SCSI DIFFSENS line to determine the SCSI bus-operating mode. The DS2125 switches to the termination mode that is appropriate for the bus based on the value of the DIFFSENS voltage. These modes are LVD mode, SE mode, and HVD isolation mode. LVD MODE A precision laser-trimmed resistor string with two amplifiers provides LVD termination. This configuration yields 105W differential and 150W common-mode impedance. A 112mV fail-safe bias is maintained when no drivers are connected to the SCSI bus. SE MODE When the external driver for a given signal line turns off, the active terminator pulls that signal line to 2.85V (quiescent state). The terminating resistors maintain their 110W value. HVD ISOLATION MODE The DS2125 identifies that there is an HVD device on the SCSI bus and isolates the termination pins from the bus. When ISO is pulled high, the termination pins are isolated from the SCSI bus, and VREF remains active. During thermal shutdown, the termination pins are isolated from the SCSI bus, and VREF becomes high impedance. The DIFFSENSE driver is shut down during either of these two events. An internal pulldown resistor assures that the DS2125 is terminating the bus if the ISO pin is left floating. To ensure proper operation, the TPWR pin should be connected to the SCSI bus TERMPWR line. As with all analog circuitry, the TERMPWR and VDD lines should be bypassed locally. A 2.2mF capacitor and a 0.01mF highfrequency capacitor are recommended between TPWR and ground, and placed as close as possible to the DS2125. The DS2125 should be placed as close as possible to the SCSI connector to minimize signal and power trace length, thereby resulting in less input capacitance and reflections, which can degrade the bus signals. To maintain the specified regulation, a 4.7mF capacitor is required between the VREF pin and ground of each DS2125. A high-frequency capacitor (0.1mF ceramic recommended) can also be placed on the VREF pin in applications that use fast rise/fall-time drivers. Figure 2 shows a typical SCSI bus configuration. REFERENCE DOCUMENTS SCSI Parallel Interface 2 (SPI-2) T10 PROJECT DOCUMENT Project: 1142-M, 1998 ftp://ftp.t10.org/t10/drafts/spi2/spi2r20b.pdf SCSI Parallel Interface 3 (SPI-3) Project: 1302-D, 1999 ftp://ftp.t10.org/t10/drafts/spi3/spi3r14.pdf NCITS.336:2000 SCSI Parallel Interface 4 (SPI-4) Project: 1365-D, 200x ftp://ftp.t10.org/t10/drafts/spi4/spi4r10.pdf INCITS.362:2002 TITLE T10 COMMITTEE FTP LINK SUPPLIERS SUPPLIER PHONE WEBSITE American National Standards Institute (ANSI) 212-642-4900 www.ansi.org/ Global Engineering Documents 800-854-7179 http://global.ihs.com/ CHIP INFORMATION TRANSISTOR COUNT: 8382 MOS and 87 BiPOLAR PROCESS: BiCMOS SUBSTRATE CONNECTED TO GROUND THERMAL INFORMATION Theta-JA: 65°C/W 6 of 7 ANSI DOCUMENT NO. X3.302:1998 DS2125 Ultra3 LVD/SE SCSI 15-Line Terminator PACKAGE INFORMATION (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/DallasPackInfo.) 7 of 7 Maxim/Dallas Semiconductor cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim/Dallas Semiconductor product. No circuit patent licenses are implied. Maxim/Dallas Semiconductor reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2004 Maxim Integrated Products · Printed USA are registered trademarks of Maxim Integrated Products, Inc., and Dallas Semiconductor Corporation.