DS2118MB+T&R;

DS2118M Ultra3 LVD/SE SCSI Terminator www.maxim-ic.com FEATURES PIN CONFIGURATION Fully Compliant with SCSI SPI-2, SPI-3, SPI-4, Ultra160, and Ultra320 VREF NC NC R1P R1N R2P R2N HS GND HS GND HS GND R3P R3N R4P R4N R5P R5N ISO GND Provides Multimode Low-Voltage Differential/Single-Ended (LVD/SE) Termination for Nine Signal Line Pairs Autoselection of LVD or SE Termination 5% Tolerance on SE and LVD Termination Resistance Low Power-Down Capacitance of 3pF On-Board Thermal Shutdown Circuitry SCSI Bus Hot-Plug Compatible Fully Supports Actively Negated SE SCSI Signals 1 36 35 2 3 DS2118M 34 33 4 32 5 31 6 30 7 29 8 28 9 27 10 26 11 25 12 24 13 23 14 22 15 21 16 20 17 19 18 TPWR HVD LVD SE R9N R9P R8N R8P HS GND HS GND HS GND R7N R7P R6N R6P DIFF_CAP DIFFSENSE MSTR/SLV SSOP ORDERING INFORMATION VOLTAGE TEMP RANGE PIN-PACKAGE (V) DS2118MB 5 36 SSOP (0.300") 0°C to +70°C DS2118MB+ 5 36 SSOP (0.300") 0°C to +70°C 36 SSOP (0.300")/Tape and DS2118MB/T&R 5 0°C to +70°C Reel 36 SSOP (0.300")/Tape DS2118MB+T&R 5 0°C to +70°C and Reel PART TOP MARK* DS2118MB DS2118MB DS2118MB DS2118MB + Denotes a lead-free/RoHS-compliant package. * The top mark includes a "+" on lead-free packages. 1 of 10 REV: 010406 DS2118M DETAILED DESCRIPTION The DS2118M Ultra3 LVD/SE SCSI terminator is both a low-voltage differential (LVD) and singleended (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 DS2118M will use LVD termination. If any SE devices are connected to the bus, the DS2118M will use SE termination. This is accomplished automatically inside the part by sensing the voltage on the SCSI bus DIFFSENS line. For the LVD termination, the DS2118M integrates two current sources with nine precision resistor strings. For the SE termination, one regulator and nine precision 110Ω resistors are used. Three DS2118M terminators are needed for a wide SCSI bus. REFERENCE DOCUMENTS Small Computer Systems Interface (SCSI-3) Small Computer Systems Interface (SCSI-3) Small Computer Systems Interface (SCSI-3) Small Computer Systems Interface (SCSI-3) SCSI Parallel Interface (SPI) SCSI Parallel Interface 2 (SPI-2) SCSI Parallel Interface 3 (SPI-3) SCSI Parallel Interface 4 (SPI-4) Project: 0855-M, 1995 Project: 1142-M, 1998 Project: 1302-D, 1999 Project: 1365-D, 200x Available From: American National Standards Institute (ANSI) Phone: (212) 642-4900 Global Engineering Documents 15 Inverness Way East; Englewood, CO 80112 Phone: (800) 854-7179 2 of 10 DS2118M FUNCTIONAL DESCRIPTION The DS2118 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 will be applied to the termination resistors. If the SCSI bus is in LVD mode, then the 1.25V reference will be used. If the SCSI bus is in SE mode, then the 2.85V reference will be used. That same control logic will switch in/out parallel resistors to change the total termination resistance accordingly. Finally, in SE mode the Rp pins will be switched to ground. The DIFFSENSE circuitry decodes trinary logic. There will be 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. That indicates the mode of the bus to be HVD, SE, or LVD, respectively. The DS2118M’s DIFF_CAP pin monitors the DIFFSENS line to determine the proper operating mode of the device; this mode is indicated by the SE/LVD/HVD outputs. The DIFFSENSE pin can also drive the SCSI DIFFSENS line (when MSTR/SLV = 1) to determine the SCSI bus operating mode. The DS2118M switches to the termination mode that is appropriate for the bus based on the value of the DIFFSENS voltage. These modes are: LVD Mode: LVD termination is provided by a precision laser-trimmed resistor string with two amplifiers. This configuration yields a 105Ω differential and 150Ω common-mode impedance. A fail-safe bias of 112mV 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 will pull that signal line to 2.85V (quiescent state). When used with an active negation driver, the power amp can sink 22mA per line while keeping the voltage reference in regulation. The terminating resistors maintain their 110Ω value. HVD Isolation Mode: The DS2118M identifies that there is an HVD (high-voltage differential) 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, VREF remains active, and the bus mode indicators (SE/LVD/HVD) remain active. During thermal shutdown, the termination pins are isolated from the SCSI bus, VREF becomes high impedance, and the bus mode indicators (SE/LVD/HVD) remain active. The DIFFSENSE driver is shut down during either of these two events. An internal pulldown resistor assures that the DS2118M will be 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 2.2µF capacitor and a 0.01µF high-frequency capacitor is recommended between TPWR and ground and placed as close as possible to the DS2118M. The DS2118M 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 4.7µF capacitor is required between the VREF pin (VREF) and ground of each DS2118M. A high frequency cap (0.1µF ceramic recommended) can also be placed on the 3 of 10 DS2118M VREF pin in applications that use fast rise/fall time drivers. A typical SCSI bus configuration is shown in Figure 2. NOTES: 1) DIFFSENS. Refers to the SCSI bus signal. 2) DIFFSENSE. Refers to the DS2118M pin name and internal circuitry capable of driving the DIFFSENS line. 3) DIFF_CAP. Refers to the DS2118M pin name and internal circuitry relating to monitoring the DIFFSENS line. 4 of 10 DS2118M Figure 1. DS2118M Block Diagram 5 of 10 DS2118M Figure 2. SCSI Bus Configuration 6 of 10 DS2118M PIN DESCRIPTION PIN NAME 1 VREF 2, 3 4–7, 11–16, 22–25, 29–32 8, 10, 26, 9, 28, 27 NC RxP, RxN 17 18 19 20 21 33 34 35 36 FUNCTION Reference Voltage. 2.85V reference in SE mode and 1.25V reference in LVD mode; must be decoupled with a 4.7µF cap. No Connection. Do not connect these pins. Signal Termination. Connect to SCSI bus signal lines. Heat Sink Ground. Internally connected to the mounting pad. Should be grounded. Isolation. When pulled high, the DS2118M isolates its bus pins (RxP, ISO FxP) from the SCSI bus. GND Ground. Signal ground; 0V. Master/Slave. Mode-select for the noncontrolling terminator. When MSTR/SLV pulled high (MSTR), the DIFFSENSE driver is enabled. DIFFSENSE DIFFSENSE. Output to drive the SCSI bus DIFFSENS line. DIFFSENSE Capacitor. Connect 0.1µF capacitor for DIFFSENSE DIFF_CAP filter. Input to detect the type of device (differential or single-ended) on the SCSI bus. Single-Ended. SE output of DIFFSENSE receiver; indicates SE bus SE operation. Low-Voltage Differential. LVD output of DIFFSENSE receiver; LVD indicates LVD bus operation. High-Voltage Differential. HVD output of DIFFSENSE receiver; HVD indicates HVD bus operation or thermal shutdown. Termination Power. Connect to the SCSI TERMPWR line and TPWR decouple with 2.2µF capacitor. HS GND RECOMMENDED OPERATING CONDITIONS PARAMETER Termpower SE Mode Voltage LVD Mode SYMBOL VTPWR(SE) MIN 4.0 Logic 0 VTPWR(LVD) VIL 2.7 -0.3 Logic 1 VIH 2.0 VAMB 0 Operating Temperature 7 of 10 TYP MAX 5.5 UNITS V 5.5 +0.8 V V VTPWR + 0.3 70 V °C NOTES DS2118M SINGLE-ENDED CHARACTERISTICS PARAMETER SE Termination Resistance SE Voltage Reference SE Output Current Output Capacitance SYMBOL MIN TYP MAX UNITS NOTES RSE 104.5 110 115.5 Ω 1 VREF lOSE COUT 2.7 3.0 25.4 3 V mA pF 2 3 MAX UNITS NOTES LOW-VOLTAGE DIFFERENTIAL CHARACTERISTICS PARAMETER Differential Mode Termination Resistance Common Mode Termination Resistance Differential Mode Bias Common Mode Bias SYMBOL MIN TYP RDM 100 110 Ω RCM 110 190 Ω VDM VCM 100 1.125 125 1.375 mV V 4 SYMBOL ITPMR IIH IIL IOH IOL MIN MAX UNITS mA µA µA mA mA NOTES 4 VSEOR -0.3 0.5 V VLVDOR 0.7 1.9 V VHVDOR 2.4 VTPWR + 0.3 V VDSO 1.2 1.4 V 8, 9 IDSH 5 15 mA 8, 10, 12 IDSL 20 200 µA 8, 11 ºC 3 DC CHARACTERISTICS PARAMETER Termpower Current Input Leakage High Input Leakage Low Output Current High Output Current Low DIFFSENS SE Operating Range DIFFSENS LVD Operating Range DIFFSENS HVD Operating Range DIFFSENSE Driver Output Voltage DIFFSENSE Driver Source Current DIFFSENSE Driver Sink Current Thermal Shutdown TYP 12 -1.0 1.0 -1.0 4.0 150 8 of 10 5, 7 6, 7 DS2118M REGULATOR CHARACTERISTICS PARAMETER Line Regulation Load Regulation Current Limit Sink Current SYMBOL LIREG LOREG ILIM ISINK MIN 200 NOTES: 1) VLINE = 0V to 3V. 2) VLINE = 0.2V. 3) Guaranteed by design. 4) All lines open. 5) VOUT = 2.4V. 6) VOUT = 0.4V. 7) SE/LVD/HVD pins only. 8) MSTR/SLV = 1. 9) IDS = 0mA to 5mA. 10) VDSO = 0V. 11) VDSO = 2.75V. 12) TPWR = 5.5V. 9 of 10 TYP 1.0 1.3 550 MAX 2.5 3.5 UNITS % % mA mA NOTES DS2118M 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.) 10 of 10 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 © 2006 Maxim Integrated Products • Printed USA The Maxim logo is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Dallas Semiconductor Corporation.