DS2114 DS2114 SCSI Terminator FEATURES • Fully compliant with SCSI, SCSI–2 and SCSI–3 standards • Provides active termination for nine signal lines • Laser–trimmed 110 ohms termination resistors have 2% tolerance • Low dropout voltage regulator • Fully supports actively negated SCSI signals PIN ASSIGNMENT TERMPWR1 1 16 NC R1 2 15 VREF2 R2 3 14 R9 R3 4 13 R8 R4 5 12 R7 R5 6 11 R6 VREF1 7 10 NC GND 8 9 TERMPWR2 DS2114Z 16–PIN SOIC (150 MIL) • Onboard thermal shutdown circuitry • Narrow 16–pin plastic SOIC (DS2114Z) DESCRIPTION The SCSI–2 and SCSI–3 standards recommend the use of active terminations at both ends of every cable segment in a SCSI system with single–ended drivers and receivers. The DS2114 SCSI Terminator, which is fully compliant with these standards, enables the designer to gain the benefits of active termination: greater immunity to voltage drops on the TERMPWR (TERMination PoWeR) line, enhanced high–level noise im- munity, intrinsic TERMPWR decoupling, and very low quiescent current consumption. The DS2114 integrates a regulator and nine precise 110 ohms termination resistors into a monolithic IC. The DS2114 is intended for cable end terminator assemblies and devices where the terminators do not need to be isolated from the SCSI bus. 070198 1/6 DS2114 FUNCTIONAL DESCRIPTION The DS2114 consists of a bandgap reference, buffer amplifier, and nine termination resistors (Figure 1). The bandgap reference circuit produces a precise 2.55 volts level which is fed to a buffer amplifier. The buffer produces a 2.85 volts level and is capable of sourcing at least 24 mA into each of the termination resistors when the signal line is low (active). When the driver for a given signal line turns off, the terminator will pull the signal line to 2.85 volts (quiescent state). To handle actively negated SCSI signals, the buffer can sink at least 200 mA and Vref will move less than 60 mV. When all lines settle in the quiescent state, the regulator will consume about 2.5 mA. To ensure proper operation, both the TERMPWR1 and TERMPWR2 pins must be connected to the SCSI bus TERMPWR line and both the VREF1 and VREF2 pins must be tied together externally. Each DS2114 requires a 4.7 µF capacitor connected between the VREF pins and ground. Figure 2 details a typical SCSI bus configuration. In an 8–bit wide SCSI bus arrangement (“A” Cable), two DS2114’s would be needed at each end of the SCSI cable in order to terminate the 18 active signal lines. In a 16–bit wide SCSI bus arrangement (“P” Cable), three DS2114’s would be needed at each end of the SCSI cable in order to terminate the 27 active signal lines. DS2114 BLOCK DIAGRAM Figure 1 TERMPWR1 TERMPWR2 BANDGAP REFERENCE 110 ohms R1 110 ohms R2 110 ohms R3 + – 110 ohms R4 110 ohms R5 110 ohms R6 110 ohms GND R7 110 ohms R8 110 ohms R9 VREF1 VREF2 070198 2/6 DS2114 TYPICAL SCSI BUS CONFIGURATION Figure 2 Termination Power Line + C2 DS2114 C1 + TERMPWR1 TERMPWR2 VREF1 VREF2 GND R1 SCSI CABLE R8 R9 DS2114 C1 + TERMPWR1 TERMPWR2 VREF1 VREF2 GND R1 R2 SCSI BUS TRANSCEIVER SCSI BUS TRANSCEIVER SCSI BUS TRANSCEIVER SCSI BUS TRANSCEIVER R9 NOTES: 1. C1 = 4.7 µF tantalum C2 = 2.2 µF tantalum or 4.7 µF aluminum 2. If the DS2114 is to be embedded into a peripheral that will act as a target on a SCSI bus, it is recommended that TERMPWR be derived from the SCSI cable, not generated locally. In this configuration, if a power failure occurs in the peripheral, it will not affect the bus. 3. A high frequency bypass capacitor (0.1 µF recommended) can be added in parallel to C1 for applications using fast rise/fall time drivers. 070198 3/6 DS2114 PIN DESCRIPTION Table 1 DS2114Z PIN SYMBOL 1 TERMPWR1 2 R1 Signal Termination 1. 110 ohms termination. 3 R2 Signal Termination 2. 110 ohms termination. 4 R3 Signal Termination 3. 110 ohms termination. 5 R4 Signal Termination 4. 110 ohms termination. 6 R5 Signal Termination 5. 110 ohms termination. 7 VREF1 8 GND 9 TERMPWR2 11 R6 Signal Termination 6. 110 ohms termination. 12 R7 Signal Termination 7. 110 ohms termination. 13 R8 Signal Termination 8. 110 ohms termination. 14 R9 Signal Termination 9. 110 ohms termination. 10, 16 NC No Connect. Do not connect any signal to these pins. 15 VREF2 070198 4/6 DESCRIPTION Termination Power 1. Should be connected to the SCSI TERMPWR line. Must be decoupled with either a 2.2 µF or 4.7 µF. See Figure 2. Reference Voltage 1. Must be externally connected directly to the VREF2 pin. Must be decoupled with a 4.7 µF capacitor as shown in Figure 2. Ground. Signal ground; 0.0 volts. Termination Power 2. Should be connected to the SCSI TERMPWR line. Must be decoupled with either a 2.2 µF or 4.7 µF. See Figure 2. Reference Voltage 2. Must be externally connected directly to the VREF1 pin. Must be decoupled with a 4.7 µF capacitor as shown in Figure 2. DS2114 ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature –1.0V to +7.0V 0°C to 70°C –55°C to +125°C 260°C for 10 seconds * This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. The Dallas Semiconductor DS2114 is built to the highest quality standards and manufactured for long term reliability. All Dallas Semiconductor devices are made using the same quality materials and manufacturing methods. However, the DS2114 is not exposed to environmental stresses, such as burn–in, that some industrial applications require. For specific reliability information on this product, please contact the factory in Dallas at (972) 371–4448. (0°C to 70°C) RECOMMENDED OPERATING CONDITIONS PARAMETER SYMBOL MIN VTP 4.00 SYMBOL MIN TERMPWR Voltage TYP MAX UNITS 5.50 V TYP MAX UNITS NOTES 5 250 8 mA mA 1, 3 1, 4 116 ohms 1, 2 °C 1, 5 pF 1, 2, 5 (0°C to 70°C) DC CHARACTERISTICS PARAMETER NOTES TERMPWR Current ITP ITP Termination Resistance RTERM 110 Die Thermal Shutdown TSD 150 Termination Capacitance CT 5.0 (0°C to 70°C) REGULATOR CHARACTERISTICS PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Output Voltage VREF 2.7 2.85 3.0 V 1, 2 1.0 V 3, 5 Drop Out Voltage VDROP 0.75 Line Regulation LIREG 1.0 Output Current IOUT Load Regulation LOREG 1.3 Current Limit ILIM 280 Sink Current ISINK 200 2.0 % 1, 4 24.0 mA 6 3.0 % 1, 3 500 mA 1 mA 1 NOTES: 1. 4.00 volts < TERMPWR < 5.50 volts. 2. 0.0 volts < signal lines < TERMPWR. 3. All signal lines = 0.0 volts. 4. All signal lines open. 5. Guaranteed by design; not production tested. 6. VSIGNAL = 0.2V. 070198 5/6 DS2114 DS2114Z SCSI TERMINATOR 16–PIN SOIC (150 MIL) ÎÎ ÎÎ PKG 16–PIN DIM MIN MAX A IN. MM 0.053 1.35 0.069 1.75 A1 IN. MM 0.004 0.10 0.010 0.25 A2 IN. MM 0.048 1.24 0.062 1.57 b IN. MM 0.012 0.30 0.020 0.50 C IN MM 0.007 0.17 0.011 0.28 D IN. MM 0.386 9.80 0.393 9.98 e IN. MM 0.050 BSC 1.27 BSC E1 IN. MM 0.150 3.81 0.158 4.01 H IN. MM 0.230 5.84 0.244 6.20 L IN. MM 0.016 0.40 0.050 0.89 0° 8° Θ 070198 6/6