DS2105 DS2105 SCSI Terminator FEATURES • Fully PIN ASSIGNMENT compliant with SCSI–1, Fast SCSI and Ultra TERMPWR1 1 16 PD 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 SCSI • Functionally compatible to the DS21S07A, targeted for high volume applications • Provides active termination for nine signal lines • Laser–trimmed 110 ohm termination resistors have 5% tolerance • Low dropout voltage • Power–down mode isolates termination resistors from the bus • Fully supports actively negated SCSI signals • Onboard thermal shutdown circuitry • 16–pin plastic SOIC (DS2105) TERMPWR2 DS2105Z 16–PIN SOIC (150 MIL) TERMPWR1 1 16 PD R1 2 15 VREF2 R2 3 14 NC R3 4 13 R9 R4 5 12 R8 R5 6 11 R7 VREF1 7 10 R6 GND 8 9 TERMPWR2 DS2105S 16–PIN SOIC (300 MIL) DESCRIPTION Fast SCSI and Ultra SCSI require the use of active terminations at both ends of every cable segment in a SCSI system with single–ended drivers and receivers. The DS2105 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 immunity, intrinsic TERMPWR decoupling, and very low quiescent current consumption. The DS2105, which integrates a regulator and nine precise switched 110 ohm termination resistors into a monolithic IC, is a functionally compatible version of the DS21S07A. With relaxed output current and termination tolerances, the DS2105 is intended for high volume applications which require active termination but not the high performance of the DS21S07A. The DS2105 is offered in both 300 mil and 150 mil SOIC packages. 022698 1/7 DS2105 FUNCTIONAL DESCRIPTION The DS2105 consists of a bandgap reference, buffer amplifier, and nine termination resistors (Figure 1). The bandgap reference circuit produces a precise 2.55V level which is fed to a buffer amplifier. The buffer produces a 2.85V 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 2.85V (quiescent state). To handle actively negated SCSI signals, the buffer can sink 200 mA, and VREF will move less than 60 mV. When all lines settle in the quiescent state, the regulator will consume about 5 mA. When the DS2105 is put into power–down mode by bringing PD low, the power–down circuitry will turn off the transistors on each signal line. This will isolate the DS2105 from the signal lines and effectively remove it from the circuit. The power–down pin (PD) has an internal 50KΩ pull–up resistor. To place the DS2105 into an active state, the PD pin should be left open circuited. 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 DS2105 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 DS2105’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 DS2105’s would be needed at each end of the SCSI cable in order to terminate the 27 active signal lines. DS2105 BLOCK DIAGRAM Figure 1 PD TERMPWR1 TERMPWR2 50K ohm POWER DOWN CIRCUITRY 110 ohms R1 110 ohms R2 BANDGAP REFERENCE 110 ohms R3 110 ohms R4 110 ohms R5 110 ohms R6 GND 110 ohms R7 110 ohms R8 110 ohms R9 VREF1 VREF2 022698 2/7 DS2105 TYPICAL SCSI BUS CONFIGURATION Figure 2 Termination Power Line + C2 DS2105 C1 + TERMPWR1 TERMPWR2 VREF1 VREF2 GND R1 SCSI CABLE R8 R9 SCSI BUS TRANSCEIVER SCSI BUS TRANSCEIVER DS2105 C1 + TERMPWR1 TERMPWR2 VREF1 VREF2 GND R1 R2 R9 SCSI BUS TRANSCEIVER SCSI BUS TRANSCEIVER NOTES: 1. C1 = 4.7 µF tantalum C2 = 2.2 µF tantalum or 4.7 µF aluminum 2. If the DS2105 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. 022698 3/7 DS2105 PIN DESCRIPTION Table 1 DS2105S PIN DS2105Z PIN SYMBOL DESCRIPTION 1 1 TERMPWR1 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. 2 2 R1 Signal Termination 1. 110 ohm termination. 3 3 R2 Signal Termination 2. 110 ohm termination. 4 4 R3 Signal Termination 3. 110 ohm termination. 5 5 R4 Signal Termination 4. 110 ohm termination. 6 6 R5 Signal Termination 5. 110 ohm termination. 7 7 VREF1 8 8 GND 9 9 TERMPWR2 10 11 R6 Signal Termination 6. 110 ohm termination. 11 12 R7 Signal Termination 7. 110 ohm termination. 12 13 R8 Signal Termination 8. 110 ohm termination. 13 14 R9 Signal Termination 9. 110 ohm termination. 15 15 VREF2 16 16 PD Power Down. When tied low, the DS2105 enters a power–down mode. Contains an internal 50K pull–up. Strap low to deactivate the DS2105, leave open circuited to activate the DS2105. 14 10 NC No Connect. Do not connect any signal to this pin. 022698 4/7 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; 0.0V. 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. DS2105 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. (0°C to 70°C) RECOMMENDED OPERATING CONDITIONS PARAMETER SYMBOL MIN VTP 4.00 PD Active VPDA PD Inactive VPDI SYMBOL MIN TERMPWR Voltage TYP MAX UNITS 5.25 V –0.3 +0.8 V 2.0 VTP +0.3 V TYP MAX UNITS NOTES 5 250 8 mA mA 1, 3 1, 4 µA 1, 2, 5 118 ohm 1, 2 °C 1 pF 1, 2, 5, 6 µA 1, 8 µA 1, 7 (0°C to 70°C) DC CHARACTERISTICS PARAMETER NOTES TERMPWR Current ITP ITP Power Down Current IPD 500 Termination Resistance RTERM Die Thermal Shutdown TSD 150 Power Down Termination Capacitance CPD 3.0 Input Leakage High IIH Input Leakage Low IIL 110 5.0 –1.0 1.0 (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 Drop Out Voltage Output Current VDROP 0.75 IOUT 1.0 V 3, 6 24.0 mA 9 Line Regulation LIREG 1.0 2.0 % 1, 4 Load Regulation LOREG 1.3 3.0 % 1, 2 mA 1 mA 1 Current Limit ILIM Sink Current ISINK 350 200 NOTES: 1. 4.00V < TERMPWR < 5.25V. 2. 0.0V < signal lines < 3.0V. 3. All signal lines = 0.0V. 4. All signal lines open. 5. PD = 0.0V. 022698 5/7 DS2105 6. Guaranteed by design; not production tested. 7. R1 through R9 only. 8. R1 through R9 and PD. 9. VSIGNAL=0.2V. DS2105Z 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 022698 6/7 DS2105 DS2105S SCSI TERMINATOR 16–PIN SOIC (300 MIL) The chamfer on the body is optional. If it is not present, a terminal 1 identifier must be positioned so that 1/2 or more of its area is contained in the hatched zone. PKG 16–PIN DIM MIN MAX A IN. MM 0.094 2.38 0.105 2.68 A1 IN. MM 0.004 0.102 0.012 0.30 A2 IN. MM 0.089 2.26 0.095 2.41 b IN. MM 0.013 0.33 0.020 0.51 C IN MM 0.009 0.229 0.013 0.33 D IN. MM 0.398 10.11 0.412 10.46 e IN. MM 0.050 BSC 1.27 BSC E1 IN. MM 0.290 7.37 0.300 7.62 H IN MM 0.398 10.11 0.416 10.57 L IN MM 0.016 0.40 0.040 1.02 0° 8° Θ 022698 7/7