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| DS21S07A DS21S07A SCSI Terminator FEATURES PIN ASSIGNMENT TERMPWR1 R1 R2 R3 R4 R5 VREF1 GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 PD VREF2 NC R9 R8 R7 R6 TERMPWR2 * Fully SCSI compliant with SCSI-1, Fast SCSI and Ultra * Backward compatible to the DS2107 and DS2107A * Provides active termination for nine signal lines * Laser-trimmed 110 2% tolerance ohm termination resistors have * Low dropout voltage regulator * Power-down from the bus mode isolates termination resistors DS21S07AS 16-PIN SOIC (300 MIL) TERMPWR1 HS-GND R1 R2 R3 R4 R5 HS-GND VREF1 GND 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 PD VREF2 HS-GND NC R9 R8 R7 R6 HS-GND TERMPWR2 * SCSI bus hot plug-compatible * Fully supports actively negated SCSI signals * Onboard thermal shutdown circuitry * 16-pin plastic SOIC (DS21S07AS) and 20-pin plastic TSSOP (Thin Shrink Small Outline Package) (DS21S07AE) DS21S07AE 20-PIN TSSOP (173 MIL) ACTUAL FOOTPRINT SIZE .41" .26" .41" .27" DS21S07AS DS21S07AE 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 DS21S07A 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 DS21S07A integrates a regulator and nine precise switched 110 ohm termination resistors into a monolithic IC. The DS21S07A can be electrically isolated from the SCSI bus without physical removal from the SCSI device. 022798 1/7 DS21S07A FUNCTIONAL DESCRIPTION The DS21S07A 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 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. When the DS21S07A 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 DS21S07A from the signal lines and effectively remove it from the circuit. The power-down pin (PD) has an internal 50K pull-up resistor. To place the DS21S07A into an active state, the PD pin should be left open circuited. When installed on disk drives or RAID system components, the DS21S07A will not affect the SCSI bus during a hot plug operation. 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 DS21S07A requires a 4. 7 F 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 DS21S07A'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 DS21S07A's would be needed at each end of the SCSI cable in order to terminate the 27 active signal lines. DS21S07A 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 - 022798 2/7 DS21S07A TYPICAL SCSI BUS CONFIGURATION Figure 2 Termination Power Line + C2 DS21S07A TERMPWR1 TERMPWR2 VREF1 VREF2 GND R1 DS21S07A TERMPWR1 TERMPWR2 VREF1 VREF2 GND R1 R2 C1 + SCSI Cable R8 R9 C1 + R9 SCSI Bus Transceiver SCSI Bus Transceiver SCSI Bus Transceiver SCSI Bus Transceiver NOTES: 1. C1 = 4.7 F tantalum C2 = 2.2 F tantalum or 4.7 F aluminum 2. If the DS21S07A is to be embedded into a peripheral that will act as a target on a SCSI bus, it is that recommended 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 F recommended) can be added in parallel to C1 for applications using fast rise/fall time drivers. 022798 3/7 DS21S07A PIN DESCRIPTION Table 1 DS21S07AE PIN 1 DS21S07AS PIN 1 SYMBOL TERMPWR1 DESCRIPTION Termination Power 1. Should be connected to the SCSI TERMPWR line. Must be decoupled with either a 2.2 F or 4.7 F. See Figure 2. Signal Termination 1. 110 ohm termination. Signal Termination 2. 110 ohm termination. Signal Termination 3. 110 ohm termination. Signal Termination 4. 110 ohm termination. Signal Termination 5. 110 ohm termination. Reference Voltage 1. Must be externally connected directly to the VREF2 pin. Must be decoupled with a 4.7 F 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 F or 4.7 F. See Figure 2. Signal Termination 6. 110 ohm termination. Signal Termination 7. 110 ohm termination. Signal Termination 8. 110 ohm termination. Signal Termination 9. 110 ohm termination. No Connect. Do not connect any signal to this pin. Reference Voltage 2. Must be externally connected directly to the VREF1 pin. Must be decoupled with a 4.7 F capacitor as shown in Figure 2. Power Down. When tied low, the DS21S07A enters a powerdown mode. Contains an internal 50K pull-up. Strap low to deactivate the DS21S07A, leave open circuited to activate the DS21S07A. Heat Sink Ground. Internally connected to the mounting pad. Should be either grounded or electrically isolated from other circuitry. 3 4 5 6 7 9 2 3 4 5 6 7 R1 R2 R3 R4 R5 VREF1 10 11 8 9 GND TERMPWR2 13 14 15 16 17 19 10 11 12 13 14 15 R6 R7 R8 R9 NC VREF2 20 16 PD 2, 8, 12, 18 N/A HS-GND 022798 4/7 DS21S07A ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature -1.0V to +7.0V 0C to 70C -55C to +125C 260C 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. RECOMMENDED OPERATING CONDITIONS PARAMETER TERMPWR Voltage PD Active PD Inactive SYMBOL VTP VPDA VPDI MIN 4.00 -0.3 2.0 TYP MAX 5.50 +0.8 VTP +0.3 UNITS V V V (0C to 70C) NOTES DC CHARACTERISTICS PARAMETER TERMPWR Current Power Down Current Termination Resistance Die Thermal Shutdown Power Down Termination Capacitance Input Leakage High Input Leakage Low SYMBOL ITP ITP IPD RTERM TSD CPD IIH IIL -1.0 1.0 108 150 3.0 5.0 MIN TYP 2.5 100 110 MAX 250 5 150 112 UNITS mA mA A ohms C pF A A (0C to 70C) NOTES 1, 3 1, 4 1, 2, 5 1, 2 1, 6 1, 2, 5, 6 1, 8 1, 7 REGULATOR CHARACTERISTICS PARAMETER Output Voltage Drop Out Voltage Line Regulation Load Regulation Current Limit Sink Current SYMBOL VREF VDROP LIREG LOREG ILIM ISINK 200 MIN 2.79 TYP 2.85 0.50 1.0 1.3 350 MAX 2.93 0.75 2.0 3.0 UNITS V V % % mA mA (0C to 70C) NOTES 1, 2 3, 6 1, 4 1, 3 1 1 022798 5/7 DS21S07A NOTES: 1. 4.00V < TERMPWR < 5.50V. 2. 0.0V < signal lines < TERMPWR. 3. All signal lines = 0.0V. 4. All signal lines open. 5. PD = 0.0V. 6. Guaranteed by design; not production tested. 7. R1 through R9 only. 8. R1 through R9 and PD. DS21S07AS SCSI TERMINATOR 16-PIN SOIC (300 MIL) K G PKG DIM A IN. MM B IN. MM C IN. MM E IN. MM A C F IN. MM G IN. MM H IN. MM J IN. MM K IN. MM J L L IN. MM phi 0.016 0.40 0 0.040 1.02 8 0.094 2.38 0.105 2.68 16-PIN MIN 0.402 10.21 0.290 7.37 0.089 2.26 0.004 0.102 MAX 0.412 10.46 0.300 7.65 0.095 2.41 0.012 0.30 B H 1 E 0.050 BSC 1.27 BSC 0.398 10.11 0.009 0.229 0.013 0.33 0.416 10.57 0.013 0.33 0.019 0.48 F phi 022798 6/7 DS21S07A DS21S07AE SCSI TERMINATOR 20-PIN TSSOP D n E H SEE DETAIL A c B e1 A2 A A1 L DETAIL A phi G DIM A MM A1 MM A2 MM C MM L MM e1 MM B MM D MM E MM G MM H MM phi MIN - 0.05 0.75 0.09 0.50 MAX 1.10 - 1.05 0.18 0.70 0.65 BSC 0.18 6.40 0.30 6.90 4.40 NOM 0.25 REF 6.25 0 6.55 8 022798 7/7 |
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