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| DS2107A DS2107A 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 compliant with SCSI and SCSI-2 standards * Backward compatible to the DS2107S * Provides active termination for 9 signal lines * Laser-trimmed 1% tolerance 110 ohm termination resistors have * Low dropout voltage * Power-down mode isolates termination resistors from the bus DS2107AS 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 * Handles actively negated SCSI signals * Onboard thermal shutdown circuitry * 16-pin plastic SOIC (DS2107AS) and 20-pin plastic thin SSOP (DS2107AE) DS2107AE 20-Pin TSSOP (173 mil) ACTUAL FOOTPRINT SIZE .41" .26" .41" .27" DS2107AS DS2107AE DESCRIPTION The SCSI-2 standard recommends the use of active terminations at both ends of every cable segment in a SCSI system with single-ended drivers and receivers. The DS2107A SCSI Terminator, which is fully compliant with the standard, 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 DS2107A integrates a regulator and nine precise switched 110 ohm termination resistors into a monolithic IC. 022698 1/7 DS2107A FUNCTIONAL DESCRIPTION The DS2107A 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. When all lines settle in the quiescent state, the regulator will consume about 5 mA. When the DS2107A is put into powerdown mode by bringing PD low, the power-down circuitry will turn off the transistors on each signal line. This will isolate the DS2107A from the signal lines and effectively remove it from the circuit. The power-down pin (PD) has an internal 50K ohm pull-up resistor. To place the DS2107A 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 DS2107A requires parallel 0.1 F and 4. 7 F capacitors 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 DS2107A'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 DS2107A's would be needed at each end of the SCSI cable in order to terminate the 27 active signal lines. DS2107A 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 DS2107A TYPICAL SCSI BUS CONFIGURATION Figure 2 Termination Power Line + C3 DS2107A TERMPWR1 TERMPWR2 VREF1 VREF2 GND R1 SCSI Cable R8 R9 C3 + DS2107A TERMPWR1 TERMPWR2 VREF1 VREF2 GND R1 R2 C1 C2 + C1 C2 + R9 SCSI Bus Transceiver SCSI Bus Transceiver SCSI Bus Transceiver SCSI Bus Transceiver NOTES: 1. C1 = 0.1F ceramic C2 = 4.7F tantalum C3 = 2.2 F tantalum or 4.7 F aluminum 2. If the DS2107A 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. 022698 3/7 DS2107A PIN DESCRIPTION Table 1 DS2107AE PIN 1 DS2107AS PIN 1 SYMBOL TERMPWR1 DESCRIPTION Termination Power 1. Should be connected to the SCSI TERMPWR line. Must be decoupled with either a 2.2F or 4.7F. 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 4.7F and a 0.1F 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 2.2F or 4.7F. 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 4.7F and a 0.1F as shown in Figure 2. Power Down. When tied low, the DS2107A enters a power-down mode. Contains an internal 50K pull-up. Strap low to deactivate the DS2107A, leave open circuited to activate the DS2107A. 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 022698 4/7 DS2107A 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 5.25 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 PD Hysteresis SYMBOL ITP ITP IPD RTERM TSD CPD HPD 108 MIN TYP 5 100 110 150 8.5 280 10 112 MAX 250 8 UNITS mA mA A ohms C pF mV (0C to 70C) NOTES 1,3 1,4 1,2,5 1,2 1 1,2,5,6 1 REGULATOR CHARACTERISTICS PARAMETER Output Voltage Drop Out Voltage Line Regulation Load Regulation Current Limit Sink Current SYMBOL VREF VDROP LIREG LOREG ILIM ISINK 300 MIN 2.79 TYP 2.85 0.75 1.0 1.3 350 200 MAX 2.91 1.0 2.0 3.0 400 UNITS V V % % mA mA (0C to 70C) NOTES 1,2 3,6 1,4,6 1,2,6 1 1 NOTES: 1. 2. 3. 4. 5. 6. 4.00V < TERMPWR < 5.25V. 0.0V < signal lines < 3.0V. All signal lines = 0.0V. All signal lines open. PD = 0.0V. Guaranteed by design; not production tested. 022698 5/7 DS2107A DS2107AS SCSI TERMINATOR 16-PIN SOIC (300 MIL) K G B H 1 A C phi F E J L PKG DIM A IN. MM B IN. MM C IN. MM E IN. MM F IN. MM G IN. MM H IN. MM J IN. MM K IN. MM L IN. MM phi 16-PIN MIN 0.402 10.21 0.290 7.37 0.089 2.26 0.004 0.102 0.094 2.38 MAX 0.412 10.46 0.300 7.65 0.095 2.41 0.012 0.30 0.105 2.68 0.050 BSC 1.27 BSC 0.398 10.11 0.009 0.229 0.013 0.33 0.016 0.40 0 0.416 10.57 0.013 0.33 0.019 0.48 0.040 1.02 8 022698 6/7 DS2107A DS2107AE SCSI TERMINATOR 20-PIN TSSOP (PRELIMINARY) 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 022698 7/7 |
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