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DS2105
DS2105 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 R9 R8 R7 R6 NC TERMPWR2
* Fully
SCSI
compliant with SCSI-1, Fast SCSI and Ultra
* Functionally compatible to the DS21S07A, targeted
for high volume applications
* Provides active termination for nine signal lines * Laser-trimmed 110
5% tolerance ohm termination resistors have
* Low dropout voltage * Power-down
from the bus mode isolates termination resistors
DS2105Z 16-PIN SOIC (150 MIL)
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 supports actively negated SCSI signals * Onboard thermal shutdown circuitry * 16-pin plastic SOIC (DS2105)
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.
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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 50K 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 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 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
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DS2105
TYPICAL SCSI BUS CONFIGURATION Figure 2
Termination Power Line + C2
DS2105
TERMPWR1 TERMPWR2 VREF1 VREF2 GND R1
DS2105
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 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 F recommended) can be added in parallel to C1 for applications using fast rise/fall time drivers.
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DS2105
PIN DESCRIPTION Table 1
DS2105S PIN 1 DS2105Z 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. 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 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. No Connect. Do not connect any signal to this pin.
2 3 4 5 6 7
2 3 4 5 6 7
R1 R2 R3 R4 R5 VREF1
8 9
8 9
GND TERMPWR2
10 11 12 13 15
11 12 13 14 15
R6 R7 R8 R9 VREF2
16
16
PD
14
10
NC
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DS2105
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 Input Leakage High Input Leakage Low SYMBOL ITP ITP IPD RTERM TSD CPD IIH IIL -1.0 1.0 110 150 3.0 5.0 MIN TYP 5 500 118 MAX 250 8 UNITS mA mA A ohm C pF A A
(0C to 70C)
NOTES 1, 3 1, 4 1, 2, 5 1, 2 1 1, 2, 5, 6 1, 8 1, 7
REGULATOR CHARACTERISTICS
PARAMETER Output Voltage Drop Out Voltage Output Current Line Regulation Load Regulation Current Limit Sink Current SYMBOL VREF VDROP IOUT LIREG LOREG ILIM ISINK 200 1.0 1.3 350 MIN 2.7 TYP 2.85 0.75 MAX 3.0 1.0 24.0 2.0 3.0 UNITS V V mA % % mA mA
(0C to 70C)
NOTES 1, 2 3, 6 9 1, 4 1, 2 1 1
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.
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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)
PKG DIM A IN. MM A1 IN. MM A2 IN. MM b IN. MM C IN MM D IN. MM e IN. MM E1 IN. MM H IN. MM L IN. MM
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II II
16-PIN MIN 0.053 1.35 0.004 0.10 0.048 1.24 0.012 0.30 0.007 0.17 0.386 9.80 MAX 0.069 1.75 0.010 0.25 0.062 1.57 0.020 0.50 0.011 0.28 0.393 9.98 0.050 BSC 1.27 BSC 0.150 3.81 0.230 5.84 0.016 0.40 0 0.158 4.01 0.244 6.20 0.050 0.89 8
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 DIM A IN. MM A1 IN. MM A2 IN. MM b IN. MM C IN MM D IN. MM e IN. MM E1 IN. MM H IN MM L IN MM 16-PIN MIN 0.094 2.38 0.004 0.102 0.089 2.26 0.013 0.33 0.009 0.229 0.398 10.11 MAX 0.105 2.68 0.012 0.30 0.095 2.41 0.020 0.51 0.013 0.33 0.412 10.46
0.050 BSC 1.27 BSC 0.290 7.37 0.398 10.11 0.016 0.40 0 0.300 7.62 0.416 10.57 0.040 1.02 8
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