DS21T05Z+ Fast Delivery |IC PHOENIX CO.,LIMITED

DS21T05Z+ ,SCSI TerminatorFUNCTIONAL DESCRIPTIONThe DS21T05 consists of a bandgap reference, buffer amplifier, and nine termi ..
DS21T06 , SCSI Terminator
DS21T07 ,SCSI TerminatorFUNCTIONAL DESCRIPTIONThe DS21T07 consists of a bandgap reference, buffer amplifier, and nine termi ..
DS21T07E ,SCSI TerminatorFUNCTIONAL DESCRIPTIONThe DS21T07 consists of a bandgap reference, buffer amplifier, and nine termi ..
DS21T07S ,SCSI TerminatorFUNCTIONAL DESCRIPTIONThe DS21T07 consists of a bandgap reference, buffer amplifier, and nine termi ..
DS21T07S+ ,SCSI TerminatorFEATURES PIN ASSIGNMENT Fully compliant with SCSI–1, Fast SCSI andUltra SCSI1 16TERMPWR1 PD Backw ..
E53NA50 ,NABSOLUTE MAXIMUM RATINGSSymbol Parameter Value UnitV Drain-source Voltage (V =0) 500 VDS GSV 500 VD ..

DS21T05Z+
SCSI Terminator
FEATURESFully compliant with SCSI-1, Fast SCSI and
Ultra SCSIFunctionally compatible to the DS21T07,
targeted for high volume applicationsProvides active termination for nine signal
linesLaser-trimmed 110-ohm termination resistors
have 5% toleranceLow dropout voltagePower-down mode isolates termination
resistors from the busSCSI bus hot-plug compatibleFully supports actively negated SCSI signalsOnboard thermal shutdown circuitry16-pin plastic narrow SOIC
PIN ASSIGNMENT
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 DS21T05 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 DS21T05,
which integrates a regulator and nine precise-switched, 110-ohm termination resistors into a monolithic
IC, is a functionally compatible version of the DS21T07. With relaxed output current and termination
tolerances, the DS21T05 is intended for high volume applications which require active termination but
not the high performance of the DS21T07.
FUNCTIONAL DESCRIPTION
The DS21T05 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
DS21T05
SCSI Terminator
www.dalsemi.com
TERMPWR1
VREF1
GND
DS21T05Z 16-Pin SOIC (150-mil)
VREF2
TERMPWR2
VREF2
TERMPWR2
TERMPWR1
VREF1
GND
DS21T05S 16-Pin SOIC (300-mil)
DS21T05
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 DS21T05 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 DS21T05 from the signal lines and effectively remove it from the circuit. The power-down pinPD) has an internal 50 kΩ=pullup resistor. To place the DS21T05 into an active state, the PD pin should
be left open circuited. When installed on disk drives or RAID system components, the DS21T05 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
DS21T05 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, two DS21T05s 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, three DS21T05’s would be needed at each end of the SCSI cable in order to terminate the
27 active signal lines.
DS21T05 BLOCK DIAGRAM Figure 1
DS21T05
TYPICAL SCSI BUS CONFIGURATION Figure 2
NOTES:
1. C1 = 4.7 μF tantalum
C2 = 2.2 μF tantalum or 4.7 μF aluminum
2. If the DS21T05 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.
DS21T05DS21T05
DS21T05
PIN DESCRIPTION Table 1
DS21T05Z
PIN
SYMBOLDESCRIPTIONTERMPWR1Termination 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.
2R1Signal Termination 1. 110-ohm termination.
3R2Signal Termination 2. 110-ohm termination.
4R3Signal Termination 3. 110-ohm termination.
5R4Signal Termination 4. 110-ohm termination.
6R5Signal Termination 5. 110-ohm termination.
7VREF1Reference 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.GNDGround. Signal ground; 0.0V.TERMPWR2Termination 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.NCNo Connect. Do not connect any signal to this pin.R6Signal Termination 6. 110-ohm termination.R7Signal Termination 7. 110-ohm termination.R8Signal Termination 8. 110-ohm termination.R9Signal Termination 9. 110-ohm termination.VREF2Reference 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.PDPower Down. When tied low, the DS21T05 enters a power-down
mode. Contains an internal 50K pull-up. Strap low to deactivate the
DS21T05, leave open circuited to activate the DS21T05.
DS21T05
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground-1.0V to +7.0V
Operating Temperature0°C to 70°C
Storage Temperature-55°C to +125°C
Soldering Temperature260°C for 10 secondsThis 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 DS21T05 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 DS21T05 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.
RECOMMENDED OPERATING CONDITIONS(0°C to 70°C)
PARAMETERSYMMINTYPMAXUNITSNOTES
TERMPWR VoltageVTP4.005.50V ActiveVPDA-0.3+0.8V InactiveVPDI2.0VTP + 0.3V
DC CHARACTERISTICS(0°C to 70°C)
PARAMETERSYMBOLMINTYPMAXUNITSNOTES
TERMPWR CurrentITP
ITP5
1, 3
1, 4
Power-Down CurrentIPD500μA1, 2, 5
Termination ResistanceRTERM107.5110119.5ohm1, 2
Die Thermal ShutdownTSD150°C1, 6
Power Down
Termination Capacitance
CPD3.0pF1, 2, 5, 6
Input Leakage HighIIH-1.0μA1, 8
Input Leakage LowIIL1.0μA1, 7
REGULATOR CHARACTERISTICS(0°C to 70°C)
PARAMETERSYMBOLMINTYPMAXUNITSNOTES
Output VoltageVREF2.72.853.1V1, 2
Drop Out VoltageVDROP0.751.0V3, 6
Output CurrentIOUT25.2mA9
Line RegulationLIREG1.02.0%1, 4
Load RegulationLOREG1.33.0%1, 2
Current LimitILIM350mA1
Sink CurrentISINK200mA1
DS21T05
NOTES:
1. 4.00V < TERMPWR < 5.50V.
2. 0.0V < signal lines < 3.0V.
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.
9. VSIGNAL = 0.2V.
DS21T05Z SCSI TERMINATOR 16-PIN SOIC (150-MIL)
PKG16-PIN
DIMMINMAX
A IN.
A1 IN.
A2 IN.
b IN.
C IN.
D IN.
e IN.
0.050 BSC
1.27 BSC
E1 IN.
H IN.
6.20

Partno	Mfg	Dc	Qty	Available	Descript
DS21T05Z+	MAX	N/a	75	avai	SCSI Terminator