DS2108S/T&R ,Differential SCSI Switchable TerminatorFEATURES PIN ASSIGNMENT Fully compliant with SCSI, SCSI-2 and SCSI-3 standards1 24TPWR PD Conform ..
DS2109 ,Plug and Play SCSI TerminatorFUNCTIONAL DESCRIPTIONSCSI–2 (X3.131–1994) The DS2109 is designed to be a single chip terminationSC ..
DS2117M ,Ultra2 LVD/SE SCSI TerminatorFUNCTIONAL DESCRIPTIONThe DS2117 combines LVD and SE termination with DIFFSENSE sourcing and detect ..
DS2118M ,Ultra3 LVD/SE SCSI TerminatorFEATURES PIN CONFIGURATION Fully Compliant with SCSI SPI-2, SPI-3, SPI-4, Ultra160, and Ultra32 ..
DS2118MB ,Ultra2 LVD/SE SCSI TerminatorFEATURES PIN CONFIGURATION Fully Compliant with SCSI SPI-2, SPI-3, SPI-4, Ultra160, and Ultra32 ..
DS2118M-B ,Ultra2 LVD/SE SCSI TerminatorFEATURES PIN CONFIGURATION Fully Compliant with SCSI SPI-2, SPI-3, SPI-4, Ultra160, and Ultra32 ..
DS2108S/T&R
Differential SCSI Switchable Terminator
FEATURESFully compliant with SCSI, SCSI-2 and SCSI-
3 standardsConforms to EIA RS-485 standardProvides differential termination for 9 pairs of
signal linesOperates with SCSI signal voltages of -7 to
+12 VoltsLaser-trimmed 330 and 150-ohm termination
resistors have ±5% tolerance over full
temperature rangeSwitchable power-down modeLow power down capacitance of 6 pF24-pin plastic SOIC (DS2108S)
PIN ASSIGNMENT
DESCRIPTIONThe DS2108 SCSI Terminator has been specifically designed for High Voltage Differential (HVD) SCSI
systems requiring switchable termination. The DS2108 integrates eighteen 330-ohm and nine 150-ohm
precise switched termination resistors into a monolithic IC. The surface mount SOIC package saves board
space over conventional resistor SIPs. The termination resistors can be isolated from the SCSI bus under
software or hardware control. While in the powered down mode, the DS2108 isolates the nine terminator
blocks from the bus while adding only 6 pF capacitance to each signal line of the SCSI bus.
FUNCTIONAL DESCRIPTIONThe DS2108 consists of power-down circuitry, eighteen 330-ohm and nine 150-ohm termination resistors
(Figure 1). The DS2108 can be removed from the circuit by bringing the power down pin (PD) low. The
power down capacitance on the terminating resistors is 6 pF, well below the SCSI-3 allotment of 25 pF.
The DS2108 supports SCSI signal voltages of -7 to +12 volts when powered on or off. When all lines
settle into the quiescent state (no signal transitions), 56 mA is typically consumed. Only 1 mA is
typically consumed in the powered down mode.
DS2108
Differential SCSI Switchable Terminator
www.dalsemi.comGND
R1P
R3P
R4P
R5P
R6P
R7P
R8P
R9P
GND
R2P
TPWR
R1N
R2N
R4N
R5N
R6N
R7N
R8N
R9N
TPWR
R3N
DS2108S 24-Pin SOIC (300-mil)
DS2108
DS2108 BLOCK DIAGRAM Figure 1
DS2108
TYPICAL DIFFERENTIAL SCSI BUS CONFIGURATION Figure 2
NOTES:1. Two DS2108s required per 8–bit SCSI device and three DS2108s per 16–bit SCSI device.
2. Mid–bus termination effectively removed by grounding PD pin.
3. Termination power to be provided as specified in SCSI–3 Parallel Interface (SPI) document.
4. Local TERMPWR bypassing is recommended by the SPI document with values shown. The bypass
capacitors should be located as close as possible to the DS2108s. Only one pair of capacitors is
required per SCSI device (may be shared between DS2108s on same device).
PIN DESCRIPTION Table 1
PINSYMBOLDESCRIPTION1, 11TPWR
Termination Power. Should be connected to the SCSI TERMPWR line.Bypass with a 2.2 μF cap in parallel with a 0.1 μF cap as shown in Figure
2, 3, 4, 5, 6,
7, 8, 9, 10
R1N…R9N
Signal Termination Negative. Connect to –SIGNAL of SCSI bus.NC
No Connect. Do not connect any signal to this pin.13, 23GND
Ground. Signal ground; 0.0V.14, 15, 16,
17, 18, 19,
20, 21, 22
R1P…R9P
Signal Termination Positive. Connect to +SIGNAL of SCSI bus.PD
Power Down. When tied low, the DS2108 enters a power-down mode.Contains an internal 50K pull-up. Strap low to deactivate the DS2108,
leave open circuited to activate the DS2108.
DS2108
ABSOLUTE MAXIMUM RATINGS*Voltage on Any Pin Relative to Ground-7.0V to +12.0V
Operating Temperature0°C to 70°C
Storage Temperature-55°C to +125°C
Soldering Temperature260°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.
RECOMMENDED OPERATING CONDITIONS(0°C to 70°C)
PARAMETERSYMMINTYPMAXUNITSNOTESTERMPWR VoltageVTP4.005.25V ActiveVPDA-0.30.8V InactiveVPDI2.00VTP +
DC CHARACTERISTICS
PARAMETERSYMBOLMINTYPMAXUNITSNOTES
TERMPWR CurrentITP5665mA1, 6
Power-down CurrentIPD12mA1, 5
Command Mode
Voltage
Vem7.012.0V7, 8
Termination ResistanceRTTN313.5330346.5ohms2
Termination ResistanceRTNP142.5150157.5ohms3
Termination ResistanceRTPG313.5330346.5ohms4
Power-down
Termination
Capacitance
CPD56pF1, 5, 7
NOTES:1. 4.00V < TERMPWR < 5.25V
2. 330 Ω=resistor between TERMPWR and -SIGNAL.
3. 150 Ω=resistor between -SIGNAL and +SIGNAL.
4. 330 Ω=resistor between +SIGNAL and GDN.
5. PD = 0.0V.
6. Signal pins left open.
7. Guaranteed by design; not production tested.
8. Signal lines RxN and RxP only.
DS2108
24-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
½ or more of its area is contained in the hatched zone.
PKG24-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.
L IN.
1.02
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