DS2114
DS2114
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
NC
VREF2
R9
R8
R7
R6
NC
TERMPWR2
•
Fully compliant with SCSI, SCSI–2 and SCSI–3 stan-
dards
•
Provides active termination for nine signal lines
•
Laser–trimmed 110 ohms termination resistors have
2% tolerance
•
Low dropout voltage regulator
•
Fully supports actively negated SCSI signals
•
Onboard thermal shutdown circuitry
•
Narrow 16–pin plastic SOIC (DS2114Z)
DS2114Z 16–PIN SOIC (150 MIL)
DESCRIPTION
The SCSI–2 and SCSI–3 standards recommend the
use of active terminations at both ends of every cable
segment in a SCSI system with single–ended drivers
and receivers. The DS2114 SCSI Terminator, which is
fully compliant with these standards, enables the de-
signer to gain the benefits of active termination: greater
immunity to voltage drops on the TERMPWR (TER-
Mination PoWeR) line, enhanced high–level noise im-
munity, intrinsic TERMPWR decoupling, and very low
quiescent current consumption. The DS2114 integrates
a regulator and nine precise 110 ohms termination re-
sistors into a monolithic IC. The DS2114 is intended for
cable end terminator assemblies and devices where the
terminators do not need to be isolated from the SCSI
bus.
070198 1/6
DS2114
FUNCTIONAL DESCRIPTION
The DS2114 consists of a bandgap reference, buffer
amplifier, and nine termination resistors (Figure 1). The
bandgap reference circuit produces a precise 2.55 volts
level which is fed to a buffer amplifier. The buffer pro-
duces a 2.85 volts 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 2.85 volts (quiescent state). To handle actively ne-
gated SCSI signals, the buffer can sink at least 200 mA
and V
ref
will move less than 60 mV. When all lines settle
in the quiescent state, the regulator will consume about
2.5 mA.
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 DS2114 requires
a 4.7
µF
capacitor connected between the VREF pins
and ground. Figure 2 details a typical SCSI bus configu-
ration. In an 8–bit wide SCSI bus arrangement (“A”
Cable), two DS2114’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 DS2114’s would be needed at each end of
the SCSI cable in order to terminate the 27 active signal
lines.
DS2114 BLOCK DIAGRAM
Figure 1
TERMPWR1
TERMPWR2
BANDGAP
REFERENCE
110 ohms
R1
110 ohms
R2
110 ohms
+
R3
110 ohms
R4
110 ohms
R5
110 ohms
R6
110 ohms
–
GND
110 ohms
R7
R8
110 ohms
R9
VREF1
VREF2
070198 2/6
DS2114
TYPICAL SCSI BUS CONFIGURATION
Figure 2
Termination Power Line
+
C2
DS2114
TERMPWR1
TERMPWR2
VREF1
VREF2
GND
R1
DS2114
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
µF
tantalum
C2 = 2.2
µF
tantalum or 4.7
µF
aluminum
2. If the DS2114 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.
070198 3/6
DS2114
PIN DESCRIPTION
Table 1
DS2114Z
PIN
1
2
3
4
5
6
7
8
9
11
12
13
14
10, 16
15
SYMBOL
TERMPWR1
R1
R2
R3
R4
R5
VREF1
GND
TERMPWR2
R6
R7
R8
R9
NC
VREF2
DESCRIPTION
Termination 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.
Signal Termination 1.
110 ohms termination.
Signal Termination 2.
110 ohms termination.
Signal Termination 3.
110 ohms termination.
Signal Termination 4.
110 ohms termination.
Signal Termination 5.
110 ohms termination.
Reference 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.
Ground.
Signal ground; 0.0 volts.
Termination 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.
Signal Termination 6.
110 ohms termination.
Signal Termination 7.
110 ohms termination.
Signal Termination 8.
110 ohms termination.
Signal Termination 9.
110 ohms termination.
No Connect.
Do not connect any signal to these pins.
Reference 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.
070198 4/6
DS2114
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
Operating Temperature
Storage Temperature
Soldering Temperature
–1.0V to +7.0V
0°C to 70°C
–55°C to +125°C
260°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 maxi-
mum rating conditions for extended periods of time may affect reliability.
The Dallas Semiconductor DS2114 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 DS2114 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
PARAMETER
TERMPWR Voltage
SYMBOL
V
TP
MIN
4.00
TYP
MAX
5.50
UNITS
V
(0
°
C to 70
°
C)
NOTES
DC CHARACTERISTICS
PARAMETER
TERMPWR Current
Termination Resistance
Die Thermal Shutdown
Termination Capacitance
SYMBOL
I
TP
I
TP
R
TERM
T
SD
C
T
110
150
5.0
MIN
TYP
5
MAX
250
8
116
UNITS
mA
mA
ohms
°C
pF
(0
°
C to 70
°
C)
NOTES
1, 3
1, 4
1, 2
1, 5
1, 2, 5
REGULATOR CHARACTERISTICS
PARAMETER
Output Voltage
Drop Out Voltage
Line Regulation
Output Current
Load Regulation
Current Limit
Sink Current
SYMBOL
V
REF
V
DROP
LI
REG
I
OUT
LO
REG
I
LIM
I
SINK
280
200
1.3
MIN
2.7
TYP
2.85
0.75
1.0
MAX
3.0
1.0
2.0
24.0
3.0
500
UNITS
V
V
%
mA
%
mA
mA
(0
°
C to 70
°
C)
NOTES
1, 2
3, 5
1, 4
6
1, 3
1
1
NOTES:
1. 4.00 volts < TERMPWR < 5.50 volts.
2. 0.0 volts < signal lines < TERMPWR.
3. All signal lines = 0.0 volts.
4. All signal lines open.
5. Guaranteed by design; not production tested.
6. V
SIGNAL
= 0.2V.
070198 5/6
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