DS2114
SCSI Terminator
DS2114
070198 1/6
FEATURES
Fully compliant with SCSI, SCSI2 and SCSI3 stan-
dards
Provides active termination for nine signal lines
Lasertrimmed 110 ohms termination resistors have
2% tolerance
Low dropout voltage regulator
Fully supports actively negated SCSI signals
Onboard thermal shutdown circuitry
Narrow 16pin plastic SOIC (DS2114Z)
PIN ASSIGNMENT
1
2
3
4
5
6
7
8
9
DS2114Z 16PIN SOIC (150 MIL)
TERMPWR1
R1
R2
R3
R4
R5
VREF1
GND
NC
VREF2
R9
R8
R7
R6
NC
TERMPWR2
11
12
13
14
15
16
10
DESCRIPTION
The SCSI2 and SCSI3 standards recommend the
use of active terminations at both ends of every cable
segment in a SCSI system with singleended 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 highlevel 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.
DS2114
070198 2/6
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
F capacitor connected between the VREF pins
and ground. Figure 2 details a typical SCSI bus configu-
ration. In an 8bit 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 16bit 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
GND
TERMPWR1
TERMPWR2
BANDGAP
REFERENCE
R1
R2
R3
R4
R5
R6
R7
R8
R9
VREF1
VREF2
+
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
DS2114
070198 3/6
TYPICAL SCSI BUS CONFIGURATION Figure 2
Termination Power Line
SCSI
BUS
TRANSCEIVER
SCSI
BUS
TRANSCEIVER
SCSI
BUS
TRANSCEIVER
SCSI
BUS
TRANSCEIVER
DS2114
TERMPWR1
TERMPWR2
VREF1
VREF2
GND
R1
R2
R9
DS2114
R8
TERMPWR1
TERMPWR2
VREF1
VREF2
GND
R1
R9
SCSI
CABLE
C1
+
C1
+
+
C2
NOTES:
1. C1 = 4.7
F tantalum
C2 = 2.2
F tantalum or 4.7
F 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
F recommended) can be added in parallel to C1 for applications using
fast rise/fall time drivers.
DS2114
070198 4/6
PIN DESCRIPTION Table 1
DS2114Z
PIN
SYMBOL
DESCRIPTION
1
TERMPWR1
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.
2
R1
Signal Termination 1. 110 ohms termination.
3
R2
Signal Termination 2. 110 ohms termination.
4
R3
Signal Termination 3. 110 ohms termination.
5
R4
Signal Termination 4. 110 ohms termination.
6
R5
Signal Termination 5. 110 ohms termination.
7
VREF1
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.
8
GND
Ground. Signal ground; 0.0 volts.
9
TERMPWR2
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.
11
R6
Signal Termination 6. 110 ohms termination.
12
R7
Signal Termination 7. 110 ohms termination.
13
R8
Signal Termination 8. 110 ohms termination.
14
R9
Signal Termination 9. 110 ohms termination.
10, 16
NC
No Connect. Do not connect any signal to these pins.
15
VREF2
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.
DS2114
070198 5/6
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
1.0V to +7.0V
Operating Temperature
0
C to 70
C
Storage Temperature
55
C to +125
C
Soldering Temperature
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 burnin, that some industrial applications require. For
specific reliability information on this product, please contact the factory in Dallas at (972) 3714448.
RECOMMENDED OPERATING CONDITIONS
(0
C to 70
C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
TERMPWR Voltage
V
TP
4.00
5.50
V
DC CHARACTERISTICS
(0
C to 70
C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
TERMPWR Current
I
TP
I
TP
5
250
8
mA
mA
1, 3
1, 4
Termination Resistance
R
TERM
110
116
ohms
1, 2
Die Thermal Shutdown
T
SD
150
C
1, 5
Termination Capacitance
C
T
5.0
pF
1, 2, 5
REGULATOR CHARACTERISTICS
(0
C to 70
C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
Output Voltage
V
REF
2.7
2.85
3.0
V
1, 2
Drop Out Voltage
V
DROP
0.75
1.0
V
3, 5
Line Regulation
LI
REG
1.0
2.0
%
1, 4
Output Current
I
OUT
24.0
mA
6
Load Regulation
LO
REG
1.3
3.0
%
1, 3
Current Limit
I
LIM
280
500
mA
1
Sink Current
I
SINK
200
mA
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.
DS2114
070198 6/6
DS2114Z SCSI TERMINATOR 16PIN SOIC (150 MIL)
PKG
16PIN
DIM
MIN
MAX
A IN.
MM
0.053
1.35
0.069
1.75
A1 IN.
MM
0.004
0.10
0.010
0.2
5
A2 IN.
MM
0.048
1.24
0.062
1.57
b IN.
MM
0.012
0.30
0.020
0.50
C IN
MM
0.007
0.17
0.011
0.28
D IN.
MM
0.386
9.80
0.393
9.98
e IN.
MM
0.050 BSC
1.27 BSC
E1 IN.
MM
0.150
3.81
0.158
4.01
H IN.
MM
0.230
5.84
0.244
6.20
L IN.
MM
0.016
0.40
0.050
0.89
0
8
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