DS2105 [DALLAS]
SCSI Terminator; SCSI终结者
| 型号： | DS2105 |
| 厂家： | 
DALLAS SEMICONDUCTOR |
| 描述： | SCSI Terminator |
| 文件： | 总7页 (文件大小：103K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DS2105
DS2105
SCSI Terminator
FEATURES
PIN ASSIGNMENT
• Fully compliant with SCSI–1, Fast SCSI and Ultra
TERMPWR1
PD
1
2
3
4
16
15
14
SCSI
VREF2
R1
R2
R3
R9
R8
• Functionally compatible to the DS21S07A, targeted
for high volume applications
13
12
R7
R6
5
R4
R5
• Provides active termination for nine signal lines
11
6
7
8
VREF1
GND
NC
• Laser–trimmed 110 ohm termination resistors have
5% tolerance
10
9
TERMPWR2
DS2105Z 16–PIN SOIC (150 MIL)
• Low dropout voltage
TERMPWR1
PD
1
2
3
4
• Power–down mode isolates termination resistors
16
15
14
VREF2
NC
from the bus
R1
R2
R3
• Fully supports actively negated SCSI signals
• Onboard thermal shutdown circuitry
• 16–pin plastic SOIC (DS2105)
R9
13
12
R8
R7
5
R4
R5
11
6
7
8
VREF1
GND
R6
10
9
TERMPWR2
DS2105S 16–PIN SOIC (300 MIL)
DESCRIPTION
Fast SCSI and Ultra SCSI require the use of active ter-
minations 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 volt-
age 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 regula-
tor and nine precise switched 110 ohm termination re-
sistors 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 termina-
tion but not the high performance of the DS21S07A.
The DS2105 is offered in both 300 mil and 150 mil SOIC
packages.
022698 1/7
DS2105
from the circuit. The power–down pin (PD) has an inter-
nal 50KΩ pull–up resistor. To place the DS2105 into an
active state, the PD pin should be left open circuited.
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 pro-
duces 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
signalline turns off, the terminator will pull the signal line
to 2.85V (quiescent state). To handle actively negated
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
mustbetiedtogetherexternally. EachDS2105requires
a 4.7 µF capacitor connected between the VREF pins
andground. Figure2detailsatypicalSCSIbusconfigu-
ration. 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), threeDS2105’swouldbeneededateachendof
the SCSI cable in order to terminate the 27 active signal
lines.
SCSI signals, the buffer can sink 200 mA, and V
will
REF
move less than 60 mV. When all lines settle in the quies-
cent 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
DS2105 BLOCK DIAGRAM Figure 1
PD
TERMPWR1
POWER
DOWN
CIRCUITRY
TERMPWR2
50K ohm
110 ohms
110 ohms
R1
R2
BANDGAP
REFERENCE
110 ohms
110 ohms
110 ohms
R3
R4
R5
R6
R7
R8
110 ohms
110 ohms
110 ohms
110 ohms
GND
R9
VREF1
VREF2
022698 2/7
DS2105
TYPICAL SCSI BUS CONFIGURATION Figure 2
Termination Power Line
+
DS2105
C2
DS2105
TERMPWR1
TERMPWR2
VREF1
TERMPWR1
TERMPWR2
VREF1
VREF2
VREF2
+
+
C1
C1
SCSI
CABLE
GND
R1
GND
R1 R2
R8 R9
R9
SCSI
BUS
TRANSCEIVER
SCSI
BUS
TRANSCEIVER
SCSI
BUS
SCSI
BUS
TRANSCEIVER
TRANSCEIVER
NOTES:
1. C1 = 4.7 µF tantalum
C2 = 2.2 µF tantalum or 4.7 µF 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 µF recommended) can be added in parallel to C1 for applications using
fast rise/fall time drivers.
022698 3/7
DS2105
PIN DESCRIPTION Table 1
DS2105S
PIN
DS2105Z
PIN
SYMBOL
DESCRIPTION
1
1
TERMPWR1 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.
2
3
4
5
6
7
2
3
4
5
6
7
R1
R2
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.
R3
R4
R5
VREF1
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.
8
9
8
9
GND
Ground. Signal ground; 0.0V.
TERMPWR2 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.
10
11
12
13
15
11
12
13
14
15
R6
R7
Signal Termination 6. 110 ohm termination.
Signal Termination 7. 110 ohm termination.
Signal Termination 8. 110 ohm termination.
Signal Termination 9. 110 ohm termination.
R8
R9
VREF2
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.
16
14
16
10
PD
NC
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.
022698 4/7
DS2105
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
Operating Temperature
–1.0V to +7.0V
0°C to 70°C
Storage Temperature
Soldering Temperature
–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 maximum rating
conditions for extended periods of time may affect reliability.
RECOMMENDED OPERATING CONDITIONS
(0°C to 70°C)
PARAMETER
TERMPWR Voltage
PD Active
SYMBOL
MIN
4.00
–0.3
2.0
TYP
MAX
5.25
+0.8
UNITS
NOTES
V
TP
V
V
V
V
PDA
PD Inactive
V
PDI
V
+0.3
TP
DC CHARACTERISTICS
PARAMETER
(0°C to 70°C)
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
TERMPWR Current
I
I
250
8
mA
mA
1, 3
1, 4
TP
5
TP
Power Down Current
Termination Resistance
Die Thermal Shutdown
I
500
µA
ohm
°C
1, 2, 5
1, 2
PD
R
110
118
5.0
TERM
T
150
3.0
1
SD
Power Down Termination
Capacitance
C
pF
1, 2, 5, 6
PD
Input Leakage High
Input Leakage Low
I
–1.0
µA
µA
1, 8
1, 7
IH
I
1.0
IL
REGULATOR CHARACTERISTICS
(0°C to 70°C)
PARAMETER
Output Voltage
Drop Out Voltage
Output Current
Line Regulation
Load Regulation
Current Limit
SYMBOL
MIN
TYP
2.85
0.75
MAX
3.0
UNITS
V
NOTES
1, 2
3, 6
9
V
REF
2.7
V
DROP
1.0
V
I
24.0
2.0
mA
%
OUT
LI
REG
1.0
1.3
350
1, 4
1, 2
1
LO
3.0
%
REG
LIM
I
mA
mA
Sink Current
I
200
1
SINK
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.
022698 5/7
DS2105
6. Guaranteed by design; not production tested.
7. R through R only.
1
9
8. R through R and PD.
1
9
9. V
=0.2V.
SIGNAL
DS2105Z SCSI TERMINATOR 16–PIN SOIC (150 MIL)
PKG
DIM
16–PIN
MIN
MAX
A IN.
MM
0.053
1.35
0.069
1.75
A1 IN.
MM
0.004
0.10
0.010
0.25
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
Θ
0°
8°
022698 6/7
DS2105
DS2105S SCSI TERMINATOR 16–PIN SOIC (300 MIL)
Thechamferonthebodyisoptional. Ifitisnotpresent, a
terminal 1 identifier must be positioned so that 1/2 or
more of its area is contained in the hatched zone.
PKG
DIM
16–PIN
MIN
MAX
A IN.
MM
0.094
2.38
0.105
2.68
A1 IN.
MM
0.004
0.102
0.012
0.30
A2 IN.
MM
0.089
2.26
0.095
2.41
b IN.
MM
0.013
0.33
0.020
0.51
C IN
MM
0.009
0.229
0.013
0.33
D IN.
MM
0.398
10.11
0.412
10.46
e IN.
MM
0.050 BSC
1.27 BSC
E1 IN.
MM
0.290
7.37
0.300
7.62
H IN
MM
0.398
10.11
0.416
10.57
L IN
MM
0.016
0.40
0.040
1.02
Θ
0°
8°
022698 7/7
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