DS21T07E [MAXIM]
SCSI Terminator, 9-Line, 110ohm, PDSO20, 0.173 INCH, PLASTIC, TSSOP-20;
| 型号： | DS21T07E |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | SCSI Terminator, 9-Line, 110ohm, PDSO20, 0.173 INCH, PLASTIC, TSSOP-20 光电二极管 接口集成电路 |
| 文件： | 总7页 (文件大小：106K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DS21T07
SCSI Terminator
www.dalsemi.com
FEATURES
PIN ASSIGNMENT
ꢀ Fully compliant with SCSI–1, Fast SCSI and
Ultra SCSI
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
TERMPWR1
PD
VREF2
NC
R9
R8
R7
R6
ꢀ Backward compatible to the DS2107,
DS2107A, and DS21S07
ꢀ Provides active termination for nine signal
lines
ꢀ Laser–trimmed 110 ohms termination
resistors have 2% tolerance
ꢀ Low dropout voltage regulator
ꢀ Power–down mode isolates termination
resistors from the bus
ꢀ SCSI bus hot–plug compatible
ꢀ Fully supports actively negated SCSI signals
ꢀ Onboard thermal shutdown circuitry
ꢀ 16–pin plastic SOIC (DS21T07S) and 20–pin
plastic TSSOP (Thin Shrink Small Outline
Package) (DS21T07E)
R1
R2
R3
R4
R5
VREF1
GND
TERMPWR2
DS21T07S 16-pin SOIC (300-mil)
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
TERMPWR1
HS-GND
R1
PD
VREF2
HS-GND
NC
R9
R8
R2
R3
R4
R5
R7
R6
HS-GND
VREF1
GND
HS-GND
TERMPWR2
DS21T07E 20-pin TSSOP (173-mil)
ACTUAL FOOTPRINT SIZE
0.41”
0.26”
0.41”
0.27”
DS21T07S
DS21T07E
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 DS21T07 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 DS21T07
integrates a regulator and nine precise switched 110 ohms termination resistors into a monolithic IC. The
DS21T07 can be electrically isolated from the SCSI bus without physical removal from the SCSI device.
1 of 7
112099
DS21T07
FUNCTIONAL DESCRIPTION
The DS21T07 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
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 2.85V (quiescent state). To handle actively negated SCSI signals,
the buffer can sink at least 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 DS21T07 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 DS21T07 from the signal lines and effectively remove it from the circuit. The power-
down pin (PD ) has an internal 50KΩ=pullup resistor. To place the DS21T07 into an active state, the PD
pin should be left open circuited. When installed on disk drives or RAID system components, the
DS21T07 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
DS21T07 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 DS21T07’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, three DS21T07’s would be needed at each end of the SCSI cable in order to terminate the
27 active signal lines.
DS21T16 BLOCK DIAGRAM Figure 1
2 of 7
DS21T07
TYPICAL SCSI BUS CONFIGURATION Figure 2
DS21T07
DS21T07
NOTES:
1. C1 = 4.7 µF tantalum
C2 = 2.2 µF tantalum or 4.7 µF aluminum
2. If the DS21T07 is to be embedded into a peripheral that will act as a target on a SCSI bus, it is that
recommended 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.
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DS21T07
PIN DESCRIPTION Table 1
DS21T16E DS21T16S
SYMBOL
DESCRIPTION
PIN
PIN
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.
3
4
5
6
7
9
2
3
4
5
6
7
R1
R2
R3
R4
R5
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.
VREF1
10
11
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.
13
14
15
16
17
19
10
11
12
13
14
15
R6
R7
R8
R9
NC
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 this pin.
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.
VREF2
20
16
Power Down. When tied low, the DS21T07 enters a
power-down mode. Contains an internal 50K pullup.
Strap low to deactivate the DS21T07, leave open
circuited to activate the DS21T07.
PD
2, 8,
12, 18
N/A
HS-GND
Heat Sink Ground. Internally connected to the
mounting pad. Should be either grounded or electrically
isolated from other circuitry.
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DS21T07
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.
The Dallas Semiconductor DS21T07 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 DS21T07 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)
PARAMETER
SYM
VTP
MIN
4.00
-0.3
TYP
MAX
5.50
+0.8
UNITS NOTES
TERMPWR Voltage
V
V
VPDA
PD Active
VPDI
2.0
VTP + 0.3
V
PD Inactive
DC CHARACTERISTICS
(0°C to 70°C)
PARAMETER
SYMBOL
MIN
TYP
MAX
250
8
UNITS
mA
NOTES
1, 3
TERMPWR Current
ITP
ITP
5
mA
1, 4
Power-Down Current
Termination Resistance
Die Thermal Shutdown
Power-Down
Termination Capacitance
Input Leakage High
Input Leakage Low
IPD
100
110
150
150
112
µA
ohms
°C
1, 2, 5
1, 2
1, 6
RTERM
TSD
CPD
108
150
3.0
1.0
pF
1, 2, 5, 6
IIH
IIL
-1.0
µA
µA
1, 8
1, 7
REGULATOR CHARACTERISTICS
(0°C to 70°C)
PARAMETER
Output Voltage
Drop Out Voltage
Output Current
Line Regulation
Load Regulation
Current Limit
SYMBOL
VREF
MIN
2.79
TYP
2.85
0.50
MAX
2.93
0.75
25.2
2.0
UNITS
NOTES
V
V
mA
%
%
mA
mA
1, 2
3, 6
9
1, 4
1, 3
1
VDROP
IOUT
LIREG
LOREG
ILIM
1.0
1.3
350
3.0
Sink Current
ISINK
200
1
5 of 7
DS21T07
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.
DS21T07S SCSI TERMINATOR 16-PIN SOIC (300-mil)
PKG
16-PIN
MIN MAX
DIM
A IN.
MM
B IN.
MM
C IN.
MM
E IN.
MM
F IN.
MM
G IN.
MM
H IN.
MM
J IN.
MM
K IN.
MM
L IN.
MM
phi
0.402 0.412
10.21 10.46
0.290 0.300
7.37
0.089 0.095
2.26 2.41
0.004 0.012
0.102 0.30
0.094 0.105
2.38 2.68
0.050 BSC
7.65
1.27 BSC
0.398 0.416
10.11 10.57
0.009 0.013
0.229
0.013 0.019
0.33 0.48
0.016 0.040
0.33
0.40
0°
1.02
8°
6 of 7
DS21T07
DS21T07E SCSI TERMINATOR 20-PIN TSSOP
DIM
A MM
A1 MM
A2 MM
C MM
L MM
e1 MM
B MM
D MM
E MM
G MM
H MM
phi
MIN
-
0.05
0.75
0.09
0.50
0.65 BSC
0.18
6.40
4.40 NOM
0.25 REF
6.25
0°
MAX
1.10
-
1.05
0.18
0.70
0.30
6.90
6.55
8°
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