DS21T07 Datasheet by Maxim Integrated

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FEATURES
Fully compliant with SCSI–1, Fast SCSI and
Ultra SCSI
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)
PIN ASSIGNMENT
ACTUAL FOOTPRINT SIZE
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.
DS21T07
SCSI Terminato
r
www.dalsemi.com
1
2
3
4
5
6
7
8
9
10
17
20
19
18
16
15
14
13
12
11
PD
VREF2
HS-GND
R9
R8
R7
R6
HS-GND
TERMPWR2
NC
TERMPWR1
HS-GND
R1
R3
R4
R5
HS-GND
VREF1
GND
R2
DS21T07E 20-
p
in TSSOP
(
173-mil
)
1
2
3
4
5
6
7
8
13
16
15
14
12
11
10
9
PD
VREF2
NC
R8
R7
R6
TERMPWR2
R9
TERMPWR1
R1
R3
R4
R5
VREF1
GND
R2
DS21T07S 16-
p
in SOIC
(
300-mil
)
0.41”
0.41”
0.26”
0.27”
DS21T07S DS21T07E
TERMPWH1 TERMFWRZ GND BANDGAP REFERENCE POWER DOWN CIRCUIT‘RY "0 OHMS IIO OHMS IIO OHMS 110 OHMS 110 OHMS IIOOHMS IIO OHMS “0 OHMS IIO OHMS R1 R2 R3 R4 R8 HQ VREF1 VREF2
DS21T07
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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 50K=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
Termination Power Line A +_L {\ (:2 I I ‘ TERMPWFII ,’ : TERMPWFH TERManz I I TERMP’WHZ VREF1 I I VREFI + L—E VREFZ I I ,l—C VREF2 c1 SCSI I ‘ c1 AB GND C LE 1 I GND RI ... an R9 . . R1 R2 ... R9 1 l I I . . l I SCSI l I SCSI BUS BUS TRANSCEIVER I I TRANSCEIVER I I I I . | I o | I . | I I I I ------ w . 1 I I l\ ‘ V I l/ I I I SCSI see: I I BUS BUS I I TRANSCEIVER TRANSCEIVER
DS21T07
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TYPICAL SCSI BUS CONFIGURATION Figure 2
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.
DS21T07 DS21T07
DS21T07
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PIN DESCRIPTION Table 1
DS21T16E
PIN DS21T16S
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.
32R1Signal Termination 1. 110 ohms termination.
43R2Signal Termination 2. 110 ohms termination.
54R3Signal Termination 3. 110 ohms termination.
65R4Signal Termination 4. 110 ohms termination.
76R5Signal Termination 5. 110 ohms termination.
97VREF1Reference 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.
10 8 GND Ground. Signal ground; 0.0V.
11 9 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 10 R6 Signal Termination 6. 110 ohms termination.
14 11 R7 Signal Termination 7. 110 ohms termination.
15 12 R8 Signal Termination 8. 110 ohms termination.
16 13 R9 Signal Termination 9. 110 ohms termination.
17 14 NC No Connect. Do not connect any signal to this pin.
19 15 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.
20 16 PD 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.
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.
DS21T07
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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 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 MIN TYP MAX UNITS NOTES
TERMPWR Voltage VTP 4.00 5.50 V
PD Active VPDA -0.3 +0.8 V
PD Inactive VPDI 2.0 VTP + 0.3 V
DC CHARACTERISTICS (0°C to 70°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
TERMPWR Current ITP
ITP 5250
8mA
mA 1, 3
1, 4
Power-Down Current IPD 100 150 µA 1, 2, 5
Termination Resistance RTERM 108 110 112 ohms 1, 2
Die Thermal Shutdown TSD 150 150 °C 1, 6
Power-Down
Termination Capacitance CPD 3.0 pF 1, 2, 5, 6
Input Leakage High IIH -1.0 µA 1, 8
Input Leakage Low IIL 1.0 µA 1, 7
REGULATOR CHARACTERISTICS (0°C to 70°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Output Voltage VREF 2.79 2.85 2.93 V 1, 2
Drop Out Voltage VDROP 0.50 0.75 V 3, 6
Output Current IOUT 25.2 mA 9
Line Regulation LIREG 1.0 2.0 % 1, 4
Load Regulation LOREG 1.3 3.0 % 1, 3
Current Limit ILIM 350 mA 1
Sink Current ISINK 200 mA 1
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DS21T07
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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
DIM MIN MAX
A IN.
MM 0.402
10.21 0.412
10.46
B IN.
MM 0.290
7.37 0.300
7.65
C IN.
MM 0.089
2.26 0.095
2.41
E IN.
MM 0.004
0.102 0.012
0.30
F IN.
MM 0.094
2.38 0.105
2.68
G IN.
MM 0.050 BSC
1.27 BSC
H IN.
MM 0.398
10.11 0.416
10.57
J IN.
MM 0.009
0.229 0.013
0.33
K IN.
MM 0.013
0.33 0.019
0.48
L IN.
MM 0.016
0.40 0.040
1.02
phi 0° 8°
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DS21T07
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DS21T07E SCSI TERMINATOR 20-PIN TSSOP
DIM MIN MAX
A MM - 1.10
A1 MM 0.05 -
A2 MM 0.75 1.05
C MM 0.09 0.18
L MM 0.50 0.70
e1 MM 0.65 BSC
B MM 0.18 0.30
D MM 6.40 6.90
E MM 4.40 NOM
G MM 0.25 REF
H MM 6.25 6.55
phi 0° 8°

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