Datasheet DS2114 Datasheet (dallas semiconductor)

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Page 1

DS2114

SCSI Terminator

FEATURES

• 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)

PIN ASSIGNMENT

TERMPWR1

R1 R2 R3

R4 R5

VREF1

GND

DS2114Z 16–PIN SOIC (150 MIL)

16 15 14 13 12

11 10

NC VREF2

R9 R8 R7 R6 NC TERMPWR2

1 2 3 4

5 6 7 8

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 designer to gain the benefits of active termination: greater immunity to voltage drops on the TERMPWR (TERMination PoWeR) line, enhanced high–level noise im-

munity, intrinsic TERMPWR decoupling, and very low quiescent current consumption. The DS21 14 integrates a regulator and nine precise 110 ohms termination resistors 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.

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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 produces 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 negated SCSI signals, the buffer can sink at least 200 mA

will move less than 60 mV . When all lines settle

and V

ref

in the quiescent state, the regulator will consume about

2.5 mA.

DS2114 BLOCK DIAGRAM Figure 1

TERMPWR1 TERMPWR2

BANDGAP

REFERENCE

–

GND

T o 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 DS21 14 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 (“A” Cable), two DS21 14’ 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 DS21 14’s would be needed at each end of the SCSI cable in order to terminate the 27 active signal lines.

110 ohms

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VREF1 VREF2

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TYPICAL SCSI BUS CONFIGURATION Figure 2

Termination Power Line

DS2114

TERMPWR1 TERMPWR2

VREF1

VREF2

GND

R1 R2R9

SCSI BUS TRANSCEIVER

SCSI CABLE

SCSI BUS TRANSCEIVER

DS2114

TERMPWR1 TERMPWR2

VREF1

VREF2

GND

R1 R9

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.

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DS2114

PIN DESCRIPTION Table 1

DS2114Z

1 TERMPWR1 Termination Power 1. Should be connected to the SCSI TERMPWR line. Must

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.

8 GND Ground. Signal ground; 0.0 volts. 9 TERMPWR2 Termination Power 2. Should be connected to the SCSI TERMPWR line. Must

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.

SYMBOL DESCRIPTION

be decoupled with either a 2.2 µF or 4.7 µF. See Figure 2.

Must be decoupled with a 4.7 µF capacitor as shown in Figure 2.

be decoupled with either a 2.2 µF or 4.7 µF. See Figure 2.

Must be decoupled with a 4.7 µF capacitor as shown in Figure 2.

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DS2114

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 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 (0°C to 70°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

TERMPWR Voltage V

4.00 5.50 V

DC CHARACTERISTICS (0°C to 70°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

TERMPWR Current I

T ermination Resistance R Die Thermal Shutdown T T ermination Capacitance C

TERM

5 110 116 ohms 1, 2 150 °C 1, 5

5.0 pF 1, 2, 5

250

mA mA

1, 3 1, 4

REGULATOR CHARACTERISTICS (0°C to 70°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Output Voltage V Drop Out Voltage V Line Regulation LI Output Current I Load Regulation LO Current Limit I Sink Current I

REF

DROP

REG

OUT

REG

LIM

SINK

2.7 2.85 3.0 V 1, 2

0.75 1.0 V 3, 5

1.0 2.0 % 1, 4

24.0 mA 6

1.3 3.0 % 1, 3 280 500 mA 1 200 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.

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DS2114

DS2114Z SCSI TERMINATOR 16–PIN SOIC (150 MIL)

PKG 16–PIN

DIM MIN MAX

A IN.MM0.053

A1 IN.MM0.004

A2 IN.MM0.048

b IN.MM0.012

C INMM0.007

D IN.MM0.386

e IN.

E1 IN.MM0.150

H IN.

L IN.MM0.016

1.35

0.10

1.24

0.30

0.17

9.80

3.81

0.230

5.84

0.40 0° 8°

0.069

1.75

0.010

0.2

0.062

1.57

0.020

0.50

0.011

0.28

0.393

9.98

0.050 BSC

1.27 BSC

0.158

4.01

0.244

6.20

0.050

0.89

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