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SLVS072C − DECEMBER 1992 − REVISED OCTOBER 1995

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POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

POST OFFICE BOX 1443

• HOUSTON, TEXAS

77251−1443

8−1

available features

• Fully Integrated 9-Channel SCSI

Termination

• No External Components Required

• Maximum Allowed Current Applied at First

High-Level Step

• 6-pF Typical Power-Down Output

Capacitance

• Wide V

term

†

(Termination Voltage)

Operating Range, 3.5 V to 5.5 V

• TTL-Compatible Disable Feature

• Compatible With Active Negation

• Thermal Regulation

description

The TL2218-285 is a current-mode 9-channel monolithic terminator specially designed for single-ended

small-computer-systems-interface (SCSI) bus termination. A user-controlled disable function is provided to

reduce standby power. No impedance-matching resistors or other external components are required for its

operation as a complete terminator.

The device operates over a wide termination-voltage (V

term

†

) range of 3.5 V to 5.5 V, offering an extra 0.5 V of

operating range when compared to the minimum termination voltage of 4 V required by other integrated active

terminators. The TL2218-285 functions as a current-sourcing terminator and supplies a constant output current

of 23 mA into each asserted line. When a line is deasserted, the device senses the rising voltage level and begins

to function as a voltage source, supplying a fixed output voltage of 2.85 V. The TL2218-285 features

compatibility with active negation drivers and has a typical sink current capability of 20 mA.

The TL2218-285 is able to ensure that maximum current is applied at the first high-level step. This performance

means that the device should provide a first high-level step exceeding 2 V even at a 10-MHz rate. Therefore,

noise margins are improved considerably above those provided by resistive terminators.

A key difference between the TL2218-285 current-mode terminator and a Boulay terminator is that the

TL2218-285 does not incorporate a low dropout regulator to set the output voltage to 2.85 V. In contrast with

the Boulay termination concept, the accuracy of the 2.85 V is not critical with the current-mode method used

in the TL2218-285 because this voltage does not determine the driver current. Therefore, the primary device

specifications are not the same as with a voltage regulator but are more concerned with output current.

The DISABLE

terminal is TTL compatible and must be taken low to shut down the outputs. The device is

normally active, even when DISABLE

is left floating. In the disable mode, only the device startup circuits remain

active, thereby reducing the supply current to just 500 µA. Output capacitance in the shutdown mode is typically

6 pF.

The TL2218-285 has on-board thermal regulation and current limiting, thus eliminating the need for external

protection circuitry. A thermal regulation circuit that is designed to provide current limiting, rather than an actual

thermal shutdown, is included in the individual channels of the TL2218-285. When a system fault occurs that

leads to excessive power dissipation by the terminator, the thermal regulation circuit causes a reduction in the

asserted-line output current sufficient to maintain operation. This feature allows the bus to remain active during

a fault condition, which permits data transfer immediately upon removal of the fault. A terminator with thermal

shutdown does not allow for data transfer until sufficient cooling has occurred. Another advantage offered by

the TL2218-285 is a design that does not require costly laser trimming in the manufacturing process.

The TL2218-285 is characterized for operation over the virtual junction temperature range of 0°C to 125°C.

†

This symbol is not presently listed within EIA/JEDEC standards for letter symbols.

TERMPWR

GND

TERMPWR

DISABLE

GND

PW PACKAGE

(TOP VIEW)

NC − No internal connection

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Summary of content (12 pages)

PAGE 1
SLVS072C − DECEMBER 1992 − REVISED OCTOBER 1995 available features • • • • • • • • PW PACKAGE (TOP VIEW) Fully Integrated 9-Channel SCSI Termination No External Components Required Maximum Allowed Current Applied at First High-Level Step 6-pF Typical Power-Down Output Capacitance Wide Vterm† (Termination Voltage) Operating Range, 3.5 V to 5.
PAGE 2
SLVS072C − DECEMBER 1992 − REVISED OCTOBER 1995 AVAILABLE OPTIONS SURFACE MOUNT (PW)† TJ CHIP FORM (Y) 0°C to 125°C TL2218-285PWLE TL2218-285Y † The PW package is only available left-end taped and reeled. TL2218-285Y chip information This chip, when properly assembled, displays characteristics similar to the TL2218-285. Thermal compression or ultrasonic bonding may be used on the doped aluminum bonding pads.
PAGE 3
SLVS072C − DECEMBER 1992 − REVISED OCTOBER 1995 functional block diagram (each channel) 1, 20 TERMPWR Feedback DISABLE Active Negation Clamp 19 Vref 4 D0 Thermal Regulation Common to All Channels absolute maximum ratings over operating free-air temperature range (unless otherwise noted) (see Figures 1, 2, and 3)† Continuous termination voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PAGE 4
SLVS072C − DECEMBER 1992 − REVISED OCTOBER 1995 CASE TEMPERATURE DISSIPATION DERATING CURVE 2400 Maximum Continuous Power Dissipation − mW Maximum Continuous Power Dissipation − mW FREE-AIR TEMPERATURE DISSIPATION DERATING CURVE 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 RθJA = 151°C/W 4800 4400 4000 3600 3200 2800 2400 2000 1600 1200 RθJC = 31°C/W 800 400 0 0 25 50 75 100 125 25 150 50 TA − Free-Air Temperature − °C
PAGE 5
SLVS072C − DECEMBER 1992 − REVISED OCTOBER 1995 recommended operating conditions MIN Termination voltage MAX UNIT 3.5 5.5 V High-level disable input voltage, VIH 2 V Low-level disable input voltage, VIL 0 Vterm 0.8 Operating virtual junction temperature, TJ 0 125 °C MIN TYP MAX UNIT 2.5 2.85 V electrical characteristics, Vterm = 4.75 V, VO = 0.
PAGE 6
SLVS072C − DECEMBER 1992 − REVISED OCTOBER 1995 THERMAL INFORMATION The need for smaller surface-mount packages for use on compact printed-wiring boards (PWB) causes an increasingly difficult problem in the area of thermal dissipation.
PAGE 7
SLVS072C − DECEMBER 1992 − REVISED OCTOBER 1995 TYPICAL CHARACTERISTICS OUTPUT CURRENT vs INPUT VOLTAGE OUTPUT VOLTAGE vs INPUT VOLTAGE 24 4 TJ = 25°C TJ = 25°C VO − Output Voltage − V VO I O − Output Current − mA 22 20 ÁÁ ÁÁ 18 16 14 3 2 1 0 3 3.5 4 4.5 VI − Input Voltage − V 5 5.5 3 3.5 Figure 4 5 5.5 Figure 5 OUTPUT CURRENT vs JUNCTION TEMPERATURE OUTPUT VOLTAGE vs JUNCTION TEMPERATURE 4 25 Vterm = 4.
PAGE 8
8−8 • • POST OFFICE BOX 655303 DALLAS, TEXAS 75265 POST OFFICE BOX 1443 HOUSTON, TEXAS 77251−1443
PAGE 9
PACKAGE OPTION ADDENDUM www.ti.
PAGE 10
PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device TL2218-285PWR Package Package Pins Type Drawing TSSOP PW 20 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2000 330.0 16.4 Pack Materials-Page 1 6.95 B0 (mm) K0 (mm) P1 (mm) 7.1 1.6 8.0 W Pin1 (mm) Quadrant 16.
PAGE 11
PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) TL2218-285PWR TSSOP PW 20 2000 367.0 367.0 38.
PAGE 12
IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46C and to discontinue any product or service per JESD48B. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.