TL2218 datasheet(6/9 Pages) TI

6 / 9 page

TL2218-285, TL2218-285Y

EXCALIBUR CURRENT-MODE SCSI TERMINATOR

SLVS072C – DECEMBER 1992 – REVISED OCTOBER 1995

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

8–6

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. In order to provide the systems designer with a better

approximation of the junction temperature rise in the thin-shrink small-outline package (TSSOP), the junction-to-lead

thermal resistance (RθJL) is provided along with the more typical values of junction-to-ambient and junction-to-case

thermal resistances, RθJA and RθJC.

RθJL is used to calculate the device junction temperature rise measured from the leads of the unit. Consequently, the

junction temperature is dependent upon the board temperature at the leads, RθJL, and the internal power dissipation

of the device. The board temperature is contingent upon several variables, including device packing density,

thickness, material, area, and number of interconnects. The RθJL value depends on the number of leads connecting

to the die-mount pad, the lead-frame alloy, area of the die, mount material, and mold compound. Since the power level

at which the TSSOP can be used is highly dependent upon both the temperature rise of the PWB and the device itself,

the systems designer can maximize this level by optimizing the circuit board. The junction temperature of the device

can be calculated using the equation TJ = (PD × RθJL) + TL where TJ = junction temperature, PD = power dissipation,

RθJL = junction-to-lead thermal resistance, and TL = board temperature at the leads of the unit.

The values of thermal resistance for the TL2218-285 PW are as follows:

Thermal Resistance

Typical Junction Rise

RθJA

151

°C/W

RθJC

°C/W

RθJL

50.5

°C/W

TYPICAL CHARACTERISTICS

Table of Graphs

FIGURE

Output current

vs Input voltage

Output voltage

vs Input voltage

Output current

vs Junction temperature

Output voltage

vs Junction temperature

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