TL2218-285_14 Datasheet, PDF (6/13 Pages) Texas Instruments – EXCALIBUR CURRENT-MODE SCSI TERMINATOR

TL2218Ć285, TL2218Ć285Y
ą
EXCALIBUR CURRENTĆMODE SCSI TERMINATOR
ą
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. 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 (R_θJL) is provided along with the more typical values of junction-to-ambient and junction-to-case
thermal resistances, R_θJA and R_θJC.
R_θJL 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, R_θJL, 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 R_θJL 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 T_J = (P_D × R_θJL) + T_L where T_J = junction temperature, P_D = power dissipation,
R_θJL = junction-to-lead thermal resistance, and T_L = board temperature at the leads of the unit.
The values of thermal resistance for the TL2218-285 PW are as follows:
Thermal Resistance
R_θJA
R_θJC
R_θJL
Typical Junction Rise
151°C/W
31 °C/W
50.5°C/W
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
IO
Output current vs Input voltage
4
VO Output voltage vs Input voltage
5
IO
Output current vs Junction temperature
6
VO Output voltage vs Junction temperature
7
8−6
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
• POST OFFICE BOX 1443 HOUSTON, TEXAS
77251−1443