參數(shù)資料
型號: mic5204
廠商: Micrel Semiconductor,Inc.
英文描述: SCSI-II Active Terminator(兼容SCSI-II的有效終端)
中文描述: 支持SCSI - II主動式終端(兼容支持SCSI - II的有效終端)
文件頁數(shù): 4/4頁
文件大?。?/td> 28K
代理商: MIC5204
MIC5204
Applications Information
Micrel
February 1999
62
MIC5204
Thermal Considerations
Part I. Layout
External Capacitors
A 2.2
μ
F capacitor is recommended between the MIC5204
output and ground to prevent oscillations due to instability.
Larger values serve to improve the regulator's transient re-
sponse. Most types of tantalum or aluminum electrolytics will
be adequate; film types will work. Many aluminum electrolytics
have electrolytes that freeze at about –30
°
C, so solid tantalums
are recommended for operation below –25
°
C. The important
parameters of the capacitor are an effective series resistance
of about 5
or less and a resonant frequency above 500kHz.
The value of this capacitor may be increased without limit.
A 1
μ
F capacitor should be placed from the MIC5204 input to
ground if there is more than 10 inches of wire between the
input and the AC filter capacitor or if a battery is used as the
input.
The MIC5204 will remain stable and in regulation with no load
in addition to the internal voltage divider.
PC Board
Dielectric
FR4
Ceramic
θ
JA
160
°
C/W
120
°
C/W
Multi-layer boards having a ground plane, wide traces near
the pads, and large supply bus lines provide better thermal
conductivity. The "worst case" value of 160
°
C/W assumes no
ground plane, minimum trace widths, and a FR4 material
board.
Part II. Nominal Power Dissipation and Die Temperature
The MIC5204BM at a 25
°
C ambient temperature will operate
reliably at up to 625mW power dissipation when mounted in
the "worst case" manner described above. At an ambient
temperature of 55
°
C, the device may safely dissipate 440mW.
These power levels are equivalent to a die temperature of
125
°
C, the recommended maximum temperature for non-
military grade silicon integrated circuits. In normal SCSI
terminator applications, the average power dissipation is very
small and this minimum geometry heat sink is suitable. The
total dissipation does not approact the 400mW to 625mW
range described above.
For MIC5204BS (SOT-223 package) heat sink characteris-
tics, please refer to Micrel Application Hint 17, “P.C. Board
Heat Sinking”. As with the SO-8, average power dissipation
in SCSI terminator applications is low and a minimum pad size
is generally adequate.
The MIC5204BM (8-pin surface mount package) has the
following thermal characteristics when mounted on a single
layer copper-clad printed circuit board.
245 mil
30 mil
50 mil
50 mil
150 mil
Minimum recommended board pad size, SO-8.
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