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參數(shù)資料
| 型號(hào)： | REG5608 |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | Low Capacitance 18-Line SCSI Active Terminator(低電容的18線SCSI有源終端) |
| 中文描述： | 低電容18行的SCSI主動(dòng)終結(jié)者（低電容的18線的SCSI有源終端） |
| 文件頁(yè)數(shù)： | 4/5頁(yè) |
| 文件大?。?/td> | 156K |
| 代理商： | REG5608 |
4
REG5608
TYPICAL PERFORMANCE CURVES
T
A
= 25
°
C, TERMPWR = 4.75V unless otherwise noted.
APPLICATION INFORMATION
Figure 1 shows a typical SCSI parallel bus termination
circuit. Bypass capacitors should be connected to TERMPWR
and Reg Out pins as shown.
Line capacitance of the REG5608 has been reduced to less
than one-fourth that of the first-generation integrated
terminator ICs. Capacitance difference between package
types and variation by pin number is shown in the typical
performance curve, “Line Capacitance vs Pin Number.” It
shows that the SSOP package provides the lowest capaci-
tance with typical values under 2pF. This variation is
produced primarily by the differences in the interconnection
length to the IC. Of course, actual line capacitance on a
circuit board is generally determined by circuit board layout.
To achieve lowest line capacitance, minimize the total circuit
board interconnection length from the interface cable to the
SCSI transceiver IC and to the REG5608 terminator.
THERMAL CONSIDERATIONS
The REG5608 has internal current limit and thermal
shutdown that protect it from damage in case of output
short-circuit or overload. The current limit is approxi-
mately 550mA and thermal shutdown activates at a
junction temperature of approximately 145
°
C. For good
long-term reliability, the junction temperature should not
exceed 125
°
C. Any tendency to activate the thermal
shutdown during normal operation is an indication of
inadequate heat sinking and/or excessive power
dissipation.
The terminator's internal power is dissipated primarily by
conduction through the package leads to circuit board traces.
It is important to connect the six thermal ground leads (7, 8,
9, 20, 21, 22) to a large circuit trace—see Figure 2. Typical
measured values of thermal resistance for various circuit
board materials are shown. These are approximate values.
Variations in circuit board pattern, mounting techniques, air
flow, proximity to other circuit boards and heat sources will
affect thermal performance.
A simple experiment will determine whether the actual circuit
board layout is adequate (i.e.,
θ
BA
is low enough) so that the
maximum recommended junction temperature of the REG5608
will not be exceeded. The procedure uses the internal thermal
shutdown feature of the REG5608 (at T
J
≈
145
°
C) to
determine when the junction is approximately 20
°
C above the
maximum recommended junction temperature (T
J
= 125
°
C).
Operate the circuit with normal or other desired test electrical
conditions. Increase the ambient temperature and determine
the value at which thermal limit occurs (by sensing a sudden
drop in V
REG
output). At this point T
J
is approximately 145
°
C.
If this occurs at an ambient temperature of more than 20
°
C
above the system ambient temperature design goal, the T
J
will
not exceed 125
°
C under the same electrical conditions when
the ambient temperature is at the system design goal value.
TERMINATION CURRENT vs TEMPERATURE
Temperature (°C)
T
23
22
21
20
19
–25
0
25
50
75
100
125
V
LINE
= 0.5V
LINE CAPACITANCE vs PIN NUMBER
Pin Number
L
10
8
6
4
2
0
2
3
4
5
6
10
19
11
18
12
17
13
16
27
26
25
24
23
First-Generation Terminator
REG5608U SOIC Package
REG5608E SSOP Package
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| REG5608E | 制造商:BB 制造商全稱(chēng):BB 功能描述:LOW CAPACITANCE 18-Line SCSI ACTIVE TERMINATOR |
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