REG5601E Burr-Brown Corporation, REG5601E Datasheet - Page 3

• Manufacturer Part Number: REG5601E
• Description: 18-LINE SCSI ACTIVE TERMINATOR
• Manufacturer: Burr-Brown Corporation

FIGURE 2. Circuit Board Layout.
The REG5601 has current limit and thermal shutdown that
protect it from damage during output short-circuit or overload.
The current limit is approximately 1350mA and thermal
shutdown activates at a junction temperature of approxi-
mately 175 C. For good 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.
Heat is dissipated primarily by conduction through the 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. 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.
FIGURE 1. Standard SCSI Termination Application.
0 = Termination On
1 = Disconnect
Transceivers
Controller
To
NOTES: (1) Single-side layout on 0.062 inch FR4, 1 oz copper. (2) Three-layer layout on 0.062 inch FR4, 1 oz copper.
(3) Aluminum 0.062 inch substrate, 0.003 insulation, one layer, 1 oz copper (Thermal Clad, Bergqueist Co.)
PACKAGE
SO-28
SSOP-28
28
1
Disconnect
Gnd
T18
27
4V to 5.25V
(18 Lines)
REG5601
Termpwr
CIRCUIT BOARD
14
Aluminum
Aluminum
MATERIAL
1-Layer
3-Layer
1-Layer
3-Layer
4.7µF Tantalum
+
Regulator
Output
(1)
(2)
(1)
(2)
(3)
(3)
T1
2
15
JUNCTION TO LEAD +
+
4.7µF Tantalum
( C/W)
2.9V
20
20
20
20
20
20
JL
(18 Lines)
Cable
SCSI
3
Connect to circuit ground or leave open-circuit.
A simple experiment will determine whether the actual circuit
board layout is adequate (i.e.,
maximum recommended junction temperature of the REG5601
will not be exceeded. The procedure uses the internal thermal
shutdown feature of the REG5601 (at T
mine when the junction is approximately 50 C above the
maximum recommended junction temperature (T
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
If this occurs at an ambient temperature of more than 50 C
above the system ambient temperature design goal, the T
not exceed 125 C under the same electrical conditions when
the ambient temperature is at the system design goal value.
+
+
+
+
+
+
Thermal ground (leads 7, 8, 9, 20, 21, 22).
2.9V
Tantalum
BOARD TO AMBIENT
4.7µF
REG
( C/W)
+
30
21
12
36
23
13
BA
T
15
output). At this point T
J
= T
Regulator
T18
A
Output
+ P
27
D
4V to 5.25V
= JUNCTION TO AMBIENT
=
=
=
=
=
=
(18 Lines)
REG5601
Termpwr
JA
14
4.7µF Tantalum
Disconnect
+
REG5601
BA
( C/W)
is low enough) so that the
Gnd
50
41
32
56
43
33
T1
JA
J
is approximately 175 C.
2
1
28
J
0 = Termination On
1 = Disconnect
175 C) to deter-
Transceivers
Controller
J
= 125 C).
To
J
will
®