lm9072 National Semiconductor Corporation, lm9072 Datasheet - Page 12

• Manufacturer Part Number: lm9072
• Description: Dual Tracking Low-dropout System Regulator
• Manufacturer: National Semiconductor Corporation

www.national.com
Application Information
Thermal Management
The LM9072 is packaged in both a TO-263 surface mount
power package and a narrow lead-pitch TO-220 package. To
obtain operation over the highest possible load current and
input voltage ranges, care must be taken to control the
operating temperature of the device. Thermal shutdown pro-
tection is built in, with a threshold above 150˚C. Conven-
tional heat-sinking techniques can be used with the TO-220
package. When applying the TO-263 package, on board
heat-sinking is important to prevent premature thermal shut-
down. More copper foil area under the tab of the device will
directly improve the operating
which will reduce the junction temperature of the device.
The
heat sink) is rated at 80˚C/W. The effective
Electro-Magnetic Compatibility (EMC)
The LM9072 offers good immunity to high frequency inter-
ference in a standard Bulk Current Injection (BCI) test
(ISO11452 Part 4 test method). The following test conditions
and configuration ( Figure 9 ) can be used to observe this
performance.
Frequency Range
Modulation 1
Modulation 2
Dwell Time
Frequency Steps
J-A
value for the TO-263 package (still air, no additional
2 MHz (from 10 MHz to 200 MHz)
1 MHz (from 1 MHz to 10 MHz)
1 kHz sine wave, 80% AM
J-A
of the TO-263 package,
CW (no modulation)
FIGURE 8. Typical TO-263 PC Board Heatsinking
1 MHz to 400 MHz
(Continued)
J-A
1 second
value of the
12
TO-263 package can be reduced by increasing the printed
circuit board area that is connected (soldered) to the pack-
age tab. Using 1 ounce (1.4 mils thick) copper clad with no
solder mask, an area of 0.5 square inches will reduce
50˚C/W, an area of 1.0 square inches will reduce
37˚C/W, and an area of 1.6 square inches will reduce
32˚C/W. If the printed circuit board uses a solder mask, the
copper clad area under the solder mask should be increased
by at least 50% to maintain a similar
The use of a double sided PC board with soldered filled vias
between two planes of copper, as shown in Figure 8, will
improve thermal performance while optimizing the PC board
surface area required. Using the double sided PC board
arrangement shown in Figure 8, with 1 ounce (1.4 mils thick)
copper clad with no solder mask and solder filled vias, an
area of 0.5 square inches on both sides will reduce
43˚C/W.
In this test configuration the current injected into either the
input pin or the tracking output pin is increased until a reset
output is generated. These two pins are the most critical as
they typically will connect to a module through long lengths
of wire most likely to pick up high frequency energy. Figure
10 illustrates examples of test results on the LM9072 with
both types of modulation.
These results are just examples as actual results in any
given application will depend on numerous external factors
such as component selection, pc board layout, etc. The
current power of the injected signal is expressed in dB
relative to 1 mA (i.e., 40 dBmA = 100 mA).
Test Method
20 MHz (from 200 MHz to 400 MHz)
Closed loop current probe
DS012906-24
J-A
rating.
J-A
J-A
J-A
J-A
to
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