LM2596T-3.3 National Semiconductor, LM2596T-3.3 Datasheet - Page 24

no-image

LM2596T-3.3

Manufacturer Part Number
LM2596T-3.3
Description
IC,SMPS CONTROLLER,VOLTAGE-MODE,BIPOLAR,ZIP,5PIN,PLASTIC
Manufacturer
National Semiconductor
Datasheet

Specifications of LM2596T-3.3

Svhc
NO SVHC
Rohs Compliant
NO

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
LM2596T-3.3
Manufacturer:
TI/NS
Quantity:
12 000
Part Number:
LM2596T-3.3
Manufacturer:
TI/德州仪器
Quantity:
20 000
Company:
Part Number:
LM2596T-3.3
Quantity:
280
Part Number:
LM2596T-3.3/NOPB
Manufacturer:
NS/53
Quantity:
1 424
Part Number:
LM2596T-3.3/NOPB
Manufacturer:
NS1O
Quantity:
15 404
www.national.com
Application Information
THERMAL CONSIDERATIONS
The LM2596 is available in two packages, a 5-pin TO-220
(T) and a 5-pin surface mount TO-263 (S).
The TO-220 package needs a heat sink under most condi-
tions. The size of the heatsink depends on the input voltage,
the output voltage, the load current and the ambient tem-
perature. The curves in Figure 19 show the LM2596T junc-
tion temperature rises above ambient temperature for a 3A
load and different input and output voltages. The data for
these curves was taken with the LM2596T (TO-220 pack-
age) operating as a buck switching regulator in an ambient
temperature of 25˚C (still air). These temperature rise num-
bers are all approximate and there are many factors that can
affect these temperatures. Higher ambient temperatures re-
quire more heat sinking.
The TO-263 surface mount package tab is designed to be
soldered to the copper on a printed circuit board. The copper
and the board are the heat sink for this package and the
other heat producing components, such as the catch diode
and inductor. The PC board copper area that the package is
soldered to should be at least 0.4 in
have 2 or more square inches of 2 oz. (0.0028) in) copper.
Additional copper area improves the thermal characteristics,
but with copper areas greater than approximately 6 in
small improvements in heat dissipation are realized. If fur-
ther thermal improvements are needed, double sided, mul-
tilayer PC board with large copper areas and/or airflow are
recommended.
The curves shown in Figure 20 show the LM2596S (TO-263
package) junction temperature rise above ambient tempera-
ture with a 2A load for various input and output voltages. This
data was taken with the circuit operating as a buck switching
regulator with all components mounted on a PC board to
simulate the junction temperature under actual operating
conditions. This curve can be used for a quick check for the
approximate junction temperature for various conditions, but
be aware that there are many factors that can affect the
junction temperature. When load currents higher than 2A are
used, double sided or multilayer PC boards with large cop-
per areas and/or airflow might be needed, especially for high
ambient temperatures and high output voltages.
For the best thermal performance, wide copper traces and
generous amounts of printed circuit board copper should be
used in the board layout. (One exception to this is the output
(switch) pin, which should not have large areas of copper.)
Large areas of copper provide the best transfer of heat
(lower thermal resistance) to the surrounding air, and moving
air lowers the thermal resistance even further.
Package thermal resistance and junction temperature rise
numbers are all approximate, and there are many factors
that will affect these numbers. Some of these factors include
board size, shape, thickness, position, location, and even
board temperature. Other factors are, trace width, total
printed circuit copper area, copper thickness, single- or
double-sided, multilayer board and the amount of solder on
the board. The effectiveness of the PC board to dissipate
heat also depends on the size, quantity and spacing of other
components on the board, as well as whether the surround-
ing air is still or moving. Furthermore, some of these com-
ponents such as the catch diode will add heat to the PC
board and the heat can vary as the input voltage changes.
For the inductor, depending on the physical size, type of core
2
, and ideally should
(Continued)
2
, only
24
material and the DC resistance, it could either act as a heat
sink taking heat away from the board, or it could add heat to
the board.
Capacitors
Inductor
Diode
PC board
Capacitors
Inductor
Diode
PC board
FIGURE 19. Junction Temperature Rise, TO-220
FIGURE 20. Junction Temperature Rise, TO-263
Circuit Data for Temperature Rise Curve
Circuit Data for Temperature Rise Curve
Through hole electrolytic
Through hole, Renco
Through hole, 5A 40V, Schottky
3 square inches single sided 2 oz. copper
(0.0028")
Surface mount tantalum, molded “D” size
Surface mount, Pulse Engineering, 68 µH
Surface mount, 5A 40V, Schottky
9 square inches single sided 2 oz. copper
(0.0028")
TO-220 Package (T)
TO-263 Package (S)
01258334
01258335

Related parts for LM2596T-3.3