Datasheet

LM2592HV

SNVS075C –MAY 2001–REVISED APRIL 2013

www.ti.com

Figure 35. Inverting Regulator Ground Referenced Shutdown using Opto Device

THERMAL CONSIDERATIONS

The LM2592HV is available in two packages, a 5-pin TO-220 (NDH) and a 5-pin surface mount DDPAK (KTT).

The TO-220 package needs a heat sink under most conditions. The size of the heatsink depends on the input

voltage, the output voltage, the load current and the ambient temperature. Higher ambient temperatures require

more heat sinking.

The DDPAK 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

and ideally should 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

, only small improvements in

heat dissipation are realized. If further thermal improvements are needed, double sided, multilayer PC board with

large copper areas and/or airflow are recommended.

The curves shown in Figure 36 show the LM2592HVS (DDPAK package) junction temperature rise above

ambient temperature 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

copper 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 surrounding air is still or moving. Furthermore, some of these components 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 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.

Product Folder Links: LM2592HV