LP2960

SNVS112C – APRIL 1999 – REVISED APRIL 2013

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HEATSINKING

A heatsink may be required with the LP2960 depending on the maximum power dissipation and maximum

ambient temperature of the application. Under alI possible operating conditions, the junction temperature must be

within the range specified under Absolute Maximum Ratings.

To determine if a heatsink is required, the power dissipated by the regulator, PD, must be calculated.

The figure below shows the voltages and currents which are present in the circuit, as welI as the formula for

calcuIating the power dissipated in the regulator:

Figure 27. Power Dissipation Diagram

The next parameter which must be calculated is the maximum allowable temperature rise, TR (max). This is

calculated by using the formula:

TR (max) = TJ (max) − TA (max

where

•

TJ (max) is the maximum allowable junction temperature, which is 125°C for commercial grade parts

•

TA (max) is the maximum ambient temperature which will be encountered in the application)

(2)

Using the calculated values for TR (max) and PD, the maximum allowable value for the junction-to-ambient

thermal resistance,

θ(J−A), can now be found:

θ(J−A) = TR (max)/PD

(3)

The heatsink for the LP2960 is made using the PC board copper, with the heat generated on the die being

conducted through the lead frame and out to the pins which are soldered to the PC board.

The GND pins are the only ones capable of conducting any significant amount of heat, as they are internally

attached to the lead frame on which the die is mounted.

The figure below shows recommended copper foil patterns to be used for heatsinking the DIP and Surface Mount

(SOIC) packages:

Figure 28. Heat Sink Foil Patterns

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