LM2990 datasheet(9/20 Pages) TI

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LM2990

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SNVS093D – JUNE 1999 – REVISED APRIL 2013

Typical Performance Characteristics (continued)

Maximum Power

Maximum Power Dissipation

Dissipation (TO-220)

(TO-263)(1)

Figure 23.

Figure 24.

(1)

The maximum power dissipation is a function of TJmax, θJA, and TA. The maximum allowable power dissipation at any ambient

temperature is PD = (TJmax − TA)/θJA. If this dissipation is exceeded, the die temperature will rise above 125°C, and the LM2990 will

eventually go into thermal shutdown at a TJ of approximately 160°C. For the LM2990, the junction-to-ambient thermal resistance, is

53°C/W, 73°C/W for the DDPAK/TO-263, and the junction-to-case thermal resistance is 3°C. If the DD[AK/TO-263 package is used, the

thermal resistance can be reduced by increasing the P.C. board copper area thermally connected to the package. Using 0.5 square

inches of copper area,

θJA is 50°C/W; with 1 square inch of copper area, θJA is 37°C/W; and with 1.6 or more square inches of copper

area,

θJA is 32°C/W.

Typical Applications

Figure 25. Post Regulator for an Isolated Switching Power Supply

The LM2940 is a positive 1A low dropout regulator; refer to its datasheet for further information.

Figure 26. Fixed Current Sink

Figure 27. Adjustable Current Sink

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