THERMAL METRIC(1) | LM2678 | UNIT |
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NDZ (TO-220) | KTW (TO-263) | NHM (VSON) |
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7 PINS | 7 PINS | 14 PINS |
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RθJA | Junction-to-ambient thermal resistance | See (2) | 65 | — | — | °C/W |
See (3) | 45 | — | — |
See (4) | — | 56 | — |
See (5) | — | 35 | — |
See (6) | — | 26 | — |
See (7) | — | — | 55 |
See (8) | — | — | 29 |
RθJC(top) | Junction-to-case (top) thermal resistance | 2 | 2 | — | °C/W |
(2) Junction to ambient thermal resistance (no external heat sink) for the 7-lead TO-220 package mounted vertically, with 0.5 in leads in a socket, or on a PCB with minimum copper area.
(3) Junction to ambient thermal resistance (no external heat sink) for the 7-lead TO-220 package mounted vertically, with 0.5 in leads soldered to a PCB containing approximately 4 square inches of (1 oz) copper area surrounding the leads.
(4) Junction to ambient thermal resistance for the 7-lead DDPAK mounted horizontally against a PCB area of 0.136 square inches (the same size as the DDPAK package) of 1 oz (0.0014 in thick) copper.
(5) Junction to ambient thermal resistance for the 7-lead DDPAK mounted horizontally against a PCB area of 0.4896 square inches (3.6 times the area of the DDPAK package) of 1 oz (0.0014 in thick) copper.
(6) Junction to ambient thermal resistance for the 7-lead DDPAK mounted
horizontally against a PCB copper area of 1.0064 square inches (7.4 times the
area of the DDPAK 3 package) of 1 oz (0.0014 in thick) copper. Additional copper
area reduces thermal resistance further.
(7) Junction to ambient thermal resistance for the 14-lead VSON mounted on a PCB copper area equal to the die attach paddle.
(8) Junction to ambient thermal resistance for the 14-lead VSON mounted on a PCB
copper area using 12 vias to a second layer of copper equal to die attach
paddle. Additional copper area reduces thermal resistance further. For layout
recommendations, see the
AN-1187 Leadless Leadfram Package
(LLP) application report.