application note light emitting diode this sheet contains tentative information; we may change the contents without notice. (SP-QR-C-4089A) oct. 14, 2014 tj control for good heat di ssipation in nvsu233a (u405) 1. objective the leds? light output can be affected by the heat generated from the leds/led-assembled products. also, the reliability performance can be seriously degraded, if the leds are operat ed over the absolute maximum rated junction temperature (tj). it is critical to design the heat dissi pation performance not to exceed the t jmax for nvsu 233a, to deliver high reliability/performance. this document shows the tj evaluation results by demonstrating two heat dissipation conditions. please use the data for reference to your thermal design. 2. tj calculation tj can be calculated by the following formula: tj = ts + rthj-s p d 3. ts measuring point 4. tj evaluation result example 1. copper board + heat sink b i f (a) t s ( )v f (v) t j ( ) 1.0 48.2 3.4 68 1.4 58.6 3.5 87 example 2. copper board + heat sink c i f (a) t s ( )v f (v) t j ( ) 1.0 43.6 3.4 63 1.4 51.9 3.5 80 picture 1 ts measuring point ts point tj: junction temperature ts: soldering temperature (c) rthj-s: thermal resistance (c/w) from the die to the ts measuring point * rthj-s (nvsu233a): 5.7c/w pd: input power (w) the thermocouple was solde r -attached to the ts measuring point for the evaluation. picture 3 copper board + heat sink picture 2 copper board hs-b hs-b hs-c hs-c front side reverse side front side reverse side
application note light emitting diode this sheet contains tentative information; we may change the contents without notice. (SP-QR-C-4089A) oct. 14, 2014 5. heat dissipating materials metal-based board: copper, 30mm 30mm 1.7mm heat sink b: 50mm 38mm 25mm (h), base thickness: 5 mm, fin: 8 pcs.(1mm 38mm, array: 1 8) heat sink c: 54mm 54mm 35mm (h), base thickness: 4mm, fin=64 pcs.(0.8mm 9mm, array: 5 13 note we specified the absolute maximum ratings for nvsu233a; i f = 1.4a and t jmax = 130c. we cannot guarantee the usage over these ratings. we appreciate your understanding and cooperation.
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