Specifications Download

Application Note
Tj Control for Good Heat Dissipation in NVSU333A (U385)
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 operated over the absolute
maximum rated junction temperature (Tj).
It is critical to design the heat dissipation performance not to exceed the Tjmax for NVSU333A, to deliver high
reliability/performance.
This document shows the Tj evaluation results by demonstrating three heat dissipation conditions. Please
use the data for reference to your thermal design.
Light Emitting Diode
2. Tj Calculation
Tj can be calculated by the following formula:
Tj = Ts + Rthj-s × PD
Tj: Junction Temperature
Ts: Soldering Temperature (°C)
Rthj-s: Thermal resistance (°C/W) from the die to the Ts measuring point
* Rthj-s (NVSU333A): 2.08°C/W
PD: Input Power (W)
TS Point
Picture 1 Ts Measuring Point
The thermocouple was solder-attached to
the Ts measuring point for the evaluation.
3. Ts Measuring Point
4. Tj Evaluation Result
Example 1. Copper Board + Heat Sink B
IF(A)
1.5
2.5
3.5
TS (℃)
47.6
63.2
80.1
VF(V)
3.4
3.5
3.6
Tj (℃)
58
82
107
Example 2. Copper Board + Heat Sink C
IF(A)
1.5
2.5
3.5
4.5
TS (℃)
44.6
57.6
70.8
84.7
VF(V)
3.4
3.5
3.6
3.8
Tj (℃)
55
76
97
120
Reverse Side
Front Side
Picture 2 Copper Board
HS-D
HS-D
HS-C
HS-C
Example 3. Copper Board + Heat Sink D
IF(A)
1.5
2.5
3.5
4.5
TS (℃)
32.7
38.3
45.2
52.3
VF(V)
3.4
3.6
3.7
3.8
Tj (℃)
43
57
72
88
HS-B
Front Side
HS-B
Reverse Side
Picture 3 Copper Board + Heat Sink
This sheet contains tentative information; we may change the contents without notice.
(SP-QR-C-4777B)
Oct. 17, 2015
Application Note
5. PCB Specifications
Type of Board
Land Pattern
(μm)
Insulating Layer
(μm)
Heat Conductivity
(W/(m・ K))
Board Thickness
(mm)
Notes
Cu
35
120
10
1
The thermal pad is not in contact with the copper base.
6. 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)
Light Emitting Diode
Heat Sink D: 100mm×100mm×40mm (H), Base Thickness: 7mm, Fin: 707 pcs. (Φ2.1mm, Alignment; 15×25 / 14×24)
Note
We specified the absolute maximum ratings for NVSU333A; IF= 4.5A and Tjmax = 100°C.
We cannot guarantee the usage over these ratings.
We appreciate your understanding and cooperation.
This sheet contains tentative information; we may change the contents without notice.
(SP-QR-C-4777B)
Oct. 17, 2015