32

THERMAL DESIGN

The CMA family of LED arrays can include over a hundred different LED die inside one package, and thus over a hundred different junction

temperatures (T

T

ensure that the CMA LED is being operated within its designed limits. LES temperature measurement provides additional verification of

good thermal design. Please refer to page 4 for the Operating Limit specifications.

There is no need to calculate for T

ambient (T

refer to the Thermal Management application note. For CMA soldering recommendations and information on thermal interface materials

(TIM), LES temperature measurement, and connection methods, please refer to the Cree XLamp CM Family LEDs soldering and handling

document.

To keep the CMA1306 LED at or below the maximum rated Tc, the case to ambient temperature

thermal resistance (R_c‑a) must be at or below the maximum R_c‑a value shown on the following

graphs, depending on the operating environment. The y-axis in each graph is a base 10 logarithmic

scale.

As the figure at right shows, the R_c‑a value is the sum of the thermal resistance of the TIM (R_tim)

plus the thermal resistance of the heat sink (R_hs).

R_j-c

Tc

R_tim

R_hs

Ta

R_j-c

Tc

R_c-a

Ta

CMA1306 - 9 V

0.01

0.10

1.00

10.00

100.00

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

Current (mA)

Ta = 25 °C

Ta = 55 °C

Ta = 85 °C

Ta = 105 °C

9 V