AB136 datasheet(10/22 Pages) LUMILEDS

10 / 22 page

Figure 7. Top left shows long copper trace length (red lines) with narrower trace width. Top right shows the same layout as the

left drawing but with wider trace width. The latter minimizes heat generated in the copper trace. Bottom left and right shows

optimize trace route (shortest). Depending on the operating drive current of the LED system and the electrical layout of the

LEDs (parallel-series), the copper trace width may need to be adjusted depending on the amount of current flowing through

each section of the trace. See Figure 8 for this example.

Figure 8. Top and bottom drawing each show four LEDs connected in parallel. Each LED is assumed to have the same forward

voltage and same current flowing. T

1 to T8 sections represent copper trace width. Thicker line means wider copper trace width.

Top drawing has poor electrical layout since more heat is generated in T

1 than T2, etc due to higher current flowing in T1 than

2, etc. Temperature in T1 > T2 > T3 > T4. Bottom drawing represents good electrical layout.

Since more current flows in T

5 than T6, the trace width in T5 is made correspondingly larger than T6 and so on.

Much easier will be to make the trace width the same (larger) for all of T

5 to T8. Note that as the copper trace

area is increased, this may lead to increase PCB board capacitance and may interact with other transient

tests such as electrical surge immunity test.

AB136 Datasheet(PDF) 10 Page - Lumileds Lighting Company