For the switch-mode converters, the excellent printed circuit board (PCB) layout is critical to achieving optimal system performance. If the PCB design properly, it may cause the following consequences: on the control circuit generates too much noise and affect the stability of the system ; PCB traces in excessive wear and tear affect system efficiency ; cause excessive electromagnetic interference affecting compatible systems sex .
ZXLD1370 is a switch-mode multi- topology LED driver controller , each of the different topologies are embedded with external switching devices. The LED driver suitable for buck, boost or buck - boost mode.
This article will ZXLD1370 devices , for example, discuss PCB design considerations and provide recommendations.
Considering the width of the trace
The switch mode power supply circuit , the main power switch and associated high current carrying devices . These devices are used to connect the traces have its thickness , width and length of the associated resistor. The heat generated by the current flowing through the trace when not only reduce efficiency , but will also trace the rise in temperature . In order to limit the temperature rise to ensure trace width sufficient to meet the rated switching current is very important.
The following equation shows the relationship between temperature rise and traces the cross-sectional area .
Internal trace : I = 0.024 × dT0.44 × A0.725
External trace : I = 0.048 × dT0.444 × A0.725
Where : I = maximum current (A); dT = temperature rise above ambient (℃); A = cross-sectional area (mil2).
Table 1 shows the relative current capacity of the minimum trace width. This is based on the statistical results 1oz/ft2 (35μm) copper traces temperature at 20oC under .
For surface mount devices are designed with switch-mode power converter applications, the copper surface can also be used on the PCB power devices radiator. Traces caused by the temperature rise due to the conduction current should be minimized. Proposal to limit the temperature rise traces 5oC or less.
Table 2 shows the relative current capacity of the minimum trace width. This is based on the statistical results 1oz/ft2 (35μm) copper traces temperature at 5oC under .
