MP2480 – 36V INPUT, 3A HIGH POWER LED DRIVER

MP2480 Rev. 1.01

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11

1/25/2013

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External Bootstrap Diode

An external bootstrap diode may enhance the

efficiency of the LED driver. For the cases listed

below, add an external BST diode is from a 5V

rail to the BST pin:

There is a 5V rail available in the system;

Add a diode for high duty cycle operations

frequency (over 1.5MHz) applications.

The bootstrap diode can be low-cost, such as a

IN4148 or BAT54.

Figure 2—External Bootstrap Diode

Layout Consideration

Place the input decoupling capacitors and the

pin and PGND) as possible, with short, wide

traces. This reduces the voltage spike on the

SW node and lowers the EMI noise level.

Run the feedback trace as far away from the

inductor and noisy power traces as possible.

Try to run the feedback trace on the opposite

side of the PCB to the inductor, with a ground

plane separating the traces from the inductor.

To improve thermal conduction, create a grid of

thermal vias right under the exposed pad. Use

small vias (15mil barrel diameter) so that the

holes fill during the plating process. Very large

holes can cause ‘solder-wicking’ problems

during the reflow soldering process. Use a pitch

(distance between the centers) of around 40mil

to space the vias.