AL3353

Figure 5. Typical Circuit Schematic of AL3353 Constant Output Voltage Application

For the OCP setting, OVP setting, inductor design, power MOSFET selection and Schottky diode selection, the above configuration guides for LED

driver are also applicable.

Layout Guide

The PCB layout is critical for the optimal performance of the boost converter design. A good PCB layout is fundamental to correct operation and

high performance of the converter. And the EMI performance is especially dependent on the PCB layout. So, the following important guidelines

should be followed:

1.

The traces of the power loops should be wide and short, and the power components should be placed close together to make the loop area

as small as possible. There are two high-current power loops in the converter. One is the high-current input loop, and the other is the high-

current output loop. The high-current input loop goes from the positive terminal of the CIN to the inductor, to the MOSFET, then to the

current-sense resistor, and to the negative terminal of CIN. The high-current output loop goes from the positive terminal of the CIN to the

inductor, to the diode, to the positive terminal of the COUT, reconnecting between the COUT and the CIN ground terminals.

L1

Q1

D2

Switch Node

Figure 6. The Power Loops of a Boost Converter

2.

A decoupling capacitor of the VIN pin is recommended and it should be placed as close as possible to the pin, to reduce the noise on the

power source for the internal logic circuit.

3.

To keep the gate signal clean, the gate driving trace should be placed away from the inductor, since the alternating magnetic field is the

primary noise source in a switching converter

4.

For the OVP resistor divider, the both resistors should be placed close to the IC, and the divider should be grounded close to the IC ground.

5.

For the compensation capacitor, it should be placed as close as possible to the COMP pin.

6.

Copper area of the power loop, especially around the switching node should be as big as possible for good thermal performance.

AL3353

Document number: DS41487 Rev. 2 - 2

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February 2019

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