3A, 18V, Synchronous Step-down DC/DC Converter

EC3293

Page 10 of 11

3L03N-Rev.P001

External Bootstrap Diode

An external bootstrap diode may enhance the efficiency

of the regulator, the applicable conditions of external

BOOT diode are:

● V

● Duty cycle is high: D = V

In these cases, an external BOOT diode is recommended

from the output of the voltage regulator to BOOT pin, as

shown in Figure 1.

Figure 1: Add optional external bootstrap diode to

enhance efficiency.

The recommended external BOOT diode is IN4148, and

the BOOT capacitor is 0.1 ~

1μF.

efficiency, it can add an externalSchottky diode

between IN and BOOT pins, as shown in Figure 2.

Figure 2: Add a Schottky diode to promote efficiency

Table 3: BOM selection table II.

Note: To guarantee the bandwidth, if decrease the value of

C2, then R3 must be reduced in proportion to C2, and C3

must be increased in proportion to C2.

PCB Layout Guide

PCB layout is very important to achieve stable operation.

Please follow the guidelines below.

1) Keep the path of switching current short and

minimize the loop area formed by Input capacitor,

high-side MOSFET and low-side MOSFET.

2) Bypass ceramic capacitors are suggested to be put

3) Ensure all feedback connections are short and direct.

Place

the

feedback

resistors

and

compensation

components as close to the chip as possible.

4) Rout SW away from sensitive analog areas such as

FB.

5) Connect IN, SW, and especially GND respectively to a

large copper area to cool the chip to improve thermal

performance and long-term reliability.

BOM of EC3293

Please refer to the Typical Application Circuit.

Table 2: BOM selection table I.

L1

R1

R2

R3

C2

C3

Rfreq

C8

Vout = 5.0V

6.8uH

44.2K

10K

100K

22uFx2

100pF

175K

100pF

Vout = 3.3V

4.7uH

25.7K

10K

100K

22uFx2

100pF

175K

100pF

Vout = 2.5V

4.7uH

17.1K

10K

100K

22uFx2

100pF

175K

50pF

Vout = 1.8V

3.3uH

9.5K

10K

100K

22uFx2

100pF

175K

50pF

Vout = 1.2V

2.2uH

3K

10K

62K

22uFx2

200pF

240K

20pF

Vout = 1.0V

2.2uH

0.834K

10K

62K

22uFx2

200pF

240K

20pF

Item

Reference

Part

1

C1

10μF

2

C5

100nF

3

C7

0.1μF

4

R4

100K