13

minimize the voltage drop across the bootstrap capacitor

during the on-time of the upper MOSFET. Initial calculations

bootstrap capacitor range.

For example, consider an upper MOSFET is chosen with a

drop across the bootstrap capacitor to 1V results in a value

of no less than 0.1

µF. The tolerance of the ceramic capacitor

should also be considered when selecting the final bootstrap

capacitance value.

A fast recovery diode is recommended when selecting a

bootstrap diode to reduce the impact of reverse recovery

have to be added to the gate charge of the MOSFET and

taken into consideration when calculating the minimum

bootstrap capacitance.

ISL6439 DC-DC Converter Application Circuit

Figure 8 shows an application circuit of a DC-DC Converter.

Detailed information on the circuit, including a complete Bill-

of-Materials and circuit board description, can be found in

the ISL6439 Application Note.

Component Selection Notes:

D1 - 30mA Schottky Diode, MA732 or Equivalent

2.5V @ 5A

FB

COMP

UGATE

PHASE

BOOT

GND

LGATE

ISL6439

OCSET

CPVOUT

CT1

CT2

CPGND

VCC

3.3V

GND

GND

14

1

2

3

4

5

8

6

7

9

10

11

12

13

ENABLE

9.76k

Ω

6.49k

Ω

2.26k

Ω

124

Ω

0.1

µF

1000pF

10

µF

0.22

µF

1

µF

0.1

µF

33pF

5600pF

8200pF

1.07k

Ω

Ceramic

ENABLE

FIGURE 8. 3.3V to 2.5V 5A DC-DC CONVERTER

ISL6439