ISL6439CBZ datasheet(13/16 Pages) RENESAS

13 / 16 page

FN9057.6

September 15, 2015

recommended to minimize the voltage drop across the

bootstrap capacitor during the on-time of the upper

MOSFET. Initial calculations with VBOOT2 no less than 4V

will quickly help narrow the bootstrap capacitor range.

For example, consider an upper MOSFET is chosen with a

maximum gate charge, Qg, of 100nC. Limiting the voltage

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

of no less than 0.1

F. 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

charge loss. Otherwise, the recovery charge, QRR, would

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:

C3,8,9 - Each 150F, Panasonic EEF-UE0J151R or Equivalent.

D1 - 30mA Schottky Diode, MA732 or Equivalent

L1 - 1H Inductor, Panasonic P/N ETQ-P6F1ROSFA or Equivalent.

Q1- Fairchild MOSFET; ITF86110DK8.

2.5V @ 5A

COMP

UGATE

PHASE

BOOT

GND

LGATE

ISL6439

C10

C11

C8,9

OCSET

CPVOUT

CT1

CT2

CPGND

VCC

3.3V

C12

GND

TP1

TP3

ENABLE

9.76k



6.49k



2.26k



124



0.1

F

1000pF

F

0.22

F

0.1

F

33pF

5600pF

8200pF

1.07k



Ceramic

ENABLE

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

ISL6439, ISL6439A

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