9

Schottky Selection

Rectifier D2 conducts when the upper MOSFET Q1 is off.

The diode should be a Schottky type for low power losses.

The power dissipation in the schottky rectifier is approxi-

mated by:

In addition to power dissipation, package selection and heat-

sink requirements are the main design tradeoffs in choosing

the schottky rectifier. Since the three factors are interrelated,

the selection process is an iterative procedure. The maxi-

mum junction temperature of the rectifier must remain below

the package thermal resistance specification and the schot-

tky power dissipation equation (shown above), the junction

temperature of the rectifier can be estimated. Be sure to use

the available airflow and ambient temperature to determine

the junction temperature rise.

HIP6011 DC-DC Converter Application Circuit

The Figure below shows an application circuit of a DC-DC

Converter for a microprocessor application.

+

-

+12V

HIP6011

GND

UGATE

PHASE

BOOT

VCC

+5V OR LESS

NOTE:

Q1

D2

HIP6011

RT

FB

COMP

SS

REF

GND

MONITOR AND

PROTECTION

OSC

VCC

VIN

C1-C5

L2

C6-C11

0.1

µF

2x 1

µF

0.1

µF

1

µF

33pF

0.01

µF 15K

1K

3x 680

µF

4x 1000

µF

SPARE

UGATE

OCSET

PHASE

BOOT

SPARE

CR1

Q1

3.01K

1000pF

C13

R1

R3

R4

C16

C15

R5

C14

C12

C17-C18

C19

R6

C20

4148

U1

RTN

12VCC

12

2

10

9

8

7

4

5

14

3

SPARE

CR3

1206

1206

VOUT

RTN

ENABLE

R2

1K

COMP

TP1

PHASE

TP2

6

R7

10K

Component Selection Notes:

C1-3 - 3 Each 680

µF 25W VDC, Sanyo MV-GX or Equivalent

C6-9 - 4 Each 1000

µF 6.3W VDC, Sanyo MV-GX or Equivalent

L1 - Core: Micrometals T60-52; Winding: 14Turns of 17AWG

CR1 - 1N4148 or Equivalent

CR3 - 15A, 35V Schottky, Motorola MBR1535CT or Equivalent

Q1 - Intersil MOSFET; RFP25N05

EN

VSEN

1

OVP

13

Q2

2N6394

R8

10K

R7

1K

R8

1K

+

-

+

-

HIP6011