IRU3033

8

Rev. 1.7

07/17/02

www.irf.com

Figure 5 - The circuit in figure 4 is the application of the IRU3033 in a switching mode only. This circuit can be used

to generate a low cost 5V to 3.3V for either Pentium application with AGP socket or in Pentium II applications

where it is desirable to generate an accurate on board 3.3V supply.

TYPICAL APPLICATION

5V to 3.3V for Pentium application with AGP or Pentium II application

without ATX power supply switching mode operation.

Ref Desig

Description

Qty

Part #

Manuf

U1

LDO/Switcher IC

1

IRU3033CS (8-Pin SOIC)

IR

Q2

MOSFET

1

IRL3303 (TO-220)

IR

IRL3103S (TO-263) (Note 1)

D1

Schottky Diode

1

MBR1045CT (TO-220)

MBRB1545CT (TO-263) (Note 1)

Motorola

L2

Inductor

1

Core: T50-18, L=4

mH

Micro Metal

Turns: 10T, 18 AWG

(core)

L1

Inductor

1

L=2

mH

R1

Resistor

1

22

V, 5%, SMT 1206 size

R9

Resistor

1

10

V, 5%, SMT 0805 size

R2

Resistor

1

10

V, 5%, SMT 1206 size

R3

Resistor

1

249K

V, 1%, SMT 0805 size

R4

Resistor

1

1K

V, 1%, SMT 0805 size

R5

Resistor

1

576

V, 1%, SMT 0805 size

C1, 2

Capacitor

2

6MV1500GX, 1500

mF, 6.3V, Elect

Sanyo

C3

Capacitor

1

1

mF, Ceramic, SMT 0805 size

C4

Capacitor

1

470pF, Ceramic, SMT 0805 size

Sanyo

C5

Capacitor

1

10pF, Ceramic, SMT 0805 size

Sanyo

C7

Capacitor

1

6MV1500GX, 1500

mF, 6.3V, Elect

Sanyo

C8

Capacitor

1

1

mF, Ceramic, SMT 0805 size

HS1

Heat Sink

1

For MOSFET, 577002

Aavid

HS2

Heat Sink

1

For Schottky Diode, 577002

Aavid

Note 1: For the applications where it is desirable to eliminate the heat sink, the IRL3103S for Q2 and

MBR1545CT for D2 in TO-263 packages with minimum of 1" square copper pad can be used.

5V

C1

L1

C3

Q2

C2

L2

R4

C7

D1

R2

C4

R5

R1

12V

R3

C5

C8

R9

Drv1

Gnd

Drv2

U1