IRU3034 & (PbF)

www.irf.com

8-PIN PWM SWITCHER CONTROLLER IC

WITH CURRENT LIMITING

TYPICAL APPLICATION

Figure 1 - Typical application of IRU3034.

DESCRIPTION

The IRU3034 IC provides a low cost switching controller
with true short circuit protection all in a compact 8-pin
surface mount package, providing a low cost switching
solution for dual supply processor applications that re-
quire switching regulator for the 3.3V supply such as
the applications with AGP on-board. Typically in these
applications, a dual supply regulator converts 5V to 3.3V
for I/O supply and a jumper programmable supply of
1.25V to 3.5V for Core supply. The IC uses an internal
regulator generated from the 12V supply to power the
controller as well as the 12V supply to drive the power
MOSFET, allowing a low cost N-channel MOSFET to be
used. The IC also includes an error comparator for fast
transient response, a precise voltage reference for set-
ting the output voltage as well as a direct drive of the
MOSFET for the minimum part count.

Data Sheet No. PD94148 revA

Notes: P55C, Pentium II are trademarks of Intel Corp. K5 & K6 are trademarks of AMD corp. Cyrix 6X86L, M1, M2 are trademarks of Cyrix
Corp. Power PC is trademark of IBM Corp.

OUT

12V

IRU3034

Drv

HYST

Gnd

CS-

CS+

FEATURES

8-Pin SOIC switching controller with
HICCUP current limiting reduces diode power
dissipation to less than 1% of normal operation
Soft-Start capacitor allows for smooth output
voltage ramp up
On-Board MOSFET Driver
Fastest transient response of any controller
method. (0 to 100% Duty Cycle in 100ns)
1% Internal Voltage Reference
Internal Under-Voltage Lockout protects MOSFET
during start-up

Dual supply low voltage processor applications,
such as: P55C

, CYRIX M2

, POWER PC

and AMD K6

Simple 5V to 3.3V switcher for Pentium with AGP
or Pentium II

applications

APPLICATIONS

PACKAGE ORDER INFORMATION

(癈) Basic Device Leadfree Device Package

Parts per Parts per T & R
Tube Reel Orientation

0 To 70 IRU3034CS IRU3034CS(PbF) 8-Pin Plastic SOIC(S) 95 2500 see

Fig. A

IRU3034 & (PbF)

www.irf.com

ABSOLUTE MAXIMUM RATINGS

Supply Voltages .................................................. 20V

Fb Pin Voltages ......................................................... -0.3V To 5V
Storage Temperature Range ....................................... -65 To 150癈
Operating Junction Temperature ................................. 0 To 150癈

PACKAGE INFORMATION

8-PIN PLASTIC SOIC (S)

Fb Voltage Initial Accuracy
Fb Voltage Total Variation
Fb Voltage Line Regulation
Fb Input Bias Current
Minimum On Time

Minimum Off Time

HYST

Pin Output-HI

HYST

Pin Output-LO

Supply Current
Maximum Duty Cycle
Minimum Duty Cycle
Gate Drive Rise/Fall Time
CL Threshold Current
CS Comp Common Mode
Soft-Start Current

ELECTRICAL SPECIFICATIONS

Unless otherwise specified, the following specification applies over V

=12V and T

=0 to 70 C. Low duty cycle

pulse testing is used which keeps junction and case temperatures equal to the ambient temperature.

=160 C/W

Drv

HYST

Gnd

CS-

CS+

TOP VIEW

=25 C

=1.25V

is sq wave with 300ns on

time and 2祍 off time
V

is sq wave with 300ns off

time and 2祍 on time
I

SOURCE

=500礎, V

=1.5V

SINK

=500礎, V

=1V

=1.5V

Load=IRL3303
CS+, CS- from 1.3V to 3.7V
V

CS+

CS-

12(SW)

MAX

MIN

GATE

PARAMETER

SYM TEST CONDITION

MIN TYP MAX UNITS

1.237
1.225

-1

1.250
1.250

0.2

800

70
20

1.262
1.275

100

4.5

V
V

礎

V
V

%
%

礎

IRU3034 & (PbF)

www.irf.com

PIN DESCRIPTIONS

BLOCK DIAGRAM

Figure 2 - Simplified block diagram of the IRU3034.

The PWM output of the switching controller. This pin is a totem pole drive that is con-
nected to the gate of the power MOSFET. A resistor may be placed from this pin to the
gate in order to reduce switching noise.
This pin supplies the voltage to the PWM drive and hysteresis circuitry and it is connected
to the 12V supply. A 1礔, high frequency capacitor must be connected from this pin to
ground to provide the peak current for charging and discharging of the MOSFET.
A resistor divider from this pin to the output of the switching regulator and ground sets the
Core supply voltage.
A resistor and a 10pF capacitor is connected from this pin to the V

pin to set the output

ripple voltage for the switching regulator.
This pin is connected to the IC substrate and must be connected to the lowest potential in
the system.
This pin is connected to the minus side of the external current sense resistor. An internal
current source together with an external resistor in series with this pin programs the
current limit threshold voltage. This voltage divided by the external current sense resistor
sets the current limit threshold.
This pin is connected to the plus side of the external current sense resistor. A resistor in
series with this pin and a capacitor connected between this pin and pin 6 provides a high
frequency filtering for the noise spikes of turn on and turn off switching.
This pin provides the soft-start for the regulator during power up. It also sets a long off time
when the converter goes into current limiting, providing low duty cycle for the catch diode
allowing it to survive during short circuit.

PIN # PIN SYMBOL PIN DESCRIPTION

Drv

HYST

Gnd

CS-

CS+

REF

UVLO

1.25V

PWM Control

HYST

CS+

Drv

Gnd

CS-

5V Reg

S.S. / Hiccup

Control

20uA

IRU3034 & (PbF)

www.irf.com

TYPICAL APPLICATION

Pentium Core Supply Application (IRU3034 and IRU3033 Dual Layout)
Low Cost 4-Bit VID

Figure 3 - Typical application of IRU3034 in a flexible motherboard with the 4-bit VID output voltage selection. This
circuit is done using a dual layout with the IRU3033 part. The advantage of this circuit is that it uses a single jumper
that programs the output voltage in 16 steps with 0.1V steps from 2V to 3.5V, designed for Intel P55, P54, AMD K5
& K6 as well as Cyrix M1 and M2 applications.

0 = Jumper block is installed.
1 = Jumper block is not installed.

Note: R9 can be
eliminated if dual
layout with IRU3033
is not desired.

JP1

1-2

0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1

JP1

3-4

0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1

JP1

5-6

0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1

JP1

7-8

0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1

Output

Voltage

3.5
3.4
3.3
3.2
3.1
3.0
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0

12V

R5A

R5B

R5C

R5D

R5E

3
4

5
6

7
8

JP1

OUT

Drv

HYST

Gnd

CS-/

FB2

CS+/

Drv2

SS/

IRU3034 & (PbF)

www.irf.com

Ref Desig Description Qty

Part #

Manuf

LDO/Switcher IC

IRU3034CS (8-Pin SOIC)

MOSFET

IRL3303 (TO-220)

IRL3103S (TO-263) (Note 1)

Schottky Diode

MBR1045CT (TO-220)
MBRB1545CT (TO-263) (Note1) Motorola

Inductor

Core: T50-18, L=4礖

Micro Metal

Turns: 10T, 18 AWG

(core)

Inductor

L=2礖

Resistor

22, 5%, SMT 1206 size

Resistor

10, 5%, SMT 1206 size

Resistor

324K, 1%, SMT 0805 size

R4A *

Resistor

806, 1%, SMT 0805 size

R4B *

Resistor

90.9K, 1%, SMT 0805 size

R5A

Resistor

1.24K, 1%, SMT 0805 size

R5B

Resistor

2.49K, 1%, SMT 0805 size

R5C

Resistor

4.99K, 1%, SMT 0805 size

R5D

Resistor

10K, 1%, SMT 0805 size

R5E

Resistor

1.30, 1%, SMT 0805 size

Resistor

5m, 5%, 2W

Resistor

4.99K, 1%, SMT 0805 size

Resistor

4.7K, 5% for IRU3034, open for 3033

Resistor

Open for IRU3034, 10 for IRU3033

Capacitor

6MV1500GX, 1500礔, 6.3V, Elect

Capacitor

6MV1500GX, 1500礔, 6.3V, Elect

Sanyo

Capacitor

1礔, Ceramic, SMT 0805 size

Capacitor

470pF, Ceramic, SMT 0805 size

Sanyo

Capacitor

10pF, Ceramic, SMT 0805 size

Sanyo

Capacitor

6MV1500GX, 1500礔, 6.3V, Elect

Sanyo

Capacitor

0.047礔 for 3034 , 0.1礔 for IRU3033

Capacitor

4700pF for IRU3034, open for IRU3033

HS1

Heat Sink

For MOSFET, 577002

Aavid

HS2

Heat Sink

For Schottky Diode, 577002

Aavid

*R4 is a parallel combination of R4A and R4B.

Note: 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.

PENTIUM CORE SUPPLY APPLICATION PARTS LIST

(IRU3034 and IRU3033 Dual Layout) Low Cost 4-Bit VID

协谢械泻褌褉芯薪薪褘泄 泻芯屑锌芯薪械薪褌: IRU3034PBF

协谢械泻褌褉芯薪薪褘泄泻芯屑锌芯薪械薪褌: IRU3034PBF