US3034
8 PIN PWM SWITCHER
CONTROLLER IC
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 100 nS )
1% internal voltage reference
Internal Under Voltage Lockout protects
MOSFET during start-up
PRELIMINARY DATASHEET
DESCRIPTION
The US3034 IC
provides an 8 pin 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 require 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 pro-
grammable 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 chan-
nel MOSFET to be used. The IC also includes an error
comparator for fast transient response, a precise volt-
age reference for setting the output voltage as well as a
direct drive of the MOSFET for the minimum part count.
APPLICATIONS
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
TYPICAL APPLICATION
C8
8 7 6 5
SS CS+ CS- Gnd
C6
US3034
Drv V12 Vfb Vhyst
1 2 3 4
12V
C3
R1
L1
R3
C5
L2
R8
R7
R6
Vout
C7
Q2
C1
C2
C4
R2
D1
R5
3034app1-1.0
5V
R4
Typical application of US3034
Notes: P55C,Pentium II are trade marks of Intel Corp. K5 & K6 are trade marks of AMD corp. Cyrix 6X86L,M1,M2 are trade marks of
Cyrix Corp. Power PC is trade mark of IBM Corp.
PACKAGE ORDER INFORMATION
TA (°C)
0 TO 70
Rev. 1.8
1/13/99
8 PIN PLASTIC
SOIC (S)
US3034CS
4-1
US3034
ABSOLUTE MAXIMUM RATINGS
V
12
Supply Voltages ............................................................. 20V
F.B Pin Voltages........................................................
-0.3V to 5V
Storage Temperature Range ................................. -65 TO 150
°
C
Operating Junction Temperature ............................... 0 TO 150
°
C
PACKAGE INFORMATION
8 PIN PLASTIC SOIC (S)
TOP VIEW
Drv
1
V12
2
Vfb
3
Vhyst
4
8
SS
7
CS+
6
CS-
5
Gnd
θ
JA
=160°C/W
ELECTRICAL SPECIFICATIONS
Unless otherwise specified the following specification applies over V
12
=12V, and T
A
=0 to 70°C. Low duty cycle
pulse testing are used which keeps junction and case temperatures equal to the ambient temperature.
PARAMETER
F.B Voltage Initial Accuracy
F.B Voltage Total Variation
F.B Voltage Line Regulation
F.B Input Bias Current
Min On Time
Min Off Time
Vhyst pin output-HI
Vhyst pin output-LO
Supply Current
Maximum Duty Cycle
Minimum Duty Cycle
Gate Drive Rise/Fall Time
C.L Threshold Current
C.S Comp Common Mode
Soft Start Current
SYM
V
FB
TEST CONDITION
T
J
=25°C
MIN
1.237
1.225
-1
800
800
11
1
10
100
0
70
20
0
10
4.5
TYP
1.250
1.250
0.2
MAX
1.262
1.275
+1
UNITS
V
V
%
uA
nS
nS
V
V
mA
%
%
nS
uA
V
uA
I
FB
I
12SW
D
MAX
D
MIN
V
GATE
I
CL
V
FB
=1.25V
V
FB
is sq wave with 300 ns on
time and 2 uS off time
V
FB
is sq wave with 300 ns off
time and 2 uS on time
I
SOURCE
=500uA, V
FB
=1.5V
I
SINK
=500uA, V
FB
=1V
V
FB
=1V
V
FB
=1V
V
FB
=1.5V
Load=IRL3303
C.S+ , C.S- from 1.3V to 3.7V
V
CS+
= V
CS-
4-2
Rev. 1.8
1/13/99
US3034
PIN DESCRIPTIONS
PIN #
3
6
PIN SYMBOL PIN DESCRIPTION
A resistor divider from this pin to the output of the switching regulator and ground sets the
V
FB
Core supply voltage.
This pin is connected to the minus side of the external current sense resistor. An internal
C.S-
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
C.S+
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 is connected to the IC substrate and must be connected to the lowest potential
Gnd
in the system.
The PWM output of the switching controller. This pin is a totem pole drive that is con-
Drv
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.
A resistor and a 10pF capacitor is connected from this pin to the V
FB1
pin to set the
V
HYST
output ripple voltage for the switching regulator.
This pin supplies the voltage to the PWM drive and hysterises circuitry and it is con-
V
12
nected to the 12V supply. A 1 uF, high frequency capacitor must be connected from this
pin to ground to provide the peak current for charging and discharging of the MOSFET.
This pin provides the soft start for the regulator during power up. It also sets a long off
S.S
time when the converter goes into current limiting, providing low duty cycle for the catch
diode allowing it to survive during short circuit.
7
5
1
4
2
8
BLOCK DIAGRAM
V12
2
Vhyst
4
Vfb
3
5V Reg
UVLO
R
20uA
Drv
1
CS-
6
CS+
7
SS
8
PWM Control
1.25V
3R
Vref
Gnd
5
S.S. / Hiccup
Control
3034blk1-1.1
Figure 1 - Simplified block diagram of the US3034
Rev. 1.8
1/13/99
4-3
US3034
TYPICAL APPLICATION
Pentium Core Supply Application (US3034 and US3033 Dual Layout)
Low Cost 4 Bit VID
**
R9
12V
** R9 can be elimi-
nated if dual layout
with US3033 is not
desired.
C8
C6
8 7 6 5
SS/ CS+/ CS-/ Gnd
V12 Drv2 Vfb2
U1
Drv V12 Vfb Vhyst
1 2 3 4
C3
R3
R1
L1
C5
L2
R8
R7
R6
Vout
C7
Q2
C1
C2
C4
R2
D1
JP1 1
2
3
4
5
6
7
8
R5A
R5B
R5C
R5D
R5E
R4
5V
3034app2-1.0
Figure2- Typical application of US3034 in a flexible motherboard with the 4 bit VID output voltage selection. This circuit is done
using a dual layout with the US3033 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.
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
0 = Jumper block is installed.
1 = Jumper block is not installed.
4-4
Rev. 1.8
1/13/99
US3034
Pentium Core Supply Application Parts List (US3034 and US3033 Dual Layout)
Low Cost 4 Bit VID
Ref Desig
U1
Q2
D1
L2
L1
R1
R2
R3
R4A *
R4B *
R5A
R5B
R5C
R5D
R5E
R6
R7
R8
R9
C1
C2
C3
C4
C5
C7
C8
C6
HS1
HS2
Description
LDO/Switcher IC
MOSFET
Schottky Diode
Inductor
Inductor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Capacitor
Capacitor
Capacitor
Capacitor
Capacitor
Capacitor
Capacitor
Capacitor
Heat Sink
Heat Sink
Qty
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4
1
1
1
1
Part #
US3034CS ( 8 pin SOIC)
IRL3303 (TO220)
IRL3103S (TO263) (note 1)
MBR1045CT (TO220)
MBRB1545CT (TO263) (note1)
Core:T50-18,L=4 uH
Turns: 10T, 18 AWG
L=2 uH
22 ohm,5%, SMT 1206 size
10 ohm, 5%, SMT 1206 size
324 kohm,1%, SMT 0805 size
806 ohm,1%, SMT 0805 size
90.9 kohm,1%, SMT 0805 size
1.24 kohm,1%, SMT 0805 size
2.49 kohm,1%, SMT 0805 size
4.99 kohm,1%, SMT 0805 size
10 kohm,1%, SMT 0805 size
1.30 kohm,1%, SMT 0805 size
5 miliohm,5%, 2W
4.99 kohm,1%, SMT 0805 size
4.7 kohm,5% for US3034, open for 3033
open for US3034, 10 ohm for US3033
6MV1500GX, 1500uF,6.3V, Elect
6MV1500GX, 1500uF,6.3V, Elect
1 uF,Ceramic, SMT 0805 size
470 pF,Ceramic, SMT 0805 size
10 pF,Ceramic, SMT 0805 size
6MV1500GX, 1500uF,6.3V, Elect
0.047 uF for 3034 , 0.1uf for 3033
4700pF for US3034, open for US3033
For MOSFET , 577002
For Schottky Diode , 577002
Manufacturer
Unisem
International
Rectifier
Motorola
Micro Metal
(core)
Sanyo
Sanyo
Sanyo
Sanyo
Aavid
Aavid
* R4 is a parallel combination of R4A and R4B.
Note 1: For the applications where it is desirable to eliminate the heat sink, the IRL3103S for Q2 and MBR1545CT for D2 in TO263
packages with minimum of 1" square copper pad can be used.
Rev. 1.8
1/13/99
4-5
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