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Data Sheet No. PD94148 revA
IRU3034 & (PbF)
8-PIN PWM SWITCHER CONTROLLER IC WITH CURRENT LIMITING 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 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 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 setting the output voltage as well as a direct drive of the MOSFET for the minimum part count.
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
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 SS CS+ CSC6 Drv IRU3034 Gnd
12V
R1 L1
V12
VFB VHYST C3 R3 C5 L2
R8
R7
R6 C7
VOUT
5V
C1 C2
Q2
C4 R2
D1
R4
R5
Figure 1 - Typical application of IRU3034.
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.
PACKAGE ORDER INFORMATION
TA (C) 0 To 70 Basic Device Leadfree Device IRU3034CS IRU3034CS(PbF) Parts per Tube 8-Pin Plastic SOIC(S) 95 www.irf.com Package Parts per Reel 2500 T&R Orientation see Fig. A
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IRU3034 & (PbF)
ABSOLUTE MAXIMUM RATINGS
V12 Supply Voltages .................................................. Fb Pin Voltages ......................................................... Storage Temperature Range ....................................... Operating Junction Temperature ................................. 20V -0.3V To 5V -65 To 150C 0 To 150C
PACKAGE INFORMATION
8-PIN PLASTIC SOIC (S)
TOP VIEW
Drv 1 V12 2 VFB 3 VHYST 4
8 SS 7 CS+ 6 CS5 Gnd
JA =160 C/W
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, the following specification applies over V12=12V and TA=0 to 70 C. Low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient temperature. PARAMETER Fb Voltage Initial Accuracy Fb Voltage Total Variation Fb Voltage Line Regulation Fb Input Bias Current Minimum On Time Minimum Off Time VHYST Pin Output-HI VHYST 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 SYM VFB TEST CONDITION TJ=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 UNITS 1.262 V V 1.275 % A +1 ns ns V V mA % % ns A V A
IFB
I12(SW) DMAX DMIN VGATE ICL
VFB=1.25V VFB is sq wave with 300ns on time and 2s off time VFB is sq wave with 300ns off time and 2s on time ISOURCE=500A, VFB=1.5V ISINK=500A, VFB=1V VFB=1V VFB=1V VFB=1.5V Load=IRL3303 CS+, CS- from 1.3V to 3.7V VCS+=VCS-
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IRU3034 & (PbF)
PIN DESCRIPTIONS
PIN # PIN SYMBOL Drv 1 2 3 4 5 6 V12 VFB VHYST Gnd CSPIN DESCRIPTION The PWM output of the switching controller. This pin is a totem pole drive that is connected 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 1F, 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 VFB 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.
7 8
CS+ SS
BLOCK DIAGRAM
V12 2 VHYST 4 VFB 3
5V Reg R
Drv 1
UVLO
20uA
CS6 CS+ 7 SS 8
PWM Control
1.25V 3R
VREF
Gnd 5
S.S. / Hiccup Control
Figure 2 - Simplified block diagram of the IRU3034.
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IRU3034 & (PbF)
TYPICAL APPLICATION
Pentium Core Supply Application (IRU3034 and IRU3033 Dual Layout) Low Cost 4-Bit VID
R9 C8 SS/ V12 V12
Note: R9 can be eliminated if dual layout with IRU3033 is not desired.
12V
CS-/ CS+/ VFB2 Drv2 Gnd U1 VFB VHYST L2 R3 C5 R8
C6
C3
Drv R1
R7 R6 C7
VOUT
L1
5V
C1 C2
Q2 C4 R2 D1 R5A JP1 1 2 R5B 3 4 R5C 5 6 R5D 7 8
R4
R5E
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.
JP1 JP1 JP1 JP1 Output 1-2 3-4 5-6 7-8 Voltage 0 3.5 0 0 0 1 3.4 0 0 0 0 3.3 0 1 0 1 3.2 0 1 0 0 3.1 1 0 0 1 3.0 1 0 0 0 2.9 1 1 0 1 2.8 1 1 0 0 2.7 0 0 1 1 2.6 1 0 0 1 0 2.5 1 0 1 1 2.4 1 0 0 0 2.3 1 1 0 1 2.2 1 1 1 0 2.1 1 1 0 = Jumper block is installed. 1 1 2.0 1 1 1 = Jumper block is not installed.
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IRU3034 & (PbF)
PENTIUM CORE SUPPLY APPLICATION PARTS LIST
(IRU3034 and IRU3033 Dual Layout) Low Cost 4-Bit VID Ref Desig Description Qty U1 LDO/Switcher IC 1 Q2 MOSFET 1 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 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 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 # IRU3034CS (8-Pin SOIC) IRL3303 (TO-220) IRL3103S (TO-263) (Note 1) MBR1045CT (TO-220) MBRB1545CT (TO-263) (Note1) Core: T50-18, L=4H Turns: 10T, 18 AWG L=2H 22, 5%, SMT 1206 size 10, 5%, SMT 1206 size 324K, 1%, SMT 0805 size 806, 1%, SMT 0805 size 90.9K, 1%, SMT 0805 size 1.24K, 1%, SMT 0805 size 2.49K, 1%, SMT 0805 size 4.99K, 1%, SMT 0805 size 10K, 1%, SMT 0805 size 1.30, 1%, SMT 0805 size 5m, 5%, 2W 4.99K, 1%, SMT 0805 size 4.7K, 5% for IRU3034, open for 3033 Open for IRU3034, 10 for IRU3033 6MV1500GX, 1500F, 6.3V, Elect 6MV1500GX, 1500F, 6.3V, Elect 1F, Ceramic, SMT 0805 size 470pF, Ceramic, SMT 0805 size 10pF, Ceramic, SMT 0805 size 6MV1500GX, 1500F, 6.3V, Elect 0.047F for 3034 , 0.1F for IRU3033 4700pF for IRU3034, open for IRU3033 For MOSFET, 577002 For Schottky Diode, 577002 Manuf IR IR
Motorola Micro Metal (core)
Sanyo Sanyo Sanyo Sanyo
Aavid 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.
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IRU3034 & (PbF)
TYPICAL APPLICATION
5V to 3.3V for Pentium Application with AGP or Pentium II Application without ATX power supply Switching mode Operation. (IRU3034 and IRU3033 Dual Layout)
12V
R9 C8 SS/ V12 V12 C3 Drv CS-/ VFB2 CS+/ Drv2 Gnd R8 C5 L2 R6 C7 D1 R4 R7 C6
U1
VFB VHYST R3
R1 L1
VOUT
5V
C1 C2
Q2
C4 R2
R5
Figure 4 - The circuit in figure 4 is the application of the IRU3034 which is done using a dual layout with 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.
Ref Desig U1 Q2 D1 L2 L1 R1 R9 R2 R3 R4 R5 R6 R7 R8 C1, 2 C3 C4 C5 C6 C7 C8 HS1 HS2 Description LDO/Switcher IC MOSFET Schottky Diode Inductor Inductor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor 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 2 1 1 1 1 2 1 1 1 Part # IRU3034CS (8-Pin SOIC) IRL3303 (TO-220) IRL3103S (TO-263) (Note 1) MBR1045CT (TO-220) MBRB1545CT (TO-263) (Note1) Core: T50-18, L=4H Turns: 10T, 18 AWG L=2H 22, 5%, SMT 1206 size Open for IRU3034, 10 for IRU3033 10, 5%, SMT 1206 size 249K, 1%, SMT 0805 size 1K, 1%, SMT 0805 size 576, 1%, SMT 0805 size 5m, 5%, 2W 4.99K, 1%, SMT 0805 size 4.7K, 5% for IRU3034, Open for IRU3033 6MV1500GX, 1500F, 6.3V, Elect 1F, Ceramic, SMT 0805 size 470pF, Ceramic, SMT 0805 size 10pF, Ceramic, SMT 0805 size 4700pF for IRU3034, Open for IRU3033 6MV1500GX, 1500F, 6.3V, Elect 0.047F for IRU3034 , 0.1F for 3033 For MOSFET, 577002 For Schottky Diode, 577002 Manuf IR IR Motorola Micro Metal (core)
Sanyo Sanyo Sanyo Sanyo Aavid Aavid
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.
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IRU3034 & (PbF)
TYPICAL APPLICATION
5V to 3.3V with loss-less short circuit protection (Output UVLO detection)
C8
SS V12
CS-
CS+ Gnd R6 C5 L2 C6
12V
C3
U1
R7
Drv
VFB VHYST R3
R1 L1
VOUT 5V
C1 C2 C4 Q2 R2 R5 C7 D1 R4
Figure 5 - The circuit in figure 5 is designed to provide loss-less output short detection by detecting the DC voltage across the inductor and shutting down the MOSFET and entering HICCUP mode. Note that the current limit point is a function of the inductor resistance and in this application with approximately 8m resistance the peak CL is set at 10A. See application note on how to set the current limiting threshold.
Ref Desig Description Qty Part # Manuf
U1 Q2 D1 L2 L1 R1,2 R3 R4 R5 R7 R6 C1 C2 C3 C5 C6 C7 C8
Switcher IC MOSFET Schottky Diode Inductor Inductor Resistor Resistor Resistor Resistor Resistor Resistor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor
1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 2 1
IRU3034CS (8-Pin SOIC) IRL3303 (TO-263) PBYR735 (Axial Thru Hole pkg) PBYR1035B (SMT, T-263 pkg) Core: T50-18, L=4H Turns: 7T, 18 AWG L=H 10, 5%, SMT 182K, 1%, SMT 1K, 1%, SMT 576, 1%, SMT 3.83K, 1%, SMT 1K, 1%, SMT 470F, Elect 6MV1000GX, 1000F, 6.3V, Elect 1F, Ceramic, SMT 10pF, Ceramic, SMT 0.1F 6MV1000GX, 1000F, 6.3V, Elect 0.047F
IR IR Motorola Micro Metal (core)
Sanyo Sanyo Sanyo
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IRU3034 & (PbF)
APPLICATION INFORMATION
Introduction The IRU3034 device is an application specific product designed to provide an on-board switching supply for the new generation of microprocessors requiring separate Core and I/O supplies where the load current demand from the I/O supply requires this regulator to also be a switching regulator such as the motherboard applications with AGP slot or the Pentium II with on-board 5V to 3.3V converter. The IRU3034 provides an easy and low cost switching regulator solution for Vcore and 3.3V supplies with true short circuit protection. Switching Controller Operation The operation of the switching controller is as follows: After the power is applied, the output drive pin (Drv) goes to 100% duty cycle and the current in the inductor charges the output capacitor causing the output voltage to increase. When output reaches a pre-programmed set point the feedback pin (VFB) exceeds 1.25V causing the output drive to switch Low and the VHYST pin to switch High which jumps the feedback pin higher than 1.25V resulting in a fixed output ripple which is given by the following equation: Vo = (Rt/Rh)x11 Where: Rt = Resistor connected from VOUT to the VFB pin of IRU3034. Rh = Resistor connected from VFB pin to VHYST pin. For example, if Rt=1K and Rh=422K, then the output ripple is: Vo = (1/422)x11 = 26mV The advantage of fixed output ripple is that when the output voltage changes from 2V to 3.5V, the ripple voltage remains the same which is important in meeting the Intel maximum tolerance specification. Soft-Start The soft-start capacitor must be selected such that during the start-up when the output capacitors are charging up, the peak inductor current does not reach the current limit threshold. A minimum of 0.1F capacitor insures this for most applications. During start-up the soft-start capacitor is charged up to approximately 6V keeping the output shutdown before an internal 10A current source start discharging the soft-start capacitor which slowly ramps up the inverting input of the PWM comparator, VFB. This insures the output to ramp up at the same rate as the soft-start cap thereby limiting the input current. For example, with 0.1F and the 10A internal current source the ramp up rate is: (V/t) = I/Css = 10/0.1 = 100V/s or 0.1V/ms Assuming that the output capacitance is 6000F, the peak input current will be: IIN(pk) = Cssx(V/t) = 6000Fx(0.1V/ms) = 0.6A The soft start capacitor also provides a delay in the turn on of the output which is given by: TD = CssxK Where: K = 30ms/F For example for Css=0.1F, TD = 0.1x30 = 3ms Switcher Current Limit Protection The IRU3034 uses an external current sensing resistor and compares the voltage drop across it to a programmed voltage which is set externally via a resistor (RCL) placed between the CS- terminal of the IC and VOUT. Once the voltage across the sense resistor exceeds the threshold, the soft-start capacitor pulls up to 12V, pulling up the inverting pin of the error comparator higher than noninverting which causes the external MOSFET to shut off. At this point the CS comparator changes its state and pulls the soft-start capacitor to Vcc which is 12V and shutting the PWM drive. After the output drive is turned off, an internal 10A current source slowly discharges the soft-start capacitor to approximately 5.7V, before the output starts to turn back on causing a long delay before the MOSFET turns back on. This delay causes the catch diode to cool off between the current limit cycles allowing the converter to survive a short circuit condition. An example is given below as how to select the current limiting components. Assuming the desired current limit point is set to be 20A and the current sense resistor Rs=5m, then the current limit programming resistor, RCL is calculated as: Vcs = ICLxRs = 20x0.005 = 0.1V RCL = Vcs/IB = (0.1V)/(20A) = 5K Where: IB = 20A is the internal current source of IRU3034
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IRU3034 & (PbF)
The peak power dissipated in the CS resistor is: Ppk = ICL xRs = 20 x0.005 = 2W
2 2
The bottom resistor of the divider is then calculated using the following equations: RB = Rt / X Where: RB = Bottom resistor of the divider VREF = 1.25V Typical X = [(Vo + (Vo/2)) / VREF] - 1 X=[(3.38+ (0.044/2)) / 1.25] - 1 = 1.72 RB = 1000 / 1.72 = 580 Select RB = 576, 1% Frequency Calculation The IRU3034 frequency of operation is calculated using the following formula: Fs = [(Vox(1-D)xESR)] / (LxVo) Where: Vo = Output voltage (V) D = Duty cycle ESR = Output capacitor ESR (V) L = Output inductance (H) Vo = Output ripple voltage (V) For our example: D (Vo + Vf) / VIN Where: Vf = Forward voltage drop of the Schottky diode. D = (3.38 + 0.5) / 5 = 0.78 The ESR=18m for 2 of the Sanyo 1500F, 6MV1500GX caps. If L=3.5H then, Fs is calculated as follows: Fs = [(3.38 x (1-0.78) x 0.018)] = 0.087 (3.5 x 0.044) (MHz)
However, the average power dissipated is much lower than 2W due to the long off time caused by the hiccup circuit of IRU3034. The average power is in fact the short circuit period divided by the short circuit period plus the off time or "Hiccup" period. For example, if the short circuit lasts for Tsc=100s before the IRU3034 enters hiccup, the average power is calculated as: PAVG = 0.5xPpkxDsc Where: Dsc = Tsc / THCP THCP = CssxM M = 200ms/F Css = The soft-start capacitor For example: For Css=0.1F and Tsc=500s=0.5ms THCP = 0.1x200 = 20ms PAVG = 0.5x2x(0.5/20) = 25mW Without "Hiccup" technique, the power dissipation of the resistor is 2W. Switcher Output Voltage Setting The output voltage can be set using the following equations: Assuming, Vo=3.38V and the selected output ripple is 1.3%(44mV) of the output voltage, a set of equations are derived that selects the resistor divider and the hysteresis resistor: Assuming, Rt = 1K, 1%: RH = (11xRt) / Vo Where: Rt = Top resistor of the resistor divider RH = Hysteresis resistor connected between pins 3 and 4 of the IRU3034 Vo = Selected output ripple (typically 1% to 2% of output voltage) Assuming, Vo=44mV: RH = (11x1000) / 0.044 = 250K Select RH = 249K, 1%
Fs = 87KHz
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IRU3034 & (PbF)
TYPICAL PERFORMANCE CHARACTERISTICS
IRU3034 Output Voltage IRU3034 Hysteresis Frequency
1.28 Max
90
80 1.27 70
1.26
60
1.25
Kilo Hertz Min -40C -25C Spec Max. 0C +25C Spec Min. +50C Vout 7V +75C +100C Vout 12V +125C Vout 20V +150C
50
Volts
40
1.24
30
20 1.23 10
1.22
0 -40C -25C 0C +25C +50C +75C +100C +125C +150C
Oscillation Frequency
Figure 6 - Output Voltage.
Figure 7 - Hysteresis Frequency.
IRU3034 Supply Current
IRU3034 Line Regulation
14.00
0.8
12.00
0.7
0.6 10.00 % Error of Nominal Vout -40C -25C 0C +25C +50C +75C +100C +125C +150C 0.5
Mili Amps
8.00
0.4
6.00
0.3
4.00 0.2
2.00
0.1
0.00
0 -40C -25C 0C +25C +50C +75C +100C +125C +150C
V12 Current
7V to 20V Line Reg
Figure 8 - Supply Current.
Figure 9 - Line Regulation.
IR WORLD HEADQUARTERS : 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105 TAC Fax: (310) 252-7903 Visit us at www.irf.com for sales contact information. Data and specifications subject to change without notice. 02/01
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IRU3034 & (PbF)
(S) SOIC Package 8-Pin Surface Mount, Narrow Body
H A B C
E
DETAIL-A PIN NO. 1 D 0.380.015 x 45 TF G
8-PIN SYMBOL A B C D E F G H I J K L T MAX MIN 4.98 4.80 1.27 BSC 0.53 REF 0.46 0.36 3.99 3.81 1.72 1.52 0.25 0.10 7 BSC 0.19 5.80 0 0.41 1.37 0.25 6.20 8 1.27 1.57
L DETAIL-A I J
K
NOTE: ALL MEASUREMENTS ARE IN MILLIMETERS.
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IRU3034 & (PbF)
1
1
1
Feed Direction Figure A
IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105 TAC Fax: (310) 252-7903 Visit us at www.irf.com for sales contact information Data and specifications subject to change without notice. 10/11/2005
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