8-PIN SWITCHER CONTROLLER 8-pin SOIC switching controller with HI
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IRU3034
8-PIN SWITCHER CONTROLLER
8-pin SOIC switching controller with HICCUP current limiting reduces diode power dissipation less than normal operation Soft start capacitor allows smooth output voltage ramp On-board MOSFET driver Fastest transient response controller method. 100% Duty Cycle 100nS internal voltage reference Internal undervoltage lockout protects MOSFET during start-up
DESCRIPTION
IRU3034 provides 8-pin cost switching controller with true short circuit protection compact 8-pin surface mount packages, providing cost switching solution dual supply processor applications that require switching regulator 3.3V supply such applications with board. Typically these applications dual supply regulator converts 3.3V supply jumper programmable supply 1.25V 3.5V CORE supply uses internal regulator generated from supply power controller well supply drive power MOSFET, allowing cost N-channel MOSFET used. also includes error comparator fast transient response, precise voltage reference setting output voltage well direct drive MOSFET minimum part count.
APPLICATIONS
Dual supply voltage processor applications, such P55C, CYRIX POWER PCand K6Simple 3.3V switcher Pentium with Pentium IIapplications
TYPICAL APPLICATION
IRU3034
Vhyst
Vout
3034app1-1.0
Typical application IRU3034
Notes: P55C, Pentium trademarks Intel Corp. trademarks corp. Cyrix 6X86L, trademarks Cyrix Corp. Power trademark Corp.
PACKAGE ORDER INFORMATION
(°C)
Rev. 1/13/99
8-PIN PLASTIC SOIC IRU3034CS
4-87
IRU3034
ABSOLUTE MAXIMUM RATINGS
Supply Voltages Voltages. -0.3V Storage Temperature Range 150° Operating Junction Temperature 150°
PACKAGE INFORMATION
8-PIN PLASTIC SOIC
VIEW
Vhyst
CSGnd
=160°C/W
ELECTRICAL SPECIFICATIONS
Unless otherwise specified following specification applies over =12V, 70°C. duty cycle pulse testing used which keeps junction case temperatures equal ambient temperature. PARAMETER Voltage Initial Accuracy Voltage Total Variation Voltage Line Regulation Input Bias Current Time Time Vhyst output-HI Vhyst output-LO Supply Current Maximum Duty Cycle Minimum Duty Cycle Gate Drive Rise/Fall Time Threshold Current Comp Common Mode Soft Start Current TEST CONDITION =25°C 1.237 1.225 1.250 1.250 1.262 1.275 UNITS
I12SW DMAX DMIN VGATE
=1.25V wave with 300ns time time wave with 300ns time time ISOURCE =500µA, =1.5V ISINK =500µA, =1.5V Load=IRL3303 C.S+ C.S- from 1.3V 3.7V VCS+ VCS-
4-88
Rev. 1/13/99
IRU3034
DESCRIPTIONS
SYMBOL DESCRIPTION resistor divider from this output switching regulator ground sets Core supply voltage. This connected minus side external current sense resistor. internal C.Scurrent source together with external resistor series with this programs current limit threshold voltage. This voltage divided external current sense resistor sets current limit threshold. This connected plus side external current sense resistor. resistor C.S+ series with this capacitor connected between this provides high frequency filtering noise spikes turn turn switching. This connected substrate must connected lowest potential system. output switching controller. This totem pole drive that conDrv nected gate power MOSFET. resistor placed from this gate order reduce switching noise. resistor 10pF capacitor connected from this VFB1 VHYST output ripple voltage switching regulator. This supplies voltage drive hysterises circuitry conV12 nected supply. 1µF, high frequency capacitor must connected from this ground provide peak current charging discharging MOSFET. This provides soft start regulator during power also sets long time when converter goes into current limiting, providing duty cycle catch diode allowing survive during short circuit.
BLOCK DIAGRAM
Vhyst
UVLO 20uA
Control
1.25V
Vref
S.S. Hiccup Control
3034blk1-1.1
Figure Simplified block diagram IRU3034
Rev. 1/13/99
4-89
IRU3034
TYPICAL APPLICATION
Pentium Core Supply Application (IRU3034 IRU3033 Dual Layout) Cost 4-Bit
eliminated dual layout with IRU3033 desired.
CS+/ CS-/ Drv2 Vfb2
Vhyst
Vout
3034app2-1.0
Figure Typical application IRU3034 flexible motherboard with output voltage selection. This circuit done using dual layout with IRU3033 part. advantage this circuit that uses single jumper that programs output voltage steps with 0.1V steps from 3.5V, designed Intel P55, P54, well Cyrix applications.
Output Voltage Jumper block installed. Jumper block installed.
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Rev. 1/13/99
IRU3034
Pentium Core Supply Application Parts List (IRU3034 IRU3033 Dual Layout) Cost
Desig Description Part Manuf
LDO/Switcher 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
IRU3034CS 8-pin SOIC) IRL3303 (TO-220) IRL3103S (TO-263) (note MBR1045CT (TO-220) MBRB1545CT (TO-263) (note1) Core: T50-18, L=4µH Turns: 10T, L=2µH ohm, 1206 size ohm, 1206 size kohm, 0805 size ohm, 0805 size 90.9 kohm, 0805 size 1.24 kohm, 0805 size 2.49 kohm, 0805 size 4.99 kohm, 0805 size kohm, 0805 size 1.30 kohm, 0805 size miliohm, 4.99 kohm, 0805 size kohm, IRU3034, open 3033 Open IRU3034, IRU3033 6MV1500GX, 1500µF, 6.3V, Elect 6MV1500GX, 1500µF, 6.3V, Elect 1µF, Ceramic, 0805 size 470pF, Ceramic, 0805 size 10pF, Ceramic, 0805 size 6MV1500GX, 1500µF, 6.3V, Elect 0.047µF 3034 0.1µf IRU3033 4700pF IRU3034, open IRU3033 MOSFET, 577002 Schottky Diode, 577002
Motorola Micro Metal (core)
Sanyo Sanyo Sanyo Sanyo
Aavid Aavid
parallel combination R4B. Note applications where desirable eliminate heat sink, IRL3103S MBR1545CT TO-263 packages with minimum square copper used.
Rev. 1/13/99
4-91
IRU3034
TYPICAL APPLICATION
3.3V Pentium Application with Pentium Application without power supply Switching mode Operation. (IRU3034 IRU3033 Dual Layout)
CS+/ CS-/ Drv2 Vfb2 Vhyst
Vout
3034app3-1.0
Figure circuit figure application IRU3034 which done using dual layout with IRU3033 switching mode only. This circuit used generate cost 3.3V either Pentium application with socket Pentium applications where desirable generate accurate board 3.3V supply.
Desig C1,2
Description LDO/Switcher 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
Part IRU3034CS 8-pin SOIC) IRL3303 (TO-220) IRL3103S (TO-263) (note MBR1045CT (TO-220) MBRB1545CT (TO-263) (note1) Core: T50-18,L=4µH Turns: 10T, L=2µH ohm, 1206 size open IRU3034, IRU3033 ohm, 1206 size kohm, 0805 size kohm, 0805 size ohm, 0805 size miliohm, 4.99 kohm, 0805 size kohm, IRU3034, open IRU3033 6MV1500GX, 1500µF, 6.3V, Elect 1µF, Ceramic, 0805 size 470pF, Ceramic, 0805 size 10pF, Ceramic, 0805 size 4700pF IRU3034, open IRU3033 6MV1500GX, 1500µF, 6.3V, Elect 0.047µF IRU3034 0.1µF 3033 MOSFET, 577002 Schottky Diode, 577002
Manuf
Motorola Micro Metal (core)
Sanyo Sanyo Sanyo Sanyo Aavid Aavid
Note applications where desirable eliminate heat sink, IRL3103S MBR1545CT TO-263 packages with minimum square copper used.
4-92
Rev. 1/13/99
IRU3034
TYPICAL APPLICATION
3.3V with loss less short circuit protection (output UVLO detection)
IRU3034
Vhyst
Vout
3034app5-1.1
Figure circuit figure designed provide lossles output short detection detecting voltage across inductor shutting down MOSFET entering HICCUP mode. Note that current limit point function inductor resistance this application with approximately resistance peak 10A. application note current limiting threshold.
Desig
Description
Part
Manuf
R1,2
Switcher MOSFET Schottky Diode Inductor Inductor Resistor Resistor Resistor Resistor Resistor Resistor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor
IRU3034CS 8-pin SOIC) IRL3303 (TO-263) PBYR735 (Axial Thru Hole pkg) PBYR1035B (SMT, T-263 pkg) Core: T50-18,L=4µH Turns: L=µH ohm, kohm, kohm, 576ohm, 3.83 kohm, kohm, 470µF, Elect 6MV1000GX, 1000µF, 6.3V, Elect 1µF, Ceramic, 10pF, Ceramic, 0.1µF 6MV1000GX, 1000µF, 6.3V, Elect 0.047µF
Motorola Micro Metal (core)
Sanyo Sanyo Sanyo
Rev. 1/13/99
4-93
IRU3034
APPLICATION INFORMATION
Introduction IRU3034 device application specific product designed provide on-board switching supply generation microprocessors requiring separate Core supplies where load current demand from supply requires this regulator also switching regulator such motherboard applications with slot Pentium with on-board 3.3V converter. IRU3034 provides easy cost switching regulator solution Vcore 3.3V supplies with true short circuit protection. Switching Controller Operation operation switching controller follows: After power applied, output drive pin, "Drv" goes 100% duty cycle current inductor charges output capacitor causing output voltage increase. When output reaches pre-programmed point feedback "Vfb" exceeds 1.25V causing output drive switch "Vhyst" switch high which jumps feedback higher than 1.25V resulting fixed output ripple which given following equation: dVo=(Rt/Rh)x11 Where: Rt=Resistor connected from Vout IRU3034 Rh=Resistor connected from Vhyst pin. example, Rt=1k Rh=422k, then output ripple dVo=(1/422)x11=26mV advantage fixed output ripple that when output voltage changes from 3.5V, ripple voltage remains same which important meeting Intel maximum tolerance specification. Soft Start soft start capacitor must selected such that during start when output capacitors charging peak inductor current does reach current limit threshold. minimum 0.1µF capacitor insures soft start capacitor also provides delay turn output which given Td=CSS*K Where K=30 ms/µF example CSS=0.1µF, Td=0.1* 30=3 Switcher Current Limit Protection IRU3034 uses external current sensing resistor compares voltage drop across programmed voltage which externally resistor (RcL) placed between "CS-" terminal Once voltage across sense resistor exceeds threshold, soft start capacitor pulls 12V, pulling inverting error comparator higher than noninverting which causes external MOSFET shut off. this point comparator changes state pulls soft start capacitor which shutting drive. After output drive turned off, internal 10µA current source slowly discharges soft start capacitor approximately 5.7V, before output starts turn back causing long delay before MOSFET turns back This delay causes catch diode cool between current limit cycles allowing converter survive short circuit condition. example given below select current limiting components. Assuming desired current limit point current sense resistor =5m, then current limit programming resistor, calculated this most applications. During start-up soft start capacitor charged approximately keeping output shutdown before internal 10µA current source start discharging soft start capacitor which slowly ramps inverting input comparator, Vfb. This insures output ramp same rate soft start thereby limiting input current. example, with 0.1µF 10µA internal current source ramp rate t)=I/Css 0.1=100V/Sec 0.1V/mSec. Assuming that output capacitance 6000µF, peak input current will Iin(pk)=Css*(V/ t)=6000µF*(0.1V/mSec)=0.6A
4-94
Rev. 1/13/99
IRU3034
Vcs=Ic L*Rs=20*0.005=0.1V L=Vcs/Ib=(0.1V)/(20µA)=5k Where: =20µA internal current source IRU3034 peak power dissipated C.S. resistor Ppk=(Ic L^2)*Rs=20^2*0.005=2W However, average power dissipated much lower than long time caused hiccup circuit 3034. average power fact short circuit period divided short circuit period plus time "hiccup" period. example, short circuit lasts TSC=100µSec before IRU3034 enters hiccup, average power calculated Pave=0.5*Ppk*DSC Where: DSC=TSC/THCP THCP=CSS*M Where M=200 ms/µF CSS, soft start capacitor example: CSS=0.1µF TSC=500µSec=0.5mS THCP=0.1* 200=20ms Pave=0.5*2*(0.5/20)=25mW Without "hiccup" technique, power dissipation resistor Switcher Output Voltage Setting output voltage using following equations: Assuming, Vo=3.38V selected output ripple 1.3%(44mV) output voltage, equations derived that selects resistor divider hysterises resistor. Assuming, Rt=1k, Rh=(11*Rt)/Vo Where: Rt=Top resistor resistor divider Rh=Hysterises resistor connected between pins IRU3034 Vo=Selected output ripple (typically output voltage)
Assuming, Vo=44mV Rh=(11*1000)/0.044=250k Select Rh=249k, bottom resistor divider then calculated using following equations: Rb=Rt/X Where: Rb=Bottom resistor divider X=[(Vo (Vo/2))/Vref] Vref=1.25 typical X=[(3.38+ (0.044/2))/1.25] 1.72 Rb=1000/1.72=580 Select Rb=576 Frequency Calculation IRU3034 frequency operation calculated using following formula: Fs=[(Vo*(1-D)*ESR)]/(L*Vo) (MHz) Where: Vo=Output voltage D=Duty cycle ESR=Output capacitor L=Output inductance (µH) Vo=Output ripple voltage example: D(Vo Vf)/Vin Where, Vf=Forward voltage drop Schottky diode D=(3.38 0.5)/5=0.78 ESR=18m Sanyo 1500µF, 6MV1500GX caps. L=3.5µH then, calculated follows: 0.087 87kHz
Rev. 1/13/99
4-95
IRU3034
Notes
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Rev. 1/13/99
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