DROPOUT POSITIVE ADJUSTABLE REGULATOR FEATURES Guaranteed 1.3V Dr

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DROPOUT POSITIVE ADJUSTABLE REGULATOR FEATURES Guaranteed 1.3V Dr

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IRU1050
DROPOUT POSITIVE ADJUSTABLE REGULATOR FEATURES
Guaranteed 1.3V Dropout Full Load Current Fast Transient Response Voltage Reference Initial Accuracy Output Current Limiting Built-in Thermal Shutdown
IRU1050 dropout three-terminal adjustable regulator with minimum output current capability. This product specifically designed provide well regulated supply voltage applications such PentiumP54C,P55Cas well GTL+ termination Pentium Proand Klamathprocessor applications. IRU1050 also well suited other processors such Cyrix Power PCapplications. IRU1050 guaranteed have <1.3V dropout full load current making ideal provide well regulated outputs 2.5V 3.6V with 4.75V input supply.
APPLICATIONS
Voltage Processor Applications such P54C, P55C, Cyrix POWER GTL+ Termination PENTIUM PRO, KLAMATH Voltage Memory Termination Applications Standard 3.3V Chipset Logic Applications
TYPICAL APPLICATION
1500uF
IRU1050
US1050
Vout
3.38V
1500uF
1050app1-1.1
Typical Application IRU1050 3.38V regulator designed meet Intel P54C processors
Notes: Pentium P54C, P55C, Klamath, Pentium Pro,VRE trademarks Intel Corp. Cyrix trademark Cyrix Corp. Power trademark Corp.
PACKAGE ORDER INFORMATION
(°C) 3-PIN PLASTIC TO-220 IRU1050CT 3-PIN PLASTIC TO-263 IRU1050CM 2-PIN PLASTIC ULTRA THIN-PAK IRU1050CP 3-PIN PLASTIC TO-252 IRU1050CD
Rev. 10/27/00
2-49
IRU1050
ABSOLUTE MAXIMUM RATINGS
Input Voltage Power Dissipation Internally Limited Storage Temperature Range -65° 150° Operating Junction Temperature Range 150°
PACKAGE INFORMATION
3-PIN PLASTIC TO-220
FRONT VIEW
3-PIN PLASTIC TO-263
FRONT VIEW
2-PIN PLASTIC ULTRA THIN-PAK PLASTIC TO-252
FRONT VIEW FRONT VIEW
Vout
Vout
Vout
Vout
Vout
Vout
JT=2.7°C/W JA=60°C/W
JA=35°C/W Square
JA=70°C/W Square
JA=70°C/W 0.5"
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over, Cin=1µF, Cout =10µF, Tj=0 150° Typical values refer Tj=25° PARAMETER Reference Voltage Line Regulation Load Regulation (note Dropout Voltage (note Current Limit Minimum Load Current (note Thermal Regulation Ripple Rejection Adjust Current Adjust Current Change Temperature Stability Long Term Stability Output Noise IADJ VREF TEST CONDITION Io=10mA, Tj=25° (Vin-Vo)=1.5V 1.243 Io=10mA, (Vin-Vo)=1.5V 1.237 Io=10mA,1.3V<(Vin-Vo)<7V Vin=3.3V, Vadj=0, 10mA<Io<5A Note Io=5A Vin=3.3V, dVo=100mV Vin=3.3V, Vadj=0V Pulse, Vin-Vo=3V, Io=5A f=120HZ, Co=25µF Io=2.5A, Vin-Vo=3V Io=10mA, Vin-Vo=1.5V, Tj=25 Io=10mA, Vin-Vo=1.5V Io=10mA, Vin-Vo=1.5V, Tj=25 Vin=3.3V, Vadj=0V, Io=10mA Tj=125° 1000 Tj=25° 10hz<f<10khz 0.01 0.003 0.02 1.250 1.250 1.257 1.263 UNITS
Note duty cycle pulse testing with Kelvin connections required order maintain accurate data. Note Dropout voltage defined minimum differential voltage between Vout required maintain regulation Vout. measured when output voltage drops below nominal value.
Note Minimum load current defined minimum current required output order output voltage maintain regulation. Typically resistor dividers selected such that automatically maintains this current.
2-50
Rev. 10/27/00
IRU1050
DESCRIPTIONS
SYMBOL Vout DESCRIPTION resistor divider from this Vout ground sets output voltage. output regulator. minimum 10µF capacitor must connected from this ground insure stability. input regulator. Typically large storage capacitor connected from this ground insure that input voltage does below minimum drop voltage during load transient response. This must always 1.3V higher than Vout order device regulate properly.
BLOCK DIAGRAM
Vout
1.25V CURRENT LIMIT
THERMAL SHUTDOWN
1050blk1-1.0
Figure Simplified block diagram IRU1050
APPLICATION INFORMATION
Introduction
IRU1050 adjustable Dropout (LDO) regulator three-terminal device which easily programmed with addition external resistors voltages within range 1.25 This regulator unlike first generation regulators such LM117 that required differential between input regulated output, only needs 1.3V differential maintain output regulation. This requirement today's microprocessors that need typically 3.3V supply often generated from supply. Another major requirement these microprocessors such Intel P54Cis need switch load current from zero several amps tens nanoseconds processor pins, which translates approximately 500nS current step regulator. addition, output voltage tolerances also extremely tight they include transient response part specification.For example Intel specification calls total ±100mV including initial tolerance, load regulation 4.6A load step. IRU1050 specifically designed meet fast current transient needs well providing accurate initial voltage, reducing overall system cost with need fewer output capacitors.
Rev. 10/27/00
2-51
IRU1050
Output Voltage Setting
IRU1050 programmed voltages range 1.25V 5.5V with addition external resistors according following formula: VOUT VREF IADJ Where VREF Typically IADJ Typically shown figure regulation achieved when bottom side connected load side resistor connected directly case Vout regulator load. fact, connected load side, effective resistance between regulator load gained factor (1+R2/ R1), effective resistance will Rp(eff)=Rp*(1+R2/ R1). important note that high current applications, this represent significant percentage overall load regulation must keep path from regulator load short possible minimize this effect.
PARASITIC LINE RESISTANCE
Vout
Vout
Vout
US1050 IRU1050
IRU1050 US1050
Vref IAdj 50uA
1050app2-1.0
Figure Typical application IRU1050 programming output voltage IRU1050 keeps constant 1.25V between output adjust pin. placing resistor across these pins constant current flows through adding Iadj current into resistor producing voltage equal (1.25/R1)*R2 Iadj*R2 which will added 1.25V output voltage. This summarized above equation. Since minimum load current requirement IRU1050 10mA, typically selected resistor that automatically satisfies minimum current requirement. Notice that since Iadj typically range 50uA only adds small error output voltage should only considered when very precise output voltage setting required. example, typical 3.3V application where R1=121 R2=200 error Iadj only 0.3% nominal point.
1050app3-1.0
Figure Schematic showing connection best load regulation
Stability
IRU1050 requires output capacitor part frequency compensation order make regulator stable. Typical designs microprocessor applications standard electrolytic capacitors with typical range 100m output capacitance 1000µF. Fortunately capacitance increases, decreases resulting fixed time constant. IRU1050 takes advantage this phenomena making overall regulator loop stable.For most applications minimum 100µF aluminum electrolytic capacitor such Sanyo MVGX series, Panasonic series well Nichicon series insures both stability good transient response.
Load Regulation
Since IRU1050 only three-terminal device, possible provide true remote sensing output voltage load. Figure shows that best load
2-52
Rev. 10/27/00
IRU1050
Thermal Design
IRU1050 incorporates internal thermal shutdown that protects device when junction temperature exceeds maximum allowable junction temperature. Although this device operate with junction temperatures range 150° recommended that selected heat sink chosen such that during maximum continuous load operation junction temperature kept below this number. example below shows steps selecting proper regulator heat sink worst case current consumption using Intel 200MHz microprocessor load. Assuming following specifications: IOUT
T=Temperature Rise Above Ambient =117 Next, heat sink with lower than calculated Step must selected. this simply look graphs "Heat Sink Temp Rise Above Ambient" "Power Dissipation" select heat sink that results lower temperature rise than calculated previous step. following heat sinks from AAVID Thermaloy meet this criteria.
Flow (LFM) 6021PB 6021PB 6073PB 6109PB 7141D 534202B 534202B 507302 575002 576802B
Thermalloy AAVID
steps selecting proper heat sink keep junction temperature below 135° given Calculate maximum power dissipation using: VIN- =4.6 Select package from regulator data sheet record junction case tab) thermal resistance. Selecting TO-220 package gives =2.7° Assuming that heat sink black anodized, calculate maximum heat sink temperature allowed: Assume, cs=0.05° (heat-sink-to-case thermal resistance black anodized) TJ-PD
Note: further information regarding above companies their latest product offerings application support contact your local representative numbers listed below: AAVID Thermalloy (603) 3400 (214) 243-4321
Designing Microprocessor Applications
mentioned before, IRU1050 designed specifically provide power generation voltage processors requiring voltages range 2.5V 3.6V generated stepping down supply. These processors demand fast regulator that supports their large load current changes. worst case current step seen regulator anywhere range with slew rate 500nS which could happen when processor transitions from "Stop Clock" mode "Full Active" mode. load current step processor actually much faster, order 20nS, however, decoupling capacitors placed cavity processor socket handle this transition until regulator responds load current levels. Because this requirement selection high frequency output capacitor imperative design these regulator circuits.
=135- (2.7 0.05 =116 With maximum heat sink temperature calculated previous step, heat-sink-to-air thermal resistance (sa) calculated first calculating temperature rise above ambient follows: =116
Rev. 10/27/00
2-53
IRU1050
Figure shows effects fast transient output voltage regulator. shown this figure, output capacitor produces instantaneous drop equal (VESR =ESR*I) effect will equal rate change output current times inductance capacitor. =L*I/t). output capacitance effect droop output voltage proportional time takes regulator respond change current, where response time regulator.
Sanyo MVGX series good choice achieve both price performance goals.The 6MV1500GX, 1500µF, 6.3V less than typical. Selecting these capacitors parallel which achieves design goal. next step calculate drop capacitance discharge make sure that this drop voltage less than selected drop previous step. output capacitance 5X1500µF 7500µF 7500 Where regulator response time
LOAD CURRENT
1050plt1-1.0
LOAD CURRENT RISE TIME
output voltage, need select Figure Typical regulator response fast load current step example regulator design meet Intel P54CVRE specification given below. Assume specification processor shown Table
Type Processor Intel-P54C Vout Nominal 3.50 Imax Allowed Output Tolerance ±100
Assuming R1=121
0.1%
VOUT 217.8 VREF Select R2=218
0.1%
Selecting both resistors 0.1% tolerance, results least amount error introduced resistor dividers leaving ±1.3% error budget IRU1050 reference which within initial accuracy device. Finally, input capacitor selected follows: Assming that input voltage drop 150mV before main power supply responds, that main power supply response time uSec, then minimum input capacitance 4.6A load step given =1530 0.15
Table Processor Specification first step select voltage step allowed output output capacitor's ESR: Assuming regulator's initial accuracy plus resistor divider tolerance (±1.5% 3.5V nominal), then total step allowed ESL, Assuming that drop -10mV, remaining step will Therefore output capacitor must
2-54
Rev. 10/27/00
IRU1050
should less than:
(VIN VOUT VDROP)
Where VDROP Input voltage drop allowed step Maximum regulator dropout voltage Load current step -0.15 =0.032
Selecting Sanyo 1500 same type output capacitors meets requirements. Figure shows completed schematic example.
1500uF Vout
3.50V
1500uF 0.1% 0.1%
US1050 IRU1050
1050app4-1.1
Figure Final schematic Intel application
Layout Consideration
output capacitors must located close Vout terminal device possible. recommended section layer board plane connect output capacitors prevent high frequency oscillation that result excessive trace inductance.
Rev. 10/27/00
2-55
IRU1050
Notes
2-56
Rev. 10/27/00

DROPOUT POSITIVE ADJUSTABLE REGULATOR FEATURES Guaranteed 1.3V Dr

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