7.5A DROPOUT POSITIVE ADJUSTABLE REGULATOR FEATURES Dropout Full

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7.5A DROPOUT POSITIVE ADJUSTABLE REGULATOR FEATURES Dropout Full

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IRU1075
7.5A DROPOUT POSITIVE ADJUSTABLE REGULATOR FEATURES
Dropout Full Load Current Fast Transient Response Voltage Reference Initial Accuracy Output Current Limiting Built-in Thermal Shutdown
IRU1075 dropout three-terminal adjustable regulator with minimum 7.5A output current capability. This product specifically designed provide well regulated supply voltage applications such PentiumP54C, P55Cas well GTL+ termination Pentium Proand Klamathprocessor applications. IRU1075 also well suited other processors such Cyrix, Power PCapplications. IRU1075 guaranteed have <1.2V dropout full load current making ideal provide well regulated outputs such 3.3V with input supply voltage 4.5V minimum.
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
IRU1075
Vout
3.3V
1075app1-1.0
1500uF
Typical application IRU1075 3.3V regulator
Notes: Pentium P54C, P55C, Klamath, Pentium Pro, trademarks Intel Corp. Cyrix trademark Cyrix Corp. Power trademark Corp.
PACKAGE ORDER INFORMATION
(°C) 3-PIN PLASTIC TO-220 IRU1075CT 3-PIN PLASTIC TO-263 IRU1075CM 3-PIN PLASTIC
ULTRA THIN-PAK
IRU1075CP
Rev. 9/14/99
2-61
IRU1075
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
3-PIN PLASTIC ULTRA THIN-PAK
FRONT VIEW
Vout
Vout
Vout
Vout
Vout
Vout
JT=2.7°C/W JA=60°C/W
JA=35°C/W Square
JA=35°C/W Square
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 Pulse, Vin-Vo=3V, Io=7.5A f=120HZ, Co=25µF Io=7.5A, 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 0.003 0.02 VREF TEST CONDITION Io=10mA, Tj=25° (Vin-Vo)=1.5V 1.238 Io=10mA, (Vin-Vo)=1.5V Io=10mA, 1.3V<(Vin-Vo)<7V Vin=3.3V, Vadj=0, 10mA<Io<7.5A Io=7.5A Io=4A Vin=3.3V, dVo=100mV Vin=3.3V, Vadj=0V 0.92 1.225 1.250 1.250 1.262 1.275 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.
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Rev. 9/14/99
IRU1075
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
opamp2
1.25V
CURRENT LIMIT
1900
THERMAL SHUTDOWN
1075blk1-1.0
Figure Simplified block diagram IRU1075
APPLICATION INFORMATION
Introduction
IRU1075 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 nanoRev. 9/14/99
seconds processor pins, which translates approximately 500nS current step regulator. addition, output voltage tolerances also extremely tight they include transient response part specification. example Intel specification calls total ±100mV including initial tolerance, load regulation 4.6A load step. IRU1075 specifically designed meet fast current transient needs well providing accurate initial voltage, reducing overall system cost with need fewer output capacitors.
2-63
IRU1075
Output Voltage Setting
IRU1075 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
IRU1075
Vref
Vout
IRU1075
1075app2-1.0
IAdj 50uA
Figure Typical application IRU1075 programming output voltage IRU1075 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 IRU1075 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.
1075app3-1.0
Figure Schematic showing connection best load regulation
Stability
IRU1075 requires output capacitor part frequency compensation order make regulator stable. Typical designs microprocessor applications standard electrolytic capacitors with typical range output capacitance 1000µF. Fortunately capacitance increases, decreases resulting fixed time constant. IRU1075 takes advantage this phenomena making overall regulator loop stable. 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 IRU1075 only three-terminal device, possible provide true remote sensing output voltage load. Figure shows that best load
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Rev. 9/14/99
IRU1075
Thermal Design
IRU1075 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: =3.5 IOUT
With maximum heat sink temperature calculated previous step, heat-sink-to-air thermal resistance (sa) calculated first calculating temperature rise above ambient follows: =116 T=Temperature Rise Above Ambient =117
=4.6
steps selecting proper heat sink keep junction temperature below 135° given Calculate maximum power dissipation using: VIN-
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.
=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 =135 0.05 =116
Thermalloy AAVID
Flow (LFM) 6021PB 6021PB 6073PB 6109PB 7141D 534202B 534202B 507302 575002 576802B
Rev. 9/14/99
2-65
IRU1075
Notes
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Rev. 9/14/99

7.5A DROPOUT POSITIVE ADJUSTABLE REGULATOR FEATURES Dropout Full

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