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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IRU1030
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
IRU1030 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. IRU1030 also well suited other processors such Cyrix Power PCapplications. IRU1030 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
IRU1030
US1030
Vout
3.3V
1500uF
1030app1-1.1
Typical Application IRU1030 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 IRU1030CT 3-PIN PLASTIC TO-263 IRU1030CM 3-PIN PLASTIC TO-252 IRU1030CD
Rev. 3/26/98
2-37
IRU1030
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 TO-252
FRONT VIEW
Vout Vout
Vout Vout
Vout
JT=2.7°C/W JA=60°C/W
JA=35°C/W Square
JA=70°C/W 0.5" 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 VREF TEST CONDITION Io=10mA, Tj=25° (Vin-Vo)=1.5V 1.243 1.250 Io=10mA, (Vin-Vo)=1.5V 1.237 1.250 Io=10mA, 1.3V<(Vin-Vo)<7V Vin=3.3V, Vadj=0, 10mA<Io<3A Note Io=3A Vin=3.3V, dVo=100mV Vin=3.3V, Vadj=0V Pulse, Vin-Vo=3V, Io=3A f=120HZ, Co=25µF Io=1.5A, 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 1.257 1.263 UNITS
IADJ
Note duty cycle pulse testing with Kelvin connections required order maintain accurate data. Note Dropout voltage defined minimum differential voltage between 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. 3/26/98
IRU1030
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
1030blk1-1.0
Figure Simplified block diagram IRU1030
APPLICATION INFORMATION
Introduction
IRU1030 adjustable Dropout (LDO) regulator three-terminal device which easily programmed with addition external resistors voltages within range 1.25 5.5V. 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. example Intel specification calls total ±100mV including initial tolerance, load regulation 4.6A load step. IRU1030 specifically designed meet fast current transient needs well providing accurate initial voltage, reducing overall system cost with need fewer output capacitors.
Rev. 3/26/98
2-39
IRU1030
Output Voltage Setting
IRU1030 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.
Vout
Vout
PARASITIC LINE RESISTANCE
US1030 IRU1030
Vref
Vout
US1030 IRU1030
IAdj 50uA
1030app2-1.0
Figure Typical application IRU1030 programming output voltage
1030app3-1.0
IRU1030 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 IRU1030 10mA, typically selected resistor that automatically satisfies minimum current requirement. Notice that since Iadj typically range 50µA 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.
Figure Schematic showing connection best load regulation
Stability
IRU1030 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. IRU1030 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 IRU1030 only three-terminal device, possible provide true remote sensing output voltage load. Figure shows that best load
2-40
Rev. 3/26/98
IRU1030
Thermal Design
IRU1030 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 GTL+ terminator using separate regulator each end. Assuming following specifications: IOUT
T=Temperature Rise Above Ambient 86.7 17.8 4.86 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 Thermalloy meet this criteria.
=2.7
steps selecting proper heat sink keep junction temperature below 135° given Calculate maximum power dissipation using: IOUT VOUT) (3.3 1.5) 4.86 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 4.86 (2.7+ 0.05 =1217 With maximum heat sink temperature calculated previous step, heat-sink-to-air thermal resistance (sa) calculated first calculating temperature rise above ambient follows: =1217- 86.7
Thermalloy AAVID
6109PB 575002
Flow (LFM) 6110PB 7141 7178 507302 576802B 577102
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 IRU1030 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 capacitors imperative design these regulator circuits.
Rev. 3/26/98
2-41
IRU1030
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. 6MV1500GX, 1500µF, 6.3V less than typ. Selecting single capacitor achieves design goal. next step calculate drop capacitance discharge make sure that this drop voltage less than selected drop previous step. With output capacitance being 1500µF: 1500 Where regulator response time
LOAD CURRENT
1030plt1-1.0
output voltage, need select
LOAD CURRENT RISE TIME
Assuming R1=121 Figure Typical regulator response fast load current step example regulator design meet Intel Pentium GTL+ specification given below. Assume specification processor shown Table
Type Processor Pentium Vout Nominal 1.50 Imax Allowed Output Tolerance ±150
0.5%
VOUT VREF
Select 24.3 0.5% Selecting both resistors 0.5% tolerance, results least amount error introduced resistor dividers leaving ±1.3% error budget IRU1030 reference which within initial accuracy device. Finally, input capacitor selected follows: Assuming that input voltage drop 150mV before main power supply responds, that main power supply response time 50µSec, then minimum input capacitance 2.7A load step given 0.15
Table GTL+ Specification Pentium first step select voltage step allowed output output capacitor's ESR: Assuming regulator's initial accuracy plus resistor divider tolerance (±2% 1.5V nominal), then total step allowed ESL, -120 Assuming that drop -10mV, remaining step will -110mV. Therefore output capacitor must
2-42
Rev. 3/26/98
IRU1030
should less than:
(VIN VOUT VDROP)
Where VDROP Input voltage drop allowed step Maximum regulator dropout voltage Load current step (3.3 -12- 0.15
0.16
Selecting single 1500µF same type output capacitors exceeds requirements. However, same input capacitor also support second regulator other temrination. Figure shows completed schematic example.
3.3V
1500uF
Vout
1.5V
1500uF 0.5% 24.3 0.5% 0.5%
US1030 IRU1030
Vref
0.5%
1030app4-1.2
Figure Final schematic half GTL+ termination regulator
Layout Consideration
output capacitors must located close Vout terminal device possible. recommended section layer board plane connect Vout output capacitors prevent high frequency oscillation that result excessive trace inductance.
Rev. 3/26/98
2-43
IRU1030
Notes
2-44
Rev. 3/26/98

DROPOUT POSITIVE ADJUSTABLE REGULATOR FEATURES Guaranteed 1.3V Dr

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