IRU1150资料

Data Sheet No. PD94129

IRU1150

4A ULTRA LOW DROPOUT POSITIVE

FEATURES

0.7V Dropout at 4A

Fast Transient Response

1% Voltage Reference Initial AccuracyBuilt-In Thermal Shutdown

ADJUSTABLE REGULATORDESCRIPTION

The IRU1150 is a 4A regulator with extremely low drop-out voltage using a proprietary bipolar process thatachieves comparable equivalent on-resistance to that ofdiscrete MOSFETs. This product is specifically designedto provide well regulated supply for applications requir-ing 2.8V or lower voltages from 3.3V ATX power supplieswhere high efficiency of a switcher can be achieved with-out the cost and complexity associated with switchingregulators. One such application is the new graphic chipsets that require anywhere from 2.4V to 2.7V supplysuch as the Intel I740 chip set.

APPLICATIONS

3.3V to 2.7V Intel I740 Chip Set

TYPICAL APPLICATION

3.3VC1100uFVINVCTRL54321R1102R2118C3100uFIRU1150VOUTAdjVSENSE2.7V5VC2100uF Figure 1 - Typical application of IRU1150 in a 3.3V to 2.7V for I740 chip.

PACKAGE ORDER INFORMATION

TJ (°C) 5-PIN PLASTIC 5-PIN PLASTIC 8-PIN PLASTIC TO-263 (M) Ultra Thin-PakTM (P) SOIC (S) 0 To 125 IRU1150CM IRU1150CP IRU1150CSRev. 1.603/18/02

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IRU1150

ABSOLUTE MAXIMUM RATINGS

Input Voltage (VIN) .................................................... 7VControl Input Voltage (VCTRL) ..................................... 14V

Power Dissipation ..................................................... Internally LimitedStorage Temperature Range ...................................... -65°C To 150°COperating Junction Temperature Range ..................... 0°C To 150°C

PACKAGE INFORMATION 5-PIN PLASTIC TO-263 (M) 5-PIN PLASTIC ULTRA THIN-PAKTM (P) 8-PIN PLASTIC SOIC (S)FRONT VIEW5FRONT VIEWVINVCTRLVOUTAdjVSENSE5VINVCTRLVOUTAdjVSENSETOP VIEWTab isVOUT4321Tab isVOUT4321VCTRLVINAdjVSENSE12348765VOUTVOUTVOUTVOUT θJA=35°C/W for 0.5\" square pad θJA=35°C/W for 0.5\" square pad θJA=55°C/W for 1\" Sq pad areaELECTRICAL SPECIFICATIONS

Unless otherwise specified, these specifications apply over CIN=1mF, COUT=10mF, and TJ=0 to 1258C.Typical values refer to TJ=258C. VOUT=VSENSE.PARAMETERReference VoltageLine Regulation

Load Regulation (Note 1)Dropout Voltage (Note 2)(VCTRL - VOUT)

SYM VREF

TEST CONDITION

VCTRL=2.7 to 12V, VIN=2.05V to 5.5V,

MIN1.225

TYP1.250

MAX1.275

UNITS V mV mV V

Io=10mA to 4A, VADJ=0V

VCTRL=2.5V to 7V, VIN=1.75V to 5.5V,

Dropout Voltage (Note 2)(VIN - VOUT)

Current Limit

Minimum Load Current (Note 3)Thermal RegulationRipple RejectionControl Pin Current

Adjust Pin Current IADJ

Io=10mA ,VADJ=0V -5 -0.2 +5VCTRL=2.75V, VIN=2.1V,Io=10mA to 4A, VADJ=0V -5 3 +5VADJ=0V for all conditions below:VIN=2.05V, Io=1.5A 1.00 1.15VIN=2.05V, Io=3A 1.05 1.15VIN=2.05V, Io=4A 1.13 1.20VADJ=0V for all conditions below:VCTRL=2.75V, Io=1.5A 0.26 0.38VCTRL=2.75V, Io=3A 0.50 0.60VCTRL=2.75V, Io=4A 0.70 1.15VCTRL=2.75V, VIN=2.05V,DVo=100mV, VADJ=0V4.2 4.656VCTRL=5V, VIN=3.3V, VADJ=0V1 1030ms Pulse 0.01VCTRL=5V, VIN=5V, Io=4A, VADJ=0V70TJ=258C, VRIPPLE=1VPP at 120HzVADJ=0V for all below conditions:VCTRL=2.75V, VIN=2.05V, Io=1.5A 16 25VCTRL=2.75V, VIN=2.05V, Io=3A 36 50VCTRL=2.75V, VIN=2.05V, Io=4A 67 85VCTRL=2.75V, VIN=2.05V, VADJ=0V 50 V

A

mA%/W dB

mA

mA

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IRU1150

Note 1: Low duty cycle pulse testing with Kelvin con-nections is required in order to maintain accurate data.Note 2: Dropout voltage is defined as the minimum dif-ferential between VIN and VOUT required to maintain regu-lation at VOUT. It is measured when the output voltagedrops 1% below its nominal value.

Note 3: Minimum load current is defined as the mini-mum current required at the output in order for the out-put voltage to maintain regulation. Typically the resistordividers are selected such that it automatically main-tains this current.

PIN DESCRIPTIONS

PIN # PIN SYMBOLPIN DESCRIPTION1VSENSEThis pin is the positive side of the reference which allows remote load sensing to achieve

excellent load regulation.23

AdjVOUT

A resistor divider from this pin to the VOUT pin and ground sets the output voltage.The output of the regulator. A minimum of 10mF capacitor must be connected from thispin to ground to insure stability.

This pin is the supply pin for the internal control circuitry as well as the base drive for thepass transistor. This pin must always be higher than the VOUT pin in order for the device toregulate. (See specifications)

The input pin of the regulator. Typically a large storage capacitor is connected from thispin to ground to insure that the input voltage does not sag below the minimum drop outvoltage during the load transient response. This pin must always be higher than VOUT inorder for the device to regulate. (See specifications)

4VCTRL

5VIN

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IRU1150

BLOCK DIAGRAM

VIN5VCTRL43VOUT1VSENSE1.25VCURRENTLIMIT++THERMALSHUTDOWN2AdjFigure 2 - Simplified block diagram of the IRU1150.

APPLICATION INFORMATION

Introduction

The IRU1150 adjustable regulator is a five-terminal de-vice designed specifically to provide extremely low drop-out voltages comparable to the PNP type without thedisadvantage of the extra power dissipation due to thebase current associated with PNP regulators. This isdone by bringing out the control pin of the regulator thatprovides the base current to the power NPN and con-necting it to a voltage that is grater than the voltage presentat the VIN pin. This flexibility makes the IRU1150 idealfor applications where dual inputs are available such asa computer mother board with an ATX style power sup-ply that provides 5V and 3.3V to the board. One suchapplication is the new graphic chip sets that require any-where from 2.4V to 2.7V supply such as the Intel I740chip set. The IRU1150 can easily be programmed withthe addition of two external resistors to any voltageswithin the range of 1.25 to 5.5 V. Another major require-ment of these graphic chips such as the Intel I740 is theneed to switch the load current from zero to several ampsin tens of nanoseconds at the processor pins, whichtranslates to an approximately 300 to 500ns of currentstep at the regulator. In addition, the output voltage tol-erances are also extremely tight and they include thetransient response as part of the specification.The IRU1150 is specifically designed to meet the fastcurrent transient needs as well as providing an accurateinitial voltage, reducing the overall system cost with the

need for fewer number of output capacitors. Another fea-ture of the device is its true remote sensing capabilitywhich allows accurate voltage setting at the load ratherthan at the device.

Output Voltage Setting

The IRU1150 can be programmed to any voltages in therange of 1.25V to 5.5V with the addition of R1 and R2external resistors according to the following formula:

R2

VOUT = VREF 3 o1 + p + IADJ 3 R2

R1Where:

VREF = 1.25V TypicallyIADJ = 50mA Typically

R1 and R2 as shown in Figure 3:

VINVINVOUTVOUT

IRU1150VCTRLVCTRLAdjVSENSEVREFR1IADJ = 50uAR2Figure 3 - Typical application of the IRU1150

for programming the output voltage.

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The IRU1150 keeps a constant 1.25V between the VSENSEpin and the VADJ pin. By placing a resistor R1 acrossthese two pins and connecting the VSENSE and VOUT pintogether, a constant current flows through R1, adding tothe Iadj current and into the R2 resistor producing a volt-age equal to the (1.25/R1)3R2 + IADJ3R2. This voltageis then added to the 1.25V to set the output voltage.This is summarized in the above equation. Since theminimum load current requirement of the IRU1150 is10mA, R1 is typically selected to be a 121V resistor sothat it automatically satisfies this condition. Notice thatsince the IADJ is typically in the range of 50mA it onlyadds a small error to the output voltage and should beconsidered when very precise output voltage setting isrequired.

Load Regulation

Since the IRU1150 has separate pins for the output (VOUT)and the sense (VSENSE), it is ideal for providing true re-mote sensing of the output voltage at the load. Thismeans that the voltage drops due to parasitic resistancesuch as PCB traces between the regulator and the loadare compensated for using remote sensing. Figure 4shows a typical application of the IRU1150 with remotesensing.

VINVinVOUTFor most applications a minimum of 100mF aluminumelectrolytic capacitor such as Sanyo, MVGX series,Panasonic FA series as well as the Nichicon PL seriesinsures both stability and good transient response.Thermal Design

The IRU1150 incorporates an internal thermal shutdownthat protects the device when the junction temperatureexceeds the allowable maximum junction temperature.Although this device can operate with junction tempera-tures in the range of 1508C, it is recommended that theselected heat sink be chosen such that during maxi-mum continuous load operation the junction tempera-ture is kept below this number. The example belowshows the steps in selecting the proper surface mountpackage.

Assuming, the following conditions:

VOUT = 2.7VVIN = 3.3VVCTRL = 5V

IOUT = 2A (DC Avg)

Calculate the maximum power dissipation using the fol-lowing equation:

IOUT

PD = IOUT 3 (VIN - VOUT) +o p3 (VCTRL - VOUT)

60

2

PD = 2 3 (3.3 - 2.7) +o p3 (5 - 2.7) = 1.28W

60

IRU1150VCTRLVCTRLAdjVSENSER1RL

Using table below select the proper package and theamount of copper board needed.PkgTO-263TO-263TO-263TO-263SO-8

Copper θJA(°C/W) Max Pd Max Pd Area (TA=25°C) (TA=45°C)1.4\"X1.4\" 25 4.4W 3.6W1.0\"X1.0\" 30 3.7W 3.0W0.7\"X0.7\" 35 3.1W 2.6WPad Size 45 2.4W 2.0W1.0\"X1.0\" 55 2.0W 1.63W

R2Figure 4 - Schematic showing connection

for best load regulation.Stability

The IRU1150 requires the use of an output capacitor aspart of the frequency compensation in order to make theregulator stable. Typical designs for the microprocessorapplications use standard electrolytic capacitors withtypical ESR in the range of 50 to 100mV and an outputcapacitance of 500 to 1000mF. Fortunately as the ca-pacitance increases, the ESR decreases resulting in afixed RC time constant. The IRU1150 takes advantageof this phenomena in making the overall regulator loopstable.

Note: Above table is based on the maximum junctiontemperature of 1358C.

As shown in the above table, any of the two packageswill do the job. For low cost applications the SO-8 pack-age is recommended.

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IRU1150

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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