IRU1010 DROPOUT POSITIVE ADJUSTABLE REGULATOR DESCRIPTION IR

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IRU1010 DROPOUT POSITIVE ADJUSTABLE REGULATOR DESCRIPTION IR

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Data Sheet PD94119
IRU1010
DROPOUT POSITIVE ADJUSTABLE REGULATOR DESCRIPTION
IRU1010 dropout, three-terminal adjustable regulator with minimum output current capability. This product specifically designed provide well regulated supply voltage applications such high speed termination current 3.3V logic supply. IRU1010 also well suited other applications such sound cards. IRU1010 guaranteed have <1.3V dropout full load current making ideal provide well regulated outputs 2.5V 3.6V with 4.75V input supply.
FEATURES
Guaranteed 1.3V Dropout Full Load Current Fast Transient Response Voltage Reference Initial Accuracy Built-In Thermal Shutdown Available SOT-223, D-Pak, Ultra Thin-Pak 8-Pin SOIC Surface-Mount Packages
APPLICATIONS
Sound Card Applications Voltage High Speed Termination Applications Standard 3.3V Chip Logic Applications
TYPICAL APPLICATION
10uF
22uF
IRU1010
Vout
2.85V
1010app1-1.4
Figure Typical application IRU1010 2.85V SCSI termination regulator
PACKAGE ORDER INFORMATION
(°C) 2-PIN PLASTIC TO-252 (D-Pak) IRU1010CD 3-PIN PLASTIC SOT-223 IRU1010CY 2-PIN PLASTIC Ultra Thin-Pak IRU1010CP 8-PIN PLASTIC SOIC IRU1010CS
Rev. 06/29/01
IRU1010
ABSOLUTE MAXIMUM RATINGS
Input Voltage (Vin) Power Dissipation Storage Temperature Range Operating Junction Temperature Range Internally Limited -65°C 150°C 150°C
PACKAGE INFORMATION
2-PIN PLASTIC TO-252 (D-Pak)
FRONT VIEW
3-PIN PLASTIC SO-223
VIEW
2-PIN ULTRA THIN-PAK
FRONT VIEW
8-PIN PLASTIC SOIC
VIEW
Vout
Vout
Vout
Vout
Vout Vout Vout Vout
JA=70!C/W 0.5"
JA=90!C/W 0.4"
JA=70!C/W 0.5"
JA=55!C/W
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over Cin=1µF, Cout=10µF, Tj=0 150!C. Typical values refer Tj=25!C. 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!C, (Vin-Vo)=1.5V Io=10mA, (Vin-Vo)=1.5V Io=10mA, 1.3V<(Vin-Vo)<7V Vin=3.3V, Vadj=0, 10mA<Io<1A Note Io=1A Vin=3.3V, dVo=100mV Vin=3.3V, Vadj=0V 30ms Pulse, Vin-Vo=3V, Io=1A f=120Hz, Co=25µF Tantalum, Io=0.5A, Vin-Vo=3V Io=10mA, Vin-Vo=1.5V, Tj=25!C, Io=10mA, Vin-Vo=1.5V Io=10mA, Vin-Vo=1.5V, Tj=25!C Vin=3.3V, Vadj=0V, Io=10mA Tj=125!C, 1000Hrs Tj=25!C, 10Hz<f<10KHz 1.238 1.250 1.225 1.250 1.262 1.275 0.02 UNITS
0.01 0.003
Iadj
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.
Rev. 06/29/01
IRU1010
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 dropout 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
1010blk1-1.0
Figure Simplified block diagram IRU1010
APPLICATION INFORMATION
Introduction
IRU1010 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 three-terminal regulators such LM117 that required differential between input regulated output, only needs 1.3V differential maintain output regulation. This requirement today's voltage applications that typically need 3.3V supply often generated from supply. Other applications such high speed memory termination need switch load current from zero full load tens nanoseconds their pins, which translates approximately 500ns current step regulator. addition, output voltage tolerances sometimes tight they include transient response part specification. IRU1010 specifically designed meet fast current transient needs well providing accurate initial voltage, reducing overall system cost with need fewer output capacitors.
Rev. 06/29/01
IRU1010
Output Voltage Setting IRU1010 programmed voltages range 1.25V 5.5V with addition external resistors according following formula: VOUT VREF IADJ 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
Where: VREF 1.25V Typically IADJ 50µA Typically shown figure
Vout
Vout
Vout
IRU1010
Vref IAdj 50uA
IRU1010
1010app2-1.0
1010app3-1.0
Figure Typical application IRU1010 programming output voltage
Figure Schematic showing connection best load regulation Stability IRU1010 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. IRU1010 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. Thermal Design IRU1010 incorporates internal thermal shutdown that protects device when junction temperature exceeds maximum allowable junction temperature. Although this device operate with junction temperatures range 150!C, recommended that selected heat sink chosen such that during maximum continuous load operation junction temperature kept below this number. example below SCSI terminator application shows steps sellect-
IRU1010 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 IRU1010 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. Load Regulation Since IRU1010 only three-terminal device, possible provide true remote sensing output voltage load. Figure shows that best load regulation achieved when bottom side connected load side resistor connected directly case Vout
Rev. 06/29/01
IRU1010
proper regulator surface-mount package. (See IRU1015 non-surface-mount packages) Assuming following specifications: 0.5V 2.85V IOUT(MAX) 0.8A 35!C Where: forward voltage drop D1diode shown Figure steps selecting right package with proper board area heatsinking keep junction temperature below 135!C given Calculate maximum power dissipation using: IOUT (VIN VOUT) 2.85) 1.32W Calculate maximum allowed example: JA(MAX) 75.6!C/W 1.32 output voltage, need select Assuming 121, 2.85 VOUT 154.8 1.25 VREF Select 154,
10uF
Vout
2.85V
22uF
IRU1010
1010app4-1.3
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.
Select package from datasheet with lower than calculated previous step. Selecting TO-252 (D-Pak) with least 0.5" square 0.062" board using copper 70°C/W which lower than calculated number.
Rev. 06/29/01
IRU1010
Notes
WORLD HEADQUARTERS Kansas St., Segundo, California 90245, Tel: (310) 252-7105 Fax: (310) 252-7903 Visit www.irf.com sales contact information. Data specifications subject change without notice. 02/01
Rev. 06/29/01

IRU1010 DROPOUT POSITIVE ADJUSTABLE REGULATOR DESCRIPTION IR

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