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Data Sheet No. PD94254
IRU1246 / IRU1247-18 / IRU1247-25
2A FIXED AND ADJUSTABLE DUAL VOLTAGE REGULATOR
PRELIMINARY DATA SHEET
FEATURES
Low Dropout Voltage Fast Transient Response Built-In Thermal Shutdown Output Current Limiting D-Pak, Ultra Thin-Pak and SOIC Fixed 3.3V and Adjustable, or Fixed 3.3V and 1.8V, or Fixed 3.3V and 2.5V
DESCRIPTION
The IRU1246/47 family of voltage regulators contain two integrated, low dropout linear voltage regulators in three different packages, such as new 5-Pin Ultra Thin-Pak surface mount, 5-Pin D-Pak and 8-Pin SOIC. The IRU1246 provides 3.3V fixed and adjustable outputs. The IRU1247-18 provides fixed 3.3V and 1.8V. The IRU124725 provides fixed 3.3V and 2.5V output. These products are stable with both Ceramic and Tantalum output capacitors. The adjustable output provides a voltage from 1.25V and up using a simple resistor divider. The input supply for both regulators is supplied from a single 5V supply. Each regulator is capable of 2 amps continuous load current. Both outputs, for each device, are current limit protected as well as having a thermal shutdown that protects the device from excessive temperature.
APPLICATIONS
Motherboard with Multiple Supplies Hard Disk Drivers, CD-ROMs, DVDs ADSL and Cable Modems High Efficiency Linear Regulators
TYPICAL APPLICATION
3.3V
Vout1 C2 4.7uF Y5V Ceramic
5 4 3 2 1
C1 10uF Tant R1 100 1% R2 100 1%
U1 IRU1246
Vout2 Gnd Vadj Vin
2.5V
C3 4.7uF Y5V Ceramic
Vin
Vo = Vref xo1 + o
R1 p R2
Figure 1 - Typical application of IRU1246 in 5-Pin TO-252 (D-Pak) package.
Note: All caps must be located as close to the pins as physically possible using a plane connection.
PACKAGE ORDER INFORMATION
TJ (C) 0 To 150 0 To 150 0 To 150
Rev. 1.6 07/13/01
5-PIN TO-252 (D-Pak) IRU1246CD IRU1247-18CD IRU1247-25CD
5-PIN TO-263 8-PIN PLASTIC Ultra Thin-Pak (P) SOIC POWER (S) IRU1246CP IRU1246CS IRU1247-18CP IRU1247-18CS IRU1247-25CP IRU1247-25CS
OUTPUT VOLTAGE #1 3.3V Fixed 3.3V Fixed 3.3V Fixed
OUTPUT VOLTAGE #2 Adjustable 1.8V Fixed 2.5V Fixed
1
IRU1246 / IRU1247-18 / IRU1247-25
ABSOLUTE MAXIMUM RATINGS
Input Voltage (VIN) .................................................... 7V Storage Temperature Range ...................................... -65C To 150C Operating Junction Temperature Range ..................... 0C To 150C
PACKAGE INFORMATION
5-PIN PLASTIC TO-252 (D-Pak)
FRONT VIEW 5 4 3 2 1 FRONT VIEW
5-PIN ULTRA THIN-PAK (P)
FRONT VIEW FRONT VIEW 5 4 3 2 1
8-PIN PLASTIC POWER SOIC (S)
TOP VIEW TOP VIEW 8 Gnd 7 Gnd 6 Gnd 5 Gnd Vin 1 NC 2 Vout1 3 Vout2 4 8 Gnd 7 Gnd 6 Gnd 5 Gnd
Vout2 Vout1 Gnd NC Vin
Vout1 Vout2 Gnd Vadj Vin
5 4 3 2 1
Vout2 Vout1 Gnd NC Vin
Vout1 Vout2 Gnd Vadj Vin
5 4 3 2 1
Vin 1 Vadj 2 Vout2 3 Vout1 4
IRU1246
IRU1247
IRU1246
IRU1247
IRU1246
IRU1247
JA=358C/W with 1" Copper area
JA=25$C/W with 1" Copper area
JA=55C/W for 1" Sq pad
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over Vin=5.0V, Cin=Cout=4.7F. Typical values refer to TJ=25C. IFL1=2A, IFL2=2A PARAMETER SYM Output Voltage #1 Vo1 Output Voltage #1 Vo1 Output Voltage #2(IRU1246) Vo2 Output Voltage #2(IRU1246) Vo2 Output Voltage #2(IRU1247-18) Vo2 Output Voltage #2(IRU1247-18) Vo2 Output Voltage #2(IRU1247-25) Vo2 Output Voltage #2(IRU1247-25) Vo2 Line Regulation RegLINE Load Regulation RegLOAD Dropout Voltage (Output #1) VDO1 Dropout Voltage (Output #2) VDO2 Current Limit (Output #1) IoL1 Current Limit (Output #2) IoL2 Minimum Load Current (Output #1) Io1(MIN) Minimum Load Current (Output #2) Io2(MIN) Thermal Regulation Regtherm Ripple Rejection (Vcc to Output #1) PSRR1 Ripple Rejection (Vcc to Output #2) PSRR2 Temperature Stability StabTEMP Long Term Stability StabLONG RMS Output Noise Vn Vin Quiescent current IQ1 TEST CONDITION Io2=10mA, TJ=25C Io1=10mA, TJ=0 to 125C Io1=10mA, TJ=25C, Vo=Vadj Io1=10mA, TJ=0 to 125C, Vo=Vadj Io1=10mA, TJ=25C Io1=10mA, TJ=0 to 125C Io1=10mA, TJ=25C Io1=10mA, TJ=0 to 125C Io=10mA, Vcc 5% Note 1, 10mA1.3 1.3
2.1 2.1 5 5 0.1 40 40 0.5 0.3 0.003 10
2
Rev. 1.6 07/13/01
IRU1246 / IRU1247-18 / IRU1247-25
Note 1: Low duty cycle pulse testing with Kelvin connections is required in order to maintain accurate data. Note 2: Dropout voltage is defined as the minimum differential voltage between Vin and Vout required to maintain regulation at Vout. It is measured when the output voltage drops 1% below its nominal value. Note 3: Minimum load current is defined as the minimum current required at the output in order for the output voltage to maintain regulation. Note 4: Temperature stability is the change in output from nominal over the operating temperature range. Note 5: Guaranteed by design, but not tested in production.
PIN DESCRIPTIONS
IRU1246 PIN # PIN SYMBOL 1 Vin PIN DESCRIPTION The power input pin of the regulator. Typically a large storage capacitor is connected from this pin to ground to insure that the input voltage does not sag below the minimum dropout voltage during the load transient response. This pin must always be higher than both Vout pins by the amount of the dropout voltage in order for the device regulate properly. A resistor divider from this pin to Vout2 (pin4) and ground sets the output voltage. This pin is connected to ground. It is also the TAB of the Ultra Thin-Pak package. The output #2 (adjustable) of the regulator. A minimum of 4.7F capacitor must be connected from this pin to ground to insure stability. The output #1 (3.3V) of the regulator. A minimum of 4.7F capacitor must be connected from this pin to ground to insure stability.
2 3 4 5
Vadj Gnd Vout2 Vout1
IRU1247-18, IRU1247-25 PIN # PIN SYMBOL 1 Vin PIN DESCRIPTION The power input pin of the regulator. Typically a large storage capacitor is connected from this pin to ground to insure that the input voltage does not sag below the minimum dropout voltage during the load transient response. This pin must always be higher than both Vout pins by the amount of the dropout voltage in order for the device to regulate properly. No connection. This pin is connected to ground. It is also the TAB of the Ultra Thin-Pak package. The output #1 (1.8V for 1247-18 and 2.5V for 1247-25) of the regulator. A minimum of 4.7F capacitor must be connected from this pin to ground to insure stability. The output #2 (3.3V) of the regulator. A minimum of 4.7F capacitor must be connected from this pin to ground to insure stability.
2 3 4 5
NC Gnd Vout1 Vout2
Rev. 1.6 07/13/01
3
IRU1246 / IRU1247-18 / IRU1247-25
APPLICATION INFORMATION
Thermal The following thermal design check illustrates the method used to calculate the maximum junction temperature of the regulator. Power Flex Package (Ultra Thin-Pak) RTHJA = 25C/W (Note 1) TA = 45C V5 = 5V I2.5 = 0.30A I3.3 = 0.80A V2.5 = 2.5V V3.3 = 3.3V PD = (V5-V3.3) x I3.3 + (V5-V2.5) x I2.5 PD = (5 -3.3) x 0.8 + (5-2.5) x 0.3 = 2.11W T = PD x RTHJA = 2.11 x 25 = 53C TJ = TA + T = 45 + 53 = 98C TJ = 98C Note 1: This thermal impedance is for a four-layer board mounted on a minimum of one inch square area. It is possible to further reduce this by mounting the device close to other thermally conductive elements such as mounting screws. Layout Consideration The IRU1246/1247-xx like many other high speed regulators requires that the output capacitors to be close to the device for stability reasons. For power consideration, a ground plane pad of approximately one inch square pad on the component side must be dedicated to the device where all ground pins are connected to dissipate the power. If multilayer board is used, it is recommended that the inner layers of the board are also dedicated to the size of the pad for better thermal characteristics.
4
Rev. 1.6 07/13/01
IRU1246 / IRU1247-18 / IRU1247-25
TYPICAL APPLICATION
3.3V 5 6 7 8
Gnd Gnd Gnd Gnd Vout1
4
C2 4.7uF Y5V Ceramic
U1 Vout2 3 IRU1246 Vadj 2
Vin
2.5V
R1 100 1% R2 100 1% C3 4.7uF Y5V Ceramic
1
C1 10uF Tant
Vin
Note: All caps must be located as close to the pins as physically possible using a plane connection.
Figure 2 - Typical application of IRU1246 in power 8-Pin SOIC package.
3.3V
Vout1
5 4 3 2 1
C1 10uF Tant R1 100, 1% R2 100, 1%
C3 4.7uF Y5V Ceramic
U1 IRU1246
Vout2 Gnd Vadj Vin
2.5V
C2 4.7uF Y5V Ceramic
Vin
Note: All caps must be located as close to the pins as physically possible using a plane connection.
Figure 3 - Typical application of IRU1246 in 5-Pin Ultra Thin-Pak package.
Rev. 1.6 07/13/01
5
IRU1246 / IRU1247-18 / IRU1247-25
TYPICAL APPLICATION
2.5V
Vout2 Vout1 U1 IRU1247-25 Gnd NC Vin
5 4 3 2 1
C1 10uF Tant
C3 4.7uF Y5V Ceramic
3.3V
C2 4.7uF Y5V Ceramic
Vin
Note: All caps must be located as close to the pins as physically possible using a plane connection.
Figure 4 - Typical application of IRU1247-25 in 5-Pin Ultra Thin-Pak and TO-252 (D-Pak) packages.
2.5V 5 6
Gnd Gnd Vout2
4
C3 4.7uF Y5V Ceramic
U1 Vout1 3 IRU1247-25 NC 2 7 Gnd 8
Gnd Vin
3.3V
C2 4.7uF Y5V Ceramic
1
C1 10uF Tant
Vin
Note: All caps must be located as close to the pins as physically possible using a plane connection.
Figure 5 - Typical application of IRU1247-25 in power 8-Pin SOIC package.
6
Rev. 1.6 07/13/01
IRU1246 / IRU1247-18 / IRU1247-25
TYPICAL APPLICATION
1.8V
Vout2 Vout1 U1 IRU1247-18 Gnd NC Vin
5 4 3 2 1
C1 10uF Tant
C3 4.7uF Y5V Ceramic
3.3V
C2 4.7uF Y5V Ceramic
Vin
Note: All caps must be located as close to the pins as physically possible using a plane connection.
Figure 6 - Typical application of IRU1247-18 in 5-Pin Ultra Thin-Pak and TO-252 (D-Pak) packages.
1.8V 5 6
Gnd Gnd Vout2
4
C3 4.7uF Y5V Ceramic
U1 Vout1 3 IRU1247-18 NC 2 7 Gnd 8
Gnd Vin
3.3V
C2 4.7uF Y5V Ceramic
1
C1 10uF Tant
Vin
Note: All caps must be located as close to the pins as physically possible using a plane connection.
Figure 7 - Typical application of IRU1247-18 in power SOIC 8-Pin package.
Rev. 1.6 07/13/01
7
IRU1246 / IRU1247-18 / IRU1247-25
Notes
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
8
Rev. 1.6 07/13/01

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