IRU3072CH

Data Sheet No. PD94698 IRU3072 20-PIN SYNCHRONOUS PWM CONTROLLER/ 3 LDO CONTROLLER FEATURES Synchronous Controller plus 3-LDO controllers Current Limit using MOSFET Sensing Dual Soft-Start Function allows power sequencing Single 5V/12V Supply Operation Programmable Switching Frequency up to 400KHz Fixed Frequency Voltage Mode 1A Peak Output Drive Capability DESCRIPTION The IRU3072 controller IC is designed to provide a low cost synchronous Buck regulator for on-board DC to DC converter for multi-output applications. The outputs can be programmed as low as 0.8V for low voltage applications. The IRU3072 features dual soft-starts which allows power sequencing between outputs. Over current limit is provided by using external MOSFET's on-resistance for optimum cost and performance. This device features a programmable frequency set from 200KHz to 400KHz, under-voltage lockout for all input supplies, dual external programmable soft-start functions as well as output under-voltage detection that latches off the device when an output short is detected. APPLICATIONS Graphic Card DDR memory source sink VTT application Applications with Multiple Outputs Low cost on-board DC to DC such as 5V to 3.3V, 2.5V or 1.8V Hard Disk Drive TYPICAL APPLICATION 3.3V Q1 VSEN33 / SDB R1 C2 10uF 2.15K R2 1K Vcc C1 1uF +5V Drv2 Fb2 VccLDO VOUT2 2.5V C3 1uF Q2 VOUT3 1.8V C4 10uF R3 1.25K R4 1K Drv3 Fb3 Vc D1 L1 U1 IRU3072 Drv4 Fb4 HDrv OCSet C5 1uF C6 0.1uF 1uH C7 2x 47uF,16V VIN=12V C8 10uF Q3 VOUT4 1.5V C9 10uF R5 866V R6 1K Q4 IRF7460 R7 6.81K Q5 IRF7460 L2 1uH C10 220pF R8 3.3K C11 15nF R9 46.4K C13 0.1uF VOUT1 1.2V @ 8A C12 3x 330uF, 40m V 6TPB330M, Poscap R10 499V Comp Rt SS1 LDrv Fb1 PGnd R11 1K C14 33nF SSLDO Gnd Figure 1 - Typical application of IRU3072. PACKAGE ORDER INFORMATION TA (°C) 0 To 70 Rev. 1.0 3/25/04 DEVICE IRU3072CH PACKAGE 20-Pin MLPQ 4x4 (H) www.irf.com 1 IRU3072 ABSOLUTE MAXIMUM RATINGS Vcc and VccLDO Supply Voltage .............................. Vc Supply Voltage .................................................... Storage Temperature Range ...................................... Operating Junction Temperature Range ..................... CAUTION: For all pins, voltage should not be below -0.5V. CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. 25V 25V -65°C To 150°C 0°C To 125°C PACKAGE INFORMATION 20-PIN MLPQ 4x4 (H) SSLDO uJA=468C/W SS1 16 15 14 13 12 11 Fb4 Fb3 19 20 18 Fb2 17 Drv4 Drv3 Drv2 VccLDO Vcc 1 2 3 4 5 6 7 8 9 10 Comp Fb1 Rt VS E N 3 3/SDB OCSet PGnd Gnd ELECTRICAL SPECIFICATIONS Unless otherwise specified, the typical specification value applies over Vcc=5V, Vc=12V, VccLDO=5V and TA=25°C. the Min and Max limits apply to the temperature range from 0 to 70°C. Low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient temperature. PARAMETER SYM Feedback Voltage Feedback Voltage VFB Fb Voltage Line Regulation LREG UVLO UVLO Threshold - Vcc UVLO VCC UVLO Hysteresis - Vcc UVLO Threshold - Vc UVLO VC UVLO Hysteresis - Vc UVLO Threshold - VccLDO UVLO VCCLDO UVLO Hysteresis - VccLDO UVLO Threshold - VSEN33 UVLO VSEN33 UVLO Hysteresis - VSEN33 UVLO Threshold - Fb1, 2, 3, 4 UVLO Fb1 UVLO Hysteresis - Fb1, 2, 3, 4 Supply Current Vcc Dynamic Supply Current Dyn I CC Vc Dynamic Supply Current Dyn I C Vcc Static Supply Current ICCQ Vc Static Supply Current ICQ TEST CONDITION MIN 0.784 5 1.2V3(12 - 1.2)/(400KHz 312V30.438A) L > 0.8mH Select inductor from Panasonic so that L=1mH. The ripple current is calculated as: DIPK_PK = (12 - 1.2) 31.2/(1mH3400KHz 312) DIPK_PK ≅ 2.7A 350 300 250 200 150 100 50 0 0 50 Rt (KV) V 100 150 200 Figure 24 - Switching frequency versus resistor Rt. Rev. 1.0 3/25/04 www.irf.com 15 IRU3072 Output capacitor selection The voltage rating of the output capacitor is the same as the output voltage. Typical available capacitors on the market are electrolytic, tantalum and ceramic. If electrolytic or tantalum capacitors are employed, the criteria is normally based on the value of Effective Series Resistance (ESR) of total output capacitor. In most cases, the ESR of the output capacitor is calculated based on the following relationship: ESR < DVRIPPLE(SPEC)/DIPK_PK or ESR < DVSTEPLOAD(SPEC)/DISTEPLOAD(MAX) Depending on which one is the requirement. Where: DVRIPPLE(SPEC) is the maximum allowed voltage ripple. DIPK_PK is the current ripple. DVSTEPLOAD(SPEC) is the maximum allowed voltage droop during the transient or step load. DISTEPLOAD(MAX) is the maximum step load current. In this example: DVSTEPLOAD(SPEC) = 150mV DISTEPLOAD(MAX) = 8A The required ESR is calculated as: ESR < 150mV/8A = 18.75mV Select three Sanyo POSCAP 6TPB330M with 6.3V 330mF and 40mV ESR will give about 13mV, which will meet the specification. Input capacitor Selection Input capacitor is dertermined by the voltage rating and input RMS current. For this application, the input RMS current is given as: IIN(RMS) = I OUT 3 D3(1-D) D = VOUT /VIN = 1.2V/12V ≅ 0.1 The input RMS current is estimated as: IIN(RMS) = 8A3 0.13(1-0.1) ≅ 2.4A ment for each MOSFET is almost the same. If logiclevel or 3V driver MOSFET is used, some caution should be taken with devices at very low VGS to prevent undesired turn-on of the complementary MOSFET, which results a shoot-through circuit. If output inductor current ripple is neglected, the RMS current of high side switch is given by: D = VOUT /VIN = 0.1 IRMS(HI) = D3IOUT = 0.138A = 2.53A The RMS current of low side switch is given as: IRMS(HI) = 1-D3IOUT = 1-0.138A = 7.6A For low side MOSFET, if it is driven by 5V, a logic gate driver MOSFET is preferred. For RDS(ON) of the MOSFET, it should be as small as possible in order to get highest efficiency. A logic driver MOSFET such as IRF7460 from International Rectifier in a SOIC 8-pin package, RDS(ON)=10mV, 20V drain source voltage rating and 12A IDS is selected for high side and low side MOSFET. Power Dissipation for MOSFETs The power dissipation for MOSFETS typically includes conduction loss and switching losses. For high side switch, the conduction loss is estimated as: PCOND(HI) = D 3IOUT 3IOUT 3RDS(ON)MAX The R DS(ON) has to consider the worst case. In the datasheet of IRF7460: RDS(ON)MAX = 14mV @ Vgs = 4.5V PCOND(HI) = 0.138A38A314mV ≅ 0.09W The switching loss is more difficult to calculate because of the parasitic parameters. In general, the switching loss can be estimated by the following: PSW = 0.53VDS 3IOUT 3(tr+tf) 3FS tr is the rising time and tf is the falling time. From IRU3072 datasheet: tr=50ns and tf=50ns PSW(HI) = 0.5312V38A3(50ns+50ns) 3400KHz PSW(HI) ≅ 1.92W The total disspation for the high side switch is: PD(HI) = PSW(HI)+PCOND(HI) ≅ 2W Select two Sanyo POSCAP -16TPB47M with 16V, 47mF and 1.4A ripple current. A 1mH, 1A small input inductor is enough for the input filer. Power MOSFET Selection In general, the MOSFET selection criteria depends on the maximum drain-source voltage, RMS current and ON resistance (RDS(ON)). For both high side and low side MOSFETs, a drain-source voltage rating higher than maximum input voltage is necessary. In the demo-board, 20V rating should be satisfied. The gate drive require- For low side switch, most of the loss are conduction loss. The low side switch power dissipation is: PD(LO) ≅ PCOND(LO) = (1-D) 3IOUT 3IOUT 3RDS(ON)MAX PD(LO) ≅ PCOND(LO) = (1-0.1) 38A38A314mV PD(LO) ≅ PCOND(LO) = 0.81W 16 www.irf.com Rev. 1.0 3/25/04 IRU3072 Estimated Temperature Rise for MOSFET The estimated junction temperature of the MOSFET is given by: TJ = TA+PD3RuJA Where: TJ is the junction temperature. TA is the ambient temperature. PD is the power dissipation. RuJA is the junction-to-ambient thermal resistance with MOSFET on 1" square PCB board and is from the data sheet. For MOSFET IRF7460 with SOIC 8-pin package, RuJA=508C/W. Assume ambient temperature is TA=358C. For high side MOSFET, the junction temperature is given as: TJ = TA+PD3RuJA = 35+2350 = 1358C < 1508C For low side MOSFET IRF7460, the maximum junction temperature can be calculated as: TJ = TA+PD3RuJA = 35+0.81350 = 768C < 1508C The maximum junction temperature of both MOSFETs is below the maximum rating of 1508C. Controller Parameter Calculation (1) Frequency Selection From Figure 23, the frequency setting resistor can be chosen to be Rt=47KV, which gives us approximately 400KHz frequency. (2) Soft-Start Capacitor Soft-start capacitor for PWM secton is selected from equation (1). Select start up time tSTART =5ms: CSS = 20mA3tSTART = 20mA35ms = 0.1mF Select C11=CSS=0.1mF (3) Over Current Limit Setting The over current limit resistor can be calculated based on Figure 17. The output current limit is set by: IO(LIM) = 10A The current ripple during nomral operation (400KHz) is given by: DIPK_PK = (12-1.2) 31.2/(1mH3400KHz 312) DIPK_PK ≅ 2.7A The over current setting I SET is: ISET = I O(LIM)-DIPK_PK/2 = 10A-2.7A/2 ≅ 8.7A The over current setting resistor: RSET = I SET 3RDS(ON)/20mA Rev. 1.0 3/25/04 For low side MOSFET IRF7460, with 4.5V gate voltage and maximum RDS(ON) of 14mV, then: RSET = 8.7A314mV/20mA = 6.09KV Select R7=RSET =6.8KV (4) Compensation Design VOUT Rf1 IRU3072 VFB Error Amp gm 1V Rf2 Cc1 Rc1 Comp Cc2 (Optional) Figure 25 - Type II compensator. For electrolytic capacitor, the frequency caused by ESR is typically at a few KHz range. A type II compensator is a good option. The detailed description is shown in application note AN-1043 from: http://www.irf.com/technical-info/appnotes.htm Select the zero crossover frequency to be 1/10 of switching frequency that is 40KHz: FO = 40KHz The compensation resistor can be calculated as: Rc1= 2p3FO3L3VOSC3VOUT (ESR3VIN3gm 3VREF) Where VOSC is the oscillator peak to peak voltage and gm is the transconductance of the error amplifier. From the datasheet we get VOSC=1.25V and gm =1000mmho. The calculated compensation resistor is: Rc1=2p3403131.2531.2/(133123100030.8) Rc1=2.98K Select R8=Rc1=3.3K The compensator capacitor is given as: Cc1 = (L3COUT )/0.75/Rc1 Cc1 = (1mH3450mF)/0.75/3.3K = 10nF Select C9=Cc1=15nF www.irf.com 17 IRU3072 (Optional) an additional capacitor Cc2 can be adopted, where: Cc2 ≅ 1/(p3Rc13FS) ≅ 220pF (5) Feedback resistor The output of PWM is determined by: VOUT = V REF3(RT+RB)/RB or RT = (VOUT /VREF-1) 3RB Where VREF=0.8V RT is the top feedback resistor and R is bottom B feedback resistor.For 1.2V output, RT =499V, RB=1K. LDO Regulator Component Selection and LDO Power MOSFET Selection The first step in selecting the power MOSFET for the linear regulator is to select its maximum R DS(ON) based on the input to output dropout voltage and maximum load current. For VOUT2=2.5V, VIN(LDO)=3.3V and I OUT2=2A: RDS(ON)MAX = (VIN(LDO)-VOUT2)/IOUT2 RDS(ON)MAX = (3.3V-2.5V)/2.0A = 0.4V Note that the MOSFET’s RDS(ON) increases with temperature, the calculated RDS(ON) has to be divided by the RDS(ON) temperature coefficienct (about 1.5) in order to get typical RDS(ON). IRLR2703s from Internation Rectifier with D2 package, 30V, VDS logic drive and 65mV is good enough to meet the requirement. To select the heat sink for the LDO MOSFET, the first step is to calculate the maximum power dissipation of the device: PD = (VIN(LDO)-VOUT )3IOUT PD = (3.3V-2.5V) 32A = 1.4W The junction temperature of MOSFET can be estimated by the following formula: TJ = TA+PD3(RuJC+RuCS+RuSA) TJ should be < TJ(MAX) @ 1508C Where: TJ = the estimated junction temperature. TA = the ambient temperature. PD = the power disspation. RuJC = the thermal resistance from junction to case. RuCS = the thermal resistance from case to heat sink. RuSA = the thermal resistance from heat sink to ambient. The required thermal resistance of heat sink should be RuSA VLDO(OUT)MAX+VGS(TH)MIN+2VBE Where: VLDO(OUT)MAX is the maximum output voltage VGS(TH)MIN is the minimum LDO MOSFET gate threshold voltage VBE is the diode drop, approximately 0.6V For this example, VGS(TH)MIN of MOSFET IRLR2703s, is 1V. Then: VCC(LDO) > 2.5V+1V+230.6V = 4.7V Select VCCLDO=12V for proper power sequence LDO Feedback Resistor Selection The output of LDO is determined by: VOUT = V REF3(RT+RB)/RB Where: VREF=0.8V RT is the top feedback resistor and R is bottom B feedback resistor. For 2.5V output, if RB=1K then: RT = (VOUT /VREF-1) 3RB = (2.5/0.8-1) 31K = 2.12K Select Rt=2.15K LDO Soft-Start Capacitor The soft-start capacitor can be estimated from equation (1). Select start up time as 2ms: CSS(LDO) = 20mA3tSTART = 20mA32ms = 0.04mF Select C12=CSS(LDO)=33nF 18 www.irf.com Rev. 1.0 3/25/04 IRU3072 Layout Consideration The layout is very important when designing high frequency switching converters. Layout will affect noise pickup and can cause a good design to perform with less than expected results. Start to place the power components, make all the connection in the top layer with wide, copper filled areas. The inductor, output capacitor and the MOSFET should be close to each other as possible. This helps to reduce the EMI radiated by the power traces due to the high switching currents through them. Place input capacitor directly to the drain of the high-side MOSFET, to reduce the ESR replace the single input capacitor with two parallel units. The feedback part of the system should be kept away from the inductor and other noise sources, and be placed close to the IC. In multilayer PCB use one layer as power ground plane and have a control circuit ground (analog ground), to which all signals are referenced. The goal is to localize the high current path to a separate loop that does not interfere with the more sensitive analog control function. These two grounds must be connected together on the PC board layout at a single point. APPLICATION EXPERIMENTAL WAVEFORMS for Application Circuit in Figures 1 and 3 Figure 26 - Transient response with 8A load. Figure 27 - Transient response (zoomed). Figure 28 - Transient response (zoomed). Rev. 1.0 3/25/04 www.irf.com 19 IRU3072 TYPICAL APPLICATIONS 3.3V Q1 IRLR2703 VSEN33 / SDB Drv2 R1 2.15K Vcc C1 1uF VOUT2 2.5V Fb2 R2 1K C2 VccLDO Q2 VOUT3 1.8V R3 C4 1.24K R4 1K Drv3 Fb3 Vc L1 C5 1uF C6 0.1uF U1 IRU3072 Drv4 Fb4 HDrv 1uH C7 16TPB47M 47uF, 16V VIN=5V C8 10uF Q3 VOUT4 1.5V R5 C9 C10 866 R6 1K Q4 IRF7460 R7 L2 1uH 100pF R8 6.8K R9 46.4K C11 10nF OCSet 6.8K Comp Rt LDrv Q5 IRF7460 VOUT1 1.2V @ 8A C12 3x 6TPB330M 6.3V, 330uF, 40mV R10 SS1 C13 0.1uF C14 33nF Fb1 PGnd R11 1K 1K SSLDO Gnd Figure 29 - IRU3072 typical application with one bus input voltage VCC=VBUS =5V and 3.3V for LDO. 3.3V Q1 IRLR2703 VSEN33 / SDB Drv2 R1 Vcc C1 1uF VOUT2 2.5V Fb2 C2 2.15K R2 1K VccLDO 12V Q2 VOUT3 1.8V R3 C4 1.24K R4 1K Drv3 Fb3 Vc C3 1uF L1 C7 16TPB47M 47uF, 16V 1uH U1 IRU3072 Drv4 Fb4 HDrv OCSet R7 6.8K Q4 IRF7460 VIN=5V C8 10uF Q3 VOUT4 1.5V R5 C9 C10 866 R6 1K L2 1uH Q5 IRF7460 100pF R8 6.8K C11 10nF R9 46.4K VOUT1 0.8V C12 3x 6TPB330M 6.3V, 330uF, 40m V Comp Rt SS1 LDrv Fb1 PGnd C13 0.1uF C14 33nF SSLDO Gnd Figure 30 - IRU3072 Typical application with 5VBUS input and 12V for the driver (charge pump is saved). 20 www.irf.com Rev. 1.0 3/25/04 IRU3072 TYPICAL APPLICATIONS 3.3V Q1 IRLR2703 VSEN33 / SDB R1 2.15K R2 1K Vcc C1 1uF +5V Drv2 Fb2 VccLDO VOUT2 2.5V C2 C3 1uF Q2 VOUT3 1.8V R3 C4 1.24K R4 1K Drv3 Fb3 Vc D1 D2 L1 U1 IRU3072 Drv4 Fb4 HDrv C5 1uF C6 0.1uF 1uH C7 47uF,16V VIN=12V C8 10uF Q3 VOUT4 1.5V R5 C9 C10 866 R6 1K Q4 IRF7460 R7 L2 1uH Q5 IRF7460 82pF R8 10K C11 3.3nF R9 47K C13 0.1uF OCSet 4.7K VOUT1 1.2V @ 5A C12 2x 47uF Ceramic R11 4.64K C15 220pF R12 124K Comp Rt SS1 LDrv R10 62K C14 33nF SSLDO Fb1 Gnd PGnd Figure 31 - IRU3072 typical application with ceramic capacitor output. 3.3V Q1 IRLR2703 VSEN33 / SDB R1 2.15K R2 1K Vcc C1 1uF R12 200V Drv2 Fb2 VOUT2 2.5V C2 VccLDO Q2 VOUT3 1.8V R3 C4 1.24K R4 1K Drv3 Fb3 Vc L1 C5 1uF C6 0.1uF U1 IRU3072 Drv4 Fb4 HDrv C7 16TPB47M 47uF, 16V 1uH C8 10uF VIN=12V Q3 VOUT4 1.5V R5 C9 C10 866 R6 1K Q4 IRF7460 R7 L2 1uH 220pF R8 3.3K C11 15nF R9 47K OCSet 6.8K VOUT1 1.2V Q5 IRF7460 C12 3x 6TPB330M 6.3V, 330uF, 40mV Comp Rt LDrv R10 SS1 C13 0.1uF C14 33nF Fb1 PGnd R11 1K 1K SSLDO Gnd Figure 32 - IRU3072 typical application with one bus input voltage VCC=VBUS =12V and 3.3V for LDO. Rev. 1.0 3/25/04 www.irf.com 21 IRU3072 TYPICAL APPLICATION R13 1K R12 200V 3.3V Q1 IRLR2703 VSEN33 / SDB Drv2 R1 2.15K Vcc C1 1uF VOUT2 2.5V Fb2 R2 1K C2 VccLDO Q2 Drv3 R3 1.24K Vc L1 C5 1uF C6 0.1uF VOUT3 1.8V Fb3 R4 1K C4 U1 IRU3072 Drv4 Fb4 HDrv 1uH C7 16TPB47M 47uF, 16V VIN=12V C8 10uF Q3 VOUT4 1.5V R5 C9 C10 866 R6 1K Q4 IRF7460 R7 L2 1uH Q5 IRF7460 220pF R8 3.3K C11 15nF R9 47K OCSet 6.8K VOUT1 3.3V C12 3x 6TPB330M 6.3V, 330uF, 40mV Comp Rt LDrv R10 SS1 C13 0.1uF C14 33nF Fb1 PGnd R11 1K 3.125K SSLDO Gnd Figure 33 - IRU3072 typical application with one bus input voltage VCC=VBUS =12V to generate all LDO output. 22 www.irf.com Rev. 1.0 3/25/04 IRU3072 (H) MLPQ Package 20-Pin D D/2 D2 EXPOSED PAD PIN NUMBER 1 PIN 1 MARK AREA (See Note1) E/2 E E2 R L TOP VIEW e BOTTOM VIEW B A A3 SIDE VIEW A1 Note 1: Details of pin #1 are optional, but must be located within the zone indicated. The identifier may be molded, or marked features. SYMBOL DESIG A A1 A3 B D D2 E E2 e L R 20-PIN 4x4 MIN 0.80 0.00 0.18 2.00 2.00 0.45 0.09 NOM 0.90 0.02 0.20 REF 0.23 4.00 BSC 2.15 4.00 BSC 2.15 0.50 BSC 0.55 --MAX 1.00 0.05 0.30 2.25 2.25 0.65 --- NOTE: ALL MEASUREMENTS ARE IN MILLIMETERS. Rev. 1.0 3/25/04 www.irf.com 23 IRU3072 PACKAGE SHIPMENT METHOD PKG DESIG H PACKAGE DESCRIPTION MLPQ 4x4 PIN COUNT 20 PARTS PER TUBE TBD PARTS PER REEL TBD T&R Orientation Fig A Feed Direction Figure A This product has been designed and qualified for the industrial market. 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 24 www.irf.com Rev. 1.0 3/25/04