REFERENCE DESIGN International Rectifier IRDCiP2001-A • 233 Kansas Street, El Segundo, CA 90245 USA IRDCiP2001-A, 500kHz, 40A, 2-phase Synchronous Buck Converter using iP2001 Overview In this document, table 1 and figure 1 are provided to enable engineers to easily evaluate the iP2001 in a 2-phase configuration that is capable of providing up to 40A in a lab environment without airflow. Figures 3, 4, 5 and 6 and the complete bill of materials in table 2 are provided as a reference design to enable engineers to very quickly and easily design a 2-phase converter. In order to optimize this design to your specific requirements refer to the data sheet for the controller listed in the bill of materials. A variety of other controllers may also be used, but the design will require layout and control circuit modifications. Demoboard Quick Start Guide Initial Settings: z The output is set to 1.7V, but can be adjusted from 1.1 to 1.85V by setting S1 according to the VID codes provided in Table 1. Droop control is set to 50mV at 40A, but can be adjusted by following the instructions in the data sheet for the PWM controller. z The switching frequency per phase is set to 500kHz with the frequency set resistor R4. This creates an effective output frequency of 1MHz. The graph in figure 1 shows the relationship between R4 and the switching frequency per phase. This frequency may be adjusted by changing R4 according to this graph; however, extreme changes from the 500kHz set point may require redesigning the control loop and adjusting the values of input and output capacitors. Also, refer to the SOA graph in the iP2001 datasheet for maximum operating current at different frequencies. Procedure for Connecting and Powering Up Demoboard: 1. Apply input voltage (5-12V) across VIN (TP18) and PGND (TP15). Note that this input source must be applied first during the power-up sequence. 2. Apply +5V logic power across +5V (TP19) and PGND (TP20). 3. Apply load across VOUT pads (TP11 & TP12) and PGND pads (TP15 & TP16) 4. Set ENABLE high. 5. Monitor switch node signals (optional) via TP7 & TP8. 6. Adjust load accordingly. iP2001 Recommended Operating Conditions (refer to the iP2001 datasheet for maximum operating conditions) Input voltage: 5 - 12V Output voltage: 1.1 - 1.85V Output current: 20A per phase, 40A total for 2-phase demo board. Switching Freq: 500kHz per phase, 1MHz effective output frequency. 07/19/02 IRDCiP2001-A 1000 Resistance (kΩ) 100 10 1 100 1000 Output Frequency (kHz) Figure 1 - R4 vs. Frequency (per Phase) VID4 VID3 VID2 VID1 VID0 1 1 1 1 1 1 1 1 1 0 1 1 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 1 0 1 1 0 0 1 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 0 1 0 1 1 0 1 0 0 1 0 0 1 1 1 0 0 1 0 1 0 0 0 1 1 0 0 0 0 VDAC Off 1.100 1.250 1.150 1.175 1.200 1.225 1.250 1.275 1.300 1.325 1.350 1.375 1.400 1.425 1.450 VID4 VID3 VID2 VID1 VID0 0 1 1 1 1 0 1 1 1 0 0 1 1 0 1 0 1 1 0 0 0 1 0 1 1 0 1 0 1 0 0 1 0 0 1 0 1 0 0 0 0 0 1 1 1 0 0 1 1 0 0 0 1 0 1 0 0 1 0 0 0 0 0 1 1 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 VDAC 1.475 1.500 1.525 1.550 1.575 1.600 1.625 1.650 1.675 1.700 1.725 1.750 1.775 1.800 1.825 1.850 Table 1 - PWM IC Voltage Identification Codes 2 www.irf.com IRDCiP2001-A 92% fSW = 500kHz 90% 86% fSW = 1MHz VIN = 12V VOUT = 1.6V TA = 25°C Efficiency 88% 84% 82% 80% 0 5 10 15 20 25 30 35 40 Output Current (A) Figure 2 - Typical Efficiency vs. Current Refer to the following application notes for detailed guidelines and suggestions when implementing iPOWIR Technology products: AN-1028: Recommended Design, Integration and Rework Guidelines for International Rectifier’s iPOWIR Technology BGA Packages This paper discusses the assembly considerations that need to be taken when mounting iPOWIR BGA’s on printed circuit boards. This includes soldering, pick and place, reflow, inspection, cleaning and reworking recommendations. AN-1029: Optimizing a PCB Layout for an iPOWIR Technology Design This paper describes how to optimize the PCB layout design for both thermal and electrical performance. This includes placement, routing, and via interconnect suggestions. AN-1030: Applying iPOWIR Products in Your Thermal Environment This paper explains how to use the Power Loss and SOA curves in the data sheet to validate if the operating conditions and thermal environment are within the Safe Operating Area of the iPOWIR product. www.irf.com 3 8 5 9 4 10 3 11 2 12 1 TP20 PGND TP19 +5V Freq. Set Resistor 7 6 TP5 +5V 51K R4 10uF C27 GND HIP6311 FS/DIS VID0 VID1 VID2 VID3 VID4 PGOOD VSEN U1 ISEN1 PWM4 ISEN4 PWM3 ISEN3 PWM2 ISEN2 PWM1 18 17 11 12 14 13 15 16 20 0.022uF VCC 1K C1 +5V +5V 0 R11 0 R12 Note: Rx and Cx are add on components 9 8 5 4 3 2 1 19 10 * VID0 VID1 VID2 VID3 VID4 PGOOD +5V R6 10K 1K R1 22pF C28 R3 open 7 ENABLE Cx 51 4700pF R2 Rx *Rx &Cx are not parts of PCB VOUT SENSE 6 FB 4 COMP S1 C2 10uF 0 R14 +5V R16 10K R17 10K ENABLE +5V ENABLE +5V VSW2 PGND PRDY VIN PGND VSW3 VIN ENABLE PWM2 U3 IP2001 SGND VDD PRDY ENABLE PWM1 U4 IP2001 SGND VDD SWNODE2 C6 10uF SWNODE3 C9 10uF C7 10uF C10 10uF C8 10uF C11 10uF C31 10uF R8 2K 1% R7 2K 1% Vin TP18 Vin C30 10uF Vin 0.54uH L2 TP7 SWNODE2 0.54uH L3 TP8 SWNODE3 C19 100uF C22 100uF C20 100uF VOUT C23 100uF TP15 PGND TP16 PGND TP22 PGND SENSE C33 0.01uF PGNDSENSE VOUT SENSE VOUT SENSE TP21 TP11 VOUT TP12 VOUT IRDCiP2001-A Fig. 3 - Reference Design Schematic www.irf.com IRDCiP2001-A Fig. 4 - Component Placement Top Layer Fig. 5 - Component Placement Bottom Layer www.irf.com 5 IRDCiP2001-A Designator C1 C2, C6-C11, C27, C30, C31 C19, C20, C22, C23 C28 C33 Cx L2 L3 R1, R2 R11, R12, R14 R6, R16, R17 R3, R19, D2, D3 R4 R7, R8 Rx S1 ST1 - ST4 U1 U3, U4 Value 1 0.022uF 10.0uF 100uF 22.0pF 0.010uF 4700pF 0.54uH 1K 0 10K 51K 2K 51 SPST 4-40 - Value 2 Type Tolerance Package Mfr. 50V X7R 10% 0805 TDK 16V X5R 10% 1210 TDK 6.3V X5R 10% 2220 TDK 50V COG 5% 0805 TDK 50V X7R 10% 0805 TDK 50V X7R 10% 0603 TDK 27A Ferrite 20% SMT Panasonic 1/8W Thick film 5% 0805 ROHM 1/8W Thick film <50m 0805 ROHM 1/8W Thick film 5% 0805 ROHM 1/8W Thick film 5% 0805 ROHM 1/8W Thick film 5% 0805 ROHM 1/10W Thick film 5% 0603 KOA 6 position Switch SMT C&K Components Keystone PWM controller 0 - 70°C SOIC20 Intersil DC-DC 11 x 11 x 3mm IR Mfr. Part No. C2012X7R1H223K C3225X5R1C106K C5750X5R0J107K C2012COG1H220J C2012X7R1H103K C1608X7R1H472K ETQP6F0R6BFA MCR10EZHJ102 MCR10EZHJ000 MCR10EZHJ103 MCR10EZHJ513 MCR10EZHJ202 RM73B1J510J SD06H0SK 8412 HIP6311CB IP2001 Table 2 - Reference Design Bill of Materials Adjusting the Over-Current Limit R7 & R8 are the resistors used to adjust the over-current trip point. The trip point is a function of the controller and corresponds to 165% of the output current indicated on the x-axis of Fig. 6. For example, selecting a resistance of 1.5K at each phase will set the trip point to 165% of 15A, or 24.75A. The trip point for each phase on the demoboard is currently set to 165% of 20A, or 33A. 2100 2000 1900 1800 1700 RISEN (:) 1600 1500 1400 1300 1200 1100 1000 900 10 11 12 13 14 15 16 17 18 19 20 Output Current (A) Fig. 6 - RISEN vs Current (per Phase) 6 www.irf.com IRDCiP2001-A Sequencing Tip It’s important to have proper sequencing between the control IC and the iP2001 blocks. This assures the soft-start routine of the IC will properly ramp-up the output voltage during a power-up or restart from shut down event. Figure 7 shows a simple and cost effective way to synchronize the iP2001 blocks with an HIP6311 control IC in a 2 Phase configuration. Placing Schottky diodes between the iP2001’s PRDY pin and the IC’s FS/DIS pin creates an interface analogous to an AND operation. With this configuration, no single iP2001 can enable the IC independently. This configuration also resolves any differences in timing and logic thresholds between iP2001 devices. The capacitors are used to filter high frequency noise on the PRDY line. Additionally, the ENABLE pin of the iP2001 blocks can be used as the master control switch for the system. During power-up, the PRDY pin is held low until V DD reaches a typical voltage of 4.4V. Until then, the schottky diode is forward biased and clamps the FS/DIS pin well below the disable voltage of the HIP6311 IC (typically 1V). Upon reaching 4.4V, the PRDY pin transitions to a logic-level high state and releases the clamp on the FS/DIS pin. This enables the IC and allows its soft start routine to begin (see figure 8), assuming the voltage at the IC’s V CC pin is greater than its power-on reset threshold. When the ENABLE pin is held to a logic-level low state (shut down mode), the PRDY pin clamps the FS/DIS pin of the IC below the disable voltage. After the ENABLE pin transitions to a logic-level high state, the PRDY releases the clamp on the FS/DIS pin, enabling the IC and allowing its soft start routine to begin (see figure 9). During power-down, the PRDY pin transitions to a logic-level low state when the VDD reaches the under voltage lock out threshold of the iP2001 blocks. The FS/DIS pin is then clamped below the disable voltage, disabling the control IC. BAT54 PRDY1 ENABLE COMP PWM1 FB PWM2 FS/DIS ISEN2 GND ISEN3 VSEN PWM3 0.22µF iP2001 PRDY2 ENABLE BAT54 0.22µF iP2001 51k Master Control HIP6311 Fig. 7 - Sequencing Schematic www.irf.com 7 IRDCiP2001-A Ch 1: VDD Ch 2: PRDY Ch 3: VOUT Fig. 8 - VDD Rise vs. Output Timing Ch 1: ENABLE Ch 2: PRDY Ch 3: VOUT Fig. 9 - Enable On vs. Output Timing Use of this design for any application should be fully verified by the customer. International Rectifier cannot guarantee suitability for your applications, and is not liable for any result of usage for such applications including, without limitation, personal or property damage or violation of third party intellectual property rights. IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105 TAC Fax: (310) 252-7903 8 www.irf.com