IRDC3865 SupIRBuck TM USER GUIDE FOR IRDC3865 EVALUATION BOARD DESCRIPTION The IR3865 SupIRBuckTM is an easy-to-use, fully integrated and highly efficient DC/DC voltage regulator. The onboard constant on time hysteretic controller and MOSFETs make IR3865 a space-efficient solution that delivers up to 10A of precisely controlled output voltage in a 4mm x 5mm QFN package. In addition to excellent light load and full load efficiency, the IR3865 offers features such as: a 0.5V reference, programmable switching frequency, temperature compensated over current protection, thermal shutdown and optional forced continuous conduction mode. Additional features include: pre-bias startup, soft start, power good output, enable input with voltage monitoring capability and over/under voltage protection, making the device a very flexible solution that is suitable for a broad range of applications. This user guide contains the schematic, bill of materials, and operating instructions of the IRDC3865 evaluation board. Detailed product specifications, application information and performance curves at different operating conditions are available in the IR3865 data sheet. BOARD FEATURES • • • • • • • • VIN = +12V VCC = +5V VOUT = +1.05V IOUT = 0 to 10A FS = 300kHz @ CCM L = 1.5µH CIN = 22µF (ceramic 1210) + 68µF (electrolytic) COUT = 47µF (ceramic 0805) + 330µF (POSCAP) 1 IRDC3865 CONNECTIONS and OPERATING INSTRUCTIONS An input supply in the range of 7 to 16V should be connected from VIN to PGND. A maximum load of 10A may be connected to VOUT and PGND. The connection diagram is shown in Fig. 1, and the inputs and outputs of the board are listed in Table 1. IRDC3865 has two input supplies, one for biasing (VCC) and the other for input voltage (VIN). Separate supplies should be applied to these inputs. VCC input should be a well regulated 4.5V to 5.5V supply connected to VCC and PGND. Enable (EN) is controlled by the first switch of SW1, and FCCM option can be selected by the second switch of SW1. Toggle the switch to the ON position (marked by a solid square) to enable switching or to select FCCM. The absolute maximum voltage of the external signal applied to EN (TP4) and FCCM is +8V. Table 1. Connections Connection Signal Name VIN (TP2) VIN PGND (TP5) Ground for VIN VCC (TP16) VCC Input PGND (TP17) Ground for VCC Input VOUT (TP7) VOUT (+1.05V) PGND (TP10) Ground for VOUT EN (TP4) Enable Input LAYOUT The PCB is a 4-layer board. All layers are 1 oz. copper. IR3865 and other components are mounted on the top and bottom layers of the board. The power supply decoupling capacitors, bootstrap capacitor and feedback components are located close to IR3865. To improve efficiency, the circuit board is designed to minimize the length of the onboard power ground current path. 2 IRDC3865 CONNECTION DIAGRAM VIN GROUND Control Switch for: EN FCCM GROUND VCC = +5.0V VOUT = +1.05V GROUND Fig. 1: Connection Diagram of IRDC3865 Evaluation Board 3 IRDC3865 PCB Board Layout Fig. 2: Board Layout, Top Components Fig. 3: Board Layout, Bottom Components 4 IRDC3865 PCB Board Layout Fig. 4: Board Layout, Top Layer Fig. 5: Board Layout, Bottom Layer 5 IRDC3865 PCB Board Layout Fig. 6: Board Layout, Mid-layer I Fig. 7: Board Layout, Mid-layer II 6 SW1 EN / FCCM 4 3 TP11 PGOOD 1 2 TP4 EN TP17 PGND TP16 VCC TP26 AGND C23 open VCC +3.3V TP14 +3.3V NC1 SS FB GND1 PGOOD ISET FCCM R3 200K TP28 VID TP27 A C25 1uF R11 20 IR3865 PHASE C22 open R10 open TP25 B 12 U1 IR3865 1 C4 0.22uF Q1 open R9 open R6 open VSW VIN C14 open L1 1.5uH C13 open C24 open R13 open C1 1uF R8 2.55K R7 2.80K C2 22uF + C3 68uF C15 open C6 open C16 open C7 open Fig. 8: Schematic of the IRDC3865 Evaluation Board R12 4.99 C21 1uF 7 6 C20 0.1uF 5 SS 4 3 2 1 FB PGOOD ISET TP13 SS R5 10K +3.3V VSW R4 8.66K FCCM EN 17 GND 3VCBP 8 15 FF 16 EN 14 VCC 10 NC2 9 BOOT 13 VIN PGND 11 R1 10K C17 open C8 open TP6 PGNDS TP1 VINS C18 open C9 330uF TP5 PGND TP2 VIN C19 open C10 47uF 7 C26 open C11 open 1 C27 open C12 0.1uF VOUT 10 R2 10K +3.3V 2 3 6 -Vins VIN +Vins 8 -Vdd1s 2 VCC +Vdd1s 3 +3.3V -Vdd2s +Vdd2s 9 +Vout1s -Vout1s 4 VOUT +Vout2s -Vout2s 5 VCC TP10 PGND TP7 VOUT TP18 VOLTAGE SENSE TP24 PGNDS TP23 VOUTS IRDC3865 7 IRDC3865 Bill of Materials 8 IRDC3865 TYPICAL OPERATING WAVEFORMS Tested with demoboard shown in Fig. 8, VIN = 12V, VCC = 5V, VOUT = 1.05V, Fs = 300kHz, TA = 25oC, no airflow, unless otherwise specified EN EN PGOOD PGOOD SS SS VOUT VOUT 5V/div 5V/div 1V/div 500mV/div 5ms/div 5V/div 5V/div 1V/div 500mV/div 1ms/div Fig. 10: Shutdown Fig. 9: Startup VOUT VOUT PHASE PHASE iL iL 20mV/div 5V/div 1A/div 10µs/div Fig. 11: DCM (IOUT = 0.1A) 20mV/div 5V/div 5A/div 2µs/div Fig. 12: CCM (IOUT = 10A) PGOOD PGOOD SS FB VOUT VOUT iL IOUT 5V/div 1V/div 1V/div 10A/div 2ms/div Fig. 13: Over Current Protection (tested by shorting VOUT to PGND) 5V/div 1V/div 500mV/div 2A/div 50µs/div Fig. 14: Over Voltage Protection (tested by shorting FB to VOUT) 9 IRDC3865 TYPICAL OPERATING WAVEFORMS Tested with demoboard shown in Fig. 8, VIN = 12V, VCC = 5V, VOUT = 1.05V, Fs = 300kHz, TA = 25oC, no airflow, unless otherwise specified VOUT VOUT PHASE PHASE iL iL 50mV/div 5V/div 2A/div 50µs/div Fig. 15: Load Transient 0-4A 20mV/div 5V/div 5A/div 50µs/div Fig. 16: Load Transient 6-10A TYPICAL PERFORMANCE VIN = 12V, VCC = 5V, VOUT = 1.05V, Fs = 300kHz, IOUT = 10A, TA = 25oC, no airflow Fig. 17: Thermal Image (IR3865: 81oC, Inductor: 52oC, PCB: 39oC) 10 IRDC3865 TYPICAL OPERATING DATA VIN = 12V, VCC = 5V, VOUT = 1.05V, Fs = 300kHz, IOUT = 0 ~ 10A, TA = 25oC, no airflow, unless otherwise specified 95% 350 Switching Frequency (kHz) 90% Efficiency 85% 80% 75% 70% 65% 60% 55% 50% 0.01 300 250 200 150 100 50 0 0.1 1 10 0 2 4 Load Current (A) Fig. 18: Efficiency vs. Load Current 8 10 Fig. 19: Switching Frequency vs. Load Current 1.062 1.062 1.060 1.060 Output Voltage (V) Output Voltage (V) 6 Load Current (A) 1.058 1.056 1.054 1.052 1.058 1.056 1.054 1.052 1.050 1.050 0 2 4 6 Load Current (A) Fig. 20: Load Regulation 8 10 7 8 9 10 11 12 13 14 15 16 Input Voltage (V) Fig. 21: Line Regulation at 10A Load 11 IRDC3865 PCB Metal and Components Placement Lead lands (the 13 IC pins) width should be equal to nominal part lead width. The minimum lead to lead spacing should be ≥ 0.2mm to minimize shorting. Lead land length should be equal to maximum part lead length + 0.3 mm outboard extension. The outboard extension ensures a large toe fillet that can be easily inspected. Pad lands (the 4 big pads) length and width should be equal to maximum part pad length and width. However, the minimum metal to metal spacing should be no less than 0.17mm for 2 oz. Copper, or no less than 0.1mm for 1 oz. Copper, or no less than 0.23mm for 3 oz. Copper. 12 IRDC3865 Solder Resist It is recommended that the lead lands are Non Solder Mask Defined (NSMD). The solder resist should be pulled away from the metal lead lands by a minimum of 0.025mm to ensure NSMD pads. The land pad should be Solder Mask Defined (SMD), with a minimum overlap of the solder resist onto the copper of 0.05mm to accommodate solder resist misalignment. Ensure that the solder resist in between the lead lands and the pad land is ≥ 0.15mm due to the high aspect ratio of the solder resist strip separating the lead lands from the pad land. 13 IRDC3865 Stencil Design The Stencil apertures for the lead lands should be approximately 80% of the area of the lead lads. Reducing the amount of solder deposited will minimize the occurrences of lead shorts. If too much solder is deposited on the center pad, the part will float and the lead lands will open. The maximum length and width of the land pad stencil aperture should be equal to the solder resist opening minus an annular 0.2mm pull back in order to decrease the risk of shorting the center land to the lead lands when the part is pushed into the solder paste. 14 IRDC3865 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. 06/2011 15