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IRDC3473 1 user guide for IRDC3473 evaluation board the ir3473 supirbuck tm is an easy-to-use, fully integrated and highly efficient dc/dc voltage regulator. the onboard constant on time hysteretic controller and mosfets make ir3473 a space-efficient solution that delivers up to 6a of precisely controlled output voltage. ir3473 is housed in a 4mmx5mm qfn package. key features offered by ir3473 include: programmable switching frequency, soft start, temperature compensated over current protection, and thermal shutdown allowing a very flexible solution suitable for many different applications and an ideal choice for battery powered applications. additional features include pre-bias startup, a very precise 0.5v reference, forced continuous conduction mode option, over/under voltage protection, power good output, and enable input with voltage monitoring capability. this user guide contains the schematic, bill of materials, and operating instructions of the IRDC3473 evaluation board. detailed product specifications, application information and performance curves at different operating conditions are available in the ir3473 data sheet. board features sup ir buck tm description v in = +12v v cc = +5v v out = +1.05v i out = 0 to 6a f s = 300khz @ ccm l = 2.2h c in = 22f (ceramic 1210) + 68f (electrolytic) c out = 47f (ceramic 0805) + 150f (poscap) downloaded from: http:///
IRDC3473 2 connections and operating instructions 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) v out (+1.05v) pgnd (tp10) ground for v out en (tp4) enable input an input supply in the range of 8 to 19v should be connected from vin to pgnd. a maximum load of 6a may be connected to v out and pgnd. the connection diagram is shown in fig. 1, and the inputs and outputs of the board are listed in table 1. IRDC3473 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. the pcb is a 4-layer board. all layers are 1 oz. copper. ir3473 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 ir3473. to improve efficiency, the circuit board is designed to minimize the length of the on- board power ground current path. layout downloaded from: http:///
IRDC3473 3 connection diagram fig. 1: connection diagram of IRDC3473 evaluation board vin ground vout = +1.05v ground vcc = +5.0v en fccm control switch for: ground downloaded from: http:///
IRDC3473 4 fig. 2: board layout, top components pcb board layout fig. 3: board layout, bottom components downloaded from: http:///
IRDC3473 5 fig. 4: board layout, top layer pcb board layout fig. 5: board layout, bottom layer downloaded from: http:///
IRDC3473 6 fig. 6: board layout, mid-layer i fig. 7: board layout, mid-layer ii pcb board layout downloaded from: http:///
IRDC3473 7 fig. 8: schematic of the IRDC3473 evaluation board tp7 tp10 en vcc tp23 vouts tp24 pgnds c26 open c27 open vin c7open c8open c24 open c9 150uf c10 47uf c11 open c1 1uf r7 2.80k r8 2.55k c12 0.1uf pgood iset +3.3v vout vcc +3. 3v vin tp6 pgnds tp14 +3.3v u1 ir3473 3vcbp 8 fccm 1 ss 6 pgood 3 ff 15 gnd1 4 fb 5 gnd 17 nc1 7 iset 2 boot 14 vin 13 vcc 10 nc2 9 pgnd 11 phase 12 en 16 c4 0.22uf vcc tp4 en sw1 en / fccm 1 2 4 3 tp17 pgnd c20 0.1uf tp26 agnd vsw c21 1uf tp11 pgood r9open l1 2.2uh r6 open tp1 vins r4 15.8k r3200k c13 open c2 22uf c16 open + c368uf tp2 vin tp5 pgnd c14 open c17 open c18 open tp16 vcc fb r5 10k c15 open r10 open c6open tp18 voltage sense +vins 1 +vdd1s 2 +vdd2s 3 +vout1s 4 +vout2s 5 -vout2s 10 -vdd2s 8 -vout1s 9 -vins 6 -vdd1s 7 r110k fccm ir3473 +3.3v r11 20 c22 open tp25 b c25 1uf vout tp27 a +3.3v tp28 vid tp13 ss vsw r12 4.99 ss r210k c19 open q1open 2 1 3 pgnd vout r13 open c23 open downloaded from: http:///
IRDC3473 8 bill of materials qty ref designator v alue description manufacturer part number 3 c1, c21, c25 1.00uf capacitor, x7r, 1.00uf, 25v, 0.1, 0603 murata grm188r71e1 05ka12d 1 c10 47uf capacitor, 47uf, 6.3v, 805 tdk c2012x5r0j476m 2 c12, c20 0.100uf capacitor, x7r, 0.100uf, 25v, 0.1, 603 tdk c1608x7r1e104k 1 c2 22.0uf capacitor, x5r, 22.0uf, 16v, 20%, 1206 taiyo yuden emk316bj226ml-t 1 c3 68uf capacitor, electrolytic, 68uf, 25v, 0.2, smd panasonic eev-fk1e 680p 1 c4 0.22uf capacitor, x5r, 0.22uf, 10v, 0.1, 0603 tdk c1608x5r1a224k 1 c9 150uf capacitor, tantalum polymer, 150uf, 6.3v, 20%, 7343 sanyo 6tpc150m 1 l1 2.2uh inductor, ferrite, 2.2uh, 8.0a, 11.2mohm, smt cyntec pcmb065t-2r2 ms 1 r4 15.8k resistor, thick film, 15.8k, 1/10w, 0.01, 603 koa rk73h1j ltd1582f 3 r1, r2, r5 10.0k resistor, thick film, 10.0k, 1/10w, 0.01, 0603 koa rk73h1j1002f 1 r11 20 resistor, thick film, 20, 1/10w, 0.01, 603 koa rk73h1jltd20r0f 1 r12 4.99 resistor, thick film, 4.99, 1/8w, 0.01, 603 koa rk73h1j4r99f 1 r3 200k resistor, thick film, 200k, 1/10w, 0.01, 603 koa rk73h 1jltd2003f 1 r7 2.80k resistor, thick film, 2.80k, 1/10w, 0.01, 603 koa rk73h1j ltd2801f 1 r8 2.55k resistor, thick film, 2.55k, 1/10w, 0.01, 0603 koa rk73h1j 2551f 1 sw1 spst switch, dip, spst, 2 position, smt c&k components sd02 h0sk 1 u1 ir3473 4mm x 5mm qfn irf ir3473m trpbf downloaded from: http:///
IRDC3473 9 fig. 9: startup fig. 10: shutdown typical operating waveforms tested with demoboard shown in fig. 8, vin = 12v, vcc = 5v, vout = 1.05v, fs = 300khz, t a = 25 o c, no airflow, unless otherwise specified en pgood ss vout en pgood ss vout 5v/div 5v/div 1v/div 500mv/div 5ms/div 5v/div 5v/div 1v/div 500mv/div 500s/div fig. 11: dcm (i out = 0.1a) fig. 12: ccm (i out = 6a) vout phase i l vout phase i l 20mv/div 10v/div 500ma/div 5s/div 20mv/div 10v/div 5a/div 2s/div pgood vout pgood fb vout i l 5v/div 1v/div 500mv/div 2a/div 50s/div 5v/div 1v/div 500mv/div 10a/div 2ms/div ss fig. 13: over current protection (tested by shorting vout to pgnd) fig. 14: over voltage protection (tested by shorting fb to vout) i l downloaded from: http:///
IRDC3473 10 typical operating waveforms tested with demoboard shown in fig. 8, vin = 12v, vcc = 5v, vout = 1.05v, fs = 300khz, t a = 25 o c, no airflow, unless otherwise specified fig. 15: load transient 0-3a fig. 16: load transient 3-6a vout phase i l vout phase i l 50mv/div 10v/div 5a/div 100s/div 50mv/div 10v/div 2a/div 100s/div typical performance vin = 12v, vcc = 5v, vout = 1.05v, fs = 300khz, iout = 6a, t a = 25 o c, no airflow fig. 17: thermal image (ir3473: 70 o c, inductor: 49 o c, pcb: 38 o c) downloaded from: http:///
IRDC3473 11 fig. 18: efficiency vs. output current typical operating data vin = 12v, vcc = 5v, vout = 1.05v, fs = 300khz, iout = 0 ~ 6a, t a = 25 o c, no airflow, unless otherwise specified fig. 19: switching frequency vs. output current fig. 20: load regulation fig. 21: line regulation at 6a load 0 50 100 150 200 250 300 350 0123456 load current (a) switching frequency (khz) 45% 50% 55% 60% 65% 70% 75% 80% 85% 90% 0.01 0.1 1 10 load current (a) efficiency 1.040 1.045 1.050 1.055 1.060 1.065 1.070 1.075 1.080 1.085 1.090 0123456 load current (a) output voltage (v) 1.040 1.045 1.050 1.055 1.060 1.065 1.070 1.075 1.080 1.085 1.090 8 9 10 11 12 13 14 15 16 17 18 19 input voltage (v) output voltage (v) downloaded from: http:///
IRDC3473 12 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 fille t 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. downloaded from: http:///
IRDC3473 13 solder resist it is recommended that the lead lands are non solder ma sk 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. downloaded from: http:///
IRDC3473 stencil design the stencil apertures for the lead lands should be approxi mately 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 downloaded from: http:///
IRDC3473 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. 02/2011 15 downloaded from: http:///

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