1 description lt 8612 42v, 6a micropower synchronous step-down regulator demonstration circuit 2010 a is a 42v, 6 a micropower synchronous step-down regulator featuring the lt ? 8612. the demo board is designed for 5 v output from a 5.8v to 42 v input. the wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. the LT8612 is a compact, high efficiency, and high speed synchronous monolithic step-down switching regulator. the integrated power switches and inclusion of all necessary circuitry reduce the components count and solution size. ultralow 3 a quiescent current in burst mode ? operation achieves high efficiency at very light loads. fast minimum on-time of 40 ns enables high v in to low v out conversion at high frequency. the LT8612 switching frequency can be programmed either via oscillator resistor or external clock over a 200khz to 2.2 mhz range. the sync pin on the demo board is grounded by default for low ripple burst mode operation. to synchronize to an external clock, move jp1 to sync and apply the external clock to the sync turret. once jp1 is on sync position, a dc voltage of 3 v or higher can be applied to the sync turret for pulse -skipping operation. l , lt, ltc, ltm, linear technology, burst mode and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. p erformance s ummary figure 1 shows the efficiency of dc2010a circuit at 12v input. figure 2 shows the LT8612 temperature rising on dc2010a demo board under different load conditions. the rated maximum load current is 6 a, while derating is necessary for certain v in and thermal conditions. the demo board has an emi filter installed. to use the emi filter, the input should be tied to vemi terminal, not vin terminal. the LT8612 data sheet gives a complete description of the part, operation and application information. the data sheet must be read in conjunction with this demo manual for demo circuit 2010 a. the LT8612 is assembled in a 3mm 6 mm plastic qfn package with exposed pads for low thermal resistance. proper board layout is essential for minimum emi and maximum thermal performance. see the data sheet section pcb layout and high temperature considerations. design files for this circuit board are available at http://www . linear.com/demo/dc2010a specifications are at t a = 25c symbol parameter conditions min typ max units v in input supply range 5.8 42 v v out output voltage 4.875 5 5.125 v i out maximum output current derating is necessary for certain v in and thermal conditions 6 a f sw switching frequency 665 700 735 khz efe efficiency at dc v in = 12v , i out = 3a 94.3 % dc2010afa demo manual dc2010a
2 quick s tart p roce d ure demonstration circuit 2010 a is easy to set up to evalu- ate the performance of the LT8612. refer to figure 3 for proper measurement equipment setup and follow the procedure below: note. when measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. measure the input or output voltage ripple by touching the probe tip directly across the vin or vout and gnd terminals. see figure 4 for the proper scope technique. 1. place jp1 on gnd position. 2. with power off, connect the input power supply to vin and gnd. 3. with power off, connect the load from vout to gnd. 4. turn on the power at the input. note. make sure that the input voltage does not exceed 42v. 5. check for the proper output voltage (vout = 5v). note. if there is no output, temporarily disconnect the load to make sure that the load is not set too high or is shorted. 6. once the proper output voltage is established, adjust the load within the operating ranges and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 7. an external clock can be added to the sync terminal when sync function is used ( jp1 on the sync posi- tion). please make sure that r t should be chosen to set the LT8612 switching frequency equal to or below the lowest sync frequency. see the data sheet section synchronization. figure 1. efficiency vs load current (using vin terminal) figure 2. temperature rising vs input voltage description load current (a) 0 efficiency (c) 100 95 85 90 80 70 75 65 60 21 4 dc2010a f01 6 3 5 v in = 12v v out = 5v f sw = 700khz sync = gnd input voltage (v) 6 temperature rising (c) 80 70 50 60 40 20 30 10 0 1812 30 dc2010a f02 42 24 36 i out = 5a i out = 4a i out = 5.5a i out = 4.5a i out = 6a v out = 5v f sw = 700khz dc2010afa demo manual dc2010a
3 quick s tart p roce d ure figure 3. proper measurement equipment setup figure 4. measuring output ripple dc2010afa demo manual dc2010a
4 p arts list item qty reference part description manufacturer/ part number required circuit components 1 1 c2 cap., x5r, 10f, 50v, 10% 1210 murata, grm32er61h106ka12l 2 1 c8 cap., x7r, 0.1f, 25v, 10% 0603 murata, grm188r71e104ka01d 3 1 c5 cap., c0g, 10pf, 25v, 5% 0603 avx , 06033a100 jat 2a 4 1 c6 cap., x5r, 100f, 10v, 20% 1210 samsung, cl32a107mpvnnne 5 2 c7, c9 cap., x7r, 1.0f, 25v, 10% 0603 murata, grm188r71e105ka12d 6 2 c4, c15 cap., x7r, 0.1f, 50v, 10% 0402 tdk, c1005x7r1h104k 7 1 l1 ind., 3.3h, ihlp2525ez-01 vishay, ihlp2525ezer3r3m01 8 2 r1, r3 res., chip., 100k, 1/10w, 1% 0603 vishay, crcw0603100kfkea 9 1 r2 res., chip., 60.4k, 1/10w, 1% 0603 vishay, crcw060360k4fkea 10 1 r4 res., chip., 1m, 1/10w, 1% 0603 vishay, crcw06031m00fkea 11 1 r5 res., chip., 243k, 1/10w, 1%, 0603 vishay, crcw0603243kfkea 12 1 u1 ic, regulator, 28-qfn, ude linear tech., LT8612eude#pbf additional demo board circuit components 1 1 c1 cap., alum 22f, 63v sun elect., 63ce22bs 2 2 c3, c10 cap., x5r, 10f, 50v, 10% 1210 murata, grm32er61h106ka12l 3 1 c14 cap., x7r, 0.1f, 50v, 10% 0402 tdk, c1005x7r1h104k 4 0 c11 ( opt ) cap., 0603 5 1 l2 ferrite bead 100 8a smd 1812 wurth, 74279226101 6 1 l3 ind., 6.8h, ihlp3232dz-11 vishay, ihlp3232dzer6r8m 11 7 0 r 6 ( opt ) res., 0402 8 1 r7 res., chip., 0, 1/10w, 1%, 0603 vishay, crcw06030000z0ea hardware: for demo board only 1 10 e1-e10 testpoint, turret, 0.094" mill-max, 2501-2-00-80-00-00-07-0 2 1 jp1 header, 3 pin 0.079" single row sullins, nrpn031paen-rc 3 1 xjp1 shunt, 0.079" center samtec, 2sn-bk-g 4 4 mh1-mh4 stand-off, nylon 0.50" tall keystone, 8833(snap on) dc2010afa demo manual dc2010a
5 information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. s chematic diagram vin vout vin all capacitors are 0603. notes: unless otherwise specified 1. all resistors are 0603. suncon 63ce22bs * see demo manual * l2 1812 we 74279226101 l2 1812 we 74279226101 r5 243k r5 243k c9 1uf c9 1uf e2 gnd e2 gnd e9 gnd e9 gnd c11 opt c11 opt e6 en/uv e6 en/uv c15 0.1uf 0402 c15 0.1uf 0402 l3 ihlp3232dzer6r8m11 6.8uh l3 ihlp3232dzer6r8m11 6.8uh r1 100k r1 100k c2 10uf 50v 1210 c2 10uf 50v 1210 u1 LT8612eude u1 LT8612eude vin 5 vin 6 en/uv 4 sync 1 intvcc 21 tr/ss 2 rt 3 pgnd 8 fb 24 pg 23 bias 22 sw 17 sw 16 sw 15 bst 20 gnd 29 vin 7 pgnd 9 pgnd 10 sw 18 sw 19 gnd 11 gnd 12 gnd 13 gnd 14 nc 26 nc 27 nc 28 nc 25 c10 10uf 50v 1210 c10 10uf 50v 1210 jp1 gnd sync jp1 gnd sync 1 3 2 c7 1uf 25v c7 1uf 25v e5 sync e5 sync l1 3.3uh ihlp2525ezer3r3m01 l1 3.3uh ihlp2525ezer3r3m01 r2 60.4k 700khz r2 60.4k 700khz e7 tr/ss e7 tr/ss r4 1meg r4 1meg c8 0.1uf c8 0.1uf e10 vemi e10 vemi c5 10pf c5 10pf r7 0 r7 0 c6 100uf 10v 1210 c6 100uf 10v 1210 e8 pg e8 pg + c1 22uf 63v + c1 22uf 63v c3 10uf 50v 1210 c3 10uf 50v 1210 r3 100k r3 100k e4 gnd e4 gnd r6 opt r6 opt c4 0.1uf 0402 c4 0.1uf 0402 e3 vout 5v / 6a e3 vout 5v / 6a c14 0.1uf 0402 50v c14 0.1uf 0402 50v e1 vin 5.8v - 42v e1 vin 5.8v - 42v dc2010afa demo manual dc2010a
6 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com linear technology corporation 2014 lt 0915 rev a ? printed in usa demonstration board important notice linear technology corporation ( lt c ) provides the enclosed product(s) under the following as is conditions: this demonstration board ( demo board) kit being sold or provided by linear technology is intended for use for engineering development or evaluation purposes only and is not provided by lt c for commercial use. as such, the demo board herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. as a prototype, this product does not fall within the scope of the european union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. if this evaluation kit does not meet the specifications recited in the demo board manual the kit may be returned within 30 days from the date of delivery for a full refund. the foregoing warranty is the exclusive warranty made by the seller to buyer and is in lieu of all other warranties, expressed, implied, or statutory, including any warranty of merchantability or fitness for any particular purpose. except to the extent of this indemnity, neither p arty shall be liable to the other for any indirect, special, incidental, or consequential damages. the user assumes all responsibility and liability for proper and safe handling of the goods. further, the user releases lt c from all claims arising from the handling or use of the goods. due to the open construction of the product, it is the users responsibility to take any and all appropriate precautions with regard to electrostatic discharge. also be aware that the products herein may not be regulatory compliant or agency certified (fcc, ul, ce, etc.). no license is granted under any patent right or other intellectual property whatsoever. lt c assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. lt c currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. please read the demo board manual prior to handling the product . persons handling this product must have electronics training and observe good laboratory practice standards. common sense is encouraged. this notice contains important safety information about temperatures and voltages. for further safety concerns, please contact a lt c applica- tion engineer. mailing address: linear technology 1630 mccarthy blvd. milpitas, ca 95035 copyright ? 2004, linear technology corporation dc2010afa demo manual dc2010a
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