1 description lt 8610ab 42v, 3.5a micropower synchronous step-down regulator demonstration circuit 2012 a is a 42v , 3.5 a micro - power synchronous step-down regulator featuring the lt ? 8610ab . the LT8610AB is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 2.5 a of quiescent current when output is regulated at 5 v. the efficiency of the circuit is greater than 90% at light load up to 1.5 a. this is a 10% improvement over competing parts. top and bottom power switches, compensation components and other necessary circuits are inside of the LT8610AB to minimize external components and simplify design. the sync pin on the demo board is grounded by default for low ripple burst mode operation. to synchronous 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 higher than 2 v or intv cc can be applied to the sync turret for pulse-skipping operation. figure 1 shows the efficiency of the circuit at 12v input. l , lt, ltc, ltm, linear technology 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 2 shows the thermal performance of the circuit. when running at input voltage greater than 30v, 3.5a output current and 2 mhz switching frequency, the tem - perature rise will be significant. either reducing the input voltage, the output current or the switching frequency will bring the temperature down to acceptable level without external cooling. the demo board has an emi filter installed. the board and the ic are designed to minimize conducted and radi - ated emi. the conducted emi performance of the board is shown on figure 3. the limit in figure 3 is en55022 class b, average. it shows the circuit passes the test with a wide margin. the LT8610AB data sheet gives a complete description of the part, operation and application information. the data sheet must be read in conjunction with this quick start guide for dc2012a. design files for this circuit board are available at http://www .linear.com/demo/dc2012a specifications are at t a = 25c symbol parameter conditions min typ max units v in * input supply range 5.5 42 v v out output voltage 4.8 5 5.2 v i out maximum output current 3.5 a f sw switching frequency 1.85 2 2.15 mhz efe efficiency at dc i out = 1a 91 % * refer to figure 2 to determine the maximum input voltage. if ic temperature exceeds target, reduce input voltage, output current or switching frequency. dc2012af demo manual dc2012a
2 quick s tart p roce d ure dc2012a is easy to set up to evaluate the performance of the LT8610AB. refer to figure 4 and figure 5 for proper measurement equipment setup and follow the procedure below: 1. with power off, connect the input power supply to v in and gnd. 2. with power off, connect the load v out and gnd. 3. check jp1 setting 4. turn on the power at the input. 5. carefully evaluate other design parameters as needed. figure 1. LT8610AB 12v in to 5v out efficiency at 2mhz switching frequency figure 2. LT8610AB case temperature rise. v out = 5v, t a = 25c figure 3. LT8610AB demo circuit conducted emi performance load current (a) efficiency (%) dc2012a f01 100 95 90 85 80 75 70 65 60 0 0.01 1 10 0.1 v in (v) case temperature rise (c) dc2012a f02 140 120 100 80 60 40 20 0 6 11 21 36 16 3126 2mhz, 3.5a 700khz, 3.5a 2mhz, 2.5a start 150khz res bw 9khz v bw 62khz stop 30mhz dbv dc2012a f03 70 60 30 20 50 40 10 0 ?10 ?20 ?30 en55022 class b dc2012af demo manual dc2012a
3 quick s tart p roce d ure figure 4. proper measurement equipment setup figure 5. measure output ripple dc2012af demo manual dc2012a
4 p arts list item qty reference part description manufacturer/ part number required circuit components 1 1 c2 cap., x7r, 2.2f, 50v, 10%, 1206 murata, gcj31cr71h225ka12l 2 1 c4 cap., x7r, 0.22f, 16v, 10%, 0603 avx , 0603yc224 kat 2a 3 1 c5 cap., c0g, 10pf, 25v, 10%, 0402 avx , 04023a100 kat 2a 4 2 c6, c14 cap., x7r, 47f, 10v, 10%, 1210 murata, grm32er71a476ke15l 5 1 c7 cap., x7r, 1.0f, 25v, 10%, 0603 murata, grm188r71e105ka12d 6 1 c8 cap., x7r, 0.1f, 16v, 10%, 0402 murata, grm155r71c104ka88d 7 1 l1 ind., 2.2h coilcraft, xal5030-222mec 8 1 r2 res., chip, 18.2k, 1/10w, 1% 0603 vishay, crcw060318k2fkea 9 1 r3 res., chip, 49.9k, 1/16w, 1% 0402 vishay, crcw040249k9fked 10 2 r1, r4 res., chip, 1m, 1/16w, 1% 0402 vishay, crcw04021m00fked 11 1 r5 res., chip, 243k, 1/16w, 1% 0402 vishay, crcw0402243kfked 12 1 u1 ic, LT8610ABemse#pbf mse16 linear tech, LT8610ABemse#pbf additional demo board circuit components 1 1 c1 cap., alum, 22f, 63v sun elect, 63ce22bs 2 2 c3, c10 cap., x7r, 4.7f, 50v, 10%, 1206 murata, grm31cr71h475ka12l 3 1 c9 cap., x7r, 1.0f, 16v, 10%, 0805 avx , 0805yc105 kat 2a 4 1 c11, c12 cap., x7r, 0.1f, 50v, 10%, 0402 tdk, c1005x7r1h104k 5 2 c13 cap., x7r, 0.1f, 50v, 10%, 0603 murata, gcj188r71h104ka 12d 6 1 fb 1 ferrite bead 0805 tdk, mpz2012s101 at 7 1 l2 ind., 4.7h vishay, ihlp2020bz-er4r7m01 8 0 r6 res., opt , 0402 opt hardware: for demo board only 1 9 e1-e9 testpoint, turret, .094" mill-max, 2501-2-00-80-00-00-07-0 2 1 jp1 header 1x3 079 samtec, tmm-103-02-l-s 3 1 xjp1 shunt, .079" center samtec, 2sn-bk-g 4 4 mh1-mh4 stand-off, nylon 0.50" tall keystone, 8833(snap on) dc2012af demo manual dc2012a
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 5 5 4 4 3 3 2 2 1 1 d d c c b b a a all capacitors are 0402. notes: unless otherwise specified 1. all resistors are 0402. suncon 63ce22bs (2mhz) * * refer to the demo manual for vin range. vout r6 opt r6 opt r5 243k r5 243k e2 gnd e2 gnd e9 gnd e9 gnd e6 en/uv e6 en/uv c14 47uf 10v 1210 c14 47uf 10v 1210 r1 1m r1 1m c2 2.2uf 50v 1206 c2 2.2uf 50v 1206 u1 LT8610ABemse u1 LT8610ABemse vin 5 vin 6 en/uv 4 sync 1 intvcc 13 tr/ss 2 rt 3 pgnd 7 gnd 8 fb 16 pg 15 bias 14 sw 11 sw 10 sw 9 bst 12 gnd 17 c12 0.1uf 50v c12 0.1uf 50v jp1 gnd sync jp1 gnd sync 1 3 2 c7 1uf 0603 25v c7 1uf 0603 25v e5 sync e5 sync c11 0.1uf 50v c11 0.1uf 50v l1 2.2uh xal5030-222mec l1 2.2uh xal5030-222mec c13 0.1uf 0603 50v c13 0.1uf 0603 50v r2 18.2k 0603 r2 18.2k 0603 fb1 fb1 e7 tr/ss e7 tr/ss c9 1uf 0805 16v c9 1uf 0805 16v r4 1meg r4 1meg c8 0.1uf c8 0.1uf l2 4.7uh l2 4.7uh c5 10pf c5 10pf c6 47uf 10v 1210 c6 47uf 10v 1210 c3 4.7uf 50v 1206 c3 4.7uf 50v 1206 e8 pg e8 pg + c1 22uf 63v + c1 22uf 63v r3 49.9k r3 49.9k e4 gnd e4 gnd c10 4.7uf 50v 1206 c10 4.7uf 50v 1206 c4 0.22uf 0603 16v c4 0.22uf 0603 16v e3 vout 5v / 3.5a e3 vout 5v / 3.5a e1 vin 5.5v - 42v e1 vin 5.5v - 42v dc2012af demo manual dc2012a
6 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com ? linear technology corporation 2013 lt 1113 ? 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 dc2012af demo manual dc2012a
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