1 description LT8607 42v, 0.75a micropower synchronous step-down regulator demonstration circuit 2565a is a 42v, 0.75a micropower synchronous step-down regulator featuring the lt ? 8607. the demo board is designed for 5v output from a 5.5v to 42v input. the wide input range allows a variety of input sources, such as automotive batteries and indus - trial supplies. the LT8607 is a compact, high efficiency, high speed synchronous monolithic step-down switch - ing regulator that consumes less than 3a of quiescent current when output is regulated at 5v . top and bottom power switches, compensation components and other necessary circuits are inside of the LT8607 to minimize external components and simplify design. the sync pin on the demo board is grounded by default for low ripple burst mode ? operation. move jp1 to pulse skipping position can change the operation mode to pulse-skipping operation. once jp1 is on spread spec- trum position, v cc is applied to the sync pin for low emi spread spectrum operation. to synchronous to an external clock, move jp1 to sync and apply the external clock to the sync turret. figure 1 shows the efficiency of the circuit. l , lt, ltc, ltm, linear technology, the linear logo and burst mode are registered trademarks of analog devices, inc. all other trademarks are the property of their respective owners. p erformance s ummary the demo board has an emi filter installed. the radiated emi performances of the board (with emi filter) are shown in figure 2 and figure 3. the red lines in figure 2 and figure 3 are cispr25 class 5 peak limit. to use the emi filter, the input should be tied to v emi , not v in . an induc- tor l2 , which is a 0 jumper on the board by default now, can be added in the emi filter to further reduce the conducted emission. the LT8607 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 dc2565a. design files for this circuit board are available at http://www.linear.com/demo/dc2565a specifications are at t a = 25c symbol parameter conditions min typ max units v in input voltage range 5.5 42 v v out output voltage 4.8 5 5.2 v i out maximum output current 0.75 a f sw switching frequency 1.85 2 2.15 mhz efe efficiency at dc v in = 12v, i out = 0.75a 92.4 % dc2565af demo manual dc2565a
2 quick s tart p roce d ure dc2565 a is easy to set up to evaluate the performance of the LT8607. refer to figure 4 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. see figure 5 for the proper scope technique. 1. set an input power supply that is capable of 42v / 0.75a. then turn off the supply. 2. with power off, connect the supply to the input termi - nals v in and gnd. 3. turn on the power at the input. note : make sure that the input voltage never exceeds 42v. 4. check for the proper output voltage of 5v . turn off the power at the input. 5. once the proper output voltage is established, connect a variable load capable of sinking 0.75a at 5v to the output terminals v out and gnd. set the current for 0a. a. if efficiency measurements are desired, an ammeter can be put in series with the output load in order to measure the dc2565as output current. b. a voltmeter can be placed across the output ter - minals in order to get an accurate output voltage measurement. 6. turn on the power at the input. note : if there is no output, temporarily disconnect the load to make sure that the load is not set too high. 7. once the proper output voltage is established again, adjust the load and/or input within the operating range and observe the output voltage regulation, ripple volt - age, efficiency and other desired parameters. 8. an external clock can be added to the sync termi - nal when sync function is used ( jp1 on the sync position). please ensure that the chosen rt sets the LT8607 switching frequency to equal or below the low - est sync frequency. see the synchronization section in the data sheet. figure 1. efficiency vs load current at 2mhz switching frequency i out (a) 0 50 55 60 65 efficiency 70 75 100 95 90 85 80 0.15 0.3 0.45 0.6 0.75 dc2565a f01 v in = 12v v in = 24v dc2565af demo manual dc2565a
3 quick s tart p roce d ure frequency (mhz) 0 ?10 ?5 10 15 0 5 amplitude (dbuv/m) 20 25 50 vertical polarization peak detector 45 40 35 30 100 200 300 400 500 600 700 800 900 1000 dc2565a f02 class 5 peak limit fixed frequency spread spectrum mode frequency (mhz) 0 ?10 ?5 10 15 0 5 amplitude (dbuv/m) 20 25 50 45 40 35 30 100 200 300 400 500 600 700 800 900 1000 dc2565a f03 horizontal polarization peak detector class 5 peak limit fixed frequency spread spectrum mode figure 2. LT8607 demo circuit emi performance in cispr25 radiated emission test, antenna polarization: vertical (v in = 14v, v out = 5v, i out = 0.75a, 2mhz switching frequency) figure 3. LT8607 demo circuit emi performance in cispr25 radiated emission test, antenna polarization: horizontal (v in = 14v, v out = 5v, i out = 0.75a, 2mhz switching frequency) figure 4. proper measurement equipment setup figure 5. measuring output ripple v out gnd dc2565af demo manual dc2565a
4 p arts list item qty reference part description manufacturer/part number required circuit components 1 1 c2 cap., x7r, 4.7f, 50v, 10% 1206 murata, grm31cr71h475k 2 1 c4 cap., x7r, 0.22f, 16v, 10%, 0603 murata, grm188r71c224ka01d 3 1 c5 cap., c0g, 10pf, 25v, 5%, 0603 avx, 06033a100jat2a 4 1 c6 cap., x7r, 22f, 10v, 10%, 1206 murata, grm31cr71a226ke15l 5 1 c7 cap., x7r, 1.0f, 25v, 10%, 0603 murata, grm188r71e105ka12d 6 1 c8 cap., x7r, 0.01f, 16v, 10%, 0603 murata, grm188r71c103ka01d 7 1 l1 ind., 3.3h wurth electronics, 74438336033 8 1 r2 res., chip, 18.2k, 1/10w, 1%, 0603 vishay, crcw060318k2fkea 9 1 r3 res., chip, 49.9k, 1/10w, 1%, 0603 vishay, crcw060349k9fkea 10 2 r1, r4 res., chip, 1m, 1/10w, 1%, 0603 vishay, crcw06031m00fkea 11 1 r5 res., chip, 187k, 1/10w, 1%, 0603 vishay, crcw0603187kfkea 12 1 u1 ic, regulator, mse10 linear tech., LT8607emse#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, grm31cr71h475k 3 1 c9 cap., x7r, 4.7f, 16v, 10%, 0805 murata, grm21br71c475k73l 4 1 c11 cap., x7r, 1f, 50v, 10%, 0805 murata, grm21br71h105ka12l 5 2 c12, c13 cap., x7r, 0.1f, 50v, 10%, 0603 murata, grm188r71h104ka93d 6 1 fb1 ferrite bead 0805 tdk, mpz2012s331at000 7 1 l2 res., chip, 0, 3/4w, 2010 vishay, crcw20100000z0ef 8 0 r6 (opt.) res., 0603 hardware: for demo board only 1 9 e1-e9 testpoint, turret, 0.094" mill-max, 2501-2-00-80-00-00-07-0 2 1 e10 (opt.) testpoint, turret, 0.094" 3 1 jp1 double row header 2 4 0.079" wurth electronics, 62000821121 4 1 xjp1 shunt, 0.079" center wurth electronics, 60800213421 5 4 mh1-mh4 stand-off, nylon 0.50" tall wurth electronics, 702935000 dc2565af demo manual dc2565a
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 0603. notes: unless otherwise specified 1. all resistors are 0603. suncon 63ce22bs (2mhz) sync spread spectrum pulse skipping burst vout vcc vcc r2 18.2k e6 en/uv e5 sync e9 gnd l1 3.3h 74438336033 + c1 22f 63v r4 1.00m c6 22f 10v 1206 e7 tr/ss c11 1f 50v 0805 c8 0.01f c4 0.22f c10 4.7f 50v 1206 r3 49.9k e8 pg c7 1f r6 (opt) e3 vout 5v /0.75a jp1 1 2 3 5 7 4 6 8 e4 gnd l2 0 2010 r1 1.00m r5 187k c5 10pf e1 vemi 5.5v - 42v c3 4.7f 50v 1206 c13 0.1f 50v c2 4.7f 50v 1206 fb1 mpz2012s331at000 u1 LT8607emse vin 9 en/uv 10 sync 5 vcc 3 tr/ss 7 rt 4 fb 6 pg 8 sw 2 bst 1 gnd 11 c12 0.1f 50v c9 4.7f 16v 0805 e2 gnd e10 vin 5.5v - 42v dc2565af demo manual dc2565a
6 ? linear technology corporation 2017 lt 0517 ? printed in usa demonstration board important notice linear technology corporation (ltc) 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 ltc 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 party 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 ltc 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 whatsoeve r. ltc assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. ltc 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 ltc application engineer. mailing address: linear technology 1630 mccarthy blvd. milpitas, ca 95035 copyright ? 2004, linear technology corporation dc2565af demo manual dc2565a
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