1 description lt8650 s dual channel 42v , 4a synchronous step-down silent switcher with 6.2a quiescent current demonstration circuit 2407a is a dual channel 42v, 4a synchronous step-down silent switcher ? with 6.2a qui - escent current featuring the LT8650S . the lt8650 s is the second-generation silent switcher that minimizes emi and reduces pcb layout sensitivity. the demonstration circuit has two outputs : 5v and 3.3v . each output can source up to 4a continuous current at the same time. figure 1 shows the conducted emi measurements from 150khz to 30mhz. figure 2 shows the radiated emi mea - surements from 30mhz to 1ghz. all measurements were tested per cispr 25 specifications. the circuit passes the tests with wide margins. the sync pin on the demo board is grounded by default for low ripple burst mode ? operation. to synchronous to an external clock, move jp2 to fcm w/o ssm or l , lt, ltc, ltm, linear technology, the linear logo, silent switcher, and burs mode are registered trademarks of analog?devices, inc. all other trademarks are the property of their respective owners. performance summary sync position and apply the external clock to the sync turret. moving jp2 to fcm w/ssm enables spread spec - trum?mode. the demonstration circuit 2407a runs at 2mhz to mini - mize solution size. the efficiency is 92%. the ic tempera - ture rise is less than 50c when both channels run at full load, 4a each, at 2mhz. the LT8650S 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 demo circuit 2407a. design files for this circuit board are available at http: //www.linear.com/demo/dc2407a specifications are at t a = 25c symbol parameter conditions min typ max units v in input supply range 5.4 42 v v out1 output1 voltage 4.8 5 5.2 v i out1 maximum output1 current 4 a v out2 output2 voltage 3.168 3.3 3.432 v i out2 maximum output2 current 4 a f sw switching frequency 1.85 2 2.15 mhz efe efficiency at dc i out1 = 4a, i out2 = 4a , input voltage = 12v 92 % dc2407af demo manual dc2407a
2 typical performance characteristics figure 1. conducted emi performance figure 2: radiated emi performance (cispr 25 radiated emission test with class 5 peak limits) dc2407af demo manual dc2407a dc2407a demo board 9 12 15 18 21 24 27 30 ?40 ?30 (with emi filter installed) ?20 ?10 0 10 20 30 40 50 60 amplitude (dbv/m) 12v input to 5v output1 at 4a and 3.3v output2 at 4a, f sw = 2mhz dc2407 f01 dc2407a demo board (with emi filter installed) 12v input to 5v output1 at 4a and 3.3v output2 at 4a, f sw = 2mhz vertical polarization peak detector class 5 peak limit spread spectrum mode fixed frequency mode frequency (mhz) spread spectrum mode 0 100 200 300 400 500 600 700 800 900 fixed frequency mode 1000 ?5 0 5 10 15 20 25 30 35 frequency (mhz) 40 45 50 amplitude (dbv/m) dc2407 f02 0 3 6
3 demonstration circuit 2407a is easy to set up to evaluate the performance of the LT8650S. refer to figure 3 and figure 4 for proper measurement equipment setup and follow the procedure below. 1. with power off, connect the input power supply to vemi and gnd. 2. with power off, connect the loads to v out1 and gnd and v out2 and gnd. 3. turn on the power at the input. 4. carefully evaluate other design parameters as needed. quick start procedure figure 3. proper measurement equipment setup figure 4. measure output ripple vout gnd dc2407af demo manual dc2407a
4 parts list item qty reference part description manufacturer/part number required circuit components 1 2 c1, c4 cap., 10f, x5r, 50v, 10%, 1206 murata, gr m31cr61h106ka12l 2 2 c9, c10 cap., 4.7pf, c0g, 50v, 0.25pf, 0603 murata, gr m1885c1h4r7ca01d 3 2 c11, c14 cap., 4.7f, x5r, 25v, 10%, 0603 murata, gr m188r61e475ke11d 4 4 c12, c13, c33, c38 cap., 47f, x6s, 10v, 10%, 1206 murata, gr m31cc81a476me44l 5 2 c17, c18 cap., 10nf, x7r, 25v, 10%, 0603 murata, gr m188r71e103ka01d 6 3 c19, c20, c32 cap., 1f, x5r, 50v, 10%, 0603 murata, gr m188r61h105kaald 7 2 c28, c29 cap., 1f, x7s, 10v, 10%, 0402 murata, gc m155c71a105ke38d 8 2 l1, l2 inductor, 1.0h, xfl5030 coilcraft, xf l5030-102me 9 4 r1, r3, r5, r6 res., 1m, 1/10w, 1%, 0603 vishay, crcw06031 m00fkea 10 1 r7 res., 316k, 1/10w, 1%, 0603 vishay, crcw0603316kfkea 11 1 r8 res., 191k, 1/10w, 1%, 0603 vishay, crcw0603191kfkea 12 2 r11, r12 res., 100k, 1/10w, 1%, 0603 vishay, crcw0603100kfkea 13 1 r13 res., 15k, 1/10w, 1%, 0603 vishay, crcw060315 k0fkea 14 2 r14, r15 res., 0?, 1/10w, 0603 vishay, crcw06030000z0ea 15 1 u1 i.c. lt8650 sev, lga linear tech., LT8650Sev#pbf additional demo board circuit components 1 1 c2 cap., 22f, alum, 63v sun elect., 63 ce22bs 2 0 c5, c6, c30, c31 (opt) cap., option, 0402 3 0 c7, c8, c15, c16, c26, c27 (opt) cap., option, 0603 4 2 c21, c22 cap., 10f, x7r, 50v, 10%, 1210 murata, gr m32er71h106ka12l 5 4 c34-c37 cap., 0.1f, x7r, 50v, 10%, 0402 murata, gc m155r71h104ke02d 6 1 fb1 chip bead wurth elektronik, 74279226101 7 1 l3 inductor, 0.22h wurth elektronik, 744373240022 8 0 r2, r4, r9, r10 (opt) res, option 0603 hardware for demo board only 1 18 e1-e18 testpoint, turret, 0.094" pbf mill-max, 2501-2-00-80-00-00-07-0 2 1 jp1 header 3 pin 0.079 single row wurth elektronik, 62000311121 3 1 jp2 header 3 pin 0.079 double row wurth elektronik, 62000621121 4 2 xjp1, xjp2 shunt, 0.079" center wurth elektronik, 60800213421 5 4 (stand-off) stand-off, nylon 11.1mm wurth elektronik, 702934000 dc2407af demo manual dc2407a
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. schematic diagram 5 5 4 4 3 3 2 2 1 1 d d c c b b a a 1. all resistors are 0603. all capacitors are 0603. note: unless otherwise specified (fsw = 2mhz) out1 vbias fcm w / ssm fcm w/o ssm or sync burst suncon 63ce22bs c32 1uf c22 10uf 50v 1210 c19 1uf fb1 74279226101 c10 4.7pf e1 sync c33 c35 50v c15 opt c8 opt c20 1uf 50v e9 gnd jp2 1 2 3 5 6 4 e14 pg2 e18 vcc c5 opt 0402 r14 0 c38 c7 opt r8 191k c9 4.7pf c4 10uf 50v 1206 r7 316k e13 pg1 c18 10nf c37 50v jp1 1 2 3 c6 opt 0402 e8 vout2 3.3v / 4a e7 en2 c21 10uf 50v 1210 e16 temp e5 gnd c36 0.1uf 0402 e6 en1 c13 47uf 10v 1206 c29 1uf 0402 r4 opt e4 vemi 5.4v - 42v c14 4.7uf 25v c17 10nf r3 1m e15 clkout c27 opt c30 e17 vbias c34 0.1uf 0402 r13 15k LT8650Sev u1 vin1 4 vin1 5 vin2 7 vin2 8 en1 11 en2 12 bst1 24 bst2 18 rt 1 gnd 2 gnd 10 temp 13 pg1 14 pg2 15 sync 16 clkout 17 sw2 19 sw2 20 sw1 22 sw1 23 vcc 25 bias 26 vc2 32 fb2 31 ss2 30 ss1 29 fb1 28 vc1 27 gnd 33 gnd 34 gnd 35 gnd 36 gnd 37 gnd 38 r1 1m c11 4.7uf 25v r11 100k + c2 22uf 63v e11 ss1 l2 1.0uh r12 100k r9 opt e3 vout1 5v / 4a c1 10uf 50v 1206 r2 opt e2 gnd c31 c12 47uf 10v 1206 l3 0.22uh 744373240022 r6 1m c28 1uf 0402 e12 ss2 r15 0 r5 1m c16 opt r10 opt c26 opt l1 1.0uh e10 gnd vin1 vout1 vcc vout1 vin2 vout2 vout1 vcc vout2 vcc vcc vin2 vin1 dc2407af demo manual dc2407a
6 ? linear technology corporation 2017 lt 0917 ? 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 dc2407af demo manual dc2407a
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