1 description lt 8616 dual 42v synchronous monolithic step-down regulator with 6.5a quiescent current demonstration circuit 2169 a is a dual monolithic step- down dc/dc switching regulator featuring the lt ? 8616 . the LT8616 is a high efficiency, high speed, dual synchronous monolithic step-down switching regulator that consumes only 6.5 a of quiescent current with both channels enabled. the demo circuit is designed for 5v, 1.5 a and 3.3v, 2.5a outputs. both channels contain all switches and neces - sary circuitry to minimize the external components and solution size. fast minimum on time of 35 ns enables high v in to low v out conversion at high switching frequency. independent input voltage, feedback, soft-start and power good pins for each channel simplify complex power supply tracking/sequencing requirements. the inputs of the two channels are connected on the demo board by default. they can also be separated by removing the 0 resistor ( r13) from the board. each output can be independently disabled using its own en/uv pin, while v in1 must be connected to 3.4 v or above even if only channel 2 is in use. the demo board has an emi filter installed between v in2 and v emi . to use the emi filter, the inputs should be tied to v emi . the switching frequency of both channels can be pro- grammed either via an oscillator resistor or a common external clock up to 3 mhz.the sync pin on the demo board is grounded by default for burst mode ? operation. l , lt, ltc, ltm, linear technology, the linear logo and burst mode are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. p erformance s ummary to synchronize to an external clock, move jp1 to sync/ mode and apply the external clock to the sync/mode turret. the r t resistor ( r5) should be chosen to set the LT8616 internal switching frequency at least 20% below the lowest synchronization input. low ripple burst mode operation increases the efficiency at the light load while keeping the output ripple low. figure 1 and figure 2 show the demo board efficiency for each channel at 12 v input voltage in burst mode opera- tion. figure 3 shows the temperature rising on dc2169a demo board with different input voltages under full load conditions on both channels. the LT8616 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 dc2169a. the LT8616 is assembled in a 28- lead plastic tssop package. proper board layout is essential for both low emi operation and maximum thermal performance. see the data sheet sections for details. design files for this circuit board are available at http://www . linear.com/demo/dc2169a specifications are at t a = 25c symbol parameter conditions min typ max units v in1 channel 1 input supply range 5.8 42 v v in2 channel 2 input supply range 4.1 42 v v out1 channel 1 output voltage 4.88 5.02 5.15 v v out2 channel 2 output voltage 3.21 3.29 3.37 v f sw switching frequency r t = 14.7k 1.85 2.05 2.25 mhz i out1 channel 1 max output current 1.5 a i out2 channel 2 max output current 2.5 a efe efficiency at dc v in1 = v in2 = 12v, i out1 = 1.5a, i out2 = 2.5a 85.1 % dc2169af demo manual dc2169a
2 p erformance s ummary figure 1. LT8616 channel 1 efficiency vs load current load current (a) 50 efficiency (%) 70 100 60 80 90 0.6 dc2169a f01 1.5 0.30 0.9 1.2 f sw = 2mhz v in1 = 12v v out1 = 5v load current (a) 50 efficiency (%) 70 100 60 80 90 1 dc2169a f02 2.5 0.50 1.5 2 f sw = 2mhz v in2 = 12v v out2 = 3.3v input voltage (v) 20 temperature rising (c) 60 100 40 80 24 dc2169a f03 40 16 8 32 f sw = 2.05mhz v out1 = 5v, i out1 = 1.5a figure 2. LT8616 channel 2 efficiency vs load current figure 3. LT8616 temperature rising vs input voltage dc2169af demo manual dc2169a
3 dc2169a is easy to set up to evaluate the performance of the LT8616. 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. measure the input or output voltage ripple by touching the probe tip directly across the v in or v out and gnd terminals. see figure 5 for the proper scope technique. 1. place jp1 on the burst mode position. 2. with power off, connect the input power supply to v emi and gnd. make sure that the input voltage does not exceed 42v. 3. with power off, connect loads from v out1 to gnd, and v out2 to gnd. 4. turn on the power at the input. 5. check for the proper output voltages (5v and 3.3v). 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 voltages are 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/mode position). please make sure that the sync frequency is at least 20% higher than the set switching frequency. see the data sheet section synchronization. quick s tart p roce d ure v out gnd figure 4. proper measurement equipment setup figure 5. measuring input or output ripple dc2169af demo manual dc2169a
4 p arts list item qty reference part description manufacturer/ part number required circuit components 1 2 c2, c3 cap., x7r, 0.1f, 10v, 10% 0402 samsung, cl05b104kp5nnnc 2 1 c4 cap., x7r, 22f, 10v, 10% 1210 murata, grm32er71a226ke20l 3 1 c5 cap., x7r, 47f, 10v, 10% 1210 murata, grm32er71a476ke15l 4 2 c6, c7 cap., x7r, 0.01f, 10v, 10% 0603 avx , 0603zc103 kat 2a 5 2 c8, c9 cap., c0g, 4.7pf, 50v, 0.25pf 0603 avx , 06035a4r7 cat 2a 6 2 c10, c11 cap., x7r, 2.2f, 50v, 10% 1206 murata, grm31cr71h225ka88l 7 5 c12, c17, c19, c27, c28 cap., x7r, 1f, 10v, 10% 0603 avx , 0603zc105 kat 2a 8 4 c13, c14, c15, c16 cap., x7r, 0.1f, 50v, 10% 0402 tdk, c1005x7r1h104k050bb 9 1 l1 ind., 3.3h, xal4030 coilcraft, xal4030-332me 10 1 l2 ind., 2.2h, xfl4020 coilcraft, xfl4020-222me 11 6 r1, r3, r6, r8, r10, r11 res., chip, 1m, 0.1w, 1%, 0603 vishay, crcw06031m00fkea 12 1 r2 res., chip, 187k, 0.1w, 1%, 0603 vishay, crcw0603187kfkea 13 1 r4 res., chip, 316k, 0.1w, 1%, 0603 vishay, crcw0603316kfkea 14 1 r5 res., chip, 14.7k, 0.1w, 1%, 0603 vishay, crcw060314k7fkea 15 2 r7, r13 res., chip, 0, 0.1w, 0603 vishay, crcw06030000z0ea 16 1 u1 ic., LT8616efe tssop-28/eb linear tech., LT8616efe#pbf additional demo board circuit components 1 2 c1, c18 cap., alum., 22f, 63v, sun electronic industries corp., 63ce22bs 2 1 l3 chip bead, 30, mpz2012 tdk, mpz2012s300at 3 1 l4 ind., 0.22h, ihlp1212ab vishay, ihlp1212aberr22m11 4 1 c23 cap., x7r, 4.7f, 50v, 10% 1206 samsung, cl31b475kbhnnne 5 1 c24 cap., x7r, 10f, 50v, 10% 1210 murata, grm32er71h106ka12l 6 2 c25, c26 cap., x7r, 0.1f, 50v, 10% 0402 tdk, c1005x7r1h104k050bb 7 0 r9, r12 ( opt ) res., chip, 0603 hardware: for demo board only 1 16 e1-e16 testpoint, turret, .094" pbf mill-max, 2501-2-00-80-00-00-07-0 2 1 jp1 4 pin 0.079 single row header sullins, nrpn041paen-rc 3 1 xjp1 shunt, .079" center samtec, 2sn-bk-g dc2169af demo manual dc2169a
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 1. all resistors are in 0603 all capacitors are in 0603 note: unless otherwise specified 2mhz 63ce22bs 63ce22bs vin1 vin2 sync vout1 vin2 vout2 vout1 vout2 size date: ic no. rev. sheet of title: technology fax: (408)434-0507 milpitas, ca 95035 phone: (408)432-1900 1630 mccarthy blvd. ltc confidential-for customer use only customer notice linear technology has made a best effort to design a circuit that meets customer-supplied specifications; however, it remains the customer's responsibility to verify proper and reliable operation in the actual application. component substitution and printed circuit board layout may significantly affect circuit performance or reliability. contact linear technology applications engineering for assistance. this circuit is proprietary to linear technology and schematic supplied for use with linear technology parts. www.linear.com 4 demo circuit 2169a monday, january 19, 2015 1 1 dual 42v synchronous monolithic n/a LT8616efe step-down regulator with 6.5a quiescent current size date: ic no. rev. sheet of title: technology fax: (408)434-0507 milpitas, ca 95035 phone: (408)432-1900 1630 mccarthy blvd. ltc confidential-for customer use only customer notice linear technology has made a best effort to design a circuit that meets customer-supplied specifications; however, it remains the customer's responsibility to verify proper and reliable operation in the actual application. component substitution and printed circuit board layout may significantly affect circuit performance or reliability. contact linear technology applications engineering for assistance. this circuit is proprietary to linear technology and schematic supplied for use with linear technology parts. www.linear.com 4 demo circuit 2169a monday, january 19, 2015 1 1 dual 42v synchronous monolithic n/a LT8616efe step-down regulator with 6.5a quiescent current size date: ic no. rev. sheet of title: technology fax: (408)434-0507 milpitas, ca 95035 phone: (408)432-1900 1630 mccarthy blvd. ltc confidential-for customer use only customer notice linear technology has made a best effort to design a circuit that meets customer-supplied specifications; however, it remains the customer's responsibility to verify proper and reliable operation in the actual application. component substitution and printed circuit board layout may significantly affect circuit performance or reliability. contact linear technology applications engineering for assistance. this circuit is proprietary to linear technology and schematic supplied for use with linear technology parts. www.linear.com 4 demo circuit 2169a monday, january 19, 2015 1 1 dual 42v synchronous monolithic n/a LT8616efe step-down regulator with 6.5a quiescent current l2 2.2uh xfl4020-222me c26 0.1uf 0402 50v e7 sync/mode c24 10uf 50v 1210 e2 gnd c8 4.7pf e5 gnd jp1 pulse skipping burst mode sync/mode 4 pins 2mm ctrs. 1 3 2 4 e6 gnd c23 4.7uf 50v 1206 r2 187k e10 vin2 4.1v - 42v c19 1uf + c18 22uf 63v c11 2.2uf 50v 1206 c4 22uf 10v 1210 c16 0.1uf 50v 0402 e11 gnd c14 0.1uf 50v 0402 c27 1uf e1 vin1 5.8v - 42v pad150-094 e12 pg2 c2 0.1uf 10v 0402 e4 vout2 3.3v / 2.5a r6 1m c17 1uf r10 1m c6 0.01uf l3 30 ohm mpz2012s300at e8 ss2/tr2 u1 LT8616efe rt 15 fb2 26 boost2 6 pg1 11 fb1 14 sw2 3 pg2 2 vin1 19 tr/ss1 12 tr/ss2 28 intvcc 21 sw1 9 gnd 29 sync/mode 17 boost1 8 vin2 24 nc 7 en/uv1 16 enuv2 1 bias 22 nc 18 nc 23 nc 20 nc 25 fb2 27 sw2 4 sw2 5 fb1 13 sw1 10 e3 vout1 5v / 1.5a r9 opt c28 1uf c3 0.1uf 10v 0402 c12 1uf c15 0.1uf 50v 0402 r4 316k e9 ss1/tr1 r1 1m l1 3.3uh xal4030-332me r5 14.7k c13 0.1uf 50v 0402 l4 0.22uh ihlp1212aberr22m11 e15 en1 r8 1m + c1 22uf 63v e16 vemi e14 pg1 c10 2.2uf 50v 1206 c7 0.01uf c5 47uf 10v 1210 r13 0 r7 0 r11 1m e13 en2 r3 1m c9 4.7pf r12 opt c25 0.1uf 0402 50v dc2169af demo manual dc2169a
6 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com ? linear technology corporation 2015 lt 0515 ? 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 dc2169af demo manual dc2169a
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