1 description LT8304 micropower no-opto isolated flyback converter with 150v/2a switch demonstration circuit 2393a is a micropower no-opto isolated flyback converter featuring the lt ? 8304 . this demo circuit outputs 5.0v, and maintains tight regula - tion with a load current from 20ma up to 4.2a and over an input voltage from 18v to 72v. the output current capability increases with the input voltage, as shown in the performance summary table. the dc2393a needs less than 0.5% of its full output power as a minimum load to maintain good output voltage regu- lation. on the dc2393a, in order to avoid pre-loading, a 5.6v zener diode is placed between its v out + and v out C to serve as a minimum load. transformer leakage inductance causes a voltage spike on the primary side after the power switch turns off. to limit this leakage inductance spike within mosfet volt - age rating of 150v , an rc snubber and a tvs clamp are installed to damp the ringing and clamp the mosfet drain voltage to a safe level. the performance summary table summarizes the perfor - mance of the demo board at room temperature. the demo circuit can be easily modified for different applications with some pre-designed transformers. 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. performance summary the LT8304 is a simple to use monolithic micropower isolated flyback converter. by sampling the isolated output voltage directly from the primary-side flyback waveform, the part requires no third winding or opto-isolator for regulation. the output voltage is programmed with two external resistors and a third optional temperature compen - sation resistor. by integrating the loop compensation and soft-start inside, the part reduces the number of external components. boundary mode operation provides a small magnetic solution with excellent load regulation. low ripple burst mode ? operation maintains high efficiency at light load while minimizing the output voltage ripple. a 2a, 150v dmos power switch is integrated along with all the high voltage circuitry and control logic into a thermally enhanced 8-lead so package. the LT8304 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 2393a design files for this circuit board are available at http: //www.linear.com/demo/dc2393a specifications are at t a = 25c parameter conditions min typ max units input voltage 18 48 72 v output voltage v in = 18v C 72v i out = 20ma C 2a 4.75 5 5.25 v maximum output current v in = 18v 2 a v in = 24v 2.4 a v in = 48v 3.5 a v in = 72v 4.2 a output voltage ripple (peak CtoCpeak) v in = 48v, i out = 3.5a 100 mv minimum switching frequency i out = 0ma 11 khz efficiency v in = 24v, i out = 2.4a 83 % v in = 48v, i out = 3.5a 84 % dc2393af demo manual dc2393a
2 quick start procedure demonstration circuit 2393a is easy to set up to evalu - ate the performance of the LT8304. refer to figure 1 for proper measurement equipment setup and follow the procedure below: 1. with power off, connect the input power supply to the board through v in ( e1 ) and gnd ( e2 ) terminals. connect the load to the terminals v out + (e3) and v out C (e4) on the board. 2. turn on the power at the input. increase v in slowly to?18v. note: make sure that the input voltage is always within spec. to operate the board with higher input/output voltage, input capacitor, output capacitor and output diode with higher voltage ratings are needed. 3. check for the proper output voltages. the output should be regulated at 5.0v (5%). note: the LT8304 requires very small minimum load to maintain good output voltage regulation. a zener diode is placed on the output to clamp the voltage to 5.6v. this zener can be replaced with a 249? resistor at the trade off of lower efficiency. 4. once the proper output voltage is established, adjust the input voltage and load current within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. note : when measuring the input or output voltage ripples, 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 (e1) and gnd ( e2), or v out + (e3) and v out C (e4) terminals. see figure 2 for proper scope probe technique. figure 1. proper measurement equipment setup dc2393af demo manual dc2393a
3 figure 2. proper scope probe placement for measuring input or output ripple figure 3. typical efficiency and regulation curves figure 4. load transient responses (v in = 48v , load transient between 1a and 3.5a) input or output capacitor v in = 18v v in = 24v v in = 48v v in = 72v v in = 18v v in = 24v v in = 48v v in = 72v quick start procedure 5v out efficiency vs load current 5v out load and line regulation 4ms/div i out 2a/div v out 200mv/div dc2393af demo manual dc2393a 1 2 3 4 5 55 65 75 85 95 load current (a) output voltage (v) dc2393a f03b 0 1 2 3 4 5 4.90 5.00 5.10 5.20 5.30 dc2393a f04 load current (a) efficiency (%) dc2393a f03a 0
4 parts list item qty reference part description manufacturer/part number required circuit components 1 1 cin cap., alum 18f 80v sun electronic industries corporation, 80hv h18m 2 2 c1, c2 cap., 4.7f, x7s, 100v, 10% 1210 tdk, c3225x7s2a475k200ab 3 1 c3 cap., 1f, x7r, 25v, 10% 1206 murata, gr m31mr71e105ka01l 4 1 c4 cap., 270pf, c0g, 50v, 5% 0805 murata, gr m2165c1h271ja01d 5 4 c5, c6, c7, c8 cap., 100f, x5r, 6.3v, 20% 1210 murata, gr m32er60j107me20l 6 1 c9 cap., 4.7nf, x7r, 250v, 10% 1812 murata, ga343dr7gd472kw01l 7 1 d1 diode, sbr1045d1 , dpak diodes inc., sbr1045d1-13 8 1 z2 diode, cmhz5232b, sod-123 central semi., cmhz5232b 9 1 z1 diode, smbj51a, smb diodes inc., smbj51a-13-f 10 1 d2 diode, cmmr1u-02, sod-123f central semi., cmmr1u-02 11 1 r1 res., 402k, 1/10w, 1% 0603 vishay, crcw0603402kfkea 12 1 r2 res., 32.4k, 1/10w, 1% 0603 vishay, crcw060332 k4fkea 13 1 r3 res., 100?, 1w, 1% 2515 vishay, w sc2515100r0fea 14 1 r4 res., 309k, 1/8w, 1% 0805 vishay, crcw0805309kfkea 15 1 r5 res., 100k, 1/10w, 1% 0603 vishay, crcw0603100kfkea 16 1 r6 res., 10k, 1/10w, 1% 0603 vishay, crcw060310 k0fkea 17 1 t1 transformer, 750315125 wurth elektronik, 750315125 18 1 u1 ic LT8304 so8e linear tech., LT8304es8e#pbf hardware: for demo board only 1 4 e1 C e4 testpoint, turret, .094" pbf mill-max, 2501-2-00-80-00-00-07-0 dc2393af demo manual dc2393a
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 note: unless otherwise specified 1. all resistors and capacitors are 0603. * * see demo manual c3 1uf 25v 1206 r4 309k 0805 4.7nf c9 250v 1812 100uf c5 6.3v 1210 r2 32.4k z2 cmhz5232b + cin 18uf 80v 80hvh18m e2 gnd t1 750315125 5 10 7 6 9 3 e4 vout- d1 sbr1045d1 4 1 3 r6 10k r3 100 2515 r1 402k d2 cmmr1u-02 100uf c8 6.3v 1210 e1 vin 18v - 72v 100uf c6 6.3v 1210 e3 vout+ 5v r5 100k 270pf c4 0805 4.7uf 100v c2 1210 z1 smbj51a 4.7uf 100v c1 1210 u1 LT8304es8e vin 3 en/uvlo 1 rfb 6 gnd 4 sw 5 intvcc 2 rref 7 tc 8 gnd 9 100uf c7 6.3v 1210 dc2393af demo manual dc2393a
6 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com ? linear technology corporation 2016 lt 0516 ? 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 user s 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 dc2393af demo manual dc2393a
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