quick start guide for demonstration circuit 649 telecom dc/dc converter 1 ltc3803 description demonstration circuit 649 is a telecom isolated dc/dc converter featuring the ltc ? 3803 constant frequency current mode flyback controller. the dc649 converts an isolated 36v to 72v input and provides 2a of output curre nt at 5v. the 200khz constant frequency operation is maintained down to very light load to reduce low frequency noise generated over a wide range of load current. the converter provides high output voltage accuracy (typically 2%) over wide load range with no minimum load requirement. the dc649 also provides non-isolated design by removing opto coupler and lt ? 1431 circuit. the demonstration circuit can be easily modified to generate different output voltages up to 15v. the output current is limited by total output power to 10w. higher output voltages and currents can be achieved by changing the mosfet, transformer and output capacitors. please consult ltc factory for details. the dc649 has a small circuit footprint. it is a high performance and cost effective solution for telecom, automotive and power over ethernet applications. design files for this circuit board are available. call the ltc factory. ltc and lt are registered trademarks of linear technology corporation. quick start procedure demonstration circuit 649 is easy to set up to evaluate the performance of the ltc3803. for proper measurement equipment setup refer to figure 1 and follow the procedure below: note: when measuring the input or output voltage ripple, care must be taken to minimize the length of the oscilloscope probe ground lead. measure the input or output voltage rippl e by connecting the probe tip directly across the v in or v out and gnd terminals as shown in figure 2. 1. with power off, connect the input power supply to +vin and -vin. 2. turn the input power source on and slowly increase the input voltage. be careful not to exceed 72v. note: make sure that the input voltage v in does not exceed 72v. if higher operating voltage is required, power components with higher voltage ratings should be used. 3. check for proper output voltage. vout=5v. if there is no output, temporarily disconnect the load to make sure that the load is not set too high. 4. to shut the converter down, pull the shut down pin below 0.28v. note: do not apply voltage to shdn pin. 5. once the proper output voltage is established, adjust the load within 2a range and observe the output voltage regulation, ripple voltage, efficiency and other parameters.
quick start guide for demonstration circuit 649 telecom dc/dc converter 2 figure 1. proper measurement equipment setup figure 2. measuring input or output ripple
quick start guide for demonstration circuit 649 telecom dc/dc converter 3
linear technology corporation ltc3803es6 bill of material demo bd. #649a 6/23/04 item qty reference part description manufacture / part # 1 1 cin1 cap., x7r, 1uf, 100v, 10% 1210 tdk, c3225x7r2a105k 2 3 c01,c02,c03 cap., x5r, 100uf, 6.3v, 20% 1210 tdk, c3225x5r0j107m 3 1 c1 cap., x7r, 1uf, 10v, 20% 0805 taiyo yuden, lmk212bj105mg 4 1 c2 cap., x7r, 0.047uf, 10v, 10% 0805 avx, 0805zc473kat2a 5 1 c3 cap., x7r, 4.7nf, 16v, 10% 0805 avx, 0805yc472kat2a 6 0 c4 (opt.) cap., 470pf 0805 7 1 c5 cap., x5r, 1uf, 16v, 20% 0805 taiyo yuden, emk212bj105mg 8 1 c10 cap., x7r, 2200pf, 250v, 10% 1812 murata, ga343dr7gd222kw01l 9 0 c11 (opt.) cap., x7r, 22pf, 0805 avx, 0805yc222kat2a 10 1 c12 cap., c0g, 150pf, 200v, 5% 1206 avx, 12062a151jat2a 11 1 d1 schottky barrier rec., ups840 ,powermite microsemi., ups840 12 1 d2 diode, 9.1v, pdz-9.1b, sod-323 philips, pdz9.1b 13 2 d3,d4 high speed diode, bas516 sod523 philips, bas516 14 5 e1,e2,e3,e4,e5 turret, mill-max, 2501-2 15 1 q1 n-chan. mosfet, fdc2512, super-sot-6 fairchild, fdc2512 16 1 q2 tran npn, mmbta42, sot23 diodes inc., mmbta42-7 17 1 rcs res., chip, 0.068, 1% 1206 thin film., rl1632r-r068-f 18 1 rs1 res., chip, 4.7k, 5% 0805 aac, cr10-472jm 19 2 r5,r7 res., chip, 10k, 1% 0805 aac, cr10-1002fm 20 1 r1 res., chip, 220k, 5% 0805 aac, cr10-224jm 21 1 r2 res., chip, 4.75k, 1% 0805 aac, cr10-4751fm 22 0 r3 (opt.) res., chip, 82k, 0805 23 1 r4 res., chip, 8.06k, 1% 0805 aac, cr10-8061fm 24 0 r6 (opt.) res., chip, 42k, 1206 25 1 r8 res., chip, 470k, 5% 0805 aac, cr10-474jm 26 1 r18 res., chip, 220ohm, 5% 0805 aac, cr10-221jm 27 1 r19 res., chip, 100, 5% 0805 aac, cr10-101jm 28 1 r20 res., chip, 100k, 5% 1206 aac, cr18-104jm 29 1 r21 res., chip, 220, 5% 1206 aac, cr18-221jm 30 1 r22 res., chip, 6.8k, 5% 0805 aac, cr10-682jm 31 1 t1 transformer, ctx02-15242 cooper., ctx02-15242 32 1 u1 i.c., ltc3803es6, sot23-6 linear., ltc3803es6 33 1 u2 i.c., lt1431cs8, so8 linear., lt1431cs8 34 1 u3 optocouplers, moc207-m fairchild, moc207m 35 1 printed circuit board fab., demo circuit 649a 36 2 stencil stencil page 1 - of - 1
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