quick start guide for demonstration circuit 568 dual synchronous, 600ma, 1.5mhz step-down dc/dc regulator 1 ltc3407 description demonstration circuit 568 is a dual synchronous, 600ma, 1.5mhz step-down dc/dc regulator featur- ing the ltc ? 3407. the dc568 has an input voltage range of 2.5v to 5.5v, and eith er output is capable of delivering up to 600ma of output current. in burst mode ? operation, the ltc3407 requires only 40 ua of quiescent current, and the dc568 provides higher efficiency at light load curre nts. in pulse skip mode, the dc568 provides lower output ripple voltage at light load currents. in either mode, the dc568 can provide up to 96% efficiency on either channel and consumes less than 1ua in shutdown. the ltc3407 comes in a small 10-pin ms10e package, which has an exposed pad on the bottom-side of the ic for bet- ter thermal performance. these features, plus the nominal operating frequency of 1.5mhz (allowing the exclusive use of low profile surface mount compo- nents), make the dc568 demo board an ideal circuit for use in battery-powered, hand-held applications. design files for this circui t board are av ailable. call the ltc factory. ltc and burst mode is registered tradem ark of linear technology corporation. table 1 . performance summary (t a = 25c) parameter condition value minimum input voltage 2.5v maximum input voltage 5.5v output voltage v out1 v in = 2.5v to 5.5v, i out1 = 0a to 600 ma 1.2v 2% 1.5v 2% 1.8v 2% typical output ripple v out1 v in = 5v, i out1 = 600 ma (20 mhz bw) 20mv p?p line 1% output regulation load 1% output voltage v out2 v in = 2.5v to 5.5v, i out2 = 0a to 600 ma 2.5v 2% typical output ripple v out2 v in = 5v, i out2 = 600 ma (20 mhz bw) 20mv p?p line 1% output regulation load 1% nominal switching frequency 1.5 mhz quick start procedure demonstration circuit 568 is easy to set up to evaluate the performance of the ltc3407. refer to figure 1 for proper measure ment 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
quick start guide for demonstration circuit 568 dual synchronous, 600ma, 1.5mhz step-down dc/dc regulator 2 directly across the v in or v out and gnd terminals. see figure 2 for proper scope probe technique. 1. connect the input power supply to the v in and gnd terminals on the left-side of the board. do not hot-plug v in or increase v in over the rated maximum supply voltage of 5.5v, or the part may be damaged. connect the loads between the v out and gnd terminals on the right-side of the board. refer to figure 1 for the proper measurement equipment setup. 2. before proceeding to operation, insert jumpers jp1 and jp2 into the off positions, jumper jp3 into the v out 1 voltage position of choice (1.2v, 1.5v, and 1.8v), and jumper jp4 into the desired mode of operation: pulse skip or burst mode. 3. apply 3.3v at v in . measure both v out s; they should read 0v. if desired, one can measure the shutdown supply current at this point. the supply current will be approxim ately 33 ua in shutdown, with roughly 32 ua due to the optional 100k pull- up resistor of the power-on reset (por) feature. this resistor can be removed, and the actual shutdown supply current can be measured, if the por feature is not required. 4. turn on v out 1 and v out 2 by changing jumpers jp1 and jp2 from the off position(s) to the on position(s). vary the i nput voltage from 2.5v to 5.5v and adjust each load current from 0 to 600ma. both output voltages should be regulating. 5. set the load current of both outputs between 200 ma and 600 ma, and measure both output ripple voltages; they should measure less than 20 mvac each. also, observe the voltage waveform at the switch node (pin 3) of each regulator. the switching frequencies should be between 1.2 mhz and 1.8 mhz (t = 0.833 us and 0.555 us), and each switch node waveform should be rectangular in shape. 6. to change the mode of operation, change jumpers jp1 and jp2 from the on position(s) to the off position(s). then change jumper jp4 to the alternative position. re -insert jumpers jp1 and jp2 into the on position(s). observe the voltage waveform at both switch nodes. when finished, insert jumpers jp1 and jp2 to the off position(s) and disconnect the power.
quick start guide for demonstration circuit 568 dual synchronous, 600ma, 1.5mhz step-down dc/dc regulator 3 figure 1. proper measurement equipment setup figure 2. measuring input or output ripple
quick start guide for demonstration circuit 568 dual synchronous, 600ma, 1.5mhz step-down dc/dc regulator 4
linear technology corporation ltc3407ems parts list DC568A rev 3 7/9/2003 item qty re f des c part number 1 3 cout1,cout2,cin cap, x5r 10uf 6.3v 20% 0805 taiyo yuden jmk212bj106mg 2 2 c2,c1 cap, npo 10pf 50v 10% 0402 avx 04025a100kat 3 0 c3,c4 cap, 0805 tbd 4 1 c5 cap, tant 47uf 10v 20% 6032 avx tajw476m010r 5 7 e1,e2,e3,e4,e5,e6,e7 turrets mill-max 2501-2 6 3 jp1,jp2,jp4 header, 3p 2mm comm con 2802s-03-g1 7 1 jp3 header, 3x2 2mm comm con 2202s-06g1 8 2 l1,l2 ind, 2.2uh taiyo yuden lqlbc25182r2m 10 3 r1,r3,r10 res, 4.7m ohms 5% 1/16w 0402 aac cr05-475jm 11 1 r2 res, 100k ohms 1% 1/16w 0402 aac cr05-1003fm 12 2 r4,r5 res, 604k ohms 1% 1/16w 0402 aac cr05-6043fm 13 1 r6 res, 887k ohms 1% 1/16w 0402 aac cr05-8873fm 14 1 r7 res, 280k ohms 1% 1/16w 0402 aac cr05-2803fm 15 1 r8 res, 402k ohms 1% 1/16w 0402 aac cr05-4023fm 16 1 r9 res, 301k ohms 1% 1/16w 0402 aac cr05-3013fm 17 1 u1 ic, ltc3407ems linear tech. ltc3407ems 1 of 1
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