QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1381A LOW QUIESCENT CURRENT, DUAL OUTPUT SYNCHRONOUS BUCK CONVERTER

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1 QK GD F DM W Q, D YH BK D H/H Demonstration circuit is a ow Quiescent urrent, Dual utput ynchronous Buck onverter featuring the H/H. he circuit is single sided layout, while the package style for the /H is a lead (mm x mm) QF package he main features of the board include rail tracking (H only), an internal linear regulator for bias, pins for each output, a GD signal (H only) and a Mode selector that allow the converter to run in M, pulse skip or Burst Mode operation. ynchronization to an external clock is also possible. wo versions of the board are available. D is for the H, while the DB is for the H. he H offers lower quiescent current and smaller burst mode ripple, while the H offers latchoff protection and increased burst mode efficiency. he wide input voltage range of. to is suitable for automotive or other battery fed application where low quiescent current is important. he H and H datasheets give a complete description of these parts, operation and application information. he datasheets must be read in conjunction with this quick start guide for demo circuit. Design files for this circuit board are available. all the factory. Burst Mode is a trademark of inear echnology orporation able. erformance ummary ( = ) M D Minimum nput oltage. # Maximum nput oltage utput oltage =. to, = to. ±% utput oltage = 9 to, = to. ±% ominal witching Frequency fficiency, D/B ee Figures to for efficiency curves khz = = =., = 9.% ypical 9.% ypical =., = 9.% ypical 9.% ypical Measured at bulk output capacitor # Minimum input voltage required for.out regulation is 9in QK D Demonstration circuit is easy to set up to evaluate the performance of the H/H. efer to Figure for proper measurement equipment setup and follow the procedure below: : 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 probing directly across the bulk in or out capacitor. ee Figure for proper scope probe technique.. lace jumpers in the following positions:

2 QK GD F DM W Q, D YH BK J J J J J Burst Mode n n. With power off, connect the input power supply to in and GD.. urn on the power at the input. : Make sure that the input voltage does not exceed. out. heck for the proper output voltages. out =. to., out =. to. : f there is no output, temporarily disconnect the load to make sure that the load is not set too high.. nce the proper output voltages are established, adjust the loads within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters.. Different operating modes can be evaluated by changing position of jumper J. out load out in in in supply out load out out Figure. roper Measurement quipment etup

3 QK GD F DM W Q, D YH BK Figure. Measuring nput or utput ipple Directly cross Bulk apacitor KG Demonstration circuit is setup for independent soft start without tracking. he soft start ramprate is determined by the value of the capacitors and. his board can also be operated in coincident tracking mode with either output as master or both can slave an external ramp efer to able for tracking options and to the data sheet for more details. able. utput racking ptions K/ JM M FG J J K K oft tart Without racking out o connection / Don t care out o connection / Don t care oincident racking: out tracking xternal amp K onnect external ramp out tracking xternal amp K onnect external ramp out tracking out K o connection / Don t care onnect to out out tracking out K onnect to out o connection / Don t care

4 QK GD F DM W Q, D YH BK D D G D G he D sense circuit uses the resistive voltage drop across the inductor to estimate the current. n contrast to the traditional sense resistor current feedback, the D sensing circuit offers lower cost and higher efficiency, but results in less accurate current limit due to the large variation of the inductor D resistance. Furthermore, this indirect current sensing method cannot detect inductor saturation and requires the use of soft saturating inductors (such as powder iron) able. D sensing component selection M WK resulting in increased core losses or hard saturating inductors (such as ferrite) with sufficiency high current ratings resulting in increased inductor size. For modifying the demo board for D sensing, please refer to able. full load efficiency improvement of between.%.% is still possible with optional D sensing, but since the inductors are ferrite based, short circuit performance may be compromised. D WK out, 9 = pen, = hort =.kω =.kω 9 = Ω =.µf out, = pen, = hort =.9kΩ =.kω = Ω =.µf FQY YHZ Demonstration circuit s Mode selector allows the converter to run in M, pulse skip or Burst Mode operation by changing position of jumper J. For synchronizing to an external clock source, remove jumper J entirely and apply the external clock signal to the /MD pin. lease refer to datasheet for details on external clock signal requirements.

5 QK GD F DM W Q, D YH BK H Figure. ypical fficiency vs. oad urrent for board in,.out and.out H Figure. ypical fficiency vs. oad urrent for board in,.out and.out

6 QK GD F DM W Q, D YH BK H Figure. ypical fficiency vs. oad urrent for B board in,.out and.out H Figure. ypical fficiency vs. oad urrent for B board in,.out and.out

7 QK GD F DM W Q, D YH BK D G: : WH D G MMD, H D, D FF,9, D.uH DM H J. /. J uf uf. GD 9 GD J D. G.uF.uF J D GD H G ] [ GD Q BZ9 9 K K Q BZ9 9 pf pf.uf D MDH BG H.uH J. X..uF. / uf pf. DM J uf GD uf GD [] pf.k K W G.uF W H pf 9 H K/ FQ /MD GD GD K M HMD K/ H 9 pf 9 GD GD G W B BG GD X BG B W G FB FB 9 9K % G D MDH pf Q BZ9 K % H.uF H Q BZ9.K % pf K % pf.uf BG 9 > K J K.K.K.uF 9 M D.uF J M K B MD [] J J FF FF 9 [] K H J 9 9 X K J.uF K 9.K % K % H G F ] [ K. K. H GD GD K K / MD K GD X MX K ] [ Y B