rev 07/17/02 sp6641a/6641b evaluation board manual copyright sipex corporation sp6641a/6641b evaluation board schematics easy evaluation for the sp6641a/6641b single or dual cell alkaline to 3.3v or 5v output sp6641b provides up to 500ma output current with less than 50mvpp ripple high efficiency: up to 87% sot23-5 package & smt components for small, low profile power supply sp6641a/6641b low noise evaluation board l1 22uh ceramic 0.9v to 3.3v ceramic j1 1 2 3 shdn sp6641a 1 or 2 cell boost c3 1uf cer. u1 sp6641a 1 2 4 5 3 lx gnd shdn vbatt v out c1 22uf vout vbatt c2 22uf d1 schottky diode l2 sm bead u1 sp6641b 1 2 4 5 3 lx gnd shdn vbatt vout c1 100uf c2 330uf vfilter c3 1uf cer. l1 10uh 40mohm sp6641b 2 cell boost vbatt j1 1 2 3 d1 schottky diode c4 10uf ceramic 80mohm vout 1.8v to 3.3v shdn
2 using the evaluation board 1) powering up the sp6641a/6641b circuit the sp6641a/6641b evaluation board can be powered from inputs from a +0.9v to +3.3v fr om 1 or 2 alkaline cells or a power supply. connect w ith short leads directly to the ?vbatt? and ?gnd? posts. monitor the output voltage and connec t the load between the ?vout? post and the ?gnd? post. 2) using the j1 jumper: enabling the sp6641a/6641b output and using the shutdown mode the sp6641a/6641b output will be enabled if the j1 jumper is in the upper or pin 1 to 2 position. if j1 is in the pin 2 to 3 position, th e shutdown pin is brought to gnd, which puts the sp6641a/6641b in the low quiescent shutdown mode. 3) selecting the inductor in selecting an inductor, the saturation current sp ecified for the inductor needs to be greater then the sp6641a/6641b peak current to avoid satura ting the inductor, which would result in a loss in efficiency and could damage the inductor. t he sp6641a evaluation board uses a sumida cdrh5d28 22uh inductor with an isat value of 0.9a and a dcr of 0.095ohms, which easily handles the ipeak of 0.33a of the sp6641a an d will deliver high efficiencies. the sp6641b evaluation board uses a sumida cdrh5d28 10u h inductor with an isat value of 1.3a and a dcr of 0.065ohms, which easily handles the ip eak of 1.0a of the sp6641b and will deliver high efficiencies. other inductors could be selected provided their isat is greater than the ipeak of the sp6641a/6641b. 4) selecting the capacitors and filter components for the sp6641a, 22uf ceramic capacitors are used, which work well due to their inherently low esr, which will help produce low peak to peak outpu t ripple, and reduce high frequency spikes as well due to their low impedance. to obtain low p eak to peak ripple for the sp6641b, the output capacitor needs to have esr as low as 35 to 40 mohms and have a value of at least 100uf, for which the 330uf sanyo poscap was chosen for its 40mohms max. esr. other ultra low esr capacitors such the radial lead 100uf sanyo oscon or one of the new sm low esr polymer capacitors like the 100uf panasonic ud series could be used. this low ripple is obtained with no output spikes through the use of a lc filter consisting of small 0805 sm bead core l2 and 10uf ceramic capacitor c3. power supply data power supply data is provided for the ?b? version o f the sp6641b, which has a peak inductor current limit of 1a, with the 3.3v output option. f igure 1 shows the switching signals still present as 1.0v spikes on the 330uf capacitor c2. note tha t no output spikes are seen in figures 2 and 3 through the use of a small lc filter after the 33 0uf capacitor. the sp6641b?s low output ripple of 45 to 50mvpp is shown for a typical input of 2.0 v to 3.0v and an output load of 300ma.
3 figure 1. sp6641b switching signals on 330uf: vin = 2.0v, iout = 300ma, spikes = 1.0vpp figure 2. sp6641b output ripple: vin = 2.0v, iout = 300ma, vout ripple = 42mvpp, 51khz figure 3. sp6641b output ripple: vin = 3.0v, iout = 500ma, vout ripple = 54mvpp, 50khz
4 figure 4: sp6641a/6641b component placement figure 5: sp6641a/6641b pc layout top side figure 6: sp6641a/6641b pc layout bottom side
5 table1: sp6641a bill of materials table2: sp6641b bill of materials ordering information model temperature range package type sp6641akeb-3.3...........................?..-40 c to +85 c...............sp6641a 3.3v evaluation board sp6641aek-3.3.....................................- 40 c to +85 c......................................5-pin sot23 sp6641akeb-5.0.........................??? -40 c to +85 c...........sp6641a 5.0v evaluation board sp6641aek-5.0.....................................- 40 c to +85 c......................................5-pin sot23 sp6641bkeb-3.3.........................??? -40 c to +85 c...........sp6641b 3.3v evaluation board sp6641bek-3.3.....................................- 40 c to +85 c......................................5-pin sot23 sp6641bkeb-5.0.........................??? -40 c to +85 c...........sp6641b 5.0v evaluation board sp6641bek-5.0.....................................- 40 c to +85 c......................................5-pin sot23 ref. des. qty. manufacturer part number layout size comp onent vendor lxwxh 1 sipex corp. 146-6447-03 1"x1.5" sp6641 eval pc board sipex 978-667-8700 u1 1 sipex corp. sp6641bek-3.3 or 5.0 sot23-5 5-pin sot2 3 step-up dc/dc conv sipex c1 1 sanyo video 10tpa100m 7343 poscap 10v 100uf sm 0.08 0ohm max. esr sanyo 978-922-6573 c2 1 sanyo video 6tpb330m 7343 poscap 6.3v 330uf sm 0.04 0ohm max. esr sanyo 978-922-6573 c3 1 tdk corp c2012x5r1a105m 805 ceramic 10v 1uf sm 0.02 ohm esr tdk 847-803-6100 c4 1 tdk corp c3216x5r0j106m 1206 ceramic 6.3v 10uf sm 0 .005ohm esr tdk 847-803-6100 l1 1 sumida cdrh5d28-100 5.7x5.5x3 10uh, 1.3a, 0.065ohm, sm inductor sumida 847-956-0666 l2 1 panasonic exc-ml20a390u 805 sm bead core 100mhz 800- digi-key d1 1 zetex zchs2000 sot23-6 schottky diode 2a, 0.42v zet ex 631-360-2222 tp 5 mill-max 0300-115-01-4727100 .042 dia test point fe male pin 800-digi-key j1 1 sullins ptc36saan .23x.12 3-pin header 800-digi-key 1 sullins stc02syan .2x.1 shunt 800-digi-key ref. des. qty. manufacturer part number layout size component vend or lxwxh 1 sipex corp. 146-6447-03 1"x1.5" sp6641 eval pc board sipex 978-667-8700 u1 1 sipex corp. sp6641aek-3.3 or 5.0 sot23-5 5-pin sot2 3 step-up dc/dc conv sipex c1,c2 2 tdk corp c3225x5r0j226k 1210 ceramic 6.3v 22uf s m 0.005ohm esr tdk 847-803-6100 c3 1 tdk corp c2012x5r1a105k 805 ceramic 10v 1uf sm 0.02 ohm esr tdk 847-803-6100 l1 1 sumida cdrh5d28-220 5.7x5.5x3mm 22uh, 0.90a, 0.095o hm, sm inductor sumida 847-956-0666 d1 1 stmicroelectronics stps0520z sod-123 schottky diode 0.5a, 0.385v stmicro 847-585-3023 tp 5 mill-max 0300-115-01-4727100 .042 dia test point fe male pin 800-digi-key j1 1 sullins ptc36saan .23x.12 3-pin header 800-digi-key
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