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? semiconductor components industries, llc, 2003 june, 2003 - rev. 4 1 publication order number: ncp1421/d ncp1421 600 ma sync-rect pfm step-up dc-dc converter with true-cutoff and ring-killer ncp1421 is a monolithic micropower high-frequency step-up switching converter ic specially designed for battery-operated hand-held electronic products up to 600 ma loading. it integrates sync-rect to improve efficiency and to eliminate the external schottky diode. high switching frequency (up to 1.2 mhz) allows for a low profile, small-sized inductor and output capacitor to be used. when the device is disabled, the internal conduction path from lx or bat to out is fully blocked and the out pin is isolated from the battery. this true-cutof f function reduces the shutdown current to typically only 50 na. ring-killer is also integrated to eliminate the high-frequency ringing in discontinuous conduction mode. in addition to the above, low-battery detector, logic-controlled shutdown, cycle-by-cycle current limit and thermal shutdown provide value- added features for various battery- operated applications. with all these functions on, the quiescent supply current is typically only 8.5 a. this device is available in the compact and low profile micro8 package. features ? high efficiency: 94% for 3.3 v output at 200 ma from 2.5 v input 88% for 3.3 v output at 500 ma from 2.5 v input ? high switching frequency, up to 1.2 mhz (not hitting current limit) ? output current up to 600 ma at v in = 2.5 v and v out = 3.3 v ? true-cutof f function reduces device shutdown current to typically 50 na ? anti-ringing ring-killer for discontinuous conduction mode ? high accuracy reference output, 1.20 v 1.5%, can supply 2.5 ma loading current when v out > 3.3 v ? low quiescent current of 8.5 a ? integrated low-battery detector ? open drain low-battery detector output ? 1.0 v startup at no load guaranteed ? output voltage from 1.5 v to 5.0 v adjustable ? 1.5 a cycle-by-cycle current limit ? multi-function logic-controlled shutdown pin ? on chip thermal shutdown with hysteresis ? housed in space-saving and low profile micro8 package typical applications ? personal digital assistants (pda) ? handheld digital audio products ? camcorders and digital still cameras ? hand-held instruments ? conversion from one to two alkaline, nimh, nicd battery cells to 3.0-5.0 v or one lithium-ion cells to 5.0 v micro8 dm suffix case 846a 1 8 pin connections fb out lbi/en lbo ref lx gnd bat device package shipping ordering information NCP1421Dmr2 micro8 4000 tape & reel 18 2 3 4 7 6 5 http://onsemi.com marking diagram 1421 = device code a = assembly location y = year w = work week 1421 ayw (top view)
ncp1421 http://onsemi.com 2 chip enable figure 1. detailed block diagram _zcur _mson _cen _pfm _tsdon _mainsw2on _mainswofd _synsw2on _synswofd _v refok control logic 20 mv + - pfm voltage reference ref 4 lbi/en 2 + - fb 1 + - zlc + true cutoff control v dd gnd v dd gnd + - + gnd r sense gnd sensefet m1 v dd m3 bat 5 lx 7 out 8 v bat 6 gnd v out lbo 3 _ilim 0.5 v 1.20 v m2 pin function descriptions pin symbol description 1 fb output voltage feedback input. 2 lbi/en low-battery detector input and ic enable. with this pin pulled down below 0.5 v, the device is disabled and enters the shutdown mode. 3 lbo open-drain low-battery detector output. output is low when v lbi is < 1.20 v. lbo is high impedance in shutdown mode. 4 ref 1.20 v reference voltage output, bypass with 300 nf capacitor. if this pin is not loaded, bypass with 1.0 f capacitor; this pin can be loaded up to 2.5 ma @ v out = 3.3 v. 5 bat battery input connection for internal ring-killer. 6 gnd ground. 7 lx n-channel and p-channel power mosfet drain connection. 8 out power output. out also provides bootstrap power to the device.
ncp1421 http://onsemi.com 3 maximum ratings (t c = 25 c unless otherwise noted.) rating symbol value unit power supply (pin 8) v out -0.3, 5.5 v input/output pins pin 1-5, pin 7 v io -0.3, 5.5 v thermal characteristics micro8 plastic package thermal resistance junction-to-air p d r q ja 520 240 mw c/w operating junction temperature range t j -40 to +150 c operating ambient temperature range t a -40 to +85 c storage temperature range t stg -55 to +150 c 1. this device contains esd protection and exceeds the following tests: human body model (hbm) 2.0 kv per jedec standard: jesd22-a114. *except out pin, which is 1k v. machine model (mm) 200 v per jedec standard: jesd22-a115. *except out pin, which is 100 v. 2. the maximum package power dissipation limit must not be exceeded. p d t j(max) t a r ja 3. latch-up current maximum rating: 150 ma per jedec standard: jesd78. 4. moisture sensitivity level: msl 1 per ipc/jedec standard: j-std-020a. electrical characteristics (v out = 3.3 v, t a = 25 c for typical value, -40 c t a 85 c for min/max values unless otherwise noted.) characteristic symbol min typ max unit operating v oltage v in 1.0 - 5.0 v output voltage range v out 1.5 - 5.0 v reference voltage (v out = 3.3 v, i load = 0 a, c ref = 200 nf, t a = 25 c) v ref_nl 1.183 1.200 1.217 v reference voltage (v out = 3.3 v, i load = 0 a, c ref = 200 nf, t a = -40 c to 85 c) v ref_nl 1.174 - 1.220 v reference voltage temperature coef ficient tc vref - 0.03 - mv/ c reference voltage load current (v out = 3.3 v, v ref = v ref_nl 1.5% c ref = 1.0 f) (note 5 ) i ref - 2.5 - ma reference voltage load regulation (v out = 3.3 v, i load = 0 to 100 a, c ref = 1.0 f) v ref_load - 0.05 1.0 mv reference voltage line regulation (v out from 1.5 v to 5.0 v, c ref = 1.0 f) v ref_line - 0.05 1.0 mv/v fb input threshold (i load = 0 ma, t a = 25 c) v fb 1.192 1.200 1.208 v fb input threshold (i load = 0 ma, t a = -40 c to 85 c) v fb 1.184 - 1.210 v lbi input threshold (i load = 0 ma, t a = -40 c to 85 c) v lbi 1.162 1.230 v lbi input threshold (t a = 25 c) v lbi 1.182 1.200 1.218 v internal nfet on-resistance r ds(on)_n - 0.3 - w internal pfet on-resistance r ds(on)_p - 0.3 - w lx switch current limit (n-fet) (note 7) i lim - 1.5 - a operating current into bat (v bat = 1.8 v, v fb = 1.8 v, v lx = 1.8 v, v out = 3.3 v) i qbat - 1.3 3 a operating current into out (v fb = 1.4 v, v out = 3.3 v) i q - 8.5 14 a lx switch max. on-time (v fb = 1.0 v, v out = 3.3 v, t a = 25 c) t on 0.46 0.72 1.15 s lx switch min. off-time (v fb = 1.0 v, v out = 3.3 v, t a = 25 c) t off - 0.12 0.22 s fb input current i fb - 1.0 50 na true-cutoff current into bat (lbi/en = gnd, v out = 0, v in = 3.3 v, lx = 3.3 v) i bat - 50 - na bat-to-lx resistance (v fb = 1.4 v, v out = 3.3 v) (note 7) r bat_lx - 100 - w lbi/en input current i lbi - 1.5 50 na 5. loading capability increases with v out.
ncp1421 http://onsemi.com 4 electrical characteristics (v out = 3.3 v, t a = 25 c for typical value, -40 c t a 85 c for min/max values unless otherwise noted.) characteristic symbol min typ max unit lbo low output voltage (v lbi = 0, i sink = 1.0 ma) v lbo_l - - 0.2 v soft start time (v in = 2.5 v, v out = 5.0 v, c ref = 200 nf) (note 6) t ss - 1.5 20 ms en pin shutdown threshold (t a = 25 c) v shdn 0.35 0.5 0.67 v thermal shutdown temperature (note 7) t shdn - - 145 c thermal shutdown hysteresis (note 7) t sdhys - 30 - c 6. design guarantee, value depends on voltage at v out. 7. values are design guaranteed.
ncp1421 http://onsemi.com 5 typical operating characteristics 1.180 1.185 1.190 1.195 1.200 1.205 0.0 0.1 0.2 0.3 0.4 0.5 0.6 -40 -20 0 20 40 60 80 100 ambient temperature, t a / c switch on resistance, r ds(on) / p-fet (m2) n-fet (m1) v out = 3.3 v -40 -20 0 20 40 60 80 100 ambient temperature, t a / c reference voltage, v ref /v 0.5 0.6 0.7 0.8 0.9 1.0 -40 -20 0 20 40 60 80 100 0.6 0.9 1.1 1.4 1.6 0 50 100 150 200 25 0 t a = 25 c output loading current, i load /ma minimum startup ba ttery voltage, v batt /v figure 2. reference voltage vs. output current figure 3. reference voltage vs. voltage at out pin figure 4. reference voltage vs. temperature figure 5. switch on resistance vs. temperature figure 6. l x switch max. on time vs. temperature figure 7. minimum startup battery voltage vs. loading current 1.180 1.190 1.200 1.210 1.220 1 10 100 1000 v out = 3.3 v l = 10 h c in = 22 f c out = 22 f c ref = 1.0 f t a = 25 c ambient temperature, t a / c l x switch maximum, on time, t on / s output current, i load /ma reference voltage, v ref /v v in = 1.5 v v in = 2.0 v v in = 2.5 v 1.180 1.190 1.210 1.220 c ref = 200 nf i ref = 0 ma t a = 25 c voltage at out pin, v out /v reference voltage, v ref /v v out = 3.3 v c ref = 200 nf i ref = 0 ma 1.5 2 2.5 3 3.5 4 4.5 5 1.200
ncp1421 http://onsemi.com 6 typical operating characteristics 50 60 70 80 90 100 1 10 100 1000 v in = 1.5 v v out = 1.8 v l = 2.2 h c in = 22 f c out = 22 f t a = 25 c output loading current, i load /ma efficiency/% 50 60 70 80 90 100 1 10 100 1000 v in = 1.5 v v out = 5.0 v l = 2.2 h c in = 22 f c out = 22 f t a = 25 c output loading current, i load /ma efficiency/% 50 60 70 80 90 100 1 10 100 1000 v in = 2.0 v v out = 3.3 v l = 10 h c in = 22 f c out = 22 f t a = 25 c output loading current, i load /ma efficiency/% 50 60 70 80 90 100 1 10 100 1000 v in = 2.5 v v out = 5.0 v l = 6.8 h c in = 22 f c out = 22 f t a = 25 c output loading current, i load /ma efficiency/% 50 60 70 80 90 100 1 10 100 1000 v in = 2.5 v v out = 3.3 v l = 10 h c in = 22 f c out = 22 f t a = 25 c output loading current, i load /ma efficiency/% 50 60 70 80 90 100 1 10 100 1000 figure 8. efficiency vs. load current figure 9. efficiency vs. load current figure 10. efficiency vs. load current figure 11. efficiency vs. load current figure 12. efficiency vs. load current figure 13. efficiency vs. load current v in = 3.3 v v out = 5.0 v l = 12 h c in = 22 f c out = 22 f t a = 25 c output loading current, i load /ma efficiency/%
ncp1421 http://onsemi.com 7 typical operating characteristics -10 -5 5 10 10 100 1000 v out = 3.3 v l = 5.6 h c in = 22 f c out = 22 f t a = 25 c 0 10 20 30 40 50 1.5 1.7 1.9 2.1 2.3 2.5 figure 14. output voltage change vs. load current figure 15. output voltage change vs. load current figure 16. battery input voltage vs. output ripple voltage figure 17. low battery detect figure 18. no load operating current vs. input voltage at out pin v in = 2.5 v v in = 2.0 v 0 output loading current, i load /ma output voltage change/% -10 -5 5 10 10 100 1000 v out = 5.0 v l = 5.6 h c in = 22 f c out = 22 f t a = 25 c v in = 3.3 v v in = 1.5 v 0 output loading current, i load /ma output voltage change/% v in = 2.5 v 300 ma battery input voltage, v batt /v ripple voltage, v ripple /mv p- p 100 ma 500 ma v in = 2.5 v v out = 3.3 v l = 6.8 h c in = 22 f c out = 22 f t a = 25 c upper trace: input voltage waveform, 1.0 v/division lower trace: output voltage waveform, 2.0 v/division figure 19. startup transient response 2.5 5.0 7.5 10 12.5 15 1.5 2.0 2.5 3.0 3.5 5.0 input voltage at out pin, v out /v no load operating current, i batt / a 4.0 4.5 upper trace: voltage at lbi pin, 1.0 v/division lower trace: voltage at lbo pin, 1.0 v/division v in = 2.5 v v out = 5.0 v i load = 10 ma
ncp1421 http://onsemi.com 8 typical operating characteristics (v in = 2.5 v, v out = 3.3 v, i load = 50 ma; l = 5.6 h, c out = 22 f) upper trace: output voltage ripple, 20 mv/division lower trace: voltage at lx pin, 1.0 v/division figure 20. discontinuous conduction mode switching waveform (v in = 2.5 v, v out = 3.3 v, i load = 500 ma; l = 5.6 h, c out = 22 f) upper trace: output voltage ripple, 20 mv/division lower trace: voltage at lx pin, 1.0 v/division figure 21. continuous conduction mode switching waveform figure 22. line transient response for v out = 3.3 v figure 23. line transient response for v out = 5.0 v (v in = 1.5 v to 2.5 v; l = 5.6 h, c out = 22 f, i load = 100 ma) upper trace: output voltage ripple, 100 mv/division lower trace: battery voltage, v in, 1.0 v/division (v in = 1.5 v to 2.5 v; l = 5.6 h, c out = 22 f, i load = 100 ma) upper trace: output voltage ripple, 100 mv/division lower trace: battery voltage, v in, 1.0 v/division figure 24. load transient response for v in = 2.5 v figure 25. load transient response for v in = 3.0 v (v out = 5.0 v, i load = 50 ma to 500 ma; l = 5.6 h, c out = 22 f) upper trace: output voltage ripple, 100 mv/division lower trace: load current, i load , 500 ma/division (v out = 3.3 v, i load = 50 ma to 500 ma; l = 5.6 h, c out = 22 f) upper trace: output voltage ripple, 50 mv/division lower trace: load current, i load , 500 ma/division
ncp1421 http://onsemi.com 9 detailed operation description ncp1421 is a monolithic micropower high-frequency step-up voltage switching converter ic specially designed for battery operated hand-held electronic products up to 600 ma loading. it integrates a synchronous rectifier to improve efficiency as well as to eliminate the external schottky diode. high switching frequency (up to 1.2 mhz) allows for a low profile inductor and output capacitor to be used. low-battery detector, logic-controlled shutdown, and cycle-by-cycle current limit provide value-added features for various battery-operated applications. with all these functions on, the quiescent supply current is typically only 8.5 a. this device is available in a compact micro8 package. pfm regulation scheme from the simplified functional diagram (figure 1), the output voltage is divided down and fed back to pin 1 (fb). this voltage goes to the non-inverting input of the pfm comparator whereas the comparator's inverting input is connected to the internal voltage reference, ref. a switching cycle is initiated by the falling edge of the comparator, at the moment the main switch (m1) is turned on. after the maximum on-time (typically 0.72 s) elapses or the current limit is reached, m1 is turned off and the synchronous switch (m2) is turned on. the m1 off time is not less than the minimum off-time (typically 0.12 s), which ensures complete energy transfer from the inductor to the output capacitor. if the regulator is operating in continuous conduction mode (ccm), m2 is turned off just before m1 is supposed to be on again. if the regulator is operating in discontinuous conduction mode (dcm), which means the coil current will decrease to zero before the new cycle starts, m1 is turned off as the coil current is almost reaching zero. the comparator (zlc) with fixed offset is dedicated to sense the voltage drop across m2 as it is conducting; when the voltage drop is below the offset, the zlc comparator output goes high and m2 is turned off. negative feedback of closed-loop operation regulates voltage at pin 1 (fb) equal to the internal reference voltage (1.20 v). synchronous rectification the synchronous rectifier is used to replace the schottky diode to reduce the conduction loss contributed by the forward voltage of the schottky diode. the synchronous rectifier is normally realized by powerfet with gate control circuitry that incorporates relatively complicated timing concerns. as the main switch (m1) is being turned off and the synchronous switch m2 is just turned on with m1 not being completely turned off, current is shunt from the output bulk capacitor through m2 and m1 to ground. this power loss lowers overall efficiency and possibly damages the switching fets. as a general practice, a certain amount of dead time is introduced to make sure m1 is completely turned off before m2 is being turned on. the previously mentioned situation occurs when the regulator is operating in ccm, m2 is being turned off, m1 is just turned on, and m2 is not being completely turned off. a dead time is also needed to make sure m2 is completely turned off before m1 is being turned on. as coil current is dropped to zero when the regulator is operating in dcm, m2 should be off. if this does not occur, the reverse current flows from the output bulk capacitor through m2 and the inductor to the battery input, causing damage to the battery. the zlc comparator comes with fixed offset voltage to switch m2 off before any reverse current builds up. however, if m2 is switched off too early, large residue coil current flows through the body diode of m2 and increases conduction loss. therefore, determination of the of fset voltage is essential for optimum performance. with the implementation of the synchronous rectification scheme, efficiency can be as high as 94% with this device. cycle-by-cycle current limit in figure 1, a sensefet is used to sample the coil current as m1 is on. with that sample current flowing through a sense resistor, a sense-voltage is developed. the threshold detector (i lim ) detects whether the sense-voltage is higher than the preset level. if the sense voltage is higher than the present level, the detector output notifies the control logic to switch off m1, and m1 can only be switched on when the next cycle starts after the minimum off-time (typically 0.12 s). with proper sizing of the sensefet and sense resistor, the peak coil current limit is typically set at 1.5 a. voltage reference the voltage at ref is typically set at 1.20 v and can output up to 2.5 ma with load regulation 2% at v out equal to 3.3 v. if v out is increased, the ref load capability can also be increased. a bypass capacitor of 200 nf is required for proper operation when ref is not loaded. if ref is loaded, a 1.0 f capacitor at the ref pin is needed. true-cutoff the ncp1421 has a true-cutof f function controlled by the multi-function pin lbi/en (pin 2). internal circuitry can isolate the current through the body diode of switch m2 to load. thus, it can eliminate leakage current from the battery to load in shutdown mode and significantly reduce battery current consumption during shutdown. the shutdown function is controlled by the voltage at pin 2 (lbi/en). when pin 2 is pulled to lower than 0.3 v, the controller enters shutdown mode. in shutdown mode, when switches m1 and m2 are both switched off, the internal
ncp1421 http://onsemi.com 10 reference voltage of the controller is disabled and the controller typically consumes only 50 na of current. if the pin 2 voltage is raised to higher than 0.5 v (for example, by a resistor connected to v in) , the ic is enabled again, and the internal circuit typically consumes 8.5 a of current from the out pin during normal operation. low-battery detection a comparator with 30 mv hysteresis is applied to perform the low-battery detection function. when pin 2 (lbi/en) is at a voltage (defined by a resistor divider from the battery voltage) lower than the internal reference voltage of 1.20 v, the comparator output turns on a 50 low side switch. it pulls down the voltage at pin 3 (lbo) which has hundreds of k of pull-high resistance. if the pin 2 voltage is higher than 1.20 v + 30 mv, the comparator output turns off the 50 low side switch. when this occurs, pin 3 becomes high impedance and its voltage is pulled high again. applications information output voltage setting a typical application circuit is shown in figure 26. the output voltage of the converter is determined by the external feedback network comprised of r1 and r2. the relationship is given by: v out 1.20 v 1 r1 r2
where r1 and r2 are the upper and lower feedback resistors, respectively. low battery detect level setting the low battery detect voltage of the converter is determined by the external divider network that is comprised of r3 and r4. the relationship is given by: v lb 1.20 v 1 r3 r4
where r3 and r4 are the upper and lower divider resistors respectively. inductor selection the ncp1421 is tested to produce optimum performance with a 5.6 h inductor at v in = 2.5 v and v out = 3.3 v, supplying an output current up to 600 ma. for other input/output requirements, inductance in the range 3 h to 10 h can be used according to end application specifications. selecting an inductor is a compromise between output current capability, inductor saturation limit, and tolerable output voltage ripple. low inductance values can supply higher output current but also increase the ripple at output and reduce efficiency. on the other hand, high inductance values can improve output ripple and efficiency; however, it is also limited to the output current capability at the same time. another parameter of the inductor is its dc resistance. this resistance can introduce unwanted power loss and reduce overall efficiency. the basic rule is to select an inductor with the lowest dc resistance within the board space limitation of the end application. in order to help with the inductor selection, reference charts are shown in figure 27 and 28. capacitors selection in all switching mode boost converter applications, both the input and output terminals see impulsive voltage/current waveforms. the currents flowing into and out of the capacitors multiply with the equivalent series resistance (esr) of the capacitor to produce ripple voltage at the terminals. during the syn-rect switch-off cycle, the charges stored in the output capacitor are used to sustain the output load current. load current at this period and the esr combine and reflect as ripple at the output terminals. for all cases, the lower the capacitor esr, the lower the ripple voltage at output. as a general guideline, low esr capacitors should be used. ceramic capacitors have the lowest esr, but low esr tantalum capacitors can also be used as an alternative. pcb layout recommendations good pcb layout plays an important role in switching mode power conversion. careful pcb layout can help to minimize ground bounce, emi noise, and unwanted feedback that can affect the performance of the converter. hints suggested below can be used as a guideline in most situations. grounding a star-ground connection should be used to connect the output power return ground, the input power return ground, and the device power ground together at one point. all high-current paths must be as short as possible and thick enough to allow current to flow through and produce insignificant voltage drop along the path. the feedback signal path must be separated from the main current path and sense directly at the anode of the output capacitor. components placement power components (i.e., input capacitor, inductor and output capacitor) must be placed as close together as possible. all connecting traces must be short, direct, and thick. high current flowing and switching paths must be kept away from the feedback (fb, pin 1) terminal to avoid unwanted injection of noise into the feedback path. feedback network feedback of the output voltage must be a separate trace detached from the power path. the external feedback network must be placed very close to the feedback (fb, pin 1) pin and sense the output voltage directly at the anode of the output capacitor.
ncp1421 http://onsemi.com 11 typical application circuit lbi/en fb lbo ref bat gnd lx out 1 2 3 4 8 7 6 5 ncp1421 r4 330 k r2 200 k shutdown open drain input low battery open drain output c3 200 nf r1 350 k c2 22 f + v out =3.3 v 500 ma c1 22 f v in l 6.5 h figure 26. typical application schematic for 2 alkaline cells supply r3 220 k c4 10 p* *optional general design procedures switching mode converter design is considered a complicated process. selecting the right inductor and capacitor values can allow the converter to provide optimum performance. the following is a simple method based on the basic first-order equations to estimate the inductor and capacitor values for ncp1421 to operate in continuous conduction mode (ccm). the set component values can be used as a starting point to fine tune the application circuit performance. detailed bench testing is still necessary to get the best performance out of the circuit. design parameters: v in = 1.8 v to 3.0 v, typical 2.4 v v out = 3.3 v i out = 500 ma (600 ma max) v lb = 2.0 v v out- ripple = 45 mv p- p at i out = 500 ma calculate the feedback network: select r2 = 200 k r1 r2 v out v ref 1
r1 200 k 3.3 v 1.20 v 1
350 k calculate the low battery detect divider: v lb = 2.0 v select r4 = 330 k r3 r4 v lb v ref 1
r3 300 k 2.0 v 1.20 v 1
220 k determine the steady state duty ratio, d, for typical v in . the operation is optimized around this point: v out v ref 1 1 d d 1 v in v out 1 2.4 v 3.3 v 1 0.273 determine the average inductor current, i lavg, at maximum i out : i lavg i out 1 d 500 ma 1 0.273 688 ma determine the peak inductor ripple current, i ripple- p, and calculate the inductor value: assume i ripple- p is 20% of i lavg . the inductance of the power inductor can be calculated as follows: l v in t on 2i ripple p 2.4 v 0.75 s 2 (137.6 ma) 6.5 h a standard value of 6.5 h is selected for initial trial. determine the output voltage ripple, v out- ripple, and calculate the output capacitor value: v out- ripple = 40 mv p- p at i out = 500 ma c out i out t on v out ripple i out esr cout where t on = 0.75 us and esr cout = 0.05 w , c out 500 ma 0.75 s 45 mv 500 ma 0.05 18.75 f from the previous calculations, you need at least 18.75 f in order to achieve the specified ripple level at the conditions stated. practically, a capacitor that is one level larger is used to accommodate factors not taken into
ncp1421 http://onsemi.com 12 account in the calculations. therefore, a capacitor value of 22 f is selected. the ncp1421 is internally compensated for most applications, but in case additional compensation is required, the capacitor c4 can be used as external compensation adjustment to improve system dynamics. in order to provide an easy way for customers to select external parts for ncp1421 in different input voltage and output current conditions, values of inductance and capacitance are suggested in figure 27, 28 and 29. 0 2 4 6 8 10 12 14 16 1.4 1.8 2.0 2.2 2.4 2.6 2.8 3.0 figure 27. suggested inductance of v out = 3.3 v figure 28. suggested inductance of v out = 5.0 v figure 29. suggested capacitance for output capacitor 1.6 input voltage (v) inductor value ( h) i out = 500 ma 0 3 6 9 12 15 18 21 1.6 2.2 2.5 2.8 3.1 3.4 3.7 4.0 1.9 input voltage (v) inductor value ( h) i out = 500 ma output current (ma) capacitor value ( f) capacitor esr (m ) v out- ripple = 45 mv v out- ripple = 50 mv v out- ripple = 40 mv 25 33 50 100 40 35 30 25 20 15 10 5 0 200 250 300 350 400 450 500 550 600 table 1. suggestions for passive components output current inductors capacitors 500 ma sumida cr43, cr54,cdrh6d28 series panasonic ecj series kemet tl494 series 250 ma sumida cr32 series panasonic ecj series kemet tl494 series
ncp1421 http://onsemi.com 13 package dimensions micro8 dm suffix case 846a-02 issue e s b m 0.08 (0.003) a s t dim min max min max inches millimeters a 2.90 3.10 0.114 0.122 b 2.90 3.10 0.114 0.122 c --- 1.10 --- 0.043 d 0.25 0.40 0.010 0.016 g 0.65 bsc 0.026 bsc h 0.05 0.15 0.002 0.006 j 0.13 0.23 0.005 0.009 k 4.75 5.05 0.187 0.199 l 0.40 0.70 0.016 0.028 notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: millimeter. 3. dimension a does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.15 (0.006) per side. 4. dimension b does not include interlead flash or protrusion. interlead flash or protrusion shall not exceed 0.25 (0.010) per side. -b- -a- d k g pin 1 id 8 pl 0.038 (0.0015) -t- seating plane c h j l
ncp1421 http://onsemi.com 14 on semiconductor and are registered trademarks of semiconductor components industries, llc (scillc). scillc reserves the right to mak e changes without further notice to any products herein. scillc makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does scillc assume any liability arising out of the application or use of any product or circuit, and s pecifically disclaims any and all liability, including without limitation special, consequential or incidental damages. typicalo parameters which may be provid ed in scillc data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including typicalso must be validated for each customer application by customer's technical experts. scillc does not convey any license under its patent rights nor the rights of others. scillc products are not designed, intended, or authorized for use as components in systems intended for surgical implant into t he body, or other applications intended to support or sustain life, or for any other application in which the failure of the scillc product could create a sit uation where personal injury or death may occur. should buyer purchase or use scillc products for any such unintended or unauthorized application, buyer shall indem nify and hold scillc and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized u se, even if such claim alleges that scillc was negligent regarding the design or manufacture of the part. scillc is an equal opportunity/affirmative action employ er. publication ordering information japan : on semiconductor, japan customer focus center 2-9-1 kamimeguro, meguro-ku, tokyo, japan 153-0051 phone : 81-3-5773-3850 on semiconductor website : http://onsemi.com for additional information, please contact your local sales representative. ncp1421/d sensefet is a trademark of semiconductor components industries, llc (scillc). micro8 is a trademark of international rectifier. literature fulfillment : literature distribution center for on semiconductor p.o. box 5163, denver, colorado 80217 usa phone : 303-675-2175 or 800-344-3860 toll free usa/canada fax : 303-675-2176 or 800-344-3867 toll free usa/canada email : onlit@hibbertco.com n. american technical support : 800-282-9855 toll free usa/canada

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