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? semiconductor components industries, llc, 2003 november, 2003 ? rev. 5 1 publication order number: ncp1402/d ncp1402 200 ma, pfm step-up micropower switching regulator the ncp1402 series are monolithic micropower step?up dc to dc converter that are specially designed for powering portable equipment from one or two cell battery packs.these devices are designed to start?up with a cell voltage of 0.8 v and operate down to less than 0.3 v. with only three external components, this series allow a simple means to implement highly efficient converters that are capable of up to 200 ma of output current at v in = 2.0 v, v out = 3.0 v. each device consists of an on?chip pfm (pulse frequency modulation) oscillator, pfm controller, pfm comparator, soft?start, voltage reference, feedback resistors, driver, and power mosfet switch with current limit protection. additionally, a chip enable feature is provided to power down the converter for extended battery life. the ncp1402 device series are available in the thin sot?23?5 package with five standard regulated output voltages. additional voltages that range from 1.8 v to 5.0 v in 100 mv steps can be manufactured. features ? extremely low start?up voltage of 0.8 v ? operation down to less than 0.3 v ? high efficiency 85% (v in = 2.0 v, v out = 3.0 v, 70 ma) ? low operating current of 30 a (v out = 1.9 v) ? output voltage accuracy 2.5% ? low converter ripple with typical 30 mv ? only three external components are required ? chip enable power down capability for extended battery life ? micro miniature thin sot?23?5 packages typical applications ? cellular telephones ? pagers ? personal digital assistants (pda) ? electronic games ? portable audio (mp3) ? camcorders ? digital cameras ? handheld instruments ordering information sot23?5 (tsop?5, sc59?5) sn suffix case 483 1 5 pin connections and marking diagram 1 3 gnd ce 2 out nc 4 lx 5 xxxyw (top view) xxx = marking y = year w = work week see detailed ordering and shipping information in the ordering information section on page 3 of this data sheet. http://onsemi.com
ncp1402 http://onsemi.com 2 1 3 gnd ce 2 out nc 4 lx 5 ncp1402 figure 1. typical step?up converter application v out v in power switch out 2 ? + voltage reference soft?start pfm controller pfm oscillator driver v lx limiter pfm comparator nc 3 gnd 4 lx 5 1 ce figure 2. representative block diagram pin function descriptions pin # symbol pin description 1 ce chip enable pin 1 ce chi enable in (1) the chip is enabled if a voltage which is equal to or greater than 0.9 v is applied ( ) th hi i di bl d if l hi h i l h v i li d () g q g (2) the chip is disabled if a voltage which is less than 0.3 v is applied (3) the chip will be enabled if it is left floating (3) the chip will be enabled if it is left floating 2 out output voltage monitor pin, also the power supply pin of the device 3 nc no internal connection to this pin 4 gnd ground pin 5 lx external inductor connection pin to power switch drain
ncp1402 http://onsemi.com 3 ordering information device output voltage device marking package shipping ncp1402sn19t1 1.9 v dau ncp1402sn27t1 2.7 v dae ncp1402sn30t1 3.0 v daf sot23?5 3000 units per reel ncp1402sn33t1 3.3 v dag sot 23?5 3000 u n i ts p er r ee l ncp1402sn40t1 4.0 v dcr ncp1402sn50t1 5.0 v dah note: the ordering information lists five standard output voltage device options. additional device with output voltage ranging from 1.8 v to 5.0 v in 100 mv increments can be manufactured. contact your on semiconductor representative for availability. absolute maximum ratings rating symbol value unit power supply voltage (pin 2) v out 6.0 v input/output pins lx (pin 5) lx peak sink current v lx i lx ?0.3 to 6.0 400 v ma ce (pin 1) input voltage range input current range v ce i ce ?0.3 to 6.0 ?150 to 150 v ma thermal resistance junction to air r q ja 250 c/w operating ambient temperature range (note 2) t a -40 to +85 c operating junction temperature range t j -40 to +125 c storage temperature range t stg -55 to +150 c notes: 1. this device series contains esd protection and exceeds the following tests: human body model (hbm) 2.0 kv per jedec standard: jesd22?a114. machine model (mm) 200 v per jedec standard: jesd22?a115. 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.
ncp1402 http://onsemi.com 4 electrical characteristics (for all values t a = 25 c, unless otherwise noted.) characteristic symbol min typ max unit oscillator switch on time (current limit not asserted) t on 3.6 5.5 7.6 s switch minimum off time t off 1.0 1.45 1.9 s maximum duty cycle d max 70 78 85 % minimum start?up voltage (i o = 0 ma) v start ? 0.8 0.95 v minimum start?up voltage temperature coefficient (t a = ?40 c to 85 c) v start ? ?1.6 ? mv/ c minimum operation hold voltage (i o = 0 ma) v hold 0.3 ? ? v soft?start time (v out 0.8 v) t ss 0.3 2.0 ? ms lx (pin 5) internal switching n?channel fet drain voltage v lx ? ? 6.0 v lx pin on?state sink current (v lx = 0.4 v) device suffix: 19t1 27t1 30t1 33t1 40t1 50t1 i lx 110 130 130 130 130 130 145 180 190 200 210 215 ? ? ? ? ? ? ma voltage limit v lxlim 0.45 0.65 0.9 v off?state leakage current (v lx = 6.0 v, t a = ?40 c to 85 c) i lkg ? 0.5 1.0 m a ce (pin 1) ce input voltage (v out = v set x 0.96) high state, device enabled low state, device disabled v ce(high) v ce(low) 0.9 ? ? ? ? 0.3 v ce input current (note 6) high state, device enabled (v out = v ce = 6.0 v) low state, device disabled (v out = 6.0 v, v ce = 0 v) i ce(high) i ce(low) ?0.5 ?0.5 0 0.15 0.5 0.5 m a total device output voltage device suffix: 19t1 27t1 30t1 33t1 40t1 50t1 v out 1.853 2.632 2.925 3.218 3.900 4.875 1.9 2.7 3.0 3.3 4.0 5.0 1.948 2.768 3.075 3.383 4.100 5.125 v output voltage temperature coefficient (t a = ?40 c to +85 c) device suffix: 19t1 27t1 30t1 33t1 40t1 50t1 v out ? ? ? ? ? ? 150 150 150 150 150 150 ? ? ? ? ? ? ppm/ c operating current 2 (v out = v ce = v set +0.5 v, note 5) i dd2 ? 13 15 m a off?state current (v out = 5.0 v, v ce = 0 v, t a = ?40 c to +85 c, note 6) i off ? 0.6 1.0 m a operating current 1 (v out = v ce = v set x 0.96) device suffix: 19t1 27t1 30t1 33t1 40t1 50t1 i dd1 ? ? ? ? ? ? 30 39 42 45 55 70 50 60 60 60 100 100 m a 5. v set means setting of output voltage. 6. ce pin is integrated with an internal 10 m w pull?up resistor.
ncp1402 http://onsemi.com 5 100 60 80 40 20 0 3.0 2.0 3.5 2.5 1.5 4.0 40 0 1.9 60 40 20 v out , output voltage (v) 1.6 i o , output current (ma) figure 3. ncp1402sn19t1 output voltage vs. output current figure 4. ncp1402sn30t1 output voltage vs. output current v out , output voltage (v) 6.0 5.0 4.0 3.0 1.0 figure 5. ncp1402sn50t1 output voltage vs. output current i o , output current (ma) figure 6. ncp1402sn19t1 efficiency vs. output current i o , output current (ma) efficiency (%) v out , output voltage (v) figure 7. ncp1402sn30t1 efficiency vs. output current i o , output current (ma) figure 8. ncp1402sn50t1 efficiency vs. output current i o , output current (ma) efficiency (%) 2.1 20 60 0 80 100 v in = 0.9 v ncp1402sn19t1 l = 47 m h t a = 25 c i o , output current (ma) 1.7 1.8 2.0 80 100 120 140 160 180 200 0 60 40 20 80 100 120 140 160 180 200 2.0 060 40 20 80 100 120 140 160 180 200 0 60 40 20 80 100 120 140 160 180 200 060 40 20 80 100 120 140 160 180 200 100 60 80 40 20 0 060 40 20 80 100 120 140 160 180 200 efficiency (%) v in = 1.2 v v in = 1.5 v v in = 0.9 v v in = 1.2 v v in = 1.5 v v in = 2.5 v v in = 2.0 v ncp1402sn30t1 l = 47 m h t a = 25 c v in = 0.9 v v in = 1.2 v v in = 1.5 v v in = 4.0 v v in = 2.0 v v in = 3.0 v v in = 0.9 v v in = 1.2 v v in = 1.5 v v in = 0.9 v v in = 1.2 v v in = 1.5 v v in = 2.0 v v in = 2.5 v v in = 0.9 v v in = 1.2 v v in = 1.5 v v in = 2.0 v v in = 3.0 v v in = 4.0 v ncp1402sn19t1 l = 47 m h t a = 25 c ncp1402sn50t1 l = 47 m h t a = 25 c ncp1402sn50t1 l = 47 m h t a = 25 c ncp1402sn30t1 l = 47 m h t a = 25 c
ncp1402 http://onsemi.com 6 100 60 80 40 20 0 0 20 40 60 80 100 3.1 2.9 2.8 3.0 2.7 3.2 60 ?50 2.0 25 0 ?25 v out , output voltage (v) 1.6 temperature ( c) figure 9. ncp1402sn19t1 output voltage vs. temperature figure 10. ncp1402sn30t1 output voltage vs. temperature v out , output voltage (v) 5.2 5.1 5.0 4.9 4.8 4.7 figure 11. ncp1402sn50t1 output voltage vs. temperature temperature ( c) figure 12. ncp1402sn19t1 operating current 1 vs. temperature temperature ( c) i dd1 , operating current 1 (ma) v out , output voltage (v) figure 13. ncp1402sn30t1 operating current 1 vs. temperature temperature ( c) figure 14. ncp1402sn50t1 operating current 1 vs. temperature temperature ( c) i dd1 , operating current 1 (ma) i dd1 , operating current 1 (ma) 2.1 20 80 40 0 100 temperature ( c) 1.7 1.8 1.9 50 75 100 ?50 25 0 ?25 50 75 10 0 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 10 0 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ncp1402sn19t1 v out = 1.9 v x 0.96 open?loop test ncp1402sn30t1 v out = 3.0 v x 0.96 open?loop test ncp1402sn50t1 v out = 5.0 v x 0.96 open?loop test ncp1402sn19t1 v out = 1.9 v x 0.96 open?loop test ncp1402sn30t1 v out = 3.0 v x 0.96 open?loop test ncp1402sn50t1 v out = 5.0 v x 0.96 open?loop test
ncp1402 http://onsemi.com 7 1.5 ?50 6.5 25 5.5 0 ?25 t on , switch on time ( m s) 5.0 temperature ( c) figure 15. ncp1402sn19t1 switch on time vs. temperature figure 16. ncp1402sn30t1 switch on time vs. temperature t on , switch on time ( m s) 7.0 6.5 6.0 5.5 5.0 4.5 figure 17. ncp1402sn50t1 switch on time vs. temperature temperature ( c) figure 18. ncp1402sn19t1 minimum switch off time vs. temperature temperature ( c) t off , minimum switch off time ( m s) t on , switch on time ( m s) figure 19. ncp1402sn30t1 minimum switch off time vs. temperature temperature ( c) figure 20. ncp1402sn50t1 minimum switch off time vs. temperature temperature ( c) t off , minimum switch off time ( m s) 7.5 1.6 1.4 1.7 1.9 temperature ( c) 6.0 7.0 50 75 100 6.5 5.5 5.0 7.5 6.0 7.0 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 1.5 1.6 1.4 1.3 1.7 1.8 1.5 1.6 1.4 1.3 1.7 1.8 t off , minimum switch off time ( m s) ncp1402sn19t1 v out = 1.9 v x 0.96 open?loop test ncp1402sn30t1 v out = 3.0 v x 0.96 open?loop test ncp1402sn50t1 v out = 5.0 v x 0.96 open?loop test ncp1402sn19t1 v out = 1.9 v x 0.96 open?loop test ncp1402sn30t1 v out = 3.0 v x 0.96 open?loop test ncp1402sn50t1 v out = 5.0 v x 0.96 open?loop test ?50 25 0 ?25 50 75 100 1.8
ncp1402 http://onsemi.com 8 250 230 190 210 170 150 200 225 250 275 300 160 90 60 d max , maximum duty cycle (%) 40 temperature ( c) figure 21. ncp1402sn19t1 maximum duty cycle vs. temperature figure 22. ncp1402sn30t1 maximum duty cycle vs. temperature 100 70 60 90 50 40 figure 23. ncp1402sn50t1 maximum duty cycle vs. temperature temperature ( c) figure 24. ncp1402sn19t1 lx pin on?state current vs. temperature temperature ( c) i lx , lx pin on?state current (ma) figure 25. ncp1402sn30t1 lx pin on?state current vs. temperature temperature ( c) figure 26. ncp1402sn50t1 lx pin on?state current vs. temperature temperature ( c) 100 120 180 140 100 200 temperature ( c) 50 70 80 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 175 ncp1402sn19t1 v out = 1.9 v x 0.96 open?loop test ncp1402sn30t1 v out = 3.0 v x 0.96 open?loop test ncp1402sn50t1 v out = 5.0 v x 0.96 open?loop test ncp1402sn19t1 v out = 1.9 v x 0.96 v lx = 0.4 v open?loop test ncp1402sn50t1 v out = 5.0 v x 0.96 v lx = 0.4 v open?loop test ncp1402sn30t1 v out = 3.0 v x 0.96 v lx = 0.4 v open?loop test d max , maximum duty cycle (%) 100 90 80 70 60 50 40 d max , maximum duty cycle (%) 80 i lx , lx pin on?state current (ma) i lx , lx pin on?state current (ma)
ncp1402 http://onsemi.com 9 0.8 0.2 0.0 1.0 0.4 0.6 ?50 25 0 ?25 50 75 100 3.0 2.5 1.0 1.5 0.5 0.0 2.5 0.8 0.2 v lxlim , v lx voltage limit (v) 0.0 temperature ( c) figure 27. ncp1402sn19t1 v lx voltage limit vs. temperature figure 28. ncp1402sn30t1 v lx voltage limit vs. temperature v lxlim , v lx voltage limit (v) figure 29. ncp1402sn50t1 v lx voltage limit vs. temperature temperature ( c) figure 30. ncp1402sn19t1 switch?on resistance vs. temperature temperature ( c) v lxlim , v lx voltage limit (v) figure 31. ncp1402sn30t1 switch?on resistance vs. temperature temperature ( c) figure 32. ncp1402sn50t1 switch?on resistance vs. temperature temperature ( c) r ds(on) , switch?on resistance ( w ) 1.0 1.5 3.0 2.0 1.0 3.5 4.0 temperature ( c) 0.4 0.6 0.8 0.2 0.0 1.0 0.4 0.6 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 ?50 25 0 ?25 50 75 100 r ds(on) , switch?on resistance ( w )r ds(on) , switch?on resistance ( w ) 2.0 3.0 2.5 1.0 1.5 0.5 0.0 2.0 ncp1402sn19t1 v out = 1.9 v x 0.96 v lx = 0.4 v open?loop test ncp1402sn19t1 open?loop test ncp1402sn30t1 open?loop test ncp1402sn50t1 open?loop test ncp1402sn50t1 v out = 5.0 v x 0.96 v lx = 0.4 v open?loop test ncp1402sn30t1 v out = 3.0 v x 0.96 v lx = 0.4 v open?loop test
ncp1402 http://onsemi.com 10 1.5 0.5 1.0 0.0 2.0 1.5 0.5 1.0 0.0 2.0 1.5 0.5 1.0 0.0 2.0 0.8 0.4 0.0 1.0 0.2 0.6 ?50 0.8 50 0.4 25 ?25 v start /v hold , startup/hold voltage (v) 0.0 figure 33. ncp1402sn19t1 startup/hold voltage vs. temperature figure 34. ncp1402sn30t1 startup/hold voltage vs. temperature figure 35. ncp1402sn50t1 startup/hold voltage vs. temperature figure 36. ncp1402sn19t1 startup/hold voltage vs. output current i o , output current (ma) v start /v hold , startup/hold voltage (v) figure 37. ncp1402sn30t1 startup/hold voltage vs. output current 1.0 04050 30 20 60 10 70 v start ncp1402sn19t1 l = 22 m h c out = 10 m f i o = 0 ma temperature ( c) 0.2 0.6 75 100 figure 38. ncp1402sn50t1 startup/hold voltage vs. output current 0 v hold ?50 50 25 ?25 v start /v hold , startup/hold voltage (v) v start ncp1402sn30t1 l = 22 m h c out = 10 m f i o = 0 ma temperature ( c) 75 100 0 v hold ?50 0.8 50 0.4 25 ?25 v start /v hold , startup/hold voltage (v) 0.0 1.0 v start ncp1402sn50t1 l = 22 m h c out = 10 m f i o = 0 ma temperature ( c) 0.2 0.6 75 100 0 v hold v start ncp1402sn19t1 l = 47 m h c out = 68 m f t a = 25 c v hold 80 90 100 i o , output current (ma) v start /v hold , startup/hold voltage (v) 04050 30 20 60 10 70 v start v hold 80 90 100 i o , output current (ma) v start /v hold , startup/hold voltage (v) 04050 30 20 60 10 70 v start v hold 80 90 100 ncp1402sn50t1 l = 47 m h c out = 68 m f t a = 25 c ncp1402sn30t1 l = 47 m h c out = 68 m f t a = 25 c
ncp1402 http://onsemi.com 11 figure 39. ncp1402sn19t1 operating waveforms (medium load) figure 40. ncp1402sn19t1 operating waveforms (heavy load) figure 41. ncp1402sn30t1 operating waveforms (medium load) figure 42. ncp1402sn30t1 operating waveforms (heavy load) figure 43. ncp1402sn50t1 operating waveforms (medium load) figure 44. ncp1402sn50t1 operating waveforms (heavy load) v out = 1.9 v, v in = 1.2 v, i o = 30 ma, l = 47 h, c out = 68 f 1. v lx , 1.0 v/div 2. v out , 20 mv/div, ac coupled 3. i l , 100 ma/div 2 s/div v out = 3.0 v, v in = 1.2 v, i o = 30 ma, l = 47 h, c out = 68 f 1. v lx , 2.0 v/div 2. v out , 20 mv/div, ac coupled 3. i l , 100 ma/div 5 s/div v out = 3.0 v, v in = 1.2 v, i o = 70 ma, l = 47 h, c out = 68 f 1. v lx , 2.0 v/div 2. v out , 20 mv/div, ac coupled 3. i l , 100 ma/div v out = 1.9 v, v in = 1.2 v, i o = 70 ma, l = 47 h, c out = 68 f 1. v lx , 1.0 v/div 2. v out , 20 mv/div, ac coupled 3. i l , 100 ma/div 5 s/div 2 s/div 2 s/div v out = 5.0 v, v in = 1.5 v, i o = 30 ma, l = 47 h, c out = 68 f 1. v lx , 2.0 v/div 2. v out , 20 mv/div, ac coupled 3. i l , 100 ma/div 2 s/div v out = 5.0 v, v in = 1.5 v, i o = 60 ma, l = 47 h, c out = 68 f 1. v lx , 2.0 v/div 2. v out , 20 mv/div, ac coupled 3. i l , 100 ma/div
ncp1402 http://onsemi.com 12 figure 45. ncp1402sn19t1 load transient response figure 46. ncp1402sn19t1 load transient response figure 47. ncp1402sn30t1 load transient response figure 48. ncp1402sn30t1 load transient response figure 49. ncp1402sn50t1 load transient response figure 50. ncp1402sn50t1 load transient response v in = 1.2 v, l = 47 h, c out = 68 f 1. v out = 1.9 v (ac coupled), 100 mv/div 2. i o = 0.1 ma to 80 ma v in = 1.2 v, l = 47 h, c out = 68 f 1. v out = 1.9 v (ac coupled), 100 mv/div 2. i o = 80 ma to 0.1 ma v in = 2.4 v, l = 47 h, c out = 68 f 1. v out = 5.0 v (ac coupled), 100 mv/div 2. i o = 0.1 ma to 80 ma v in = 2.4 v, l = 47 h, c out = 68 f 1. v out = 5.0 v (ac coupled), 100 mv/div 2. i o = 80 ma to 0.1 ma v in = 1.5 v, l = 47 h, c out = 68 f 1. v out = 3.0 v (ac coupled), 100 mv/div 2. i o = 0.1 ma to 80 ma v in = 1.5 v, l = 47 h, c out = 68 f 1. v out = 3.0 v (ac coupled), 100 mv/div 2. i o = 80 ma to 0.1 ma
ncp1402 http://onsemi.com 13 2.5 1.0 3.0 1.5 2.0 3.5 0 60 60 40 20 v ripple , ripple voltage (mv) 0 figure 51. ncp1402sn19t1 ripple voltage vs. output current figure 52. ncp1402sn30t1 ripple voltage vs. output current figure 53. ncp1402sn50t1 ripple voltage vs. output current figure 54. ncp1402snxxt1 operating current 1 vs. output voltage v out , output voltage (v) i dd1 , operating current 1 (ma) figure 55. ncp1402snxxt1 pin on?state current vs. output voltage figure 56. ncp1402snxxt1 switch?on resistance vs. output voltage 80 134 25 v in = 1.2 v ncp1402sn19t1 l = 47 m h c out = 68 f t a = 25 c 85 c i o , output current (ma) 20 40 100 80 100 120 140 160 180 200 v in = 0.9 v v in = 1.5 v 0 60 60 40 20 v ripple , ripple voltage (mv) 0 80 v in = 1.2 v ncp1402sn30t1 l = 47 m h c out = 68 f t a = 25 c i o , output current (ma) 20 40 100 80 100 120 140 160 180 20 0 v in = 0.9 v v in = 1.5 v 0 60 60 40 20 v ripple , ripple voltage (mv) 0 80 v in = 1.2 v ncp1402sn50t1 l = 47 m h c out = 68 f t a = 25 c i o , output current (ma) 20 40 100 80 100 120 140 160 180 200 v in = 0.9 v v in = 1.5 v v in = 2.0 v v in = 2.5 v v in = 2.0 v v in = 3.0 v v in = 4.0 v 60 0 80 20 40 100 6 25 c ?40 c ncp1402snxxt1 v out = v set x 0.96 open?loop test v out , output voltage (v) r ds(on) , switch?on resistance ( ) 134 25 85 c 6 25 c ?40 c ncp1402snxxt1 v out = v set x 0.96 v lx = 0.4 v open?loop test v out , output voltage (v) i lx , lx pin on?state current (ma) 134 25 85 c 220 100 260 140 180 300 6 25 c ?40 c ncp1402snxxt1 v out = v set x 0.96 v lx = 0.4 v open?loop test
ncp1402 http://onsemi.com 14 300 200 0 400 0 125 3 2 1 i in(no load) , no load input current ( m a) 0 v in , input voltage (v) figure 57. ncp1402snxxt1 no load input current vs. input voltage figure 58. ncp1402snxxt1 maximum output current vs. input voltage i o(max) , max. output current (ma) 150 0 1.9 v ncp1402snxxt1 l = 47 m h i o = 0 ma t a = 25 c v in , input voltage (v) 25 50 75 100 45 100 6 2.7 v 3.0 v 3.3 v 5.0 v 1.9 v 2.7 v 3.0 v 3.3 v 5.0 v ncp1402snxxt1 l = 47 m h t a = 25 c 123 45 detailed operating description operation the ncp1402 series are monolithic power switching regulators optimized for applications where power drain must be minimized. these devices operate as variable frequency, voltage mode boost regulators and designed to operate in continuous conduction mode. potential applications include low powered consumer products and battery powered portable products. the ncp1402 series are low noise variable frequency voltage?mode dc?dc converters, and consist of soft?start circuit, feedback resistor, reference voltage, oscillator, pfm comparator, pfm control circuit, current limit circuit and power switch. due to the on?chip feedback resistor network, the system designer can get the regulated output voltage from 1.8 v to 5 v with a small number of external components. the operating current is typically 30 a (v out = 1.9 v), and can be further reduced to about 0.6 a when the chip is disabled (v ce < 0.3 v). the ncp1402 operation can be best understood by examining the block diagram in figure 2. pfm comparator monitors the output voltage via the feedback resistor. when the feedback voltage is higher than the reference voltage, the power switch is turned off. as the feedback voltage is lower than reference voltage and the power switch has been off for at least a period of minimum off?time decided by pfm oscillator, the power switch is then cycled on for a period of on?time also decided by pfm oscillator, or until current limit signal is asserted. when the power switch is on, current ramps up in the inductor, storing energy in the magnetic field. when the power switch is off, the energy in the magnetic field is transferred to output filter capacitor and the load. the output filter capacitor stores the charge while the inductor current is high, then holds up the output voltage until next switching cycle. soft start there is a soft start circuit in ncp1402. when power is applied to the device, the soft start circuit pumps up the output voltage to approximately 1.5 v at a fixed duty cycle, the level at which the converter can operate normally. what is more, the start?up capability with heavy loads is also improved. regulated converter voltage (v out ) the v out is set by an internal feedback resistor network. this is trimmed to a selected voltage from 1.8 to 5.0 v range in 100 mv steps with an accuracy of 2.5%. current limit the ncp1402 series utilizes cycle?by?cycle current limiting as a means of protecting the output switch mosfet from overstress and preventing the small value inductor from saturation. current limiting is implemented by monitoring the output mosfet current build?up during conduction, and upon sensing an overcurrent conduction immediately turning off the switch for the duration of the oscillator cycle. the voltage across the output mosfet is monitored and compared against a reference by the vlx limiter. when the threshold is reached, a signal is sent to the pfm controller block to terminate the power switch conduction. the current limit threshold is typically set at 350 ma. enable / disable operation the ncp1402 series offer ic shut?down mode by chip enable pin (ce pin) to reduce current consumption. an internal pull?up resistor tied the ce pin to out pin by default i.e. user can float the pin ce for permanent aono. when voltage at pin ce is equal or greater than 0.9 v, the chip will be enabled, which means the regulator is in normal operation. w hen voltage at pin ce is less than 0.3 v, the chip is disabled, which means ic is shutdown. important: do not apply a voltage between 0.3 v and 0.9 v to pin ce as this is the ce pin's hyteresis voltage range. clearly defined output states can only be obtained by applying voltage out of this range.
ncp1402 http://onsemi.com 15 applications circuit information 1 3 gnd ce 2 out nc 4 lx 5 ncp1402 figure 59. typical application circuit v out c2 68 f d1 l1 47 h c1 10 f v in step?up converter design equations ncp1402 step?up dc?dc converter designed to operate in continuous conduction mode can be defined by: calculation equation l m v in 2 v out i omax i pk (v in v s) t on l i min i min (t on t off )i o t off (v in v s )t on 2l t off (v in v s) t on (v out v f v in ) q (i l i o )t off v ripple q c out (i l i o )esr *notes: i pk ? peak inductor current i min ? minimum inductor current i o ? desired dc output current i omax ? desired maximum dc output current i l ? average inductor current v in ? nominal operating dc input voltage v out ? desired dc output voltage v f ? diode forward voltage v s ? saturation voltage of the internal fet switch q ? charge stores in the c out during charging up v ripple ? output ripple voltage esr ? equivalent series resistance of the output capacitor m ? an empirical factor, when v out 3.0 v, m = 8 x 10 ?6 , otherwise m = 5.3 x 10 ?6 . external component selection inductor the ncp1402 is designed to work well with a 47 h inductor in most applications. 47 h is a sufficiently low value to allow the use of a small surface mount coil, but large enough to maintain low ripple. low inductance values supply higher output current, but also increase the ripple and reduce efficiency. note that values below 27 h is not recommended due to ncp1402 switch limitations. higher inductor values reduce ripple and improve efficiency, but also limit output current. the inductor should have small dcr, usually less than 1 to minimize loss. it is necessary to choose an inductor with saturation current greater than the peak current which the inductor will encounter in the application. diode the diode is the main source of loss in dc?dc converters. the most importance parameters which affect their efficiency are the forward voltage drop, v f , and the reverse recovery time, t rr . the forward voltage drop creates a loss just by having a voltage across the device while a current flowing through it. the reverse recovery time generates a loss when the diode is reverse biased, and the current appears to actually flow backwards through the diode due to the minority carriers being swept from the p?n junction. a schottky diode with the following characteristics is recommended: small forward voltage, v f < 0.3 v small reverse leakage current fast reverse recovery time/ switching speed rated current larger than peak inductor current, i rated > i pk reverse voltage larger than output voltage, v reverse > v out input capacitor the input capacitor can stabilize the input voltage and minimize peak current ripple from the source. the value of the capacitor depends on the impedance of the input source used. small esr (equivalent series resistance) tantalum or ceramic capacitor with value of 10 f should be suitable.
ncp1402 http://onsemi.com 16 output capacitor the output capacitor is used for sustaining the output voltage when the internal mosfet is switched on and smoothing the ripple voltage. low esr capacitor should be used to reduce output ripple voltage. in general, a 47 uf to 68 uf low esr (0.15 to 0.30 ) tantalum capacitor should be appropriate. for applications where space is a critical factor, two parallel 22 uf low profile smd ceramic capacitors can be used. an evaluation board of ncp1402 has been made in the size of 23 mm x 20 mm only, as shown in figures 60 and 61. please contact your on semiconductor representative for availability. the evaluation board schematic diagram, the artwork and the silkscreen of the surface?mount pcb are shown below: 20 mm 20 mm figure 60. ncp1402 pfm step?up dc?dc converter evaluation board silkscreen figure 61. ncp1402 pfm step?up dc?dc converter evaluation board artwork (component side) 23 mm 23 mm
ncp1402 http://onsemi.com 17 components supplier parts supplier part number description phone inductor, l1 sumida electric co. ltd. cd54?470l inductor 47 h / 0.72 a (852)?2880?6688 schottky diode, d1 on semiconductor corp. mbr0520lt1 schottky power rectifier (852)?2689?0088 output capacitor, c2 kemet electronics corp. T494D686K010AS low esr tantalum capacitor 68 f / 10 v (852)?2305?1168 input capacitor, c1 kemet electronics corp. t491c106k016as low profile tantalum capacitor 10 f / 16 v (852)?2305?1168 pcb layout hints grounding one point grounding should be used for the output power return ground, the input power return ground, and the device switch ground to reduce noise as shown in figure 62, e.g. : c2 gnd, c1 gnd, and u1 gnd are connected at one point in the evaluation board. the input ground and output ground traces must be thick enough for current to flow through and for reducing ground bounce. power signal traces low resistance conducting paths should be used for the power carrying traces to reduce power loss so as to improve efficiency (short and thick traces for connecting the inductor l can also reduce stray inductance), e.g. : short and thick traces listed below are used in the evaluation board: 1. trace from tp1 to l1 2. trace from l1 to lx pin of u1 3. trace from l1 to anode pin of d1 4. trace from cathode pin of d1 to tp2 output capacitor the output capacitor should be placed close to the output terminals to obtain better smoothing effect on the output ripple. 1 3 gnd ce 2 out nc 6 lx 5 ncp1402 on tp1 tp4 tp2 tp3 v in gnd v out gnd c2 68 m f/10 v l1 47 m h jp1 enable c1 10 m f/16 v off d1 mbr0520lt1 figure 62. ncp1402 evaluation board schematic diagram ++
ncp1402 http://onsemi.com 18 package dimensions sot23?5 (tsop?5, sc59?5) sn suffix case 483?02 issue c notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: millimeter. 3. maximum lead thickness includes lead finish thickness. minimum lead thickness is the minimum thickness of base material. 4. a and b dimensions do not include mold flash, protrusions, or gate burrs. dim min max min max inches millimeters a 2.90 3.10 0.1142 0.1220 b 1.30 1.70 0.0512 0.0669 c 0.90 1.10 0.0354 0.0433 d 0.25 0.50 0.0098 0.0197 g 0.85 1.05 0.0335 0.0413 h 0.013 0.100 0.0005 0.0040 j 0.10 0.26 0.0040 0.0102 k 0.20 0.60 0.0079 0.0236 l 1.25 1.55 0.0493 0.0610 m 0 10 0 10 s 2.50 3.00 0.0985 0.1181 0.05 (0.002) 123 54 s a g l b d h c k m j __ _ _ 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 an y particular purpose, nor does scillc assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including wi thout limitation special, consequential or incidental damages. atypicalo parameters which may be provided in scillc data sheets and/or specifications can and do vary in different application s and actual performance may vary over time. all operating parameters, including atypicalso 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 the 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 indemnify and hold scillc and its officers, employees, subsidiaries, af filiates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, direct ly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that scillc was negligent regarding the design or manufacture of the part. scillc is an equal opportunity/affirmative action employer. this literature is subject to all applicable copyright laws and is not for resale in any manner. publication ordering information n. american technical support : 800?282?9855 toll free usa/canada japan : on semiconductor, japan customer focus center 2?9?1 kamimeguro, meguro?ku, tokyo, japan 153?0051 phone : 81?3?5773?3850 ncp1402/d 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 : orderlit@onsemi.com on semiconductor website : http://onsemi.com order literature : http://www.onsemi.com/litorder for additional information, please contact your local sales representative.

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