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innovative power tm - 1 - www.active-semi.com copyright ? 2009 active-semi, inc. features ? 2a output current ? up to 96% efficiency ? 4.5v to 24v input range ? 10a shutdown supply current ? 400khz switching frequency ? adjustable output voltage ? cycle-by-cycle current limit protection ? thermal shutdown protection ? frequency foldback at short circuit ? stability with wide range of capacitors, including low esr ceramic capacitors ? sop-8 package applications ? tft lcd monitors ? portable dvds ? car-powered or battery-powered equipments ? set-top boxes ? telecom power supplies ? dsl and cable modems and routers ? termination supplies general description the act4060a is a current-mode step-down dc/dc converter that provides up to 2a of output current at 400khz switching frequency. the device utilizes active-semi?s proprietary high voltage process for operation with input voltages up to 24v. the act4060a provides fast transient response and eases loop stabilizat ion while providing excellent line and load regulation. this device features a very low on-resistance power mosfet which provides peak operating efficiency up to 96%. in shutdown mode, the act4060a consumes only 10 a of supply current. this device also integrates protection features including cycle-by-cycle current limit, thermal shutdown and frequency fold-back at short circuit. the act4060a is available in a sop-8 package and requires very few external devices for operation. typical application circuit act4060a rev 1, 25-jun-09 wide input 2a step down converter act4060a bs in en comp fb sw g enable up to 24v + 2.5v/2a
act4060a rev 1, 25-jun-09 innovative power tm - 2 - www.active-semi.com copyright ? 2009 active-semi, inc. ordering information part number temperature range package pins packing act4060ash -40c to 85c sop-8 8 tube act4060ash-t -40c to 85c sop-8 8 tape & reel pin descriptions pin name description 1 bs bootstrap. this pin acts as the positive rail for the high-side switch?s gate driver. connect a 10nf capacitor between bs and sw. 2 in input supply. bypass this pin to g with a low esr capacitor. see input capacitor in the application information section. 3 sw switch output. connect this pin to the switching end of the inductor. 4 g ground. 5 fb feedback input. the voltage at this pin is regulated to 1.293v. connect to the resistor divider between output and ground to set output voltage. 6 comp compensation pin. see stability compensation in the application information section. 7 en enable input. when higher than 1.3v, this pin turns the ic on. when lower than 0.7v, this pin turns the ic off. output voltage is discharged when the ic is off. when left unconnected, en is pulled up to 4.5v with a 2a pull-up current. 8 n/c not connected. pin configuration sop-8 1 2 3 4 bs in sw g n/c en comp fb act4060ash 8 7 6 5
act4060a rev 1, 25-jun-09 innovative power tm - 3 - www.active-semi.com copyright ? 2009 active-semi, inc. absolute maximum ratings c parameter value unit in supply voltage -0.3 to 28 v sw voltage -1 to v in + 1 v bs voltage v sw - 0.3 to v sw + 8 v en, fb, comp voltage -0.3 to 6 v continuous sw current internally limited a junction to ambient thermal resistance ( ja ) 105 c/w maximum power dissipation 0.76 w operating junction temperature -40 to 150 c storage temperature -55 to 150 c lead temperature (soldering, 10 sec) 300 c electrical characteristics (v in = 12v, t a = 25c, unless otherwise specified.) parameter symbol test conditions min typ max unit input voltage v in v out = 3.3v, i load = 0a to 1a 4.5 24 v feedback voltage v fb 4.5v v in 24v, v comp = 1.5v 1.267 1.293 1.319 v high-side switch on resistance r onh 0.18 ? low-side switch on resistance r onl 4.5 ? sw leakage v en = 0 0 10 a current limit i lim 2.4 2.85 a comp to current limit transconductance g comp v in = 12v, v out = 5v 1.8 a/v error amplifier transconductance g ea i comp = 10a 650 a/v error amplifier dc gain a vea 4000 v/v switching frequency f sw 350 400 450 khz short circuit switching frequency v fb = 0 60 khz maximum duty cycle d max v fb = 1.1v 95 % minimum duty cycle v fb = 1.4v 0 % enable threshold voltage hysteresis = 0.1v 0.7 1 1.3 v enable pull-up current pin pulled up to 4.5v typically when left unconnected 2 a supply current in shutdown v en = 0 10 20 a ic supply current in operation v en = 3v, v fb = 1.4v 0.55 ma thermal shutdown temperature hysteresis = 10c 160 c c : do not exceed these limits to prevent dama ge to the device. exposure to absolute maxi mum rating conditions for long periods m ay affect device reliability.
act4060a rev 1, 25-jun-09 innovative power tm - 4 - www.active-semi.com copyright ? 2009 active-semi, inc. functional block diagram functional description as seen in functional block diagram , the act4060a is a current mode pulse width modulation (pwm) converter. the converter operates as follows: a switching cycle starts when the rising edge of the oscillator clock output causes the high-side power switch to turn on and the low-side power switch to turn off. with the sw side of the inductor now connected to in, the inductor current ramps up to store energy in the magnetic field. the inductor current level is measured by the current sense amplifier and added to the oscillator ramp signal. if the resulting summation is higher than the comp voltage, the output of the pwm comparator goes high. when this happens or when oscillator clock output goes low, the high-side power switch turns off and the low-side power switch turns on. at this point, the sw side of the inductor swings to a diode voltage below ground, causing the inductor current to decrease and magnetic energy to be transferred to output. this state continues until the cycle starts again. the high-side power switch is driven by logic using bs as the positive rail. this pin is charged to v sw + 6v when the low-side power switch turns on. the comp voltage is the integration of the error between fb input and the internal 1.293v reference. if fb is lower than the reference voltage, comp tends to go higher to increase current to the output. current limit happens when comp reaches its maximum clamp value of 2.55v. the oscillator normally switches at 400khz. however, if fb voltage is less than 0.7v, then the switching frequency decreases until it reaches a typical value of 60khz at v fb = 0.5v. shutdown control the act4060a has an enable input en for turning the ic on or off. when en is less than 0.7v, the ic is in 10 a low current shutdown mode and output is discharged through the low-side power switch. when en is higher than 1.3v, the ic is in normal operation mode. en is internally pulled up with a 2 a current source and can be left unconnected for always-on operation. note that en is a low voltage input with a maximum voltage of 6v, it should never be directly connected to in. thermal shutdown the act4060a automatically turns off when its junction temperature exceeds 160c. in en comp fb bs sw logic thermal shutdown regulator & reference oscillator & ramp foldback control 1.293v error amplifier enable 0.18 ? high-side power switch g pwm comp current sense amplifier 4.5 ? low-side power switch
act4060a rev 1, 25-jun-09 innovative power tm - 5 - www.active-semi.com copyright ? 2009 active-semi, inc. (3) out 2 sw in lc f 28 v + esr ripple outmax ripple r k i v = v out 1.5v 1.8v 2.5v 3.3v 5v l 6.8 h 6.8 h 10 h 15 h 22 h (2) () ripple outmax sw in out in out k i f v v v v l ? = (1) ? ? ? ? ? ? ? = 1 v 293 . 1 v r r out 2 fb 1 fb r fb1 r fb2 v out act4060a fb applications information output voltage setting figure 1: output voltage setting figure 1 shows the connections for setting the output voltage. select the proper ratio of the two feedback resistors r fb1 and r fb2 based on the output voltage. typically, use r fb2 10k ? and determine r fb1 from the following equation: inductor selection the inductor maintains a continuous current to the output load. this inductor current has a ripple that is dependent on the inductance value: higher inductance reduces the peak-to-peak ripple current. the trade off for high inductance value is the increase in inductor core size and series resistance, and the reduction in current handling capability. in general, select an inductance value l based on ripple current requirement: where v in is the input voltage, v out is the output voltage, f sw is the switching frequency, i outmax is the maximum output current, and k ripple is the ripple factor. typically, choose k ripple = 30% to correspond to the peak-to-peak ripple current being 30% of the maximum output current. with this inductor value, the peak inductor current is i out (1 + k ripple /2). make sure that this peak inductor current is less that the 3a current limit. finally, select the inductor core size so that it does not saturate at 3a. typical inductor values for various output voltages are shown in table 1. table 1: typical inductor values input capacitor the input capacitor needs to be carefully selected to maintain sufficiently low ripple at the supply input of the converter. a low esr capacitor is highly recommended. since large current flows in and out of this capacitor during switching, its esr also affects efficiency. the input capacitance needs to be higher than 10f. the best choice is the ceramic type, however, low esr tantalum or electrolytic types may also be used provided that the rms ripple current rating is higher than 50% of the output current. the input capacitor should be placed close to the in and g pins of the ic, with the shortest traces possible. in the case of tantalum or electrolytic types, they c an be further away if a small parallel 0.1f ceramic capacitor is placed right next to the ic. output capacitor the output capacitor also needs to have low esr to keep low output voltage ripple. the output ripple voltage is: where i outmax is the maximum output current, k ripple is the ripple factor, r esr is the esr of the output capacitor, f sw is the switching frequency, l is the inductor value, and c out is the output capacitance. in the case of ceramic output capacitors, r esr is very small and does not contribute to the ripple. therefore, a lower capacitance value can be used for ceramic type. in the case of tantalum or electrolytic capacitors, the ripple is dominated by r esr multiplied by the ripple current. in that case, the output capacitor is chosen to have sufficiently low esr. for ceramic output capacitor, typically choose a capacitance of about 22f. for tantalum or electrolytic capacitors, choose a capacitor with less than 50m ? esr. rectifier diode use a schottky diode as the rectifier to conduct current when the high-side power switch is off. the schottky diode must have current rating higher than the maximum output current and a reverse voltage rating higher than the maximum input voltage.
act4060a rev 1, 25-jun-09 innovative power tm - 6 - www.active-semi.com copyright ? 2009 active-semi, inc. v out c out r comp c comp 2.5v 22 f ceramic 8.2k ? 2.2nf 3.3v 22 f ceramic 12k ? 1.5nf 5v 22 f ceramic 15k ? 1.5nf 2.5v 47 f sp cap 15k ? 1.5nf 3.3v 47 f sp cap 15k ? 1.8nf 5v 47 f sp cap 15k ? 2.7nf 2.5v 470 f/6.3v/30m ? 15k ? 15nf 3.3v 470 f/6.3v/30m ? 15k ? 22nf 5v 470 f/6.3v/30m ? 15k ? 27nf (12) ( ? ) ? ? ? ? ? ? ? ? ? out out 6 esrcout v 012 . 0 , c 10 1 . 1 min r out out 5 comp c v 10 2 . 1 c ? = (f) (11) (10) (f) comp 5 comp r 10 8 . 1 c ? = (9) ( ? ) out out 8 c v 10 7 . 1 = v 3 . 1 g g 10 f c v 2 r comp ea sw out out comp = (7) comp comp 1 z c r 2 1 f = 2 i f = = comp c comp2 c comp r comp act4060a comp esrcout out 2 comp r r c c = (13) comp2 comp 3 p c r 2 1 f = 2 g f = stability compensation figure 2: stability compensation c : c comp2 is needed only for high esr output capacitor the feedback loop of the ic is stabilized by the components at the comp pin, as shown in figure 2. the dc loop gain of the system is determined by the following equation: the dominant pole p1 is due to c comp : the second pole p2 is the output pole: the first zero z1 is due to r comp and c comp : and finally, the third pole is due to r comp and c comp2 (if c comp2 is used): the following steps should be used to compensate the ic: step 1. set the cross over frequency at 1/10 of the switching frequency via r comp : but limit r comp to 15k ? maximum. step 2. set the zero f z1 at 1/4 of the cross over frequency. if r comp is less than 15k ? , the equation for c comp is: if r comp is limited to 15k ? , then the actual cross over frequency is 3.4 / (v out c out ). therefore: step 3. if the output capacitor?s esr is high enough to cause a zero at lower than 4 times the cross over frequency, an additional compensation capacitor c comp2 is required. the condition for using c comp2 is: and the proper value for c comp2 is: though c comp2 is unnecessary when the output capacitor has sufficiently low esr, a small value c comp2 such as 100pf may improve stability against pcb layout parasitic effects. table 2 shows some calculated results based on the compensation method above. table 2: typical compensation for different output voltages and output capacitors figure 4 shows an example ac t4060a application circuit generating a 3.3v/2a output.
act4060a rev 1, 25-jun-09 innovative power tm - 7 - www.active-semi.com copyright ? 2009 active-semi, inc. act4060a pcb layout guidelines. place all the power components (diode, inductor, filter capacitors) as close as possible. use short and wide trace between them. if double layer pcb is used, it is good if the bottom layer is almost fill as gr ound. use ground planes for power ground and signal ground, connect signal ground and power ground at single point close to the ic gnd. arrange the power components so that the switching current loop curl in the same direction. separate noise sensitive traces, such as the voltage feedback path, compensation from noisy sources such as inductor, diode, input capacitor. place components, such as compensation, feedback network and boost-trap capacitors, as close to the ic as possible. ceramic cap c1 is closely placed across v in and gnd of the ic, as close as possible. figure 3: act4060a pcb layout reference 1 2 3 4 5 6 7 8 c1 c3 r1 r2 r3 c2 c4 u1 d1 l1 input gnd vin+ vout gnd output multiple vias en
act4060a rev 1, 25-jun-09 innovative power tm - 8 - www.active-semi.com copyright ? 2009 active-semi, inc. figure 4: act4060a 3.3v/2a output application c c : d1 is a 40v, 3a schottky diode with low forward voltage, an ir 30bq040 or sk34 equivalent. c4 can be either a ceramic capacit or (panasonic ecj-3yb1c226m) or sp-cap (specialty polymer) aluminum electrol ytic capacitor such as panasonic eefcd0j470xr. the sp-cap is based on aluminum electrolytic capacitor technology, but uses a so lid polymer electrolyte and has very stable capacitance characteristics in both operat ing temperature and frequency compared to ceramic, polymer, and low esr tantalum capacitors. ic1 act4060a bs in en comp fb sw g enable up to 24v + v in v out r1 d1 c4 r2 r3 c1 c2 l1 c3 item description manufacturer qty reference 1 ic, act4060a active-semi 1 u1 2 15h 20%, i sat = 2.7a, i dc = 2.4a@ t = 40c taiyo yuden nr 8040t 150m 1 l1 15h 10%, i sat = 2.88a, i dc = 2.47a@ t = 40c wurth electronik 744776115 10h 20%, i sat = 3.4a, i dc = 2.5a@ t = 40c taiyo yuden nr 6045t 100m 10h 10%, i sat = 2.95a, i dc = 2.3a@ t = 40c wurth electronik 74477510 3 schottky diode sk34/40v, 3a, smb transys electronics 1 d1 schottky diode b340c/40v, 3a, smb diodes inc 1 4 ceramic cap 10f/35v, x7r, 1210 murata, tdk,taiyo yuden 1 c1 5 ceramic cap 2.2nf/6.3v, x7r, 0603 murata, tdk,taiyo yuden 1 c2 6 ceramic cap 10nf/50v, x7r, 0603 murata, tdk,taiyo yuden 1 c3 7 ceramic cap 22f/10v, x7r, 1210 murata, tdk,taiyo yuden 1 c4 sp cap 47f/6.3v, 50m ? kemet, panasonic 8 resistor, 15.5k ? , 1/16w, 1%, 0603 fenghua, neohm, yageo 1 r1 9 resistor, 10k ? , 1/16w, 1%, 0603 r2 10 resistor, 12k ? , 1/16w, 5%, 0603 r3 table 3: act4060a bill of materials (apply for 3.3v output application)
act4060a rev 1, 25-jun-09 innovative power tm - 9 - www.active-semi.com copyright ? 2009 active-semi, inc. figure 5: act4060a 5v/2a output application c c : d1 is a 40v, 3a schottky diode with low forward voltage, an ir 30bq040 or sk34 equivalent. c4 can be either a ceramic capacit or (panasonic ecj-3yb1c226m) or sp-cap (specialty polymer) aluminum electrol ytic capacitor such as panasonic eefcd0j470xr. the sp-cap is based on aluminum electrolytic capacitor technology, but uses a so lid polymer electrolyte and has very stable capacitance characteristics in both operat ing temperature and frequency compared to ceramic, polymer, and low esr tantalum capacitors. item description manufacturer qty reference 1 ic, act4060a active-semi 1 u1 2 15h 20%, i sat =2.7a, i dc = 2.4a@ t = 40c taiyo yuden nr 8040t 150m 1 l1 15h 10%, i sat = 2.88a, i dc = 2.47a@ t = 40c wurth electronik 744776115 3 schottky diode sk34/40v, 3a, smb transys electronics 1 d1 schottky diode b340c/40v, 3a, smb diodes inc 4 ceramic cap 10f/35v, x7r, 1210 murata, tdk, taiyo yuden 1 c1 5 ceramic cap 2.2nf/6.3v, x7r, 0603 murata, tdk, taiyo yuden 1 c2 6 ceramic cap 10nf/50v, x7r, 0603 murata, tdk, taiyo yuden 1 c3 7 ceramic cap 22f/10v, x7r, 1210 murata, tdk, taiyo yuden 1 c4 sp cap 47f/6.3v, 50m ? kemet, panasonic 8 resistor, 28.7k ? , 1/16w, 1%, 0603 fenghua, neohm, yageo 1 r1 9 resistor, 10k ? , 1/16w, 1%, 0603 r2 10 resistor, 15k ? , 1/16w, 5%, 0603 r3 table 4: act4060a bill of materials (apply for 5v output application) ic1 act4060a bs in en comp fb sw g enable up to 24v + v in v out r1 d1 c4 r2 r3 c1 c2 l1 c3
act4060a rev 1, 25-jun-09 innovative power tm - 10 - www.active-semi.com copyright ? 2009 active-semi, inc. typical performance characteristics (circuit of figure 4, unless otherwise specified.) efficiency vs. output current efficiency (%) 100 10 output current (ma) act4060a-001 100 1000 10000 v out = 2.5v v in = 12v efficiency vs. output current act4060a-002 v out = 5v 10 output current (ma) 100 1000 10000 v in = 7v v in = 12v input voltage (v) switching frequency (khz) act4060a-005 switching frequency vs. input voltage 405 390 385 395 400 v out = 2.5v i out = 1a 410 temperature (c) feedback voltage (v) act4060a-006 -50 0 50 feedback voltage vs. temperature 150 1.25 1.29 100 1.33 1.27 1.31 380 90 80 70 60 50 40 30 20 10 0 efficiency (%) 100 90 80 70 60 50 40 30 20 10 0 8 4 6 10 12 14 16 18 20 v in = 7v act4060a-004 maximum output current vs. duty cycle maximum output current (ma) 0 3000 4000 1000 2000 duty cycle (% ) 20 0 40 80 100 60 5000 act4060a-003 efficiency vs. output current efficiency (%) 0 60 80 20 40 100 v in = 5v v out = 3.3v v in = 12v output current (ma) 10 100 1000 10000
act4060a rev 1, 25-jun-09 innovative power tm - 11 - www.active-semi.com copyright ? 2009 active-semi, inc. typical performance characteristics cont?d (circuit of figure 4, unless otherwise specified.) act4060a-007 0 shutdown current vs. input voltage input voltage (v) shutdown current (a) 5 10 15 20 25 10 5 15 20 25
act4060a rev 1, 25-jun-09 innovative power tm - 12 - www.active-semi.com copyright ? 2009 active-semi, inc. package outline sop-8 package outline and dimensions symbol dimension in millimeters dimension in inches min max min max a 1.350 1.750 0.053 0.069 a1 0.100 0.250 0.004 0.010 a2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 c 0.190 0.250 0.007 0.010 d 4.700 5.100 0.185 0.201 e 3.800 4.000 0.150 0.157 e1 5.800 6.300 0.228 0.248 e 1.270 typ 0.050 typ l 0.400 1.270 0.016 0.050 0 8 0 8 c d b e active-semi, inc. reserves the right to modify the circui try or specifications without not ice. users should evaluate each product to make sure that it is suitable for their applications. active-semi products are not intended or authorized for use as critical components in life-support devices or systems. acti ve-semi, inc. does not assume any liability arising out of the use of any product or circuit described in this datasheet, nor does it convey any patent license. active-semi and its logo are trademarks of active-semi, inc. for more information on this and other products, contact sales@active-semi.com or visit http://www.active-semi.com. for other inquiries, please send to: 2728 orchard parkway, san jose, ca 95134-2012, usa

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