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a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 1 - de s cri p t i o n f eat u r es the A7407 is a wide input range, high - efficiency, and high frequency dc - to - dc step - down switching regulator, capable of delivering up to 0.7a of output current. with a fixed switching frequency of 660khz, this current mode pwm controlled converter allows the use of small external components, such as ceramic input and output caps, as well as small inductors. A7407 also employs a proprietary control scheme that switches the device into a power save mode during light load, thereby extending the range of high efficiency operation. an ovp function protects the ic itself and its downstream system against input voltage surges. with this ovp function, the ic can stand off input voltage as high as 42v, making it an ideal solution for industrial applications such as smart meters as well as automotive applications. in automotive systems, power comes from the battery, with its voltage typically between 9v and 24v. including cold crank and double battery jump - starts, the minimum input voltage may be as low as 4v and the maximum up to 36v, with even higher transient voltages. with these high input voltages, linear regulators cannot be used for high supply currents without overheating the regulator. instead, high efficiency switching regulators such as A7407 must be used to minimize thermal dissipation. the A7407 is available in sot - 26 package. o rde ri ng i nf o rm a t i o n p ac k ag e t y pe p ar t n um ber sot - 26 e6 A7407e6r A7407e6vr note v: halogen free package r: tape & reel ait provides all rohs products suf fix v means halogen free package ? wide input operating range from 4v to 38v ? standoff input voltage: 42v ? high efficiency at 12v in 5v out: up to 92%: ? high efficiency pfm mode at light load ? capable of delivering 0.7a ? no external compensation needed ? current mode control ? logic control shutdown ? thermal shutdown and uvlo ? available in sot - 26 package appl i c at i o n ? smart meters ? industrial applications ? automotive applications t ypi c al ap pl i c at i o n
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 2 - p i n de s cri p t i o n top view p i n # s y mb ol f u nc t i on 1 bst bootstrap pin. connect a 10nf capacitor from this pin to sw 2 gnd ground 3 fb feedback input. connect an external resistor divider from the output to fb and gnd to set v out 4 en enable pin for the ic. drive this pin high to enable the part, low to disable. 5 in supply voltage. bypass with a 10f ceramic capacitor to gnd 6 sw inductor connection. connect an inductor between sw and the regulator output.
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 3 - abso l u t e m ax i m u m r at i n g s input voltage range - 0.3v ~ 42v max operating junction temperature(tj) 150c s w, en voltage - 0.3v ~ v in +0.3v bst voltage - 0.3v ~ sw+6v fb voltage - 0.3v ~ 6v sw to ground curren t internally limited t j , operating junction temperature - 40c ~ 85c jc , package thermal resistance 110c / w t s , storage temperature - 55c ~ 150c stress beyond above listed absolute maximum ratings may lead permanent damage to the device. these are stress ratings only and operations of the device at these or any other conditions beyond those indicated in the operational sections of the specifications are not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. e l e ct ri ca l cha ra ct e ri s t i cs v in = 12v, unless otherwise specified. typical values are at t a = 25 c . p ar a met er c ond i t i ons mi n. t y p. m ax . u n it input standoff voltage 42 v input voltage range 4 38 v input uvlo rising, hysteresis=140mv 3.8 v input ovp rising, hysteresis=1.3v 38 v input supply current v fb =0.85v 0.6 ma input shutdown current 6 a fb feedback vol tage 0.8 v fb input current 0.01 a switching frequency 660 khz maximum duty cycle 90 % foldback frequency v fb = 0v 60 khz high side switch on resistance i sw =200ma 400 m high side switch current limit 1.2 a sw leakage current v in =12v,v sw =0, en= gnd 10 a en input current v in =12v ,v en =5v 1 5 a en input low voltage rising, hysteresis=100mv 0.8 1.1 1.4 v thermal shutdown hysteresis=40c 150 c
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 4 - t y p i ca l p e rf o rm a n ce cha ra ct e ri s t i cs typical values are at t a = 25c , unless otherwise specified. 1. efficiency vs. i out 2. efficiency vs. i out 3. i q vs. v in 4. v out vs. i out 5. v out vs. v in 6. v out vs. temperature
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 5 - 7. frequency vs. t emperature 8. start - up waveform with en v in =12v,v out =5v,i out =0a 9. start - up waveform with en=v in v in =12v,v out =5v,i out =0a 10. shutdown waveform with en v in =30v,v out =5v,i out =0.5a 11. switching waveform v in =12v,v out =5v,i out =0.1a 12. switching waveform v in =12v,v out =5v,i out =0.3a
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 6 - 13. load transient response v in =12v,v out =3.3v,i out =0 to 0.5a 14. load transient response v in =12v,v out =5v,i out =0 to 0.5a 15. short - circuit response v in =24v,v out =5v, i out = 0 to s hort 16. short - circuit recovery v in =24v,v out =5v,i out = short to 0a
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 7 - bl o c k d i ag r am
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 8 - d e t a il e d in f or m a t ion f u nc t i ona l de s c r i pt i ons l oo p o per at i on the A7407 is a wide input range, high - efficiency, dc - to - dc step - down switching regulator, capable of delivering up to 0.7a of output current, integrated with a 400m high side mosfet. it uses a pwm current - mode control scheme. an error amplifier integrates error between the fb signal and t he internal reference voltage. the output of the integrator is then compared to the sum of a current - sense signal and the slope compensation ramp. this operation generates a pwm signal that modulates the duty cycle of t he power mosfets to achieve regulation for output voltage. l i g ht loa d o p er at i on traditionally, a fixed constant frequency pwm dc - dc regulator always switches even when the output load is small. when energy is shuffling back and forth through the power mosfets, power is lost due to the finite rdsons of the mosfets and parasitic capacitances. at light load, this loss is prominent and efficiency is therefore very low. A7407 employs a proprietary control scheme that improves efficiency in this sit uation by enabling the device into a power save mode during light load, thereby extending the range of high effici ency operation. a pp l i c at i on i nf or mat i o n s et t i n g o ut put v ol t ag es output voltages are set by external resistors. the fb threshold is 0.8v. r top = r bottom x [(v out / 0.8) - 1] i nduc t or s el ec t i o n the peak - to - peak ripple is limited to 30% of the maximum output current. this places t he peak current far enough from the minimum over current trip level to ensure reliable operation while providing enough current ripples for the current mode converter to operate stably. in this case, for 0.7a maximum output current, the maximum inductor ripple current is 300ma. the inductor size is estimated as following eq uation: lideal= (v in(max) -v out )/i ripple *dmin*(1/f osc ) therefore, for v out =5v, t he induct or values is calculated to be l =13h. chose 10h or 15h for v out =3.3v, t he inductor values is calculate d to be l= 9.2h. chose 10h
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 9 - o ut put c a pac i t or s el ec t i on for most applications a nomi nal 22f or larger capacitor is suitable. the A7407 i nternal compensation is designed for a fixed corner frequency that is equal to fc= 8.7k h z for example, for v out =5v, l=15h, c out =22f. the output capacitor keeps output ripple small and ensures control - loop stability. the output capacitor must also have low impedance at the switching frequency. ceramic, polymer, and tantalum capacitors are suitable, with ceramic exhibiting the lowest esr and high - frequency impedance. output ripple with a ceramic output capacitor is approximately as follows: v ripple = i l(peak) [1 / (2 x f osc x c out )] if the capacitor has significant esr, the output ripple component due to capacitor esr is as follows: v ripple(esr ) = i l(peak) x esr i npu t c a pac i t or s e l ec t i on the input capacitor in a dc - to - dc converter reduces current peaks drawn from the battery or other input power source and reduces switching noise in the controller. the impedance of the input capacitor at the switching frequency should be less than that of the input source so high - frequency switching currents do not pass through the input source. the output capacitor keeps output ripple small and ensures control - loop stability. c omp on ent s s e l ec t i on v out (v) c out (f) l (h) 8 .0 22 15 to 22 5 .0 22 10 to 15 3.3 22 6.8 to 10
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 10 - p a c k a ge in f or m a t ion dimension in sot -26 package (unit : mm) sym b o l m in m ax a 1.050 1.250 a1 0.000 0.100 a2 1.050 1.150 b 0.300 0.500 c 0.100 0.200 d 2.820 3.020 e 1.500 1.700 e1 2.650 2.950 e 0.950(bsc) e1 1.800 2.000 l 0.300 0.600 0 8
a i t s em i c ond u ctor i n c . www.ait - ic.com a 74 07 dc - dc converter/ buck (step - down) 42v input standoff voltage, 0.7a step - down converter rev1. 1 - may 201 3 released , nov 201 4 updated - - 11 - i m p o rt a nt no t i ce ait semiconductor inc. (ait) rese rves the right to make changes to any its product, specifications, to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. ait semiconductor inc.'s integrated circuit products are not designed, i ntended, authorized, or warranted to be suitable for use in life support applications, devices or systems or other critical applications. use of ait products in such applications is understood to be fully at the risk of the customer. as used herei n may involve potential risks of death, personal injury, or servere property, or environmental damage. in order to minimize risks associated with the customer's applications, the customer should provide adeq uate design and operating safeguards. ait semiconductor inc. assumes to no liability to customer product design or applicat ion support. ait warrants the performance of its products of the specifications applicable at the time of sa le.

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