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a i t s em i c ond u ctor i n c . www.ait - ic.com a 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 1 - de s cri p t i o n f eat u r es the A7110 is a high - efficiency, dc - to - dc step - down switching regulators, capable of delivering up to 1.0a of output current. the device operates from an input voltage range of 2.5v to 6.5v and provides an output voltage from 0.6v to v in , making the A7110 ideal for low voltage power conversions. running at a fixed frequency of 1.5mhz allows the use of small external components, such as ceramic input and output caps, as well as small inductors, while still providing low output ripples. this low noise output along with its excellent efficiency achieved by the internal synchronous rectifier, making A7110 an ideal green replacement for large power consuming linear regulators. internal soft - start control circuitry reduces inrush current. shor t- circuit and thermal - overload protection improves design reliability. the A7110 is available in sot - 25 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 - 25 e5 A7110e5r - xxx A7110e5vr - xxx note xxx: output voltage: adj v: halogen free packag e r: tape & reel spq: 3,000pcs / reel ait provides all rohs products suffix v means halogen free package ? high efficiency: up to 96% ? capable of delivering 1.0a ? 1.5mhz switching frequency ? no external schottky diode needed ? low dropout 100% duty operati on ? internal compensation and soft - start ? current mode control ? 0.6v reference for low output voltages ? logic control shutdown (i q <1ua) ? thermal shutdown and uvlo ? available in sot - 25 package appl i c at i o n ? cellular phones ? digital cameras ? mp3 and mp4 players ? s et top boxes ? wireless and dsl modems ? usb supplied devices in notebooks ? portable devices 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 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 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 en enable pin for the ic. drive the pin to high to enable the part, and low to disable 2 gnd ground 3 sw inductor connection. connect an inductor between sw and the regulator output. 4 in supply voltage. 5 fb feedback input. connect an external resistor divider from the output to fb and gnd to set the output to a voltage between 0.6v and vin
a i t s em i c ond u ctor i n c . www.ait - ic.com a 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 3 - abso l u t e m ax i m u m r at i n g s max input voltage 7.5v t j , max operating junction temperature 125 c t a , ambient temperature - 40 c ~ 85 c maximum power dissipation sot - 25 400mw t s , storage temperature - 40 c ~ 150 c lead temperature & time 260 c, 10 s esd (hbm) >2000v 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 thos e indicated in the operational sections of the specifications are not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. re co m m e nde d o p e ra t i ng co ndi t i o ns p ar a met er s y mb ol m in m ax u n it s input volta ge range - 6.5 v operating junction temperature t j - 20 125 c
a i t s em i c ond u ctor i n c . www.ait - ic.com a 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 4 - e l e ct ri ca l cha ra ct e ri s t i cs v dd =5v, t a =25 c p ar a met er s y mb ol c ond i t i ons mi n. t y p. m ax . u n it input voltage range v dd 2.5 6.5 v feedback voltage vref 0.585 0.6 0.615 v feedback leakage current i fb 0.1 0.4 ua quiescent current i q active, v fb =0.65, no switching 80 ua shutdown 1 ua line regulation lnreg v in =2. 5 v to 6 .5v 0.04 0.2 %/v load regulation ldreg i out =0.01 to 1 .5 a 0.1 0.2 %/a switching frequency f soc 1.5 mhz pmos r dson r dson p 400 500 m nmos r dson r dson n 320 400 m peak current limit i limit 1.0 a sw leakage current i swlk v out =5.5v, v sw =0 or 5.5v, en=0v 10 ua en leakage current i enlk 1 ua en input high voltage v h_en 1.5 v en input low voltage v l_en 0.4 v
a i t s em i c ond u ctor i n c . www.ait - ic.com a 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 5 - t y p i ca l p e rf o rm a n ce cha ra ct e ri s t i cs tested under t a =25 c, unless otherwise specified 1. efficiency vs. load current 2. efficiency vs. load current 3. efficiency vs. load current 4. v fb vs. temperature
a i t s em i c ond u ctor i n c . www.ait - ic.com a 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 6 - 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 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 7 - d e t a il e d in f or m a t ion the A7110 high - efficiency switching regulator is a small, simple, dc - to - dc step - down converter capable of delivering up to 1.0a of output current. the device operates in pulse - width modulation (pwm) at 1.5mhz from a 2.5v to 6.5v input voltage and provides an output voltage from 0.6v to v in , making the A7110 ideal for on - board post - regulation applications. an internal synchronous rectifier improves efficiency and eliminates the typical schottky f ree - wheeling diode. using the on resistance of the internal high - side mosfet to sense switching currents eliminates current - sense resistors, further improving efficiency and cost. l oo p o per at i on A7110 uses a pwm current - mode control scheme. an open - loop comparator compares the integrated voltage - feedback signal against the sum of the amplified current - sense signal and the slope compensation ramp. at each rising edge of the internal clock, the internal high - side mosfet turns on until the pwm comparator terminates the on cycle. during this on - time, current ramps up through the inductor, sourcing current to the output and storing energy in the inductor. the current mode feedback system regulates the peak inductor current as a function of the output voltage err or signal. during the off cycle, the internal high - side p- channel mosfet turns off, and the internal low - side n - channel mosfet turns on. the inductor releases the stored energy as its current ramps down while still providing current to the output. c ur r ent se n s e an internal current - sense amplifier senses the current through the high - side mosfet during on time and produces a proportional current signal, which is used to sum with the slope compensation signal. the summed signal then is compared with the error amplifier output by the pwm comparator to terminate the on cycle. c ur r ent li mi t there is a cycle - by - cycle current limit on the high - side mosfet of 1.0a(min). when the current flowing out of sw exceeds this limit, the high - side mosfet turns off and the synchronous rectifier turns on. A7110 utilizes a frequency fold - back mode to prevent overheating during short - circuit output conditions. the device enters frequency fold - back mode when the fb voltage drops below 200mv, limiting the current to 1.0a (min) and reducing power dissipation. normal operation resumes upon removal of the short - circuit condition.
a i t s em i c ond u ctor i n c . www.ait - ic.com a 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 8 - s of t - s t ar t A7110 has a internal soft - start circuitry to reduce supply inrush current during startup conditions. when the device exits under - voltage lockout (uvlo), shutdown mode, or restarts following a thermal - overload event, the l soft - start circuitry slowly ramps up current available at sw. u v lo and t her ma l s hut dow n if in drops below 2.5v, the uvlo circuit inhibits switching. once in rises above 2.6v, the uvlo clears, and the soft - start sequence activates. thermal - overload protection limits total power dissipation in the device. when the junction temperature exceeds t j = +160 c, a thermal sensor forces the device into shutdown, allowing the die to cool. th e thermal sensor turns the device on again after the junction temperature cools by 15 c, resulting in a pulsed output during continuous overload conditions. following a thermal - shutdown condition, the soft - start sequence begins. d es i g n p r oc ed ur e 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 0.6v. rtop = rbottom[(v out / 0.6) - 1] 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 pow er 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. 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 o ut put c a pac i t or a nd i nd uc t or s el ec t i o n follow the below table for inductor and output cap selection: v out 1.2v 1.5v 1.8v 2.5v 3.3v c out 33 f 33 f 22 f 22 f 10 f l 1.5 h 1.5 h 2.2 h 3.3 h 4.7 h
a i t s em i c ond u ctor i n c . www.ait - ic.com a 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 9 - if much smaller values are used, inductor current rises, and a larger output capacitance may be required to suppress output ripple. larger values than lideal can be used to obtain higher output current, but typically with larger inductor size. a pp l i c at i on i nf or mat i o n layout is critical to achieve clean and stable operation. the switching power stage requires particular attention. follow these guidelines for good pc board layout: 1. place decoupling capacitors as close to the ic as possible 2. connect input and output capacitors to the same power ground node with a star ground configuration then to ic ground. 3. keep the high - current paths as short and wide as possible. keep the path of switching current (c1 to in and c1 to gnd) short. avoid vias in the switching paths. 4. if possible, connect in, sw, and gnd separately to a large copper area to help cool the ic to further improve efficiency and long - term reliability. 5. ensure all feedback connections are short and direct. place the feedback resistors as close to the ic as possible. 6. route high - speed switching nodes away from sensitive analog areas
a i t s em i c ond u ctor i n c . www.ait - ic.com a 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 10 - p a c k a ge in f or m a t ion dimension in sot - 25 (unit: mm)
a i t s em i c ond u ctor i n c . www.ait - ic.com a 71 10 dc - dc converter/ buck (step - down) 1.0a 1.5mhz synchronous rev 2.1 - jan 2009 rel eased , may 201 6 updated - - 11 - i m p o rt a nt no t i ce a it semiconductor inc. (ait) reserves 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 application sup port. ait warrants the performance of its products of the specifications applicable at the time of sa le.

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