www. belling .com .cn 1 2a 3mhz 6 v synchronous buck converter bl8076 description the bl8076 is a high efficiency synchronous, buck dc/dc converter. its input voltage range is from 2.6v to 6 v and provides an adjustable regulated output voltage from 0. 6 v to vin while delivering up to 2 a of output current. the internal synchronous switches increase efficiency and eliminate the need for an external schottky diode. it runs at a fixed 3mhz frequency, which allows the use of small inductor with l<1uh while maintaining a high efficiency and small output voltage ripple. when mode pin is connected to gnd, t he bl8076 is operat ing in pfm/ pwm au to - switch m ode which enhance the efficiency at light - load . the bl8076 is available in dfn 2 x 2 - 8 l and sot23 - 5 packages. features ? adjustable output voltage, vfb=0.6v ? maximum output current is 2 a ? range of operation input voltage: max 6 v ? standby current: 30ua (typ.) ? line regulation: 0.1 %/v (typ.) ? load regulation: 10mv (typ.) ? high efficiency, up to 96% ? environment temperature: - 4 0 ? c ~85 ? applications ? power management for 3g modem ? smart phone ? tablet pc ? set top box ? other battery powered device typical application pin out & marking note c e /cy : product code yw : date code ordering information part no. package tape&reel bl8076 ckbtr dfn2x2 - 8l 3000pcs/reel bl8076 cb5tr sot23 - 5 3000pcs/reel bl8 07 6 a g n d f b p v i n s w 1 0 f 2 2 p f v o u t 1 . 8 v / 2 a v i n 2 . 6 v ~ 5 . 5 v 1 2 0 k 6 0 k a v i n e n m o d e p g n d 1 h 1 3 2 8 7 5 6 4 l c 2 1 2 6 1 0 u f
www. belling .com .cn 2 bl8076 pinout description pin # name description 1 pgnd power ground. bypass with a 10f ceramic capacitor to pvin 2 sw inductor connection. connect an inductor between sw and the regulator output. 3 agnd analog ground, connect to pgnd 4 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 5 en enable pin for the ic. drive this pin to high to enable the part, low to disable. 6 mode when forced high, the device operates in fixed frequency pwm mode. when forced low, it enables the power save mode with automatic transition from pfm mode to fixed frequency pwm mode. this pin must be terminated. 7 avin analog power. short externally to pvin 8 pvin supply voltage. bypass with a 10f ceramic capacitor to pgnd block diagram absolute maximum rating parameter value max input voltage 6 v max operating junction temperature(tj) 1 25 ? c ambient temperature(ta) - 4 0 ? c C 85 ? c package thermal resistance ( ? jc) dfn2x2 - 8l 2 5 ? c / w power dissipation sot - 23 - 5 2 50mw storage temperature(ts) - 40 ? c - 150 ? c lead temperature & time 260 ? c , 10s esd (hbm) >2000v note: exceed these limits to damage to the device. exposure to absolute maximum rating conditions may affect device reliability. + - 0 . 6 v r e f p w m l o g i c a n t i - s h o o t t h r o u g h d r i v e r + - e a + - + - s l o p e c o m p 3 m h z o s c u v l o & t h e r m a l s h u t d o w n v c o m p i s e n s e c o m p n e t w o r k g n d s w v i n e n m o d e f b
www. belling .com .cn 3 bl8076 r ecommended work conditions parameter value input voltage range max. 6 v operating junction t emperature(tj) - 20 ? c C 125 ? c electrical characteristics ( vin= 5 v, t a =25 ? c ) symbol parameter conditions min typ max unit vdd input voltage range 2.6 6.0 v uvlo input under voltage lockout increase vin 2.1 2. 2 v vref feedback voltage vin= 5 v, ven=5v 0. 588 0. 6 0. 612 v ifb lk feedback leakage current 0. 0 1 0. 1 ua iq quiescent current active, vfb= 0.65 v , no switching 30 u a shutdown 0. 1 1 ua lnreg line regulation vin= 2.7 v to 5.5 v 0. 04 %/v ldreg load regulation iout= 0. 1 to 2 a 0. 1 5 % /a fsoc switching frequency 2.4 3 3.6 m hz rdsonp pmos rdson isw=200ma 100 120 mohm rdsonn nmos rdson isw=200ma 80 10 0 mohm ilimit peak current limit 2.5 3 a iswlk sw leakage current vout=5.5v, en=gnd 10 ua v en h , vmdh en /mode high threshold 1.5 v venl , vmdl en /mode low threshold 0.4 v ienlk , imdlk en /mode leakage current en=mode=gnd 1 ua rdischarge discharge resistance en=gnd 180 300 450 o hm typical performance characteristics (v in= 3.6 v, l=1 uh, cin=10uf, cout= 10 uf, t a =25 ? c , unless otherwise stated) 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.0 0.5 1.0 1.5 2.0 2.5 efficiency iout(a) efficiency at vout=3.3v vin=3.7v vin=4.2v vin=5.0v 0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00% 90.00% 100.00% 0.0 0.5 1.0 1.5 2.0 2.5 efficiency iout(a) efficiency at vout=1.8v vin=5.0v vin=3.0v vin=3.6v
www. belling .com .cn 4 bl8076 switching waveform vin= 3.6 v, vout=1.2v iout=0 a switching waveform vin= 3.6 v, vout=1.2v iout= 0.7 a switching waveform vin=5v, vout=3.3v, iout =0 a switching waveform vin=5v, vout=3.3v, iout= 0.5 a 0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00% 90.00% 100.00% 0.0 0.5 1.0 1.5 2.0 2.5 efficiency iout(a) efficiency at vout=1.2v vin=3.0v vin=3.6v vin=5.0v v out sw i_ inductor sw v out i_ inductor sw v out i_ inductor sw v out i_ inductor 1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 1.9 1.95 2 0 0.5 1 1.5 2 2.5 vout (v) iout(a) load regulation at vout=1.8v vin=3v vin=3.6v vin=5v
www. belling .com .cn 5 bl8076 load transient vin= 3 . 6 v, vout=1.2v, iout=0.2a/1a load transient vin=3.6v, vout=1.8v, iout=0.2a/1.5a functional decriptions the bl8076 high efficiency switching regulator is a small, simple, dc - to - dc step - down converter capable of delivering up to 2 a of output current. the device operates in pulse - width modulation (pwm) at 3 mhz from a 2.6v to 5.5v input voltage and provides an output voltage from 0.6v to vin, making the bl8076 ideal for on - board post - regulation applications. an internal synchronous r ectifier improves efficiency and eliminates the typical schottky free - 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. loop oper ation bl8076 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 i nductor current as a function of the output voltage error 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 dow n while still providing current to the output. current sense 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 si gnal. the summed signal then is compared with the error amplifier output by the pwm comparator to terminate the on cycle. current limit there is a cycle - by - cycle current limit on the high - side mosfet. when the current flowing out of sw exceeds this limit, the high - side mosfet turns off and the synchronous rectifier turns on. bl8076 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 200 mv, limiting the current to ipeak and reducing power dissipation. normal operation resumes upon removal of the short - circuit condition. soft start bl8076 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. sw v out i_ inductor i_ inductor v out sw
www. belling .com .cn 6 bl8076 uvlo and thermal shutdown if v in drops below 2v, the uvlo circuit inhibits switching. once v in rises above 2. 1 v, the uvlo clears, and the soft - start sequence activates. thermal - overload protection limits total power dissipation in the device. when the junction temperature exceeds tj= +160c, a thermal sensor forces the device into shutdown, allowing the die to cool. the thermal sensor turns the device on again after the junction temperature cools by 15c, resulting in a pulsed output du ring continuous overload conditions. following a thermal - shutdown condition, the soft - start sequence begins. design procedure inductor selection the peak - to - peak ripple is limited to 30% of the maximum output current. this places the peak current far enough from the minimum overcurrent trip level to ensure reliable operation while providing enough current ripples for the current mode converter to operate stably. in this case, for 2a maximum output current, t he maximum i nductor ripple current is 6 67 ma. the inductor size is estimated as following equatio n: l ideal =(v in(max) - v out )/i ripple *d min *(1/f osc ) therefore, for v out =1.8v, the inductor values is calculated to be l = 0.60 h . cho o se 1 h a nd f or v out =1.2v, the inductor values is calculated to be l = 0.469 h . cho o se 0.47 h the resulting ripple is i ripple =(v in(max) - v out )/l actual *d min *(1/f osc ) when, v out =1.8v, i ripple = 403ma v out =1.2v, i ripple = 665ma output capacitor selection for most applications a nominal 10f or 22f capacitor is suitable. the bl8076 internal compensation is designed for a fixed corner frequency that is equal to fc= = 50khz for example, for v out =1.8v, l=1 h, c out =10 f, for v out =1.2v, l=0.47 h, c out =22 f setting output voltage output voltages are set by external resistors. the fb_ threshold is 0.6v. r top = r bottom x [(v out / 0.6) - 1] guidelines for input capacitor and output capacitor 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. the output capacitor must also have low impedance at the switching frequency. ceramic, polymer, and tantalum capacitors are suitable, with ce ramic exhibiting the lowest esr and high - frequency impedance. output ripple with a ceramic output capacitor is approximately as follows: v ripple = il (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) = il (peak) x esr
www. belling .com .cn 7 bl8076 package out line package dfn2x2 - 8l devices per reel 30 00 pcs unit mm package specification package sot - 23 - 5 devices per reel 3000pcs unit mm package specification
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