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BL9313 3 a, 1 8 v synchronous step - down converter www.belling.com.cn 1 v1.0 description the BL9313 is a current mode monolithic buck voltage converter. operating with an i nput range of 4.5 v - 18 v, the BL9313 delivers 3a of continuous output current with two integrated n - channel mosfets. at light loads, regulators operate in low freq uency to maintain high efficiency and low output ripple. the BL9313 guarantees robustness with over current protection, thermal protection, start - up current run - away protection, and input under voltage lockout . the BL9313 is available in a 6 - pin tsot23 - 6 package, which provides a compact solution with minimal external components. features ? 4.5 v to 18 v o perating i nput r ange 3a o utput c urrent ? up to 95 % e fficiency ? h igh efficiency at light load ? fixed 420 khz switching frequency ? input u nder v oltage l ockout ? sta rt - up current run - away protection ? over current protection ? thermal protection ? available in tsot23 - 6 p ackage applications ? distributed power systems ? networking systems ? fpga, dsp, asic power supplies ? green electronics/ appliances ? notebook computers typical application
BL9313 www.belling.com.cn 2 v1.0 pin configuration absolute maximum rating 1 vin, en, sw pin ........................................................................... .............................. ........... - 0.3v to 1 9 v bst pin ................... ........... ....................................................................................sw - 0.3v to sw+6 v fb pin ...................... ................ ............... ..................................................................... ...... - 0.3v to 2.5 v junction temperature 2) 3) .............. .............. ....................................................................................... 1 50 oc lead temperature ... ................... ............... ............................................................................... .... ..... 260oc storage temperature ......... .... ........................................................... ........ ........................ - 65o c to +150 oc r ecommended operating conditions input voltage vin ...................... ....................... ...................................................... ........ ... ........ 4.5 v to 1 8 v output voltage vout ............... ................... ........ .............................................. ........ ............0.8 v to 16.2 v junction temperature (t j ) .... ...................... ..................................................... ........ ............ - 40 oc to 1 25 oc thermal performance 4 ja jc tsot23 - 6 ......... ......... .......................................................................... ..... ............... . ...........1 1 0....55 oc /w note 1) ex ceeding these ratings may damage the device . 2) the BL9313 guarantee s robust performance from - 40 c to 150 c junction temperature. t he junction temperature range specification is assured by design, characterization and correlation with statistical process controls. 3) the BL9313 includes therm al protection that is intended to protect the device in overload conditions. t hermal protection is active when j unction temperature exceeds the maximum operating junction temperature. continuous operation over the specified absolute maximum operating junct ion temperature may damage the device . 4) measured on jesd51 - 7, 4 - layer pcb .
BL9313 www.belling.com.cn 3 v1.0 electrical chara c teristics vin=12v, t a =25 , unless otherwise stated. item symbol condition min. typ. max. units v in undervoltage lockout th re shold v in _min v in fall ing 3. 9 4.1 v v in u ndervoltage lockout hysteresis v in _min_hyst v in ris ing 250 mv shutdown supply current i sd v en =0v 0. 2 0. 3 a supply current i q v en = 5 v, v fb = 2 v 80 100 a feedback voltage v fb 0.588 0.6 0.612 m v top switch resistance 5) r ds(on)t 115 m bo ttom switch resistance 5) r ds(on)b 71 m top switch leakage current i leak_top v in = 16v , v en =0v, v sw =0v 0.5 ua bottom switch leakage current i leak_ bot v in = 16v , v en =0v, v sw =0v 0.5 ua top switch current limit 5) i lim_top minimum duty cycle 5 .5 a swi tch frequency f sw 420 khz minimum on time 5) t on_min 100 ns minimum off time 5) t off_min v fb = 0.7 v 1 30 ns en shut down threshold voltage v e n _th v en falling, fb=0 v 1.2 v en shut down hysteresis v e n _hyst v en rising, fb=0 v 100 mv thermal shutdow n 5) t tsd 145 temperature hysteresis 5) t hys 20 note 5) guaranteed by design .
BL9313 www.belling.com.cn 4 v1.0 pin description pin no . name description 1 bst bo ostrap pin for top switch. a 0. 1uf or larger capacitor should be connected between this pin and the sw pin to supply current to t he top switch and top switch driver. 2 gnd power ground pin. 3 fb output feedback pin. fb senses the output voltage and is regulated by the control loop to 0. 6 v. connect a resistive divider at fb. 4 en drive en pin high to turn on the regulator and low to turn off the regulator. 5 in input voltage pin. vin supplies power to the ic. connect a 4 . 5 v to 18v supply to vin and bypass vin to gnd with a suitably large capacitor to eliminate noise on the input to the ic. 6 sw sw is the switching node that suppl ies power to the output. connect the output lc filter from sw to the output load. block diagram + - + 0 . 6 v fb + - + - + oscillator current ramp clk current sensor - current sensor + error amplifier current comparator logic control 3 . 3 v ldo + - en 1 . 2 v vin bst sw gnd 3 . 3 v internal softstart
BL9313 www.belling.com.cn 5 v1.0 typical performance characteristics vin = 12 v, vo ut = 3.3 v, l = 4.7 h, cout = 47f , ta = +25c, unless otherwise noted s tea dy state test vin= 12 v , v out = 3.3 v iout=3a s tartup through enable vin= 12 v , v out = 3.3 v iout=3a (resist ive load) s hutdown through enable vin= 12 v , v out = 3.3 v iout=3a (resist ive load) h eavy load operation 2a load m edium load operation 1a load l ight load operation 0 a load s hort circuit p rotection vin= 12 v , v out = 3.3 v iout=3a - short s hort circuit recovery vin= 12 v , v out = 3.3 v iout= short - 3a load transient 1 .5 a load 3 a load 1 .5 a load
BL9313 www.belling.com.cn 6 v1.0 typical performance characteristics ( c ontinued) quiescent current vs. temp vin= 12v , v out = 3.3 v , ven=2.5v, vfb=0.8v quiescent current vs. input voltage vin= 12v , v out = 3.3 v , ven=2.5v, vfb=0.8v quiescent current @ temperature =25 f eedback voltage vs. temp. vin= 5v , ven=2.5v, sweep fb voltage @ different temperature load regulation @ vout=3.3v efficiency @ vout=3.3v
BL9313 www.belling.com.cn 7 v1.0 f unctional description the BL9313 is a synchronous, buck voltage converter. current - mode control the BL9313 utilizes current - mode control to regulate the fb voltage. v oltage at the fb pin is regula ted at 0. 6 v so that by connecting an appropriate resistor divider between vout and gnd, designed output voltage can be achieved. pfm mode the BL9313 operates in pfm mode at light load. in pfm mode, switch frequency decrease s when load current drops to boos t power efficiency at light load by reducing switch - loss, while switch frequency increase s when load current rises, minimizing output voltage ripples. internal soft - start . soft - start makes output voltage rising smoothly follow an internal ss voltage until ss voltage is higher than the internal reference voltage. it can provide overshoot of output voltage when startup. power switch n - channel mosfet switc hes are integrated on the BL9313 to down convert the input voltage to the regulated output voltage. since the top mosfet needs a gate voltage great er than the input voltage, a boost capacitor connected between bst and sw pins is required to drive the gate of the top switch. the boost capacitor is charged by the internal 3.3v rail when sw is low. vin under - voltage protection a resistive divider can be connected between vin and ground, with the central tap connected to en, so that when vin drops to the pre - set value, en drops below 1. 2 v to trigger input under voltage lockout protection. output current run - awa y protection at start - up, due to the high voltage at input and low voltage at output, current inertia of the output inductance can be easily built up, resulting in a large start - up output current. a valley current limit is designed in the BL9313 so that on ly when output current drops below the val ley current limit can the top power switch be turned on . by such control mechanism, the output current at start - up is well controlled. over current protection and hiccup BL9313 has a cycle - by - cycle current limit. w hen the inductor current triggers current limit, BL9313 enters hiccup mode and periodically restart the chip. BL9313 will exit hiccup mode while not triggering current limit. thermal protection when the temperature of the BL9313 rises above 1 4 5 c , it is f orced into thermal shut - down. only when core temperature drops below 1 25 c can the regulator becomes active again.
BL9313 www.belling.com.cn 8 v1.0 application information o utput voltage set the output voltage is determined by the resistor divider connected at the fb pin, and the volt age ratio is : v fb v out r 2 r 2 r 1 ? ? where v fb is the feedback voltage and v out is the output voltage. c hoose r 2 around 10 k ~15 k , and then r 1 can be calculated by: r 1 v out 0.6 1 ? ? ? ? ? ? ? r 2 ? the following table lists the recommended values. v out (v) r 1 (k ) r 2 (k ) 2.5 47 15 3.3 49.5 11 5 110 15 inp ut capacitor the input capacitor is used to supply the ac input current to the step - down converter and maintaining the dc input voltage. t he ripple current through the input capacitor can be calculated by: i c1 i load v out v in 1 v out v in ? ? ? ? ? ? ? ? ? where i load is the load current, v out is the out put voltage, v in is the input voltage. thus the input capacitor can be calculated by the following equation when the input ripple voltage is determined. c 1 i load f s ? v in ? v out v in ? 1 v out v in ? ? ? ? ? ? ? ? where c 1 is the input capacitance value, f s is the switching frequency, v in is the input ripple voltage . t he input capacitor can be electrolytic, tantalum or ceramic. t o minimizing the potential noise, a small x5r or x7r ceramic capacitor, i.e. 0.1uf, should be placed as close to the ic as possible when using electrolytic cap acitors. a 22uf ceramic capacitor is recommended in typical application. output capacitor t he output capacitor is required to maintain the dc output voltage, and the capacitance value determines the output ripple voltage. t he output voltage ripple can be calculated by: ? v out v out f s l ? 1 v out v in ? ? ? ? ? ? ? ? r esr 1 8 f s ? c 2 ? ? ? ? ? ? ? ? ? where c 2 is the output capacitance value and r esr is the equivalent series resistance value of the output capacitor. t he output capacitor can be low esr electrolytic, tantalum or ceramic, which lower esr capacitors get lower output ripple voltage. t he output capacitors also affect the system stability and transient response, and a 47uf ceramic capacitor is recommended in typical application. i nductor the inductor is used to supply constant current to the output load, and the value determi nes the ripple current which affect the efficiency and the output voltage ripple. t he ripple current is typically allowed to be 30% of the maximum switch current limit, thus the inductance value
BL9313 www.belling.com.cn 9 v1.0 can be calculated by: l v out f s ? i l ? 1 v out v in ? ? ? ? ? ? ? ? where v in is the input voltage, v out is the output voltage, f s is the switching frequency, and i l is the peak - to - peak inductor ripple current. external boo t strap capacitor a boo t strap capacitor is required to supply voltage to the top switch driver. a 0.1uf low esr ceramic capacitor is r ecommended to connected to the bst pin and sw pin. load transient improvement to improve the load transient performance, a feed forward capacitor (cff) can be added in parallel with the feedback resistor (r1). ( figure 1.). at the same time, to avoid the vo ltage offset which is caused by substrate injection, a 20k resistor (r2) is recommended to insert between the fb pin and resistance divider. fb r 1 r 2 c ff r 0 20 k c 2 figure 1 pcb layout note f or minimum noise problem and best operating performance, th e pcb is preferred to following the guidelines as reference. 1. place the input decoupling capacitor as close to BL9313 (vin pin and pgnd) as possible to eliminate noise at the input pin. t he loop area formed by input capacitor and gnd must be minimized. 2. pu t the feedback trace as far away from the inductor and noisy power traces as possible. 3. the ground plane on the pcb should be as large as possible for better heat dissipation .
BL9313 www.belling.com.cn 10 v1.0 reference design reference 1 : vin : 4.5v ~ 18 v vout: 3.3v iout : 0~3a reference 2: vin : 6.5 v ~ 18 v vout: 5 v iout : 0~3a
BL9313 www.belling.com.cn 11 v1.0 package outline tsot23 - 6 unit : mm 0 10 1 . 1 m a x 0 . 7 0 . 3 0 0 0 . 1 0 . 950 bsc 1 . 90 0 . 20 2 . 6 5 0 . 3 0 2 . 85 0 . 10 0 . 3 0 . 20 1 . 5 5 0 . 1 0 0 . 4 5 0 . 1 5 0 . 2 5 0 . 15 - 0 . 05 + 0 . 1 5

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