sc46166 300ma ,500khz high efficiency step-up dc/dc converter sot-89-5 sot-23-6 description the sc46166 is a compact, high efficiency, and low voltage step-up dc/dc converter, inclu des an error amplifier, ramp generator, current comparator, sl ope compensation, current sense and driver. peak current mode pwm control with internal compensation reduces external parts count and provides a stable and high efficient operation over a wide range of load currents. the low start-up input voltage below 0.85v makes sc46166 suitable for 1 to 4 battery cells applications. a high switching frequency of 500khz minimizes overall solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. the sc46166 shifts automatically to power saving mode operation at light loads, the 20ua low quiescent current together with high efficiency maintains long battery lifetime. the device also features low shutdown current of under 1 a. features * 0.85v low start-up input voltage * high supply capability to deliver 3.3v 100ma with 1 alkaline cell * automatic power saving mode operation with 20 a quiescent supply current * up to 90% efficiency * output range: 2.5v to 6v * shutdown mode supply current : <1ua * 500khz fixed switching frequency * over temperature protection * 4kv hbm esd * small sot-23-6 & sot-89-5 package applications * mp3 players * digital cameras * pda * lcd bias supplies * portable instrument * wireless equipment ordering information package seal device sc46166 sot-23-6 46166 SC46166S sot-89-5 46166s hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 1 of 11
sc46166 block diagram absolute maximum ratings (t amb =25 c) rating unit characteristics -0.3~+6 v v dd supply voltage -0.3~+6 v lx voltage -0.3~+6 v en voltage -0.3~+6 v fb voltage -40 ~ + 85 c operating temperature -65 ~ +125 storage temperature c electrical characteristics (t amb =25 c, v in =1.5v,v dd =3.3v,load current=0 unless otherwise specified) characteristics symbol test condition min. typ. max. unit minimum start-up voltage v st i l =1ma, measured on v dd -- 0.85 0.9 v operating vdd range v dd v dd pin voltage 2.5 -- 6 v feedback reference voltage v fb 1.2 1.23 1.26 v quiescent current (power saving mode) i switch off fb=1.4v -- 20 30 a quiescent current (shutdown) i st en=0v -- 0.1 1 a quiescent current (pwm active mode) i q measured on v dd , nonswitching -- 300 360 a hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 2 of 11
sc46166 hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 3 of 11 characteristics symbol test condition min. typ. max. unit power saving mode current threshold i load l=4.7 h -- 7.5 -- ma line regulation v line 1v v in 3 v -- 2 10 mv/v load regulation v load 1ma i l 100ma -- 0.1 1 mv/ma switching frequency fs -- 450 500 550 khz max duty cycle d max fb=1.2v 90 95 -- % nmos switch on resistance r on v dd =3.3v -- 0.4 0.5 nmos switch leakage i leak v lx 5v -- 0.1 1 a nmos current limit i limit 0.75 1 1.25 a en input high v h -- 1 -- -- v en input low v l -- -- -- 0.35 v thermal shutdown temperature t j(sd) -- -- 150 -- c thermal shutdown hysterises t hyst -- -- 20 -- c pin configuration pin description pin no. sc46166 SC46166S pin name i/o pin description 1 1 en i chip enable (active high) 2 nc not connect 3 5 gnd g ground 4 4 lx i/o switch pin. connect inductor between lx and v in 5 2 v dd p power supply pin of sc46166 6 3 fb i feedback input pin function description the sc46166 is a 500khz, asynchronous boost converter housed in a compact package, includes a voltage reference, error amplifier, ramp generator, current co mparator, slope compensation, current sense and driver. the low start-up function allows sc46166 operating fr om an input voltage below 1v, 0.85v typically at v dd . in
sc46166 current mode pwm operation,sc46 166 automatically detects the output, if the output l oad current falls below an internally programmed threshold (the threshold has an de pendence on the input voltag e, output voltage and also the value of the external inductor.), it shifts to power saving mode operation, in which the ic consumes only 20 a, the efficiency is increased. however, the output ripple typically increases. power saving mode ripple can be reduced, by placing a small feed-fo rward capacitor (an empirical suggestion is around 0.1~10nf) between v out and fb pins. operating at heavy loads for a long time, the die temperature will rise, if the die temperature continues to rise and reaches 150 c, the device shuts off entirely, the part will be enabl ed again when the die temperature drops by about 20 c. applications information output voltage setting referring to the figure1, the output voltage of the switching regulator (v out ) can be set with equation following: )x1.23v r2 r1 (1v out += feedback loop design referring to application circuit of figure1, the selection of r1 and r2 are based on the trade-off between quiescent current consumption and interf erence immunity. higher r reduces t he quiescent current (path current = 1.23v/r2), however resistors beyond 5m , are not recommended. lower r gives better noise immunity, and is less sensitive to interference, layout parasitics, fb node leakage, and improper probing to fb pins. a proper value of feed-forward capacitor c1 parallel with r1 can improve the noise immunity of the feedback loops, especially in an improper layout. an empirical suggestion is around 100pf~1nf for feedback resistors of m , and 10nf~100nf for feedback resistors of hundreds k . component selection ? inductor selection the sc46166 can utilize small surface mount and chip inductors due to its fast 500khz switching frequency. typically, a 4.7 h inductor is recommended for most applications. larger values of inductance will allow greater output current capability by reducing t he inductor ripple current. increasing the inductance above will also increase size . hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 4 of 11
sc46166 the inductor current ripple is typically set for 20% to 40% of the maximum inductor current (ip). the inductor should have low esr (series resistance of the windings) to reduce the power losses, and must be able to handle the peak inductor current without saturating. to minimi ze radiated noise, use a shielded bobbin inductor. ? output and input capacitor selection low esr (equivalent series resistance) capacitors shou ld be used to minimize the output voltage ripple. multilayer ceramic capacitors are an excellent choice as they have extremely low esr and are available in small footprints. a 10 f to 22 f output capacitor is sufficient for most applic ations. larger values may be used to obtain extremely low output voltage ripple an d improve transient response. low esr input capacitors reduce input switching noise a nd reduce the peak current drawn from the battery. it follows that ceramic capacitors are also a good choice for input decoupling, and should be located as close as possible to the device. a 4.7 f input capacitor is sufficient for virtually any application. operating at light loads, a additional feed forward capacitor may be requi red (for example c1 in the figure 1)to maintain acceptable output voltage ripple. for all the three capacitors above, x5r and x7r dielectric materials are preferred, for their ability to maintain capacitance over wide volt age and temperature ranges. hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 5 of 11
sc46166 typical electrical characteristics curves (t amb =25 c, unless otherwise specified) (to be continued) hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 6 of 11
sc46166 (continued) typical electrical characteristics curves (t amb =25 c, unless otherwise specified) output ripple & lx time (1us/div) v in =1.5v v out =3.3v@100ma output ripple & lx time (1us/div) v in =3v v out =5v@100ma hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 7 of 11
sc46166 typical application circuit figure 1. application circuit for 2-cell to 3.3v boost converter note: the circuit and parameters are reference only, please set the parameters of the r eal application circuit based on the real test . hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 8 of 11
sc46166 package outline sot-23-6 unit: mm sot-89-5 unit: mm hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 9 of 11
sc46166 handling mos devices: electrostatic charges can exist in many things. all of our mos devices are internally protected against electrostatic discharge but they can be damaged if the following precautions are not taken: ? persons at a work bench should be earthed via a wrist strap. ? equipment cases should be earthed. ? ? all tools used during assembly, including solder ing tools and solder baths, must be earthed. ? mos devices should be packed for dispatch in antistatic/conductive containers. note: silan reserves the right to make changes without notice in this specification for the improvement of the design and perfo rmance. silan will supply the best possible product for customers. hangzhou silan microelectronics co.,ltd rev:1.2 2008.07.04 http://www.silan.com.cn page 10 of 11
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