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www.siliconstandard.com 1 of 12 ss6620/21/2 high efficiency synchronous step - up dc/dc converter n features l high e fficiency of 93 % (v in =2.4v, v out =3.3v, i out =200 ma ). l quiescent s upply c u r rent of 20 m a . l power - s aving s hutdown m ode (0.1 m a typical). l internal s ynchronous r ectifier ( no external d i ode ) l selectable c ur rent l imit for r educed r ipple ( ss6622). l low n oise , a nti -r inging f eature ( ss6622) l on - c hip l ow - b attery d etector. l low - b attery h ysteresis n applications l palmtop & n otebook c omputers. l pdas l wireless p hones l pocket o rganizers. l cameras. l 1 to 2 - c ell hand - h eld d evices n description the ss6620/21/22 are high-efficiency step- up dc / dc converter s, with start - up vol t age as low as 0.8v and o p erat ing with an i np ut vol t age down to 0.7v. co n su m ing only 20 m a of quie s- cent current , t hese d e vices o f fer a built - in sy n- chronous rectifier that r e duce s size and cost by eliminating the need for an exte r nal schottky d i ode , i m prov ing overall e ff i ciency by minimi z- ing losses. the switching frequency depends on the load and the input voltage and can range up to 500khz. the peak current of the internal switch i s fixed at 0.8a (ss6620), at 0.45a (ss6621), or is selectable (ss6622) for design flex i bility. ri p ple does not exceed the product of the switch current limit and the filter capacitor equivalent - series - resistance (esr) . the ss6622 also features a circuit that eliminates noise caused by indu c tor rin g ing. n typical application circuit output 3.3v, or adj. (1.8v to 4.0v) up to 300ma low - battery detect out fb gnd + on off + low - battery detect in 0.1 m f v in 22 m h 220 m f 100 m f ss6620 ss6621 ss6622 out ref lbo shdn lx lbi lbo fb re v . 2.01 6/06 /200 3
www.siliconstandard.com 2 of 12 ss6620/21/2 n ordering information ss6620cx xx ss6621cx xx ss6622cx xx pin configuration ( m so p8) top view ss6622 1 3 4 2 10 8 7 9 fb lbi lbo clsel ref out lx gnd batt shdn 5 6 ( m so p10) top view gnd 1 3 4 2 8 6 5 7 out lbi lbo ref lx shdn fb ss6620 ss6621 example: SS6620COTR in mso p 8 package in tap e & reel packing type tr: tape & reel packaging type o: msop8 (for ss6620/1) o: msop10 (for ss6622) n absolute maximum ratings supply voltage (out to gnd) 8.0v switch voltage (lx to gnd) v out + 0.3v battery voltage (batt to gnd) 6.0v , lbo to gnd 6.0v lbi, ref, fb, clsel to gnd v out +0.3v switch current (lx) - 1.5a to +1.5a output current (out) - 1.5a to +1.5a operating temperature range - 40 c ~ +85 c storage temperature range - 65 c ~ 150 c n test circuit refer to typical application circuit. shdn re v . 2.01 6/06 /200 3
www.siliconstandard.com 3 of 12 ss6620/21/2 n electrical characteristics (v batt = 2 .0v, v out =3.3v (fb=v out ), r l = , t a =25 c, unless otherwise spec i fied.) parameter test conditions min. typ. max. unit minimum input voltage 0.7 v operating voltage 1.1 4.0 v start - up voltage r l =3k w (note1) 0.8 1.1 v start - up voltage tempco - 2 mv/ c output voltage range 1.8 4.0 output voltage fb = v out 3.17 3.3 3.43 v ss6620 ss6622 (clsel=out) 300 400 steady state output current (note 2) fb=out ( v out =3.3v) ss6621 ss6622 (clsel=gnd) 150 220 ma reference voltage i ref = 0 1.199 1.23 1.261 v reference voltage tempco 0.024 mv/ c reference load reg u lation i ref = 0 to 100 m a 10 30 mv reference line reg u lation v out = 1.8v to 4v 5 10 mv/v fb , lbi input threshold 1.199 1.23 1.261 v internal s witch on - resistance i lx = 100ma 0.3 w ss6620,ss6622(clsel = out) 0.6 0.8 1.0 lx switch current limit ss6621,ss6622(clsel = gnd) 0.3 0.45 0.6 a lx leakage current v lx =0v, 4v; v out =4v 0.05 1 m a operating current into out (note 3) v fb = 1.4v , v out = 3.3v 20 35 m a shutdown current into out shdn = gnd 0.1 1 m a v out = 3.3v ,i load = 200ma 90 efficiency v out = 2v ,i load = 1ma 85 % lx switch o n - time v fb =1v , v out = 3.3v 2 4 7 m s lx switch off - time v fb =1v , v out = 3.3v 0.6 0.9 1.3 m s fb input current v fb = 1.4v 0.03 50 na re v . 2.01 6/06 /200 3
www.siliconstandard.com 4 of 12 ss6620/21/2 n electrical characteristics ( continued ) parameter test conditions min. typ. max. unit lbi input current v lbi = 1. 4v 1 50 na clsel input current ss6622 , clsel = out 1.4 3 ma shdn input current v shdn = 0 or v out 0.07 50 na lbo low output voltage v lbi = 0, i sink = 1ma 0.2 0.4 m a lbo off leakage cu r rent v lbo = 5.5v, v lbi = 5.5v 0.07 1 lbi hystereisis 50 mv damping switch resistance ss6622, v batt = 2v 50 100 w 0.2v out shdn input voltage 0.8v out v 0.2v out clsel input voltage 0.8v out v note 1: start - up voltage operation is guaranteed without the addition of an external schottky diode between the i n- put and output. note 2: steady - state output current indicates that the device maintains output voltage regulation under load. note 3: device is bootstrapped (power to the ic comes from out). this correlates directly with the actual ba t tery su p ply. n typical performance characteristics 0.01 0.1 1 10 100 1000 0 10 20 30 40 50 60 70 80 90 100 fig. 1 v out =3.3v clsel=out (0.8a) v in =2.4v v in =1.2v efficiency (%) loading ( ma) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 20 40 60 80 100 120 140 160 i_limit= 0. 4 5a , v out =3.3v input b attery c urrent ( m a) input battery voltage (v) fig. 2 no-load battery current vs. input battery voltage i_limit= 0.8a , v out =3.3v re v . 2.01 6/06 /200 3
www.siliconstandard.com 5 of 12 ss6620/21/2 n typical performance characterist ics (continued) 0.01 0.1 1 10 100 1000 fig. 3 v out = 3 .3v clsel=gnd (0.45a) efficiency (%) loading ( ma) 40 50 60 70 80 90 100 v in =2.4v v in =1.2v 0.01 0.1 1 10 100 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 fig. 4 start-up voltage vs. load current without d iode with diode start-up voltage (v) load current ( ma) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 -0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 fig. 5 shutdown current vs. v out shutdown current ( m a) v out (v) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 fig. 6 shutdown threshold vs. output voltage shutdown threshold (v) output voltage (v) 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 0 100 200 300 400 500 600 700 800 fig. 7 maximum output current vs. input voltage clsel=out clsel=gnd maximum output current ( ma) input voltage (v) v out =3.3v fig. 8 heavy load waveform lx pin waveform v out ac couple inductor current v in =2.4v v out =3.3v re v . 2.01 6/06 /200 3
www.siliconstandard.com 6 of 12 ss6620/21/2 n typical performance characteristics (continued) fig. 9 without damping ringing function fig. 10 with damping ringing function d i out =200ma v out ac couple fig. 11 load transient response v in =2.4v v out =3.3v re v . 2.01 6/06 /200 3
www.siliconstandard.com 7 of 12 ss6620/21/2 n block diagram + + + + + out vin clsel shdn lbo lbi ref fb mirror q r s f/f minimum off-time one shot r e f erence voltage gnd lx batt l 1 r 1 200 w q3 q2 q1 damp i ng switch maximum on-time out one shot c3 220 m f c1 100 m f 47 m f 0.1 m f c4 0.1 m f n pin descriptions ss6620/ ss6621 pin 1: fb - connect to out for +3.3v output. use a resistor network to set the ou t- put voltage from +1.8v to +4. 0v. pin 2: lbi - low - battery comparator input. i n te r- nally set to trip at +1. 2 3v. pin 3: lbo - open - drain low battery comparator output. output is low when v lbi is <1. 2 3v. lbo is high impedance du r- ing shutdown. pin 4: ref - 1. 2 3v reference voltage. bypass wi th a 0.1 m f c a pacitor. pin 5: shdn - shutdown input. high=operating, low=shutdown. pin 6: gnd - ground pin 7: lx - n - channel and p - channel power mosfet drain. pin 8: out - power output. out provides boo t- strap power to the ic. re v . 2.01 6/06 /200 3
www.siliconstandard.com 8 of 12 ss6620/21/2 ss6622 pin 1: fb - con nect to out for +3.3v output. use a resistor network to set the ou t- put voltage from +1.8v to +4.0v. pin 2: lbi - low - battery comparator input. i n te r- nally set to trip at +1.23v. pin 3: lbo - open - drain low battery comparator output. output is low when vlbi i s <1. 2 3v. lbo is high impedance du r- ing shutdown. pin 4: clsel - current - limit selects input. clsel= out sets the current limit to 0.8a. clsel=gnd sets the current limit to 0.45a. pin 5: ref - 1. 2 3v reference voltage. bypass with a 0.1 m f c a pacitor. pin 6: sh dn - shutdown input. high=operating, low=shutdown. pin 7: batt - battery input and damping switch connection. if damping switch is unused, leave batt unco n nected. pin 8: gnd - ground. pin 9: lx - n - channel and p - channel power mosfet drain. pin 10: out - power o utput. out provides boo t- strap power to the ic. n application information overview the ss6620/21/22 series are high efficiency, step - up dc/ dc converters , d e signed to fe a ture a built - in synchronous rectifier, which r e duces size and co st by eliminating the need for an e x ternal schottky diode. the s tart - up voltage is as low as 0.8 v and they can ope r ate with an input voltage down to 0.7v. qu i- e s cent supply cu r rent is only 20 m a. in addition, the ss6622 feature a circuit that eliminates inductor- ring ing to reduce noise. the internal p - mosfet on - resistance is typ i cally 0.3 w to i m prove overall eff i- ciency by minimizing ac loss es. the current limit of the ss6620 and ss6621 is 0.8a and 0.45a respectively. the ss6622 offers a selectable current - limit (0.45a or 0.8a). the lower current limit allows the use of a physically smaller inductor in space - sensitive appl i c a tions. pfm c ontrol s cheme the key feature of the ss6620 series is a unique minimum - off - time, current - limited, pulse - frequency - m odulation (pfm) control scheme (see block diagram) with ultra - low quiescent cu r rent . a co n- stant - peak - current limit in the switching allows the i n- ductor current to vary between this peak limit and some lesser value. the peak current of the i n ternal n - m osfet power switch can be fixed at 0.8 a, 0. 4 5a or is selectable. t he ripple vol t age do e s not e x ceed the product of the peak current limit and the filter c a pac i- tor equivalent - series - resi s tance ( esr). the switch fr e quency depends on the loading cond i tion and input voltage, and can range up to 500khz. the switching fr e quency is governed by a pair of one - shots that set a minimum off - time (1 m s ) and a max i mum on - time (4 m s ). re v . 2.01 6/06 /200 3
www.siliconstandard.com 9 of 12 ss6620/21/2 synchronous r ectification using the internal synchronous rectifier eliminates the need for an external schottky diode. therefore, the cost and board space is reduced. during the c y cle of off - time, the p - mosfet tu rns on and shunts the n - mosfet. due to the low turn - on resistance of the mo s fet, the synchronous rectifier si g nificantly i m- pr oves eff i ciency without the addition of an external comp o nent. thus, the conversion eff i cie n cy can be as high as 9 3 %. reference v oltage the reference voltage (ref) is nominally 1.2 3 v for excellent t.c. performance. in addition, the ref pin can source up to 1 00 m a to an external circuit with good load regulation (<10mv). a bypass capacitor of 0.1 m f is r e quired for proper operation and good pe r- formance . shutdown the whole circuit is shutdown when shdn v is low. during shutdown mode, current can flow from the ba t- tery to the output through the body diode of the p - mosfet. v out falls to approximately ( vin - 0.6v ) and lx remains high impedance. the capacitance and load at out determine the rate at which v out d e cays. shu t down can be pulled as high as 6 v , r e gar dless of the voltage at out. current l imit s elect p in the ss6622 series allows a selectable inductor current limit of either 0. 4 5a or 0.8 a. this allows flex i- bility in designing for higher current or smaller appl i- c a tions. clsel draws 1.4 m a when connect ed to out. batt/damping switch the ss6622 is designed with an internal damping switch (fig. 1 5 ) to reduce ringing a t lx. the damping switch suppl ies a path to quickly dissipate the e n ergy stored in the inductor and reduces the ringing at lx. damping lx ri nging do e s not reduce v out ripple, but do es reduce emi. a value of r1=200 w works well for most a p pl i cation while reducing efficiency by only 1%. la r ger r1 value s provide less damping, but less i m- pact on e ff i ciency. in principle, lower value s of r 1 are needed to fully da mp lx when the v out /v in ratio is high. selecting the o utput v oltage v out can be simply set to 3.3v by connecting the fb pin to out due to the internal resistor divider (fig. 16) . in order to adjust the output voltage, a resistor d i vider is connected to v out , fb, gnd (fig. 17 ). use the fo l lo w ing equation to calculate: r5=r6 [(v out / v ref ) - 1] w here v ref =1.2 3 v and v out may range from 1.8 v to 4 v. low - b attery d etection the ss6620 series contain an on-chip comparator with 50 mv internal hysteresis (ref, ref + 50 mv) for low battery detection. if the voltage at lbi falls b e low the internal reference voltage , lbo ( an open - drain output) sinks current to gnd. re v . 2.01 6/06 /200 3
www.siliconstandard.com 10 of 12 ss6620/21/2 component sele c tion 1. inductor selection an inductor value of 22 m h performs well in most applications. th e ss6620 series also work with inductors in the 10 m h to 47 m h range. an i n- ductor with higher peak inductor current creates a higher ou t put voltage ripple (i peak output filter c a- pacitor esr). the inductor ? s dc resistance si g- nif i cantly affects efficiency. w e can calculate the maximum output current as fo l lows: h ? ? ? ? ? ? ? - -= l2 vv ti v v i in out off lim out in ) max ( out where i out(max) =maximum output current in amps v in =input voltage l=inductor value in m h ? =efficiency (typically 0.9) t off =lx switch ? off - time in m s i lim =0.45a or 0.8a 2. capacitor selection the ou tput voltage ripple is relate d to the peak i n- du c tor current and the output capacitor esr. b e- sides output ripple voltage, the output ripple cu r- rent also needs to be con sidered . the smaller the esr of the output capacitor, the higher the ri p ple cu r rent . a fi l ter capacitor with low esr is hel p ful to the eff i ciency and st eady state output current of the ss6620 series. therefore hermei ca- pac i tor lt series with 220 m f/6.3v is reco m- mended. a smaller capacitor (down to 10 m f with higher esr) is acceptable for light loads or in a p- plications that can tolerate higher output ripple. 3. pcb layout and grounding since the ss6622?s switching frequency can range up to 500khz, the ss6622 can be very se n s i tive. c areful printed circuit la y out is i m po r- tant for minimizing ground bounce and noise. t he area around the ic ? s out pin should be as clear as po ss i ble , an d the gnd pin should be placed close to the ground plane. keep the ic ? s gnd pin and the ground leads of the input and output filter c a pac i tors less than 0.2in (5mm) apart. in addition, keep all co n nection s to the fb and lx pins as short as possible. in particular, when u s ing e x te r- nal fee d back resi s tors, locate them as close to the fb pin as po s sible. to maximize output power and e ff i ciency and minimize output ripple voltage, use a ground plane and solder the ic ? s gnd d i- rectly to the ground plane. following are the re c- ommended layout di a grams. figure 12. top layer figure 13. bottom layer figure 14. plac e ment re v . 2.01 6/06 /200 3
www.siliconstandard.com 11 of 12 ss6620/21/2 n application examples damping switch vin vout ss6622 out batt lx gnd q3 q2 q 1 l1 r 1 200 w 22 m h vout vin (ss6622) r2 100k w ss6620 s s6621 s s6622 c3 c1 l 22 m h 100 m f 220 m f 0.1 m f c2 0.1 m f c4 r1 200 w ohm low battery output r4 r3 clsel ( ss6622) lx out fb gnd ref lbi batt lbo shdn fig. 15 . simplified damping switch diagram fig. 16 v out = 3.3v application circuit. fig. 17 an adjustable output application circuit vout vin 100k w r1 200 w r2 22 m h 100 m f 220 m f 0.1 m f 0.1 m f low battery output c2 c4 c3 c1 l (ss6622) ss6622 ss6621 ss6620 r6 r5 r4 r3 shdn clsel ( ss6622) lx fb lbo gnd ref lbi batt out re v . 2.01 6/06 /200 3
in formation furnished by silicon standard corporation is believe d to be accurate and reliable. however, silicon standard corporation makes no guarantee or warranty, express or implied, as to the reliability, accuracy, timeliness or completeness of such information and assumes no responsibility for its use, or for infr i ngement of any patent or other intellectual property rights of third parties that may result from its use. silicon standard reserves the right to make changes as it deems necessary to any products described herein for any reason, including without limitat ion enhancement in reliability, functionality or design. no license is granted, whether expressly or by implication, in relation to the use of any products described herein or to the use of any information provided herein, under any patent or other intelle ctual property rights of silicon standard corporation or any third parties. www.siliconstandard.com 12 of 12 ss6620/21/2 n physical dimension l 8 lead msop (unit: mm) sy mbol min max a1 -- 0.20 a2 0.76 0.97 b 0.28 0.38 c 0.13 0.23 d 2.90 3.10 e 4.80 5.00 e1 2.90 3.10 e 0.65 l 0.40 0.66 d e e e1 a2 b a1 c l l 10 l e ad msop (unit: mm) symbol min max a1 -- 0.20 a2 0.76 0.97 b 0.15 0.30 c 0. 13 0.23 d 2.90 3.10 e 4.80 5.00 e1 2.90 3.10 e 0.50 l 0.40 0.66 d e e e1 b a2 a1 c l re v . 2.01 6/06 /200 3

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