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ltc3221/ ltc3221-3.3/ltc3221-5 1 3221f ltc3221-x v out v in v out 3221 ta01 v in 4.7 f 1 f off on gnd c + c shdn 2.2 f 6 1 2 5 4,7 3 regulated 3.3v output from 1.8v to 4.4v input v out = 3.3v 4% i out = oma to 25ma; v in >1.8v i out = oma to 60ma; v in >2v regulated 5v output from 2.7v to 5.5v input v out = 5v 4% i out = oma to 25ma; v in >2.7v i out = oma to 60ma; v in >3v supply voltage (v) 1.5 no-load input current ( a) 3.0 4.0 3221 ta01b 2.0 2.5 t a = ?5 c t a = 25 c t a = 90 c 3.5 16 14 12 10 8 6 4 2 0 4.5 micropower, regulated charge pump in 2 2 dfn the ltc 3221 family are micropower charge pump dc/dc converters that produce a regulated output at up to 60ma. the input voltage range is 1.8v to 5.5v. extremely low operating current (8a typical at no load) and low external parts count (one ? ying capacitor and two small bypass capacitors at v in and v out ) make them ideally suited for small, battery-powered applications. the ltc3221 family includes ? xed 5v and 3.3v output versions plus an adjustable version. all parts operate as burst mode switched capacitor voltage doublers to achieve ultralow quiescent current. the chips use a controlled current to supply the output and will survive a continuous short-circuit from v out to gnd. the fb pin of the adjustable ltc3221 can be used to program the desired output voltage. the ltc3221 family is available in a low pro? le (0.75mm) 2mm 2mm 6-pin dfn package. , lt, ltc and ltm are registered trademarks of linear technology corporation. burst mode is a registered trademark of linear technology corporation. all other trademarks are the property of their respective owners. features descriptio u typical applicatio u applicatio s u ultralow power: 8a quiescent current regulated output voltages: 3.3v 4%, 5v 4%, adj v in range: 1.8v to 4.4v (ltc3221-3.3) 2.7v to 5.5v (ltc3221-5) output current: up to 60ma no inductors needed very low shutdown current: <1a shutdown disconnects load from v in burst mode control short-circuit protected solution pro? le < 1mm tiny 2mm 2mm 6-pin dfn package low power 2 aa cell to 3.3v supply memory backup supplies tire pressure sensors general purpose low power li-ion to 5v supply rf transmitters glucose meters no-load input current vs supply voltage
ltc3221/ ltc3221-3.3/ltc3221-5 2 3221f v in , ? s ? h ? d ? n, fb ............................................. C 0.3v to 6v v out to gnd ............................................. C 0.3v to 5.5v v out short-circuit duration ............................ inde? nite operating temperature range (note 2) .. C 40c to 85c storage temperature range .................. C 65c to 125c maximum junction temperature .......................... 125c (note 1) the denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v in = 2.5v (ltc3221-3.3/ltc3221) or 3v (ltc3221-5), ? s ? h ? d ? n = v in , c fly = 1f, c in = 2.2f, c out = 2.2f, unless otherwise speci? ed. electrical characteristics absolute axi u rati gs w ww u for atio package/order i uu w top view 4 5 7 6 3 2 1 c + c shdn/fb* v out v in gnd t jmax = 125c, ja = 80c/w exposed pad is gnd (pin 7) must be soldered to pcb * ? s ? h ? d ? n on ltc3221-3.3;ltc3221-5 fb on ltc3221 order part number dc part marking ltc3221edc ltc3221edc-3.3 ltc3221edc-5 lccp lbqp lccn order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpbf lead free part marking: http://www.linear.com/leadfree/ consult ltc marketing for parts speci? ed with wider operating temperature ranges. symbol parameter conditions min typ max units ltc3221-3.3 v in input supply voltage 1.8 4.4 v v out output voltage 1.8v v in 4.4v, i out 25ma 2v v in < 4.4v, i out 60ma 3.168 3.3 3.432 v i cc operating supply current i out = 0ma 815 a v r output ripple v in = 2v, i out = 60ma, c out = 4.7f (note 3) 35 mv p-p ef? ciency v in = 2v, i out = 60ma (note 3) 82 % i sc output short-circuit current v out = 0v 120 240 ma ltc3221-5 v in input supply voltage 2.7 5.5 v v out output voltage 2.7v v in 5.5v, i out < 25ma 3v v in 5.5v, i out < 60ma 4.8 5 5.2 v i cc operating supply current i out = 0ma 815 a v r output ripple v in = 3v, i out = 60ma, c out = 4.7f (note 3) 45 mv p-p ef? ciency v in = 3v, i out = 60ma (note 3) 82 % i sc output short-circuit current v out = 0v 120 240 ma ltc3221 v in input supply voltage 1.8 5.5 v v fb feedback voltage 1.181 1.23 1.279 v r ol open-loop impedance v in = 1.8v, v out = 3v (note 4) 10 20 i cc operating supply current i out = 0ma 512 a i fb fb input current fb = 1.33v, v in = 2v C100 100 na
ltc3221/ ltc3221-3.3/ltc3221-5 3 3221f short-circuit current (ma) 110 130 90 50 70 150 supply voltage (v) 1.5 2.0 2.5 3.0 3.5 4.0 4.5 3221 g06 t a = ?5 c t a = 90 c t a = 25 c temperature ( c) ?0 ?5 0 25 75 50 100 125 3221 g05 v in = 3.2v shdn hi-to-lo threshold (v) 0.7 0.8 0.6 0.4 0.5 0.9 v in = 2.5v v in = 1.8v temperature ( c) ?0 ?5 0 25 75 50 100 125 3221 g04 v in = 3.2v v in = 2.5v v in = 1.8v shdn lo-to-hi threshold (v) 0.7 0.8 0.6 0.4 0.5 0.9 threshold voltage (v) 0.7 0.8 0.6 0.4 0.5 0.9 high-to-low threshold low-to-high threshold supply voltage (v) 1.5 2.0 2.5 3.0 3.5 4.0 4.5 3221 g03 the denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v in = 2.5v (ltc3221-3.3/ltc3221) or 3v (ltc3221-5), ? s ? h ? d ? n = v in , c fly = 1f, c in = 2.2f, c out = 2.2f, unless otherwise speci? ed. note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the ltc3221edc-x is guaranteed to meet performance speci? cations from 0c to 70c. speci? caiton over the C 40c to 85c operating temperature range are assured by design, characterization and correlation with statisitical process controls. note 3: guaranteed by design, not subject to test. note 4: r ol = (2v in C v out )/i out . electrical characteristics oscillator frequency vs supply voltage oscillator frequency vs temperature ? s ? h ? d ? n threshold voltage vs supply voltage ? s ? h ? d ? n lo-to-hi threshold vs temperature ? s ? h ? d ? n hi-to-lo threshold vs temperature short-circuit current vs supply voltage typical perfor a ce characteristics uw supply voltage (v) 1.5 frequency (khz) 800 750 700 500 450 600 550 650 400 2.0 2.5 3.0 3.5 4.0 4.5 3221 g01 frequency (khz) 800 750 700 500 450 600 550 650 400 temperature ( c) ?0 ?5 0 25 75 50 100 125 3221 g02 v in = 4.5v v in = 2.5v v in = 1.8v symbol parameter conditions min typ max units ltc3221-3.3/ltc3221-5 i ? s ? h ? d ? n shutdown supply current v out = 0v, ? s ? h ? d ? n = 0v 1a v ih ? s ? h ? d ? n input threshold (high) 1.3 v v il ? s ? h ? d ? n input threshold (low) 0.4 v i ih ? s ? h ? d ? n input current (high) ? s ? h ? d ? n = v in C1 1 a i il ? s ? h ? d ? n input current (low) ? s ? h ? d ? n = 0v C1 1 a ltc3221/ltc3221-3.3/ltc3221-5 f osc switching frequency v out = 2.5v 600 khz v uvlo uvlo threshold 1v
ltc3221/ ltc3221-3.3/ltc3221-5 4 3221f load current (ma) 0 50 60 70 80 60 3221 g13 40 30 20 40 100 20 10 0 output ripple (mv p-p ) c out = 2.2 f c out = 4.7 f supply voltage (v) 1.8 efficiency (%) 100 90 80 70 60 50 40 30 20 10 0 2.2 2.6 2.8 2.0 2.4 3.0 3.2 3221 g12 theoretical max i out = 1ma i out = 30ma 3221 g11 load current (ma) 0.01 excess input current (ma) 10 1 0.1 0.01 0.001 10 1 0.1 100 v in = 2.5v supply voltage (v) 1.5 no-load input current ( a) 16 14 12 4 2 8 6 10 0 2.0 2.5 3.0 3.5 4.0 4.5 3221 g10 t a = ?5 c t a = 90 c t a = 25 c effective open-loop output resistance ( ? ) 15 14 13 9 7 11 10 12 5 8 6 temperature ( c) ?0 ?5 0 25 75 50 100 3221 g09 v in = 1.8v v out = 3v 3221 g07 load current (ma) 0 output voltage (v) 3.36 3.34 3.32 3.30 3.24 3.26 3.28 3.22 3.20 3.18 3.16 100 80 60 40 20 120 v in = 3.2v v in = 2.5v v in = 1.8v load current (ma) 110 100 90 40 50 70 80 60 120 supply voltage (v) 1.5 2.0 2.5 3.5 3.0 3221 g08 t a = ?5 c t a = 90 c v out = 3.168v t a = 25 c v in = 2v i load = 60ma c out = 4.7 f, 6.3v, size 0603 3221 g14 1 s/div v out 20mv/div (ac-coupled) v in = 2v i load = 0ma to 60ma step c out = 4.7 f, 6.3v, size 0603 3221 g15 5 s/div v out 20mv/div (ac-coupled) 60ma i out 0ma load regulation output load capability at 4% below regulation effective open-loop output resistance vs temperature no-load input current vs supply voltage extra input current vs load current (i in -2 i load ) ef? ciency vs supply voltage output ripple vs load current output ripple load transient response typical perfor a ce characteristics uw (ltc3221-3.3 only)
ltc3221/ ltc3221-3.3/ltc3221-5 5 3221f load current (ma) 0 50 60 90 80 70 80 60 3221 g13 40 30 20 40 100 20 10 0 output ripple (mv p-p ) c out = 2.2 f c out = 4.7 f v in = 3v supply voltage (v) efficiency (%) 100 90 80 70 60 50 40 30 20 10 0 3221 g21 theoretical max i out = 1ma i out = 30ma 2.7 3.0 3.3 3.6 3.9 4.2 4.5 supply voltage (v) 2.7 no-load input current ( a) 16 14 12 4 2 8 6 10 0 3.0 3.3 3.6 3.9 4.2 4.5 3221 g19 t a = ?5 c t a = 90 c t a = 25 c 3221 g20 load current (ma) 0.01 excess input current (ma) 10 1 0.1 0.01 0.001 10 1 0.1 100 v in = 3v load current (ma) 110 100 90 40 50 70 80 60 120 supply voltage (v) 2.7 3.0 3.3 4.2 3.9 3.6 3221 g17 t a = ?5 c t a = 90 c v out = 4.8v t a = 25 c 3221 g16 load current (ma) 0 output voltage (v) 5.10 5.05 5.00 4.95 4.85 4.90 4.80 100 80 60 40 20 120 v in = 4.2v v in = 3.6v v in = 2.7v effective open-loop output resistance ( ? ) 15 14 13 9 7 11 10 12 5 8 6 temperature ( c) ?0 ?5 0 25 75 50 100 3221 g18 v in = 2.7v v out = 4.5v load regulation output load capability at 4% below regulation effective open-loop output resistance vs temperature typical perfor a ce characteristics uw (ltc3221-5 only) no-load input current vs supply voltage extra input current vs load current (i in -2 i load ) ef? ciency vs supply voltage output ripple vs load current output ripple load transient response v in = 3v i load = 60ma c out = 4.7 f, 6.3v, size 0603 3221 g23 1 s/div v out 50mv/div (ac-coupled) v in = 3v i load = 0ma to 60ma step c out = 4.7 f, 6.3v, size 0603 3221 g24 5 s/div v out 50mv/div (ac-coupled) 60ma i out 0ma
ltc3221/ ltc3221-3.3/ltc3221-5 6 3221f the ltc3221 family uses a switched capacitor charge pump to boost v in to a regulated output voltage. regulation is achieved by monitoring the output voltage, v out using a comparator (cmp in the block diagram) and keeping it within a hysteresis window. if v out drops below the lower trip point of cmp, v out is charged by the controlled cur- rent, i sw in series with the ? ying capacitor c fly . once v out goes above the upper trip point of cmp, or if the upper trip point is not reached after 0.8s, c fly is disconnected from v out . the bottom plate of c fly is then connected to gnd to allow i sw to replenish the charge on c fly for 0.8s. after which, i sw is turned off to keep the operating supply current low. cmp continues to monitor v out and turns on i sw if the lower threshold is reached again. shutdown mode the ? s ? h ? d ? n pin is a cmos input with a threshold voltage of approximately 0.8v. the ltc3221-3.3/ ltc3221-5 are in shutdown when a logic low is applied to the ? s ? h ? d ? n pin. in shutdown mode, all circuitry is turned off and the ltc3221-3.3/ ltc3221-5 draw only leakage current from the v in supply. furthermore, v out is disconnected from v in . since the ? s ? h ? d ? n pin is a very high impedance cmos input, it should never be allowed to ? oat. when ? s ? h ? d ? n is asserted low, the charge pump is ? rst dis- abled, but the ltc3221-3.3/ltc3221-5 continue to draw 5a of supply current. this current will drop to zero when the output voltage (v out ) is fully discharged to 0v. operatio u (refer to block diagrams) ltc3221-3.3/ltc3221-5 ltc3221 i sw cmp shdn v out c + v in c gnd 1 5 2 4 6 3 + v ref control i sw cmp fb v out c + v in c gnd 1 5 2 4 6 + v ref control 3 2 1 2 1 2 1 2 1 3221 bd block diagra w pi fu ctio s uuu c+ (pin 1): flying capacitor positive terminal. cC (pin 2): flying capacitor negative terminal. ? s ? h ? d ? n (pin 3) (ltc3221-3.3/ltc3221-5) : active low shutdown input. a low on ? s ? h ? d ? n disables the ltc3221-3.3/ ltc3221-5. ? s ? h ? d ? n must not be allowed to ? oat. fb (pin 3) (ltc3221): feedback. the voltage on this pin is compared to the internal reference voltage (1.23v) by the error comparator to keep the output in regulation. an external resistor divider is required between v out and fb to program the output voltage. gnd (pin 4): ground. should be tied to a ground plane for best performance. v in (pin 5): input supply voltage. v in should be bypassed with a 2.2f low esr capacitor. v out (pin 6): regulated output voltage. for best perfor- mance, v out should be bypassed with a 2.2f or higher low esr capacitor as close as possible to the pin. exposed pad (pin 7) ground. the exposed pad must be soldered to pcb ground to provide electrical contact and optimum thermal performance.
ltc3221/ ltc3221-3.3/ltc3221-5 7 3221f power ef? ciency the input current of a doubling charge pump like the ltc3221 family is always twice that of the output current. this is true regardless of whether the output voltage is unregulated or regulated or of the regulation method used. in an ideal unregulated doubling charge pump, conservation of energy implies that the input current has to be twice that of the output current in order to obtain an output voltage twice that of the input voltage. in a regulated charge pump like the ltc3221, the regulation of v out is similar to that of a linear regulator, with the voltage difference between 2 ? v in (input voltage plus the voltage across a fully charged ? ying capacitor) and v out being absorbed in an internal pass transistor. in the ltc3221, the controlled current i sw acts as a pass transistor. so the input current of an ideal regulated doubling charge pump is the same as an unregulated one, which is equal to twice the output current. the ef? ciency (n) of an ideal regulated doubler is therefore given by: = = = p p vi vi v v out in out out in out out in ? 2 at moderate to high output power, the switching losses and quiescent current of the ltc3221 family are negligible and the expression is valid. for example, an ltc3221-5 with v in = 3v, i out = 60ma and v out regulating to 5v, has a mea- sured ef? ciency of 82% which is in close agreement with the theoretical 83.3% calculation. the ltc3221 product family continues to maintain good ef? ciency even at fairly light loads because of its inherently low power design. maximum available output current for the adjustable ltc3221, the maximum available output current and voltage can be calculated from the effective open-loop output resistance, r ol , and effective output voltage, 2v in(min) . from figure 1 the available current is given by: i vv r out in out ol = 2 effective open-loop output resistance (r ol ) the effective open-loop output resistance(r ol ) of a charge pump is a very important parameter which determines the strength of the charge pump. the value of this parameter applicatio s i for atio wu u u operatio u (refer to block diagrams) the ltc3221 has a fb pin in place of the ? s ? h ? d ? n pin. this allows the output voltage to be programmed using an external resistive divider. burst mode operation the ltc3221 family regulates the output voltage throughout the full 60ma load range using burst mode control. this keeps the quiescent current low at light load and improves the ef? ciency at full load by reducing the switching losses. all the internal circuitry except the comparator is kept off if the output voltage is high and the ? ying capacitor has been fully charged. these circuits are turned on only if v out drops below the comparator lower threshold. at light load, v out stays above this lower threshold for a long period of time, this result in a very low average input current. soft-start and short-circuit protection the ltc3221 family uses a controlled current, i sw to deliver current to the output. this helps to limit the input and output current during start-up and output short-circuit condition. during start up i sw is used to charge up the ? ying capacitor and output capacitor, this limits the input current to approximately 240ma. during short-circuit condition, the output current is delivered through i sw and this limits the output current to approximately 120ma. this prevents excessive self-heating that causes damage to the part. figure 1. equivalent open-loop circuit + + 2v in i out v out 3221 f01 r ol
ltc3221/ ltc3221-3.3/ltc3221-5 8 3221f applicatio s i for atio wu u u depends on many factors such as the oscillator frequency (f osc ), value of the ? ying capacitor (c fly ), the nonoverlap time, the internal switch resistances (r s ) and the esr of the external capacitors. a ? rst order approximation for r ol is given below: rr fc ol s sto osc fly ? + = 2 1 14 typical r ol values as a function of temperature are shown in figure 2. esr of the output capacitor. it is proportional to the input voltage, the value of the ? ying capacitor and the esr of the output capacitor. a smaller output capacitor and/ or larger output current load will result in higher ripple due to higher output volt- age slew rates. there are several ways to reduce output voltage ripple. for applications requiring lower peak-to-peak ripple, a larger c out capacitor (4.7f or greater) is recommended. a larger capacitor will reduce both the low and high fre- quency ripple due to the lower charging and discharging slew rates, as well as the lower esr typically found with higher value (larger case size) capacitors. a low esr ce- ramic output capacitor will minimize the high frequency ripple, but will not reduce the low frequency ripple unless a high capacitance value is used. v in , v out capacitor selection the style and value of capacitors used with the ltc3221 family determine several important parameters such as output ripple, charge pump strength and minimum start- up time. to reduce noise and ripple, it is recommended that low esr (< 0.1 ) capacitors be used for both c in and c out . these capacitors should be either ceramic or tantalum and should be 2.2f or greater. aluminum capacitors are not recommended because of their high esr. flying capacitor selection warning: a polarized capacitor such as tantalum or alumi- num should never be used for the ? ying capacitor since its voltage can reverse upon start-up of the ltc3221. low esr ceramic capacitors should always be used for the ? ying capacitor. the ? ying capacitor controls the strength of the charge pump. in order to achieve the rated output current, it is necessary to have at least 0.6f of capacitance for the ? ying capacitor. for very light load applications, the ? ying capacitor may be reduced to save space or cost.from the ? rst order approximation of r ol in the section effective open-loop output resistance, the theoretical minimum output resistance of a voltage doubling charge pump can effective open-loop output resistance ( ? ) 6 15 14 13 12 11 7 5 9 10 8 temperature ( c) ?0 ?5 100 3221 f02 050 25 75 v in = 1.8v v out = 3v figure 2. effective open-loop output resistance vs temperature output ripple low frequency regulation mode ripple exists due to the hysteresis in the comparator cmp and propagation delay in the charge pump control circuit. the amplitude and frequency of this ripple are heavily dependent on the load current, the input voltage and the output capacitor size. the ltc3221 family uses a controlled current, i sw to deliver current to the output. this helps to keep the output ripple fairly constant over the full input voltage range. typical combined output ripple for the ltc3221-3.3 with v in = 2v under maximum load is 35mv p-p using a 4.7f 6.3v x5r case size 0603 output capacitor. a high frequency ripple component may also be present on the output capacitor due to the charge transfer action of the charge pump. in this case the output can display a voltage pulse during the charging phase. this pulse results from the product of the charging current and the
ltc3221/ ltc3221-3.3/ltc3221-5 9 3221f be expressed by the following equation: r vv ifc ol min in out out osc fly () ? 21 where f osc is the switching frequency (600khz) and c fly is the value of the ? ying capacitor. the charge pump will typically be weaker than the theoretical limit due to ad- ditional switch resistance. however, for very light load ap- plications, the above expression can be used as a guideline in determining a starting capacitor value. ceramic capacitors capacitors of different materials lose their capacitance with higher temperature and voltage at different rates. for example, a ceramic capacitor made of x7r material will retain most of its capacitance from C 40c to 85c, whereas, a z5u or y5v style capacitor will lose considerable capacitance over that range. z5u and y5v capacitors may also have a very strong voltage coef? cient causing them to lose 50% or more of their capacitance when the rated voltage is applied. therefore when comparing different capacitors, it is often more appropriate to compare the amount of achievable capacitance for a given case size rather than discussing the speci? ed capacitance value. for example, over rated voltage and temperature condi- tions, a 1f 10v y5v ceramic capacitor in a 0603 case may not provide any more capacitance than a 0.22f 10v x7r capacitor available in the same 0603 case. in fact, for most ltc3221-3.3/ltc3221-5/ltc3221 applications, these capacitors can be considered roughly equivalent. the capacitor manufacturers data sheet should be consulted to determine what value of capacitor is needed to ensure 0.6f at all temperatures and voltages. table 1 shows a list of ceramic capacitor manufacturers and how to contact them. table 1. ceramic capacitor manufacturers avx www.avxcorp.com kemet www.kemet.com murata www.murata.com taiyo yuden www.t-yuden.com vishay www.vishay.com applicatio s i for atio wu u u programming the ltc3221 output voltage (fb pin) while the ltc3221-3.3/ltc3221-5 versions have internal resistive dividers to program the output voltage, the pro- grammable ltc3221 may be set to an arbitrary voltage via an external resistive divider. figure 3 shows the required voltage divider connection. figure 3. programming the adjustable ltc3221 4 3 6 v out = 1.23v (1 + ) c out v out 3221 f03 fb r1 ltc3221 r2 gnd c1 r1 r2 the voltage divider ratio is given by the expression: r r v v out 1 2123 1 = . since the ltc3221 employs a voltage doubling charge pump, it is not possible to achieve output voltages greater than twice the available input voltage. the v in supply range required for regulation is given by the following expression: maximum v in < v out + 0.6 minimum v vir or v in out out ol = + () .; 2 18 whichever is higher where r ol is the effective open-loop output resistance and i out is the maximum load current. v in cannot be higher than v out by more than 0.6v, or else the line regulation is poor. also, v in has to be higher than the minimum operating voltage of 1.8v. the sum of the voltage divider resistors can be made large to keep the quiescent current to a minimum. any standing current in the output divider (given by 1.23/r2) will be re? ected by a factor of 2 in the input current. a reasonable resistance value should be such that the standing current is in the range of 10a to 100a when v out is regulated.
ltc3221/ ltc3221-3.3/ltc3221-5 10 3221f figure 5. maximum power dissipation vs ambient temperature power dissipation (w) 2.0 3.0 1.0 1.5 2.5 0.5 0 ambient temperature ( c) ?0 ?5 25 75 125 150 3221 f05 0 50 100 ja = 80 c/w t j = 160 c applicatio s i for atio wu u u if the standing current is too low, the fb pin becomes very sensitive to the switching noise and will result in errors in the programmed v out . the compensation capacitor (c1) helps to improve the response time of the comparator and to keep the output ripple within an acceptable range. for best results, c1 should be between 22pf to 220pf. layout considerations due to high switching frequency and high transient cur- rents produced by the ltc3221 product family, careful board layout is necessary. a true ground plane and short to the pc board is recommended. connecting the gnd pin (pin 4 and pin 7 on the dfn package) to a ground plane, and maintaining a solid ground plane under the device can reduce the thermal resistance of the package and pc board considerably. derating power at high temperatures to prevent an overtemperature condition in high power applications, figure 5 should be used to determine the maximum combination of ambient temperature and power dissipation. the power dissipated in the ltc3221 family should always fall under the line shown for a given ambient temperature. the power dissipation is given by the expression: pvvi d in out out = ( ) 2 this derating curve assumes a maximum thermal resis- tance, ja , of 80c/w for 2mm 2mm dfn package. this can be achieved from a printed circuit board layout with a solid ground plane and a good connection to the ground pins of the ltc3221 and the exposed pad of the dfn package. operation out of this curve will cause the junction temperature to exceed 150c which is the maxi- mum junction temperature allowed. figure 4. recommended layout 4 5 6 v out v out 3221 f04 v in gnd 3 2 1 pin 7 2.2 f 2.2 f 1 f r1 r2 (ltc3221) connections to all capacitors will improve performance and ensure proper regulation under all conditions. figure 4 shows the recommended layout con? guration. the ? ying capacitor pins c + and c C will have very high edge rate waveforms. the large dv/dt on these pins can couple energy capacitively to adjacent printed circuit board runs. magnetic ? elds can also be generated if the ? ying capacitors are not close to the ltc3221 (i.e. the loop area is large). to decouple capacitive energy transfer, a faraday shield may be used. this is a grounded pc trace between the sensitive node and the ltc3221 pins. for a high quality ac ground it should be returned to a solid ground plane that extends all the way to the ltc3221. to reduce the maximum junction temperature due to power dissipation in the chip, a good thermal connection
ltc3221/ ltc3221-3.3/ltc3221-5 11 3221f package descriptio u information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. dc package 6-lead plastic dfn (2mm 2mm) (reference ltc dwg # 05-08-1703) 2.00 0.10 (4 sides) note: 1. drawing to be made a jedec package outline m0-229 variation of (wccd-2) 2. drawing not to scale 3. all dimensions are in millimeters 0.38 0.05 bottom view?xposed pad 0.56 0.05 (2 sides) 0.75 0.05 r = 0.115 typ 1.37 0.05 (2 sides) 1 3 6 4 pin 1 bar top mark (see note 6) 0.200 ref 0.00 ?0.05 (dc6) dfn 1103 0.25 0.05 1.42 0.05 (2 sides) recommended solder pad pitch and dimensions 0.61 0.05 (2 sides) 1.15 0.05 0.675 0.05 2.50 0.05 package outline 0.25 0.05 0.50 bsc 0.50 bsc pin 1 chamfer of exposed pad 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package
ltc3221/ ltc3221-3.3/ltc3221-5 12 3221f linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2006 lt 1006 ? printed in usa part number description comments ltc1262 12v, 30ma flash memory program supply regulated 12v 5% output, i q = 500a ltc1514/ltc1515 buck/boost charge pumps with i q = 60a 50ma output at 3.3v or 5v; 2v to 10v input ltc1516 micropower 5v charge pump i q = 12a, up to 50ma output, v in = 2v to 5v ltc1517-5/ltc1517-3.3 micropower 5v/3.3v doubler charge pumps i q = 6a, up to 20ma output ltc1522 micropower 5v doubler charge pump i q = 6a, up to 20ma output ltc1555/ltc1556 sim card interface step-up/step-down charge pump, v in = 2.7v to 10v ltc1682 low noise doubler charge pump output noise = 60v rms , 2.5v to 5.5v output ltc1751-3.3/ltc1751-5 micropower 5v/3.3v doubler charge pumps i q = 20a, up to 100ma output, sot-23 package ltc1754-3.3/ltc1754-5 micropower 5v/3.3v doubler charge pumps i q = 13a, up to 50ma output, sot-23 package ltc1755 smart card interface buck/boost charge pump, i q = 60a, v in = 2.7v to 6v ltc3200 constant frequency doubler charge pump low noise, 5v output or adjustable ltc3203/ltc3203b/ ltc3203b-1/ltc3203-1 500ma low noise high ef? ciency dual mode step up charge pumps v in : 2.7v to 5.5v, 3mm 3mm dfn-10 package ltc3204/ltc3204b-3.3/ ltc3204-5 low noise regulated charge pumps up to 150ma (ltc3204-5), up to 50ma (ltc3204-3.3) ltc3240-3.3/ltc3240-2.5 step-up/step-down regulated charge pumps up to 150ma output related parts

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