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1 ltc1046 1046fb inductorless 5v to C 5v converter generating C 5v from 5v output voltage vs load current for v + = 5v the ltc ? 1046 is a 50ma monolithic cmos switched capacitor voltage converter. it plugs in for the icl7660/ ltc1044 in 5v applications where more output current is needed. the device is optimized to provide high current capability for input voltages of 6v or less. it trades off operating voltage to get higher output current. the ltc1046 provides several voltage conversion functions: the input voltage can be inverted (v out = C v in ), divided (v out = v in/ 2) or multiplied (v out = nv in ). designed to be pin-for-pin and functionally compatible with the icl7660 and ltc1044, the ltc1046 provides 2.5 times the output drive capability. n 50ma output current n plug-in compatible with icl7660/ltc1044 n r out = 35 w maximum n 300 m a maximum no load supply current at 5v n boost pin (pin 1) for higher switching frequency n 97% minimum open-circuit voltage conversion efficiency n 95% minimum power conversion efficiency n wide operating supply voltage range: 1.5v to 6v n easy to use n low cost n conversion of 5v to 5v supplies n precise voltage division, v out = v in /2 n supply splitter, v out = v s /2 features descriptio u applicatio s u typical applicatio u , ltc and lt are registered trademarks of linear technology corporation. 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 10 f 10 f 1046 ta01 5v input 5v output + + load current, i l (ma) 0 0 output voltage (v) ? ? ? ? ? 10 20 30 40 1046 ta02 50 icl7660/ltc1044, r out = 55 w t a = 25 c ltc1046, r out = 27 w
ltc1046 2 1046fb a u g w a w u w a r b s o lu t exi t i s order part number supply voltage ....................................................... 6.5v input voltage on pins 1, 6 and 7 (note 2) ............................ C 0.3 < v in < (v + ) + 0.3v current into pin 6 .................................................. 20 m a output short circuit duration (v + 6v) ............................................... continuous wu u package / o rder i for atio ltc1046mj8 t jmax = 160 c, q ja = 100 c operating temperature range ltc1046c .................................... 0 c t a 70 c ltc1046i ................................. C 40 c t a 85 c ltc1046m (obsolete) ............ C55 c to 125 c storage temperature range ............... C 65 c to + 150 c lead temperature (soldering, 10 sec.)................. 300 c (note 1) order part number ltc1046cn8 ltc1046cs8 ltc1046in8 ltc1046is8 s8 part marking 1046 1046i t jmax = 110 c, q ja = 130 c (n8) t jmax = 150 c, q ja = 150 c (s8) 1 2 3 4 8 7 6 5 top view v + osc lv v out boost cap + gnd cap j8 package 8-lead cerdip obsolete package consider the n8 or s8 for alternate source 1 2 3 4 8 7 6 5 top view v + osc lv v out boost cap + gnd cap n8 package 8-lead pdip s8 package 8-lead plastic so consult ltc marketing for parts specified with wider operating temperature ranges. e lectr ic al c c hara terist ics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v + = 5v, c osc = 0pf, unless otherwise noted. ltc1046c ltc1046i/m symbol parameter conditions min typ max min typ max units i s supply current r l = , pins 1 and 7 no connection 165 300 165 300 m a r l = , pins 1 and 7 no connection, 35 35 m a v + = 3v v + l minimum supply voltage r l = 5k w l 1.5 1.5 v v + h maximum supply voltage r l = 5k w l 66v r out output resistance v + = 5v, i l = 50ma (note 3) 27 35 27 35 w l 27 45 27 50 w v + = 2v, i l = 10ma l 60 85 60 90 w f osc oscillator frequency v + = 5v (note 4) 20 30 20 30 khz v + = 2v 4 5.5 4 5.5 khz p eff power efficiency r l = 2.4k w 95 97 95 97 % v outeff voltage conversion r l = 97 99.9 97 99.9 % efficiency i osc oscillator sink or source v osc = 0v or v + current pin 1 = 0v l 4.2 35 4.2 40 m a pin 1 = v + l 15 45 15 50 m a
3 ltc1046 1046fb oscillator frequency, f osc (hz) 100 80 power conversion efficiency, p eff (%) 86 92 98 100 1k 10k 100k 1m 1046 g06 96 94 90 88 84 82 v + = 5v t a = 25 c c1 = c2 a = 100 m f, 1ma b = 100 m f, 15ma c = 10 m f, 1ma d = 10 m f, 15ma e = 1 m f, 1ma f = 1 m f, 15ma a c b e d f load current, i l (ma) 0 30 power conversion efficiency, p eff (%) 50 60 70 80 90 100 30 40 60 70 1046 g05 40 10 20 50 p eff i s 20 10 0 t a = 25 c v + = 5v c1 = c2 = 10 m f f osc = 30khz 30 50 60 70 80 90 100 40 20 10 0 supply current (ma) load current, i l (ma) 0 30 power conversion efficiency, p eff (%) 50 60 70 80 90 100 34 67 1046 g04 40 12 5 p eff i s 20 10 0 t a = 25 c v + = 2v c1 = c2 = 10 m f f osc = 8khz 8910 3 5 6 7 8 9 10 4 2 1 0 supply current (ma) ambient temperature ( c) ?5 10 output resistance ( w ) 30 40 50 60 70 80 25 50 100 125 1046 g03 20 ?5 0 75 c1 = c2 = 10 m f v + = 2v, c osc = 0pf v + = 5v, c osc = 0pf oscillator frequency, f osc (hz) 100 0 output resistance, r o ( w ) 200 300 400 500 1k 10k 100k 1046 g01 100 t a = 25 c v + = 5v i l = 10ma c1 = c2 = 1 m f c1 = c2 = 10 m f c1 = c2 = 100 m f cc hara terist ics uw a t y p i ca lper f o r c e (using test circuit in figure 1) output resistance vs output resistance vs output resistance vs oscillator frequency supply voltage temperature power conversion efficiency vs power conversion efficiency vs power conversion efficiency vs load current for v + = 2v load current for v + = 5v oscillator frequency supply voltage, v + (v) 0 10 output resistance, r o ( w ) 100 1000 2567 1046 g02 134 t a = 25 c i l = 3ma c osc = 100pf c osc = 0pf note 1: absolute maximum ratings are those values beyond which the life of the device may be impaired. note 2: connecting any input terminal to voltages greater than v + or less than ground may cause destructive latch-up. it is recommended that no inputs from sources operating from external supplies be applied prior to power-up of the ltc1046. note 3: r out is measured at t j = 25 c immediately after power-on. note 4: f osc is tested with c osc = 100pf to minimize the effects of test fixture capacitance loading. the 0pf frequency is correlated to this 100pf test point, and is intended to simulate the capacitance at pin 7 when the device is plugged into a test socket and no external capacitor is used. e lectr ic al c c hara terist ics
ltc1046 4 1046fb ambient temperature ( c) ?5 26 oscillator frequency, f osc (khz) 30 32 34 36 38 40 25 50 100 125 1046 g11 28 ?5 0 75 v + = 5v c osc = 0pf ambient temperature ( c) 0 1 oscillator frequency, f osc (khz) 10 100 1457 1046 g10 23 6 t a = 25 c c osc = 0pf cc hara terist ics uw a t y p i ca lper f o r c e test circuit figure 1 oscillator frequency as a oscillator frequency vs function of supply voltage temperature (using test circuit in figure 1) c osc external oscillator c2 10 m f v out v + (5v) r l i s i l 1046 f01 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 c1 10 f + + external capacitor (pin 7 to gnd), c osc (pf) 1 0.1 oscillator frequency, f osc (khz) 1 10 100 10 100 10000 1046 g09 1000 v + = 5v t a = 25 c pin 1 = open pin 1 = v + load current, i l (ma) 0 2.5 output voltage (v) 2.0 1.5 1.0 0.5 0.0 0.5 2 4 6 8 1046 g07 10 12 14 16 18 20 1.0 1.5 2.0 2.5 slope = 52 t a = 25 c v + = 2v f osc = 8khz c1 = c2 = 10 m f load current, i l (ma) 0 ? output voltage (v) ? ? ? ? 0 1 10 20 30 40 1046 g08 50 60 70 80 90 100 2 3 4 5 slope = 27 t a = 25 c v + = 5v f osc = 30khz c1 = c2 = 10 m f output voltage vs load current output voltage vs load current oscillator frequency as a for v + = 2v for v + = 5v function of c osc
5 ltc1046 1046fb u s a o pp l ic at i wu u i for atio theory of operation to understand the theory of operation of the ltc1046, a review of a basic switched capacitor building block is helpful. in figure 2, when the switch is in the left position, capacitor c1 will charge to voltage v1. the total charge on c1 will be q1 = c1v1. the switch then moves to the right, discharging c1 to voltage v2. after this discharge time, the charge on c1 is q2 = c1v2. note that charge has been transferred from the source, v1, to the output, v2. the amount of charge transferred is: d q = q1 C q2 = c1(v1 C v2). if the switch is cycled f times per second, the charge transfer per unit time (i.e., current) is: i = f ? d q = f ? c1(v1 C v2). examination of figure 4 shows that the ltc1046 has the same switching action as the basic switched capacitor building block. with the addition of finite switch on resistance and output voltage ripple, the simple theory, although not exact, provides an intuitive feel for how the device works. for example, if you examine power conversion efficiency as a function of frequency (see typical curve), this simple theory will explain how the ltc1046 behaves. the loss, and hence the efficiency, is set by the output impedance. as frequency is decreased, the output impedance will eventually be dominated by the 1/fc1 term and power efficiency will drop. the typical curves for power effi- ciency versus frequency show this effect for various capaci- tor values. note also that power efficiency decreases as frequency goes up. this is caused by internal switching losses which occur due to some finite charge being lost on each switching cycle. this charge loss per unit cycle, when multiplied by the switching frequency, becomes a current loss. at high frequency this loss becomes significant and the power efficiency starts to decrease. figure 3. switched capacitor equivalent circuit figure 4. ltc1046 switched capacitor voltage converter block diagram c2 r equiv = 1046 f03 v2 v1 r l r equiv 1 fc1 1046 f04 cap + (2) cap (4) gnd (3) v out (5) v + (8) lv (6) 3x (1) osc (7) osc +2 closed when v + > 3.0v c1 c2 boost sw1 sw2 f f + + figure 2. switched capacitor building block c1 f c2 1046 f02 v2 v1 r l rewriting in terms of voltage and impedance equivalence, i vv fc vv r equiv = () = 12 11 12 / . a new variable, r equiv , has been defined such that r equiv = 1/fc1. thus, the equivalent circuit for the switched capacitor network is as shown in figure 3.
ltc1046 6 1046fb u s a o pp l ic at i wu u i for atio lv (pin 6) the internal logic of the ltc1046 runs between v + and lv (pin 6). for v + greater than or equal to 3v, an internal switch shorts lv to gnd (pin 3). for v + less than 3v, the lv pin should be tied to ground. for v + greater than or equal to 3v, the lv pin can be tied to ground or left floating. osc (pin 7) and boost (pin 1) the switching frequency can be raised, lowered or driven from an external source. figure 5 shows a functional diagram of the oscillator circuit. by connecting the boost (pin 1) to v + , the charge and discharge current is increased and, hence, the frequency is increased by approximately three times. increasing the frequency will decrease output impedance and ripple for higher load currents. loading pin 7 with more capacitance will lower the fre- quency. using the boost pin in conjunction with external capacitance on pin 7 allows user selection of the fre- quency over a wide range. driving the ltc1046 from an external frequency source can be easily achieved by driving pin 7 and leaving the boost pin open, as shown in figure 6. the output current from pin 7 is small, typically 15 m a, so a logic gate is capable of driving this current. the choice of using a cmos logic gate is best because it can operate over a wide supply voltage range (3v to 15v) and has enough voltage swing to drive the internal schmitt trigger shown in figure 5. for 5v applications, a ttl logic gate can be used by simply adding an external pull-up resistor (see figure 6). capacitor selection while the exact values of c in and c out are noncritical, good quality, low esr capacitors such as solid tantalum are necessary to minimize voltage losses at high currents. for c in the effect of the esr of the capacitor will be multiplied by four, due to the fact that switch currents are approximately two times higher than output current, and losses will occur on both the charge and discharge cycle. this means that using a capacitor with 1 w of esr for c in will have the same effect as increasing the output imped- ance of the ltc1046 by 4 w . this represents a significant increase in the voltage losses. for c out the effect of esr is less dramatic. c out is alternately charged and dis- charged at a current approximately equal to the output current, and the esr of the capacitor will cause a step function to occur, in the output ripple, at the switch transitions. this step function will degrade the output regulation for changes in output load current, and should be avoided. realizing that large value tantalum capacitors can be expensive, a technique that can be used is to parallel a smaller tantalum capacitor with a large alumi- num electrolytic capacitor to gain both low esr and reasonable cost. where physical size is a concern some of the newer chip type surface mount tantalum capacitors can be used. these capacitors are normally rated at working voltages in the 10v to 20v range and exhibit very low esr (in the range of 0.1 w ). figure 6. external clocking c2 v + 100k osc input required for ttl logic ?v + ) 1046 f06 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 c1 nc + + figure 5. oscillator osc (7) 1046 f05 lv (6) boost (1) ~ 14pf i 2i i 2i v + schmitt trigger
7 ltc1046 1046fb u s a o pp l ic at i ty p i ca l figure 7. negative voltage converter negative voltage converter figure 7 shows a typical connection which will provide a negative supply from an available positive supply. this circuit operates over full temperature and power supply ranges without the need of any external diodes. the lv pin (pin 6) is shown grounded, but for v + 3 3v, it may be floated, since lv is internally switched to gnd (pin 3) for v + 3 3v. the output voltage (pin 5) characteristics of the circuit are those of a nearly ideal voltage source in series with an 27 w resistor. the 27 w output impedance is composed of two terms: 1) the equivalent switched capacitor resistance (see theory of operation), and 2) a term related to the on resistance of the mos switches. at an oscillator frequency of 30khz and c1 = 10 m f, the first term is: r= 1 f/2 equiv osc () = = . c1 1 15 10 10 10 67 36 w. notice that the equation for r equiv is not a capacitive reactance equation (x c = 1/ w c) and does not contain a 2 p term. the exact expression for output impedance is complex, but the dominant effect of the capacitor is clearly shown on figure 8. voltage doubler figure 9. ultraprecision voltage divider the typical curves of output impedance and power effi- ciency versus frequency. for c1 = c2 = 10 m f, the output impedance goes from 27 w at f osc = 30khz to 225 w at f osc = 1khz. as the 1/fc term becomes large compared to switch on resistance term, the output resistance is deter- mined by 1/fc only. voltage doubling figure 8 shows a two diode, capacitive voltage doubler. with a 5v input, the output is 9.1v with no load and 8.2v with a 10ma load. 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 10 f 10 f 1046 f07 v + 1.5v to 6v v out = v + required for v + < 3v t min t a t max + + 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 10 f10 f v d v d + + 1046 f08 v + 1.5v to 6v v out = 2 (v in ?) required for v + < 3v + + ultraprecision voltage divider an ultraprecision voltage divider is shown in figure 9. to achieve the 0.0002% accuracy indicated, the load current should be kept below 100na. however, with a slight loss in accuracy, the load current can be increased. 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 c1 10 f c2 10 f t min t a t max i l 100na required for v + < 6v 1046 f09 v + 3v to 12v + + 0.002% v + 2
ltc1046 8 1046fb u s a o pp l ic at i ty p i ca l battery splitter a common need in many systems is to obtain positive and negative supplies from a single battery or single power supply system. where current requirements are small, the circuit shown in figure 10 is a simple solution. it provides symmetrical positive or negative output voltages, both figure 10. battery splitter 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 c1 10 f v b 9v c2 10 f output comm0n required for v b < 6v 3v v b 12v 1046 f10 +v b /2 4.5v ? b /2 4.5v + + equal to one half the input voltage. the output voltages are both referenced to pin 3 (output common). if the input voltage between pin 8 and pin 5 is less than 6v, pin 6 should also be connected to pin 3, as shown by the dashed line. paralleling for lower output resistance additional flexibility of the ltc1046 is shown in figures 11 and 12. figure 11 shows two ltc1046s connected in parallel to provide a lower effective output resistance. if, however, the output resistance is dominated by 1/fc1, increasing the capacitor size (c1) or increasing the fre- quency will be of more benefit than the paralleling circuit shown. figure 12 makes use of stacking two ltc1046s to provide even higher voltages. in figure 12, a negative voltage doubler or tripler can be achieved depending upon how pin 8 of the second ltc1046 is connected, as shown schematically by the switch. 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 c1 10 f c1 10 f + 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 1/4 cd4077 + c2 20 f 1046 f11 v out = (v + ) optional synchronization circuit to minimize ripple v + + figure 11. paralleling for 100ma load current 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 v + 10 f c1 10 f ?v + ) + 1 2 3 4 8 7 6 5 v + osc lv v out boost cap + gnd cap ltc1046 for v out = 2v + for v out = 3v + + 10 f 10 f 1046 f12 v out + + figure 12. stacking for higher voltage
9 ltc1046 1046fb u package d e sc r i pti o j8 package 8-lead cerdip (narrow .300 inch, hermetic) (reference ltc dwg # 05-08-1110) j8 0801 .014 ?.026 (0.360 ?0.660) .200 (5.080) max .015 ?.060 (0.381 ?1.524) .125 3.175 min .100 (2.54) bsc .300 bsc (7.62 bsc) .008 ?.018 (0.203 ?0.457) 0 ?15 .005 (0.127) min .405 (10.287) max .220 ?.310 (5.588 ?7.874) 12 3 4 87 65 .025 (0.635) rad typ .045 ?.068 (1.143 ?1.650) full lead option .023 ?.045 (0.584 ?1.143) half lead option corner leads option (4 plcs) .045 ?.065 (1.143 ?1.651) note: lead dimensions apply to solder dip/plate or tin plate leads obsolete package
ltc1046 10 1046fb u package d e sc r i pti o n8 package 8-lead pdip (narrow .300 inch) (reference ltc dwg # 05-08-1510) n8 1002 .065 (1.651) typ .045 ?.065 (1.143 ?1.651) .130 .005 (3.302 0.127) .020 (0.508) min .018 .003 (0.457 0.076) .120 (3.048) min 12 3 4 87 6 5 .255 .015* (6.477 0.381) .400* (10.160) max .008 ?.015 (0.203 ?0.381) .300 ?.325 (7.620 ?8.255) .325 +.035 ?015 +0.889 0.381 8.255 () note: 1. dimensions are inches millimeters *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .010 inch (0.254mm) .100 (2.54) bsc
11 ltc1046 1046fb 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. u package d e sc r i pti o s8 package 8-lead plastic small outline (narrow .150 inch) (reference ltc dwg # 05-08-1610) .016 ?.050 (0.406 ?1.270) .010 ?.020 (0.254 ?0.508) 45 0 ?8 typ .008 ?.010 (0.203 ?0.254) so8 0303 .053 ?.069 (1.346 ?1.752) .014 ?.019 (0.355 ?0.483) typ .004 ?.010 (0.101 ?0.254) .050 (1.270) bsc 1 2 3 4 .150 ?.157 (3.810 ?3.988) note 3 8 7 6 5 .189 ?.197 (4.801 ?5.004) note 3 .228 ?.244 (5.791 ?6.197) .245 min .160 .005 recommended solder pad layout .045 .005 .050 bsc .030 .005 typ inches (millimeters) note: 1. dimensions in 2. drawing not to scale 3. these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .006" (0.15mm)
ltc1046 12 1046fb ? linear technology corporation 1991 lt/tp 0403 1k rev b ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear.com related parts part number description comments ltc1044a 12v cmos voltage converter doubler or inverter, 20ma i out , 1.5v to 12v input range lt ? 1054 switched capacitor voltage converter with regulator doubler or inverter, 100ma i out , so-8 package ltc1550 low noise, switched capacitor regulated inverter < 1mv p-p output ripple, 900khz operation, so-8 package lt1611 1.4mhz inverting switching regulator 5v to C5v at 150ma, low output noise, sot-23 package lt1617 micropower inverting switching regulator 5v to C 5v at 20 m a supply current, sot-23 package ltc1754-5 micropower regulated 5v charge pump in sot-23 5v/50ma, 13 m a supply current, 2.7v to 5.5v input range

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