1 ltc1515 series step-up/step-down switched capacitor dc/dc converters with reset daisy-chained control outputs features the ltc ? 1515, ltc1515-3/5 and ltc1515-3.3/5 are micropower switched capacitor dc/dc converters that produce a regulated output voltage by either stepping up or stepping down the input voltage. output voltage is adjustable using an external resistor divider (ltc1515) or programmable to either 3v/5v (ltc1515-3/5) or 3.3v/5v (ltc1515-3.3/5) using a logic pin. a unique architecture allows the parts to accommodate a wide input voltage range (2v to 10v) while maintaining 4% regulation. additional circuitry prevents excessive inrush current and output voltage ripple when large v in to v out differentials are present. an internal power-on reset circuit forces the por pin low on initial power-up. the por output remains low until 200ms (typ) after v out is in regulation. the parts are short-circuit and overtemperature protected. battery life is maximized by very low operating currents (i cc = 60 m a typ, i cc < 1 m a in shutdown). all three parts are available in an so-8 package. descriptio n u n adjustable/selectable 3v, 3.3v or 5v output voltages n 2v to 10v input voltage range n up to 50ma output current n only three external capacitors required n soft start limits inrush current at turn-on n low operating current: 60 m a n very low shutdown current: < 1 m a n shutdown disconnects load from v in n v out programmable to 3v/5v or 3.3v/5v n short-circuit and overtemperature protected n 650khz switching frequency n open-drain power-on reset output n available in so-8 package typical applicatio n u applicatio n s u n sim interface in gsm cellular telephones n smart card readers n local power supplies n portable equipment , ltc and lt are registered trademarks of linear technology corporation. programmable 3.3v/5v power supply with power-on reset shdn por gnd 5/3 v out v in c1 c1 + ltc1515-3.3/5 1 2 3 4 8 7 6 5 0.22 f 10 f 10 f v in
4-cell
nicd 100k v out = 3.3v or 5v
i out = 50ma on off reset 5v 3.3v ltc1515 ?ta01 + + ltc1515-x 5v output vs input voltage input voltage (v) 2 output voltage (v) 10 lt1515 ?ta02 4 6 8 3 5 7 9 5.2
5.1
5.0
4.9
4.8 i out = 10ma
5/3 = 3v
2 ltc1515 series absolute m axi m u m ratings w ww u (note 1) v in to gnd ................................................ C 0.3v to 12v v out to gnd ............................................. C 0.3v to 12v shdn, 5/3, fb to gnd .............................. C 0.3v to 12v v out short-circuit duration ............................. indefinite operating temperature range commercial ............................................. 0 c to 70 c industrial ............................................ C 40 c to 85 c storage temperature range ................ C 65 c to 150 c lead temperature (soldering, 10 sec)................. 300 c wu u package / o rder i for atio order part number order part number s8 part marking ltc1515cs8-3/5 ltc1515cs8-3.3/5 ltc1515is8-3/5 ltc1515is8-3.3/5 151535 515335 515i35 15i335 t jmax = 125 c, q ja = 110 c/w 1
2
3
4 8
7
6
5 top view v out
v in
c1 +
c1 shdn
por
5/3
gnd s8 package
8-lead plastic so ltc1515cs8 ltc1515is8 s8 part marking 1515 1515i t jmax = 125 c, q ja = 110 c/w 1
2
3
4 8
7
6
5 top view v out
v in
c1 +
c1 shdn
por
fb
gnd s8 package
8-lead plastic so consult factory for military grade parts. electrical characteristics v in = 2v to 10v, shdn = 3v, c1 = 0.22 m f, c in = c out = 10 m f unless otherwise noted (note 2). parameter conditions min typ max units v in operating voltage v out = 5v l 2.7 10 v v out = 3v/3.3v l 2.0 8 v v out = adj l 2.0 10 v v out = 3v (ltc1515-3/5) 2v v in 8v, i out 15ma l 2.88 3.0 3.12 v 3v v in 8v, i out 50ma l 2.88 3.0 3.12 v v out = 3.3v (ltc1515-3.3/5) 2v v in 8v, i out 15ma l 3.17 3.3 3.43 v 3v v in 8v, i out 50ma l 3.17 3.3 3.43 v v out = 5v (ltc1515-3/5, ltc1515-3.3/5) 2.7v v in 10v, i out 15ma l 4.8 5.0 5.2 v 3.3v v in 10v, i out 50ma l 4.8 5.0 5.2 v v fb feedback voltage ltc1515, v fb ramping negative l 1.190 1.232 1.275 v v fb feedback hysteresis ltc1515 1 % effective output resistance ltc1515, v in = 3v, step-up mode l 30 w v in operating current v in 5v, i out = 0, shdn = 3v l 60 100 m a v in > 5v, i out = 0, shdn = 3v l 75 135 m a v in shutdown current shdn = 0v, v in 5v l 1 m a shdn = 0v, v in > 5v 25 m a output ripple full load (note 2) 100 mv p-p switching frequency full load l 500 650 800 khz 5/3, shdn input threshold v il l 0.4 1.0 v v ih l 1.0 1.6 v 5/3, shdn input current 5/3, shdn = v in l C1 1 m a 5/3, shdn = 0v l C1 1 m a fb input current fb = 1.232v l C50 50 na por output low voltage i sink = 100 m a, v in = 3v l 0.05 0.4 v
3 ltc1515 series ltc1515-x 3.3v output voltage vs input voltage input voltage (v) 0 operating current ( a) 120
100
80
60
40
20 8 1515 g06 2 4 6 10 85 c ?0 c 25 c v out = 5v
i out = 0ma ltc1515-x operating current vs input voltage typical perfor m a n ce characteristics uw ltc1515-x 5v efficiency vs output current output current (ma) efficiency (%) 0.01 1 10 1515 g02 0.1 100 100
80
60
40
20
0 v out = 5v
t a = 25 c v in = 8v v in = 3.3v v in = 6v v in = 2.7v ltc1515-x 3.3v output voltage ripple vs input voltage electrical characteristics v in = 2v to 10v, shdn = 3v, c1 = 0.22 m f, c in = c out = 10 m f unless otherwise noted (note 2). parameter conditions min typ max units por leakage current v por = 5v l C1 1 m a por trip point (with respect to v out )v out ramping negative l C10 C7.5 C5 % por trip point hysteresis 1% i out short-circuit current v out = 0v l 12 40 ma t on soft start turn-on time 4 ms por delay after v out above por threshold l 140 200 280 ms the l denotes specifications which apply over the full operating temperature range. note 1: absolute maximum ratings are those values beyond which the life of the device may be impaired. note 2: for v in 3 8v, c out = 22 m f. input voltage (v) 0 output voltage ripple (mv p-p ) 250
200
150
100
50
0 8 1515 g03 2 4 6 10 v out = 3.3v
i out = 10ma
t a = 25 c c out = 10 f c out = 22 f c out = 47 f input voltage (v) 0 output voltage ripple (mv p-p ) 250
200
150
100
50
0 8 1515 g04 2 4 6 10 v out = 5v
i out = 10ma
t a = 25 c c out = 10 f c out = 47 f c out = 22 f ltc1515-x 5v output voltage ripple vs input voltage ltc1515-x 3.3v efficiency vs output current output current (ma) efficiency (%) 0.01 1 10 1515 g01 0.1 100 100
80
60
40
20
0 v out = 3.3v
t a = 25 c v in = 2v v in = 4.4v v in = 2.7v v in = 6v input voltage (v) 0 output voltage (v) 3.45
3.40
3.35
3.30
3.25
3.20 8 1515 g05 2 4 6 10 v out = 3.3v
i out = 10ma
c out = 10 f
t a = 25 c
4 ltc1515 series typical perfor m a n ce characteristics uw ltc1515-x shutdown supply current vs input voltage ltc1515-x step-down mode 5v load transient response input voltage (v) 0 positive supply current ( a) 25
20
15
10
5
0 8 1515 g12 2 4 6 10 85 c shdn = 0v ?0 c 25 c v out ac coupled 100mv/div i out 50ma/div v in = 8v, v out = 5v, c out = 10 m f, t a = 25 c 1515 g10 50ma 0ma v out ac coupled 100mv/div i out 50ma/div ltc1515-x step-up mode 5v load transient response v in = 3.3v, v out = 5v, c out = 10 m f, t a = 25 c 1515 g11 low will force v out to 3v (ltc1515-3/5) or 3.3v (ltc1515- 3.3/5). as with the shdn pin, the 5/3 pin may be driven with 3v logic over the entire v in range. the 5/3 pin may not float. fb (ltc1515) (pin 3): feedback input. the voltage on this pin is compared to the internal reference voltage (1.232v) to keep the output in regulation. an external resistor divider is required between v out and fb to adjust the output voltage. total divider resistance should not exceed 2m. gnd (pin 4): ground. should be tied to a ground plane for best performance. c1 C (pin 5): charge pump flying capacitor, negative terminal. shdn (pin 1): shutdown input. a logic low on the shdn pin puts the part into shutdown mode. a logic high (v shdn 3 1.6v) enables the part. at high v in voltages, the shdn pin may still be controlled with 3v logic without causing a large rise in v in quiescent current. the shdn pin may not float; connect to v in if unused. por (pin 2): open-drain power-on reset output. this pin will pull low upon initial power-up, during shutdown or until v out has been within 6.5% of its regulated value for more than 200ms typ. 5/3 (ltc1515-x) (pin 3): output voltage select. a logic high on the 5/3 pin will force v out to regulate to 5v. a logic pi n fu n ctio n s uuu input voltage (v) 0 efficiency (%) 100
80
60
40
20 8 1515 g09 2 4 6 10 v out = 3v
i out = 10ma
t a = 25 c ltc1515-x 3v efficiency vs input voltage ltc1515-x 5v efficiency vs input voltage input voltage (v) 2 efficiency (%) 100
80
60
40
20 10 1515 g08 4 6 8 12 v out = 5v
i out = 10ma
ta = 25 c input voltage (v) 0 efficiency (%) 100
80
60
40
20 8 1515 g07 2 4 6 10 v out = 3.3v
i out = 10ma
ta = 25 c ltc1515-x 3.3v efficiency vs input voltage
5 ltc1515 series pi n fu n ctio n s uuu c1 + (pin 6): charge pump flying capacitor, positive terminal. v in (pin 7): charge pump input voltage. may be between 2v and 10v. v in should be bypassed with a 3 10 m f low esr capacitor as close as possible to the pin for best performance. v out (pin 8): regulated output voltage. pin selectable to either 3v/5v, 3.3v/5v or adjustable using an external resistor divider (ltc1515). v out should be bypassed with a 3 10 m f low esr capacitor as close as possible to the pin for best performance. block digra m w w si plified applicatio n s i n for m atio n wu u u regulator operation the regulator section of the ltc1515, ltc1515-3/5 and ltc1515-3.3/5 consists of a charge pump, reference, comparator and some logic. the divided down output voltage is compared to the internal reference voltage. when the divided output drops below the reference volt- age, the charge pump is enabled, which boosts the output back into regulation. hysteresis in the comparator forces the regulator to burst on and off and causes approximately 100mv of peak-to-peak ripple to appear at the output. by enabling the charge pump only when needed, the parts achieve high efficiencies with low output load currents. each parts charge pump has a unique architecture that allows the input voltage to be either stepped up or stepped down to produce a regulated output. internal circuitry senses the v in to v out differential voltage and controls the charge pump operating mode. in addition, the effective output impedance of the charge pump is internally adjusted to prevent large inrush currents and allow for a wide input voltage range. when the input voltage is lower than the output voltage, the charge pump operates as a step-up voltage doubler. when the input voltage is greater than the output, the charge pump operates as a step-down gated switch. + + v os 1.232v
v ref 650khz
oscillator reset
counter step-up/step-down
charge pump v in shdn por gnd c1 c1 + v out (ltc1515-x) (ltc1515-x) ltc1515 ?bd fb
(ltc1515) 5/3
(ltc1515-x) en en
6 ltc1515 series output voltage selection the ltc1515-x versions have internal resistor networks which set the output voltage. the 5/3 pin controls an internal switch that shorts out a portion of the resistor network to change the output voltage. a logic high on this pin produces a 5v output and a low produces either a 3v output or a 3.3v output. the output voltage of the ltc1515 is selected using an external resistor divider (see figure 1). the output voltage is determined using the following formula: v out = (1.232v)[1 + (r1/r2)] the total resistance of r1 and r2 should not exceed 2m, otherwise excess ripple may appear at v out . applicatio n s i n for m atio n wu u u figure 1. ltc1515 output voltage selection shdn por gnd fb v out v in c1 c1 + ltc1515 1 2 3 4 8 7 6 5 ltc1515 ?f01 r1 r2 maximum v out and i out calculations for the ltc1515 the maximum output voltage and current available with the ltc1515 can be calculated based on the effective output resistance of the charge pump and the open circuit output voltage. in step-up mode, the open circuit output voltage is approximately 2v in (see figure 2). in step-down mode, the open circuit output voltage equals v in . the relationship between r out and v in in step-up mode is shown in figure 3. the following formulas can be used to find the maximum output voltage that may be programmed using the ltc1515 for a given minimum input voltage and output current load. step-up mode: max v out = (2)(min v in ) C (i out )(r out ) step-down mode: max v out = (min v in ) C (i out )(r out ) when v in C (i out )(r out ) is less than the programmed v out , the part will automatically switch from step-down mode to step-up mode. in both step-up mode and step- + + i out c out 2v in r out v out lt1515 ?f02 figure 2. step-up mode equivalent circuit input voltage (v) 1 output resistance ( ) 20 30 5 lt1515 ?f03 10 0 2 3 4 40 i out = 50ma i out = 20ma figure 3. step-up mode r out vs input voltage down mode, r out is internally adjusted to ensure that the maximum output current rating can be met. capacitor selection for best performance, low esr capacitors are recom- mended for both c in and c out to reduce noise and ripple. the c in and c out capacitors should be either ceramic or tantalum and should be 10 m f or greater. if the input source impedance is very low (< 0.5 w ) c in may not be needed. increasing the size of c out to 22 m f or greater will reduce output voltage ripple particularly with high v in voltages (8v or greater). a ceramic capacitor is recommended for the flying capacitor c1 with a value of 0.1 m f or 0.22 m f. smaller values may be used in low output current applications. output ripple normal ltc1515 series operation produces voltage ripple on the v out pin. output voltage ripple is required for the parts to regulate. low frequency ripple exists due to the hysteresis in the sense comparator and propagation de- lays in the charge pump enable/disable circuits. high frequency ripple is also present mainly from the esr
7 ltc1515 series applicatio n s i n for m atio n wu u u ing out of shutdown mode. whenever large v in (or boosted v in ) to v out voltage differentials are present, most charge pumps will pull large current spikes from the input supply. only the effective charge pump output impedance limits the current while the charge pump is enabled. this may disrupt input supply regulation, especially if the input supply is a low power dc/dc converter or linear regulator. the ltc1515 family minimizes inrush currents both at start-up and under high v in to v out operation. internal soft start circuitry controls the rate at which v out may be charged from 0v to its final regulated value. the typical start-up time from v out = 0v to 5v is 4ms. this corresponds to an effective v out charging current of only 12.5ma for a 10 m f output capacitor (27.5ma for 22 m f, etc.). note that any output current load present during start-up will add directly to the charging currents men- tioned above. the soft start circuitry limits start-up cur- rent both at initial power-up and when coming out of shutdown. as the v in (or boosted v in ) to v out voltage differential grows, the effective output impedance of the charge pump is automatically increased by internal voltage sensing circuitry. this feature minimizes the current spikes pulled from v in whenever the charge pump is enabled and helps to reduce both input and output ripple. power-on reset the por pin is an open-drain output that pulls low when the output voltage is out of regulation. when the v out rises to within 6.5% of regulation, an internal timer is started which releases por after 200ms (typ). in shut- down, the por output is pulled low. in normal operation, an external pull-up resistor is generally used between the por pin and v out . protection features all of the parts contain thermal shutdown and short- circuit protection features. the parts will shut down when the junction temperature reaches approximately 150 c and will resume operation once the junction temperature has dropped back to approximately 140 c. the parts will limit output current to 12ma (typ) when a short circuit condition (v out < 100mv) exists. the parts can survive an indefinite short to gnd. 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. (equivalent series resistance) in the output capacitor. typical output ripple (v in < 8v) under maximum load is 100mv peak-to-peak with a low esr, 10 m f output capaci- tor. for applications requiring v in to exceed 8v, a 22 m f or larger c out capacitor is recommended to maintain maxi- mum ripple in the 100mv range. the magnitude of the ripple voltage depends on several factors. high input voltages increase the output ripple since more charge is delivered to c out per charging cycle. a large c1 flying capacitor (> 0.22 m f) also increases ripple in step-up mode for the same reason. large output current load and/or a small output capacitor (<10 m f) results in higher ripple due to higher output voltage dv/dt. high esr capacitors (esr > 0.5 w ) on the output pin cause high frequency voltage spikes on v out with every clock cycle. there are several ways to reduce the output voltage ripple. a large c out capacitor (22 m f or greater) will reduce both the low and high frequency ripple due to the lower c out charging and discharging dv/dt and the lower esr typi- cally found with higher value (larger case size) capacitors. a low esr (<0.5 w ) ceramic output capacitor will mini- mize the high frequency ripple, but will not reduce the low frequency ripple unless a high capacitance value is cho- sen. a reasonable compromise is to use a 10 m f to 22 m f tantalum capacitor in parallel with a 1 m f to 3.3 m f ceramic capacitor on v out to reduce both the low and high frequency ripple. an rc or lc filter may also be used to reduce high frequency voltage spikes (see figure 4). inrush currents a common problem with switched capacitor regulators is inrush currentparticularly during power-up and com- 15 f
tantalum lt1515 ?f04 v out v out 8 1 f
ceramic 10 f
tantalum v out v out 8 10 f
tantalum 2 ltc1515/
ltc1515-x ltc1515/
ltc1515-x + + + figure 4. output ripple reduction techniques
8 ltc1515 series ? linear technology corporation 1997 1515f lt/tp 0298 4k ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 l (408) 432-1900 fax: (408) 434-0507 l telex: 499-3977 l www.linear-tech.com part number description comments ltc1514 series step-up/step-down switched capacitor dc/dc converters v in 2v to 10v, 3.3v and 5v versions, i out to 50ma ltc1516 micropower, regulated 5v charge pump dc/dc converter i out = 20ma (v in 3 2v), i out = 50ma (v in 3 3v) ltc1517-5 micropower, regulated 5v charge pump dc/dc converter ltc1522 without shutdown and packaged in sot-23 ltc1522 micropower, regulated 5v charge pump dc/dc converter available in 8-pin msop, 6 m a quiescent current, i out = 20ma ltc1555/ltc1556 sim power supply and level translators step-up/step-down sim power supply and level translators ltc660 100ma cmos voltage converter 5v to C 5v conversion with low voltage loss typical applicatio n s u related parts 1 2 3 4 0.150 ?0.157**
(3.810 ?3.988) 8 7 6 5 0.189 ?0.197*
(4.801 ?5.004) 0.228 ?0.244
(5.791 ?6.197) 0.016 ?0.050
0.406 ?1.270 0.010 ?0.020
(0.254 ?0.508) 45 0 ?8 typ 0.008 ?0.010
(0.203 ?0.254) so8 0996 0.053 ?0.069
(1.346 ?1.752) 0.014 ?0.019
(0.355 ?0.483) 0.004 ?0.010
(0.101 ?0.254) 0.050
(1.270)
typ dimension does not include mold flash. mold flash
shall not exceed 0.006" (0.152mm) per side
dimension does not include interlead flash. interlead
flash shall not exceed 0.010" (0.254mm) per side
*
** s8 package 8-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) package descriptio n u dimensions in inches (millimeters) unless otherwise noted. low power, low noise step-up/step-down 5v supply with reset shdn por gnd fb v out v in c1 c1 + ltc1515 1 2 3 4 8 7 6 5 0.22 f 10 f 22 f 1.4m v in = 3v to 10v on off reset ltc1515 ?ta03 402k 470k lt1121-5 in gnd out 10 f 8 3 1 v out = 5v
i out = 20ma
v ripple < 1mv p-p 5.5v + + 2 10 f + + programmable 3v/5v gsm sim card power supply shdn por gnd 5/3 v out v in c1 c1 + ltc1515-3/5 1 2 3 4 8 7 6 5 0.1 f nc 10 f 10 f li-ion v out = 3v or 5v
i out = 15ma on off 5v 3v ltc1515 ?ta04 + + positive and negative supply shdn por gnd 5/3 v out v in v in c1 c1 + ltc1515-3/5 1 2 3 4 8 7 6 5 0.22 f 0.22 f ** * central semiconductor
cmpsh-35 dual schottky
** optional circuitry for maintaining
v out with low v out loads
q1, q2: 2n3904 * 10 f v out = 5v
i out = 15ma, 2.7v v in 4.4v
i out = 50ma, 3.3v v in 4.4v v in = 2.7v to 4.4v v out = 1v to 3.5v
i out = 5ma on off nc ltc1515 ?ta05 + + 10 f 10 f 470 8.2k 2.4k + q1 q2
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