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rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ?co pyright 2000 sipex corporation 1 20ma output current at 1.2v input +2v to +5.5v output range 0.85v guaranteed start-up 83% high efficiency 1.5 a quiescent supply current at v batt reverse battery protection internal synchronous rectifier 5na logic controlled shutdown current from v batt for the sp6642 low-battery detection active low output for the sp6643 extremely small soic package pin-to-pin compatible with max1642 and max1643 sp6642/6643 description the sp6642/6643 devices are high-efficiency, low-power step-up dc-dc converters for +1v inputs ideal for single alkaline cell applications such as pagers, remote controls, and other low-power portable end products. designers can control the sp6642 device with a 1na active low shutdown input. the sp6643 features an active low output for low-battery conditions. both devices contain a 0.8 ? synchronous rectifier, an oscillator, a 0.6 ? n-channel mosfet power switch, an internal voltage reference, circuitry for pulse-frequency-modulation, and an under voltage comparator. the output voltage for the sp6642/6643 devices is preset to +3.3v + 4% or can be adjusted from +2v to +5.5v by manipulating two external resistors. v out gnd pfi v batt lx 1 2 3 4 5 6 7 8 sp6642 pfo shdn fb v out gnd pfi v batt lx 1 2 3 4 5 6 7 8 sp6643 fb battlo pfo single alkaline cell, high efficiency step-up dc-dc converter
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ?cop yright 2000 sipex corporation 2 r e t e m a r a p. n i m. p y t. x a ms t i n us n o i t i d n o c v , e g a t l o v t u p n i g n i t a r e p o m u m i n i m ) n i m ( t t a b 2 . 0vr l k 3 = ? v , e g a t l o v t u p n i g n i t a r e p o m u m i x a m ) x a m ( t t a b 5 6 . 1v v ( e g a t l o v t u p n i p u - t r a t s t t a b 2 e t o n , )5 8 . 05 7 . 0vr l k 3 = ? t , b m a 5 2 + = o c v ( e g a t l o v t u p n i p u - t r a t s t t a b t n e i c i f f e o c e r u t a r e p m e t , )2 - / v m o c e g a t l o v t u p n i n d h s v l i v h i 0 8 0 2% v f o % t t a b e h t r o f 2 4 6 6 p s v f o % t t a b e h t r o f 2 4 6 6 p s t n e r r u c t u p n i n d h s 0 1a n 2 4 6 6 p s t n e r r u c t u p n i b f 0 1a nv b f v 3 . 1 = v , e g a t l o v t e s b f b f 5 1 2 . 12 6 2 . 19 0 3 . 1v k c a b d e e f l a n r e t x e t n e r r u c t u p n i i f p 0 1 a n v i f p v m 0 5 6 = e g a t l o v p i r t i f p0 9 54 1 62 3 6v m% 1 = s i s e r e t s y h , i f p g n i l l a f e g a t l o v p i r t o l t t a b6 9 . 00 0 . 14 0 . 1vv t u o , % 2 = s i s e r e t s y h , v 3 . 3 = 3 4 6 6 p s v , e g a t l o v t u p t u o t u o 6 1 . 30 3 . 34 4 . 3vv b f v 1 . 0 < e g n a r e g a t l o v t u p t u o0 . 25 . 5v k c a b d e e f l a n r e t x e e c n a t s i s e r - n o l e n n a h c - n6 . 05 . 1 ? v t u o v 3 . 3 = e c n a t s i s e r - n o l e n n a h c - p8 . 02 . 2 ? v t u o v 3 . 3 = e g a t l o v e d o i d - h c t a c l e n n a h c - p8 . 0vi e d o i d f f o h c t i w s l e n n a h c - p , a m 0 0 1 = absolute maximum ratings these are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. exposure to absolute maximum rating conditions for extended periods of time may affect reliability. v batt to gnd.............................................-0.3 to 6.0v v out to gnd..............................................-0.3 to 6.0v lx, shdn, fb, battlo, pfo to gnd....-0.3 to 6.0v pfi to gnd...............................................-0.3 to 6.0v reverse battery current, t amb =+25 o c.............220ma (note 1) v batt forward current............................................0.5a v out , lx current......................................................1a storage temperature range............-65?c to +165?c lead temperature (soldering 10s)..................+300?c operating temperature.......................-40?c to +85?c power dissipation per package 8-pin soic (derate 4.85mw/ o c above +70 o c) ..........390mw specifications v batt = v shdn = 1.3v, i load = 0ma, fb = gnd, t amb = -40 o c to +85 o c, and typical values are at t amb = +25 o c unless otherwise noted.
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ?co pyright 2000 sipex corporation 3 specifications (continued) v batt = v shdn = 1.3v, i load = 0ma, fb = gnd, t amb = -40 o c to +85 o c, and typical values are at t amb = +25 o c unless otherwise noted. r e t e m a r a p. n i m. p y t. x a ms t i n us n o i t i d n o c v o t n i t n e r r u c t n e c s e i u q t u o i , t u o q 3 10 2 a v t u o v 5 . 3 = v o t n i t n e r r u c t n e c s e i u q t t a b i , t t a b q 5 . 15 . 2 a v t t a b v 0 . 1 = v o t n i t n e r r u c n w o d t u h s t u o i , t u o n d h s 1 0 0 . 05 . 0 a v t u o e h t r o f v 5 . 3 = 2 4 6 6 p s v o t n i t n e r r u c n w o d t u h s t t a b i , t t a b n d h s 5 0 0 . 01 . 0 a v t t a b e h t r o f v 0 . 1 = 2 4 6 6 p s v , o l t t a b d n a o f p r o f e g a t l o v t u p t u o w o l l o 4 . 0vv i f p v , v 0 = t u o i , v 3 . 3 + = k n i s a m 1 = o l t t a b d n a o f p r o f t n e r r u c e g a k a e l1 a v i f p v , v m 0 5 6 = o f p v 6 = e g a t l o v p i r t o l t t a b6 9 . 00 . 14 0 . 1vv t u o e h t r o f % 2 = s i s e r e t s y h , v 3 . 3 + = 3 4 6 6 p s k , t n a t s n o c e m i t - n o7 15 25 3- v sv < v 9 . 0 t t a b t ( v 5 . 1 < n o v / k = t t a b ) ) 3 e t o n ( o i t a r g n i k c a r t e m i t - f f o15 . 1v < v 9 . 0 t t a b v , v 5 . 1 < t u o v 3 . 3 + = y c n e i c i f f e3 8%i d a o l a m 0 2 = note 1: the reverse battery current is measured from the typical operating circuit's input terminal to gnd when the battery is connected backward. a reverse current of 220ma will not exceed package dissipation limits but, if left for an extended time (more than 10 minutes), may degrade performance. note 2: start-up guaranteed by correlation to measurements of device parameters (i.e. switch on-resistance, on-times, and output voltage trip points. note 3: toff = ratio x . this guarantees discontinous condition. note 4: specifications to -40? are guaranteed by design, not production tested. t on x v batt v out - v batt
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ?cop yright 2000 sipex corporation 4 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 output current (ma) vin = 1.6v vin = 1.2v vin = 1.0v vin = 0.85v efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 output current (ma) vin = 1.6v vin = 1.2v vin = 1.0v vin = 0.85v efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 output current (ma) vin = 1.6v vin = 1.2v vin = 1.0v vin = 0.85v efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 output current (ma) vin = 1.6v vin = 1.2v vin = 1.0v vin = 0.85v efficiency (%) figure 1. efficiency vs. output current (v out =2.4v) where l1=100 h, sumida cd54-101 figure 2. efficiency vs. output current (v out =2.4v) where l1=150 h, tdk nlc565050t-151k figure 3. efficiency vs. output current (v out =3.3v) where l1=100 h, sumida cd54-101 figure 4. efficiency vs. output current (v out =3.3v) where l1=150 h, tdk nlc565050t-151k performance characteristics refer to the circuit in figure 25 with v batt = 1.2v, r1 + r2 = 1m ? , and t amb = +25 o c unless otherwise noted.
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? co pyright 2000 sipex corporation 5 0 20 40 60 80 100 -40 -20 0 20 40 60 80 100 temperature ( o c) quiescent current ( a) 10 100 1000 10000 0.8 1.0 1.2 1.4 1.6 1.8 input voltage (v) vout = 5.0v vout = 3.3v vout = 2.4v quiescent current ( a) 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 output current (ma) vin = 1.6v vin = 1.2v vin = 1.0v vin = 0.85v efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 output current (ma) vin = 1.6v vin = 1.2v vin = 1.0v vin = 0.85v efficiency (%) figure 5. efficiency vs. output current (v out =5.0v) where l1=100 h, sumida cd54-101 figure 6. efficiency vs. output current (v out =5.0v) where l1=150 h, tdk nlc565050t-151k figure 7. no-load battery current vs. input voltage figure 8. no-load battery current vs. temperature where v batt = 1.2v, v out = 3.3v performance characteristics (continued) refer to the circuit in figure 25 with v batt = 1.2v, r1 + r2 = 1m ? , and t amb = +25 o c unless otherwise noted.
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? cop yright 2000 sipex corporation 6 figure 9. v batt and v out pin quiescent currents vs. temperature where v batt = 1.2v, v out = 3.6v figure 10. minimum start-up input voltage vs. output current where l1=100 h, sumida cd54-101 figure 11. minimum start-up input voltage vs. output current where l1=150 h, tdk nlc565050t-151k figure 12. maximum output current vs. input voltage where l1=100 h, sumida cd54-101 performance characteristics (continued) refer to the circuit in figure 25 with v batt = 1.2v, r1 + r2 = 1m ? , and t amb = +25 o c unless otherwise noted. 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 0 5 10 15 20 25 30 output current (ma) vout = 5v vout = 3.3v vout = 2.4v start-up input voltage (v) 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 0246810121416 output current (ma) vout = 5v vout = 3.3v vout = 2.4v start-up input voltage (v) 0 5 10 15 20 25 30 35 40 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 vout = 2.4v vout = 3.3v vout = 5v input voltage (v) maximum output current (ma ) 0 5 10 15 20 25 30 35 40 -40 -20 0 20 40 60 80 100 temperature ( o c) iout ibatt quiescent current ( a)
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? co pyright 2000 sipex corporation 7 figure 13. maximum output current vs. input voltage where l1=150 h, tdk nlc565050t-151k figure 14. switching waveforms: v out =3.3v, v in =1.2v, i out =12ma where 1: lx, 2v/div, l1=tdk nklc565050t-151k 2: v out , 20mv/div, 3.3v dc offset 3: inductor current, 100ma/div figure 15. load-transient response: v out =3.3v, v batt =1.2v where 1: v out , 20mv/div, 3.3v dc offset 2: load, 2ma to 20ma, 10ma/div figure 16. line-transient response: v out =3.3v, load=15ma where 1: v out , 50mv/div, 3.3v dc offset 2: v batt , 1v to 5v, 500mv/div performance characteristics (continued) refer to the circuit in figure 25 with v batt = 1.2v, r1 + r2 = 1m ? , and t amb = +25 o c unless otherwise noted. 0 2 4 6 8 10 12 14 16 18 20 22 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 input voltage (v) vout = 2.4v vout = 3.3v vout = 5v maximum output current (ma) 10msec/div 500 sec/div 500 sec/div
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? cop yright 2000 sipex corporation 8 e m a nn o i t c n u f r e b m u n n i p 2 4 6 6 p s3 4 6 6 p s v t t a b e h t r o f . y l p p u s y r e t t a b 3 4 6 6 p s e h t f o t u p n i r o s n e s e h t o t s e i t n i p s i h t , . r o t a r a p m o c o l t t a b 11 i f p s k n i s o f p , v m 4 1 6 w o l e b s p o r d i f p n o e g a t l o v e h t n e h w . t u p n i l i a f - r e w o p . t n e r r u c 22 o l t t a b v t a e g a t l o v e h t n e h w . t u p t u o w o l - y r e t t a b n i a r d - n e p o t t a b w o l e b s p o r d . t n e r r u c s k n i s o l t t a b , v 1 -3 o f p w o l e b s p o r d i f p n e h w t n e r r u c s k n i s . t u p t u o l i a f - r e w o p n i a r d - n e p o . v m 4 1 6 34 n d h sv o t t c e n n o c . t u p n i n w o d t u h s w o l - e v i t c a t t a b . n o i t a r e p o l a m r o n r o f4- b f t u p n i s i h t t c e n n o c . n o i t a r e p o t u p t u o - e l b a t s u j d a r o f t u p n i . t u p n i k c a b d e e f v n e e w t e b r e d i v i d e g a t l o v r o t s i s e r l a n r e t x e n a o t n i p t u o t c e n n o c . d n g d n a . n o i t a r e p o t u p t u o - d e x i f r o f d n g o t 55 d n g. d n u o r g y l l a c i p y t , l a i t n e t o p t i u c r i c t s e w o l e h t o t t c e n n o c 66 x l v m o r f d e t c e n n o c s i r o t c u d n i n a . l i o c t t a b h c t i w s t e f s o m l e n n a h c - n e h t o t . n i p s i h t h g u o r h t n i a r d r e i f i t c e r - s u o n o r h c n y s l e n n a h c - p e h t d n a n i a r d 77 v t u o . t u p n i r e w o p c i d n a n o i t a r e p o v 3 . 3 d e x i f r o f t u p n i k c a b d e e f . t u p t u o r e w o p v o t e s o l c r o t i c a p a c r e t l i f t c e n n o c t u o . 88 figure 17. shutdown response and inductor current: v out =3.3v, v batt =1.2v, i out =5ma where 1: v out , 1v/div 2: shdn, 2v/div 3: inductor current, 200ma/div table 1. sp6642/6643 pin descriptions performance characteristics (continued) refer to the circuit in figure 25 with v batt = 1.2v, r1 + r2 = 1m ? , and t amb = +25 o c unless otherwise noted. 10msec/div
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? co pyright 2000 sipex corporation 9 v out gnd pfi v batt lx 1 2 3 4 5 6 7 8 sp6642 pfo shdn fb v out gnd pfi v batt lx 1 2 3 4 5 6 7 8 sp6643 fb battlo pfo figure 18. pinout for the sp6642 figure 19. pinout for the sp6643
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? cop yright 2000 sipex corporation 10 description the sp6642/6643 devices are high-efficiency, low-power step-up dc-dc converters ideal for single alkaline cell applications such as pagers, remote controls, and other low-power portable end products. the sp6642 features a 5na logic-controlled shutdown mode. the sp6643 features dedicated low-battery detector circuitry. both devices contain a 0.8 ? synchronous rectifier, an oscillator, a 0.6 ? n-channel mosfet power switch, an internal voltage reference, circuitry for pulse-frequency-modulation, and an under voltage comparator. the output voltage for the sp6642/6643 devices can be adjusted from +2v to +5.5v by manipulating two external resistors. the output voltage is preset to +3.3v. theory of operation the sp6642/6643 devices are ideal for end products that function with a single alkaline cell, such as remote controls, pagers, and other portable consumer products. designers can implement the sp6642/6643 devices into applications with the following power management operating states: 1. where the primary battery is good and the load is active, and 2. where the primary battery is good and the load is sleeping. in the first operating state where the primary supply is good and the load is active, the sp6642/ 6643 devices typically offer 80% efficiency, drawing tens of milliamps. applications will predominantly operate in the second state where the primary supply is good and the load is sleeping. the sp6642/6643 devices draw a very low quiescent current while the load in its disabled state will draw typically hundreds of microamps. the pulse-frequency-modulation (pfm) circuitry provides higher efficiencies at low to moderate output loads than traditional pwm converters are capable of delivering. the on-time and minimum off-times are varied as a function of the input and output voltages: t on = k v batt t off(min) = 1.2 x k v out - v batt where t on is the on-time, k is the on-time constant typically 25v- s, v batt is the supply voltage, t off(min) is the minimum off-time, and v out is the output voltage. this allows the sp6642/6643 devices to maintain a high efficiency over a wide range of loads and input/output voltages. the dc-dc converter is powered from v out . in a state where the error comparator detects that the output voltage at v out is too low, the internal n-channel mosfet switch is turned on until the on-time is satisfied. refer to figures 20, 21 , 22 and 23 . during the on-time, current ramps up in the inductor, storing energy in a magnetic field. when the mosfet turns off, during the second half of each cycle the magnetic field collapses. this causes the inductor voltage to force current through the synchronous rectifier transferring the stored energy from the inductor to the output filter capacitor and the load. the output filter capacitor stores charge while current from the inductor is high and holds the output voltage high until the second half of the next switching cycle, smoothing power flow to the load. internal bootstrap circuitry the internal bootstrap circuitry contains a low-voltage start-up oscillator that pumps up the output voltage to approximately 1.9v so the main dc-dc converter can function. at lower battery supply voltages, the circuitry can start up with low-load conditions. designers can reduce the load as needed to allow start-up with input voltages below 1v. refer to figures 10 to 13 . once started, the output voltage can maintain the load as the battery voltage decreases below the initial start-up voltage. the start-up oscillator is powered by v batt driving a charge pump and nmos switch. during start-up, the p-channel synchronous rectifier remains off and either its body diode or an external diode is used as an output rectifier.
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? co pyright 2000 sipex corporation 11 figure 20. internal block diagram of the sp6642 gnd out 0.1 f fb lx v batt 22 f 0.1 f 22 f pfi +3.3v out shdn 100 h 350ma 0.85v to 1.65v input sp6642 pfo figure 21. sp6642 +3.3v typical application circuit timing shdn logic t-off t-on drv-p drv-n en v ref fb v batt p v out lx v ref 0.5v ref v ref v out 1.9v 0.5v ref pfi pfo start up osc n sp6642 n
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? cop yright 2000 sipex corporation 12 gnd out 0.1 f fb lx v batt 22 f 0.1 f 22 f +3.3v out 100 h 350ma 0.85v to 1.65v input sp6643 pfo pfi battlo figure 23. sp6643 +3.3v typical application circuit timing logic t-off t-on drv-p drv-n en v ref fb v batt p v out lx v ref 0.5v ref v ref start up osc n n 0.5v ref pfi pfo 1.0v battlo sp6643 1.0v figure 22. internal block diagram of the sp6643 r4 r3 gnd pfi v th sp6642 figure 24. power-fail detection circuitry power-fail detection circuitry the sp6642/6643 devices have an internal comparator for power-fail detection. this comparator can detect a loss of power at the input or output. if the voltage at pfi falls below 614mv, the pfo output sinks current to ground. hysteresis at the power-fail input is 1%. the power-fail monitor's threshold voltage is determined by two resistors, r3 and r4. refer to figure 24 . the power-fail monitor threshold voltage can be set using the following equation: where r3 and r4 are the resistors in figure 24 , v th is the desired threshold voltage of the power- fail detector, and v pfi is the 614mv reference of the power-fail comparator. since pfi leakage is 10na max, select feedback resistor r4 in the 100k ? to 1m ? . battlo for the sp6643 the sp6643 device has an internal comparator for low-battery detection. if v batt drops below 1v, battlo will sink current. battlo is an open-drain output. battlo used in conjunction with the power-fail detection circuitry (pfi/ pfo) will monitor both the input and output voltages. shutdown for the sp6642 a logic low at shdn will drive the sp6642 into a shutdown mode where pfo goes into a high-impedance state, the internal switching mosfet turns off, and the synchronous rectifier turns off to prevent reverse current from flowing from the output back to the input. designers should note that in shutdown, the output can drift to one diode drop below v batt because there is still a forward current path through the r3 = r4 x -1 v th v pfi
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? co pyright 2000 sipex corporation 13 synchronous-rectifier body diode from the input to the output. to disable the shutdown feature, designers can connect shdn to v batt . adjustable output voltage driving fb to ground (logic low) will drive the output voltage to the fixed-voltage operation of +3.3v + 4%. connecting fb to a voltage divider between v out and ground will select an adjustable output voltage between +2v and +5.5v. refer to figure 25 . fb regulates to +1.23v. since the fb leakage current is 10na maximum, designers should select the feedback resistor r2 in the 100k ? to 1m ? range. r1 can be determined with the following equation: r1 = r2 x -1 v out v ref where r3 and r4 are the feedback resistors in figure 25 , v out is the output voltage, and v ref is 1.23v. battery reversal protection the sp6642/6643 devices will tolerate single- cell battery reversal up to the package power- dissipation limits noted in the absolute maximum ratings section. an internal gnd v out 0.1 f fb lx v batt 22 f 0.1 f 22 f pfi v out = 2v to 5.2v shdn 100 h 350ma 0.88v to 1.65v input sp6642 pfo 100pf* r1 r2 *optional compensation figure 25. adjustable output voltage circuitry diode in series with an internal 5 ? resistor limits any reverse current to less than 220ma preventing damage to the devices. prolonged operation above 220ma reverse-battery current can degrade performance of the devices. the inductor it is recommended that designers implement a 100 h inductor for typical application of the sp6642/6643 devices. lower inductor values down to 68 h will increase the maximum output current. higher inductor values up to 220 h will reduce peak inductor current and any consequent ripple and noise. the saturation- current rating of the inductor selected must exceed the peak current limit synthesized by the sp6642/6643 devices' timing algorithms. this can be calculated with the following equation: i peak = k max l min where i peak is the peak current, k max is 35v- s, and l min is the minimum inductance selected. the maximum recommended i peak is 350ma. to optimize efficiency, select an inductor with a series resistance less than 1 ? . table 1 lists surface mount inductor information for the user, including series resistance and saturation current rating.
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? cop yright 2000 sipex corporation 14 it is suggested designers select the largest inductor value possible that will satisfy the load requirement and minimize peak switching current and any resultant noise and voltage ripple. a closed-core inductor, such as a toroid or shielded bobbin, will minimize any fringe magnetic fields or emi. application notes printed circuit board layout is a critical part of design. poor designs can result in excessive emi on the voltage gradients and feedback paths on the ground planes with applications involving high switching frequencies and large peak currents. excessive emi can result in instability or regulation errors. all power components should be placed on the pc board as closely as possible with the traces kept short, direct, and wide ( >50mils or 1.25mm). extra copper on the pc board should be integrated into ground as a pseudo-ground plane. on a multilayer pc board, route the star ground using component-side copper fill, then connect it to the internal ground plane using vias. for the sp6642/6643 devices, the inductor and input and output filter capacitors should be soldered with their ground pins as close together as possible in a star-ground configuration. the v out pin must be bypassed directly to ground as close to the sp6642/6643 devices as possible (within 0.2in or 5mm). the dc-dc converter and any digital circuitry should be placed on the opposite corner of the pc board as far away from sensitive rf and analog input stages. the external voltage-feedback network should be placed very close to the fb pin (within 0.2in or 5mm). any noisy traces, such as from the lx pin, should be kept away from the voltage- feedback network and separated from it using grounded copper to minimize emi. capacitor equivalent series resistance is a major contributor to output ripple, usually greater than 60%. low esr capacitors are recommended. ceramic capacitors have the lowest esr. low-esr tantalum capacitors may be a more acceptable solution having both a low esr and lower cost than ceramic capacitors. designers should select input and output capacitors with a rating exceeding the peak inductor current. do not allow tantalum capacitors to exceed their ripple-current ratings. a 22 f, 6v, low-esr, surface-mount tantalum output filter capacitor typically provides 60mv output ripple when stepping up from 1.3v to 3.3v at 20ma. an input filter capacitor can reduce peak currents drawn from the battery and improve efficiency. low-esr aluminum electrolytic capacitors are acceptable in some applications but standard aluminum electrolytic capacitors are not recommended. designers should add lc pi filters, linear post-regulators, or shielding in applications necessary to address excessive noise, voltage ripple, or emi concerns. the lc pi filter's cutoff frequency should be at least a decade or two below the dc-dc converters's switching frequency for the specified load and input voltage. inductance vendor/part resistance i sat ( h) ( ? )( m a) 68 coilcraft do1608-683 0.75 400 sumida cd54-680 0.46 610 coilcraft do1608-104 1.1 310 100 sumida cd54-101 0.7 520 tdk nlc565050t-101k 1.6 250 coilcraft do1608-154 1.7 270 150 sumida cd54-151 1.1 400 tdk nlc565050t-151k 2.2 210 220 coilcraft do1608-224 2.3 220 sumida cd54-221 1.57 350 inductor specification table 1. surface-mount inductor information
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? co pyright 2000 sipex corporation 15 p w 50 soic devices per tube 8-pin soic 13 reels: p = 8mm, w = 12mm pkg min qty per reel std qty per reel max qty per reel eu 500 2500 3000 all package dimensions in inches 1 0.013 0.005 0.0256 bsc 0.118 0.004 0.020 2 0.020 0.116 0.004 0.034 0.004 0.040 0.003 0.004 0.002 0.118 0.004 0.118 0.004 0.037 ref 0.0215 0.006 3.0 ? 3 ? r .003 12.0 ? 4 ? 0.006 0.006 0.006 0.006 0.008 0 ? - 6 ? 0.012 0.003 0.01 12.0 ? 4 ? 0.16 0.003 0.0965 0.003 0.116 0.004
rev. 10-6-00 sp6642/6643 high efficiency step-up dc-dc converter ? cop yright 2000 sipex corporation 16 ordering information model temperature range package type sp6642eu ............................................. -40 o c to +85 o c ......................................... 8-pin soic sp6643eu ............................................. -40 o c to +85 o c ......................................... 8-pin soic corporation signal processing excellence sipex corporation reserves the right to make changes to any products described herein. sipex does not assume any liability aris ing out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor t he rights of others. please consult the factory for pricing and availability on a tape-on-reel option. sipex corporation headquarters and sales office 22 linnell circle billerica, ma 01821 tel: (978) 667-8700 fax: (978) 670-9001 e-mail: sales@sipex.com sales office 233 south hillview drive milpitas, ca 95035 tel: (408) 934-7500 fax: (408) 935-7600

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