1997 10-11 mic2660 micrel 1 0 mic2660 ittybitty? charge pump preliminary information general description the mic2660 ittybitty? charge pump functions as a low- current, step-up converter where conventional inductor based, dc-to-dc converters are too complex and expensive. this device features a complete, self-contained charge pump in a tiny 5-lead sot-23-5 package. the mic2660 is powered from a 3v to 5v nominal supply and produces nominally 5v to 9v as a function of the input voltage. the output is unregulated and follows a load-line type function. the mic2660 can be used with or without external compo- nents. when used with two noncritical external capacitors, a 3v input will produce 5v at 3.8ma. with no external compo- nents, a 3v input will produce 5v at 2.5ma. the mic2660 charge pump consists of an approximately 18mhz oscillator and a voltage tripler. the mic2660 is available in the sot-23-5 package and is rated for C40 c to +85 c ambient temperature range. typical application in out mic2660 13 gnd 2 +3v input en 5 0.01? +5v, 2.5ma* output 0.01? * the output is unregulated and follows a load-line type function enable disable low-current unregulated step-up supply timing diagram en 0v 2v out 5v 1v 0v 0.2 ? 1.3 ? output vs. enable input features ? 3v input produces approx. 5v unregulated output* 3.8ma with 1 m f external output capacitor 2.5ma without external capacitor ? 5v input produces approx. 9v unregulated output* 4.5ma output without external capacitor ? cmos-logic compatible enable ? esd protected applications ? squib firing ? refresh ? burst/dump ? low duty cycle load ? lcd bias generator ? local 5v logic supply ? mosfet driver ? battery or solarcell boost ordering information part number temperature range package mic2660bm5 C40 c to +85 c sot-23-5
mic2660 micrel 10-12 1997 electrical characteristics parameter condition (note 1) min typ max units output voltage, enabled v in = 3v, v en = v in , c out = 1000pf, r l = 2k w 4.5 5 v v in = 5v, v en = v in , c out = 1000pf, r l = 2k w 8.1 9 v output voltage, disabled v in = 3v, v en = gnd, c out = 1000pf, r l = 2k w .9 1.0 1.3 v v in = 5v, v en = gnd, c out = 1000pf, r l = 2k w 2.9 3.0 3.3 v input current v in = 3v, v en = v in , r l = 2k w 14.5 19.5 ma v in = 5v, v en = v in , r l = 2k w 28.5 38.5 ma quiescent current v in = 3v, v en < 0.4v 1.5 3 m a v in = 5v, v en < 0.4v 3.5 5 m a output current v in = 3v, v en = v in , v out = v out min 1.9 2.5 ma v in = 5v, v en = v in , v out = v out min 3.4 4.5 ma enable threshold v in = 3v 1.5 v v in = 5v 2.5 v enable current v in = 5v, v en = v in 10 m a turn-on time v in = 3v load = 2k w , c out = 1000pf, note 2 200 ns turn-off time v in = 3v load = 2k w , c out = 1000pf, note 3 1.3 m s general note: devices are esd protected, however handling precautions are recommended. note 1: typicals values at t a = 25 c. minimum and maximum values at C40 c t a +85 c. note 2: turn-on time is the time between v en = 0.5 v in and v out = 0.9 (v outmax C v outmin ) for a rising en input. note 3: turn-off time is the time between v en = 0.5 v in and v out = v in C 1.9v for a falling en input. pin configuration part identification in en nc out c10 1 3 45 2 gnd sot-23-5 (m5) pin description pin number pin name pin function 1 in supply (input): +3v to +5v supply. 2 gnd ground: power return. 3 out output: charge pump output. connect to load. 4 nc not internally connected. 5 en enable (input): cmos compatible input. en high (v en = v in ) enables the charge pump . en low (v in = 0v) disables the charge pump. lead temperature, soldering 10sec. ........................ 300 c package thermal resistance sot-23-5 q ja .................................................... 220 c/w sot-23-5 q jc .................................................... 130 c/w absolute maximum ratings input voltage (v in ) ..................................................... +5.5v enable voltage (v en ) ......................................... v in + 1.3v ambient temperature range (t a ) ............. C40 c to +85 c
1997 10-13 mic2660 micrel 1 0 0 5 10 15 20 2.0 2.5 3.0 3.5 4.0 4.5 5.0 output voltage (v) supply voltage (v) output voltage vs. supply voltage c out = none t a = -55 c no load 1ma 2ma 3ma 0 5 10 15 20 2.0 2.5 3.0 3.5 4.0 4.5 5.0 output voltage (v) supply voltage (v) output voltage vs. supply voltage c out = none t a = 25 c no load 1ma 2ma 3ma 0 5 10 15 20 2.0 2.5 3.0 3.5 4.0 4.5 5.0 output voltage (v) supply voltage (v) output voltage vs. supply voltage c out = none t a = 125 c no load 1ma 2ma 3ma 0 5 10 15 20 2.0 2.5 3.0 3.5 4.0 4.5 5.0 output voltage (v) supply voltage (v) output voltage vs. supply voltage c out = 1 m f t a = -55 c no load 1ma 2ma 3ma 0 5 10 15 20 2.0 2.5 3.0 3.5 4.0 4.5 5.0 output voltage (v) supply voltage (v) output voltage vs. supply voltage c out = 1 m f t a = 25 c no load 1ma 2ma 3ma 0 5 10 15 20 2.0 2.5 3.0 3.5 4.0 4.5 5.0 output voltage (v) supply voltage (v) output voltage vs. supply voltage c out = 1 m f t a = 125 c no load 1ma 2ma 3ma 0 5 10 15 20 25 30 35 02468101214 efficiency (%) output voltage (v) efficiency vs. output voltage c out = none t a = -55 c 1ma 2ma 3ma 0 5 10 15 20 25 30 35 02468101214 efficiency (%) output voltage (v) efficiency vs. output voltage c out = none t a = 25 c 1ma 2ma 3ma 0 5 10 15 20 25 30 35 02468101214 efficiency (%) output voltage (v) efficiency vs. output voltage c out = none t a = 125 c 1ma 2ma 3ma 0 5 10 15 20 25 30 35 02468101214 efficiency (%) output voltage (v) efficiency vs. output voltage c out = 1 m f t a = -55 c 1ma 2ma 3ma 0 5 10 15 20 25 30 35 40 02468101214 efficiency (%) output voltage (v) efficiency vs. output voltage c out = 1 m f t a = 25 c 1ma 2ma 3ma 0 5 10 15 20 25 30 35 40 02468101214 efficiency (%) output voltage (v) efficiency vs. output voltage c out = none t a = 125 c 1ma 2ma 3ma typical characteristics
mic2660 micrel 10-14 1997 block diagram osc en out gnd in mic2660 2 3 d1 d2 d3 c1 c2 xlo xlo q1 q2 q4 q3 functional description refer to the block diagram. the mic2660 charge pump consists of an oscillator and a voltage tripler. a logic-high applied to en activates the charge pump. the charge pump produces an output voltage that is higher than the input voltage. supply input in (supply input) is rated for +2.7v to +5.5v. ouput out is connected to in, less 3 diode drops, at all times. enable en (enable) is a cmos input. a logic low turns the oscillator off. the threshold is approximately half the supply voltage. a floating en input may cause unpredictable operation. oscillator the oscillator produces a square wave at approximately 18mhz. it has a noninverting and an inverting output. crossover lockout the charge pump contains two crossover lockout (xlo) circuits. each crossover lockout circuit drives a totem pole, consisting of a p-channel mosfet and an n-channel mos- fet. the crossover lockout alternately switches the mosfets with no significant transition current (shoot-through current from supply to ground). tripler voltage stepup is performed by charging an internal capaci- tor then switching the charged capacitor in series with the supply voltage to produce a higher voltage. a description of the nominal voltage tripler output is: v out = 3v in C 3v d . where: v out = output voltage v in = supply voltage v d = voltage drop across forward biased diode all formulas are simplified. refer to the last paragraph of this subsection about the actual output voltage. the following sequence describes the basic operation of the tripler by showing how the voltage at the 2 and 3 nodes, v 2 and v 3 , increases. q2 turns on, completing the ground path to charge c1 (and the 2 node) to the supply voltage, less a diode voltage drop. v 2 (charging) = v in C v d1 after q2 turns off, q1 turns on. the q1-q2 side of c1 is switched (offset upward) from ground to v in . the 2 node, that was nominally at the supply voltage, becomes nominally twice the supply voltage. v 2 = v in C v d1 + v in while q1 is on, q4 is also on. when q4 is on, the nominally doubled voltage at the 2 node is applied across c2, through d2. v 3 (charging) = v in C v d1 + v in C v d2 after q4 turns off, q3 turns on. the q3-q4 side of c2 is switched from ground to v in . the 3 node, that was nomi- nally twice the supply voltage, becomes nominally three times the supply voltage. v 3 = v in C v d1 + v in C v d2 + v in the tripled voltage is available at the output through d3. v out = v in C v d1 + v in C v d2 + v in C v d3 the output is nominally 3 times the supply voltage less the voltage drop across three diodes. the actual output is lower. these simplified formulas do not show that the voltage across the capacitors decreases when charge flows to the following stage or output. an actual device also has some internal loss. esd protection zener diodes are provided at in, en, and out to limit esd voltage.
1997 10-15 mic2660 micrel 1 0 applications information electromagnetic interference the 18mhz oscillator may cause interference to radio cir- cuits. 0.01 m f bypass capacitors should be mounted close to the in and out terminals. low-side mosfet charge-pump driver a standard mosfet requires approximately 15v to fully enhance the gate for minimum r ds (on) . substituting a logic- level mosfet reduces the required gate voltage, allowing an mic2660 to be used as an low-side fet driver. a 3v powered mic2660 will fully enhance a logic-level n-channel mosfet low-side switch, with a 5k gate pull- down resistor, in less than 1ms after the enable pin rises above 1.5v. the 1nf mosfet gate capacitance will be discharged to turn-off in less than 10ms after the enable pin goes below 1.5v. enable disable in out mic2660 13 gnd 2 +3v to +5v en 5 load supply r load 1? 0.1? 100k figure 1. charge-pump driver an mic2660 boosts a 5v input to 9vC12v to fully enhance an n-channel mosfet, which may have its drain connected to a higher voltage, through a high-side load. a ttl high signal applied to cs enables the internal oscillator, which quickly develops 9vC12v at the gate of the mosfet, clamped by a zener diode. a resistor from the gate to ground ensures that the fet will turn off quickly when the mic2660 is turned off. charge-pump/dump a large capacitor can be charged to the unloaded tripled voltage output after a time based on the maximum current provided by the mic2660. a 1000 m f capacitor can be charged from 2v to approximately 12v in less than 3 seconds by a 5v powered mic2660. (i = c dv / dt ). once charged, a maximum current of 3ma may be drawn continuously at the 12v level. a high value bleeder resistor (100k) is not needed to prevent spikes from exceeding the capacitor voltage rating, since the mic2660s internal 15v esd zener limits maximum output. a 68 w resistor in series with the output limits short-circuit current to 30ma. in out mic2660 13 gnd 2 +5v en 5 +12v 1000? 0.1? 100k 68 w figure 2. charge-pump/dump 5-volt lamp flasher an ittybitty mic1557 oscillator provides a short pulse once per second, enabling the cs pin of an mic2660, which charges the gate-to-drain capacitance of a logic-level n-channel mosfet to approximately 9v, which turns on a lamp. when the cs pin is low, a 2k resistor discharges the gate capacitance, turning off the lamp. a resistor (r s ) in series with a diode determines the on time to approximately r s ||r t c t ,while r t and c t set the off time to 1.1r t c t . in out mic2660 13 gnd 2 en 5 vs cs mic1557 43 gnd 2 +5v out 5 t/t 1 5v lamp c t 0.68? irl3103 n-channel fet 0.1? 2k r s 470k r t 1m w figure 3. 5-volt lamp flasher
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