general description the ultra-small max828/max829 monolithic, cmos charge-pump inverters accept input voltages ranging from +1.5v to +5.5v. the max828 operates at 12khz, and the max829 operates at 35khz. their high efficiency (greater than 90% over most of the load-current range) and low operating current (60? for the max828) make these devices ideal for both battery-powered and board- level voltage-conversion applications. the max828/max829 combine low quiescent current and high efficiency. oscillator control circuitry and four power mosfet switches are included on-chip. applications include generating a -5v supply from a +5v logic supply to power analog circuitry. both parts come in a 5-pin sot23-5 package and can deliver 25ma with a voltage drop of 500mv. for a similar device with logic-controlled shutdown, refer to the max1719/max1720/max1721. for applica- tions requiring more power, the max860 delivers up to 50ma with a voltage drop of 600mv, in a space-saving ?ax package. applications small lcd panels cell phones medical instruments handy-terminals, pdas battery-operated equipment features 5-pin sot23-5 package 95% voltage conversion efficiency inverts input supply voltage 60a quiescent current (max828) +1.5v to +5.5v input voltage range requires only two capacitors 25ma output current max828/max829 switched-capacitor voltage inverters ________________________________________________________________ maxim integrated products 1 top view in gnd c1- c1+ out sot23-5 1 5 max828 max829 2 3 4 pin configuration negative voltage converter c1+ c1- in out gnd input supply voltage negative output voltage max828 max829 4 3 52 1 typical operating circuit 19-0495; rev 3; 9/99 part max828 euk -40? to +85? temp. range pin- package 5 sot23-5 ordering information max829 euk -40? to +85? 5 sot23-5 sot top mark aabi aabj for price, delivery, and to place orders, please contact maxim distribution at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com.
max828/max829 switched-capacitor voltage inverters 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = +5v, c1 = c2 = 10? (max828), c1 = c2 = 3.3? (max829), t a = 0? to +85?, unless otherwise noted. typical values are at t a = +25?.) electrical characteristics (v in = +5v, c1 = c2 = 10? (max828), c1 = c2 = 3.3? (max829), t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 2) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. note 1: capacitor contribution is approximately 20% of the output impedance [esr + 1 / (pump frequency x capacitance)]. note 2: all -40? to +85? specifications above are guaranteed by design. in to gnd .................................................................+6.0v, -0.3v out to gnd .............................................................-6.0v, +0.3v out output current ...........................................................50ma out short-circuit to gnd ............................................indefinite continuous power dissipation (t a = +70?) sot23-5 (derate 7.1mw/? above +70?)...................571mw operating temperature range max828euk/max829euk ...............................-40? to +85? storage temperature range .............................-65? to +160? lead temperature (soldering, 10s) .................................+300? max829 max828 r load = r load = 1k ? , t a = +25? max829 r load = 10k ? r load = 10k ? max828 conditions ? 150 260 60 90 supply current % 95 99.9 voltage conversion efficiency % 94 power efficiency khz 24.5 35 45.5 oscillator frequency 1.25 1.0 v 1.5 minimum supply voltage v 5.5 maximum supply voltage 8.4 12 15.6 units min typ max parameter t a = +25? t a = 0? to + 85? i out = 5ma t a = 0? to + 85? t a = +25? ? 65 output resistance 20 50 max829 max828 i out = 5ma max829 r load = 10k ? max828 conditions ? 325 115 supply current ? 65 output resistance khz 19 54.3 oscillator frequency v 1.5 5.5 supply voltage range 620 units min typ max parameter t a = +25? t a = +25?
max828/max829 switched-capacitor voltage inverters _______________________________________________________________________________________ 3 40 0 1.5 2.5 output resistance vs. supply voltage 5 10 35 max828/829-01 supply voltage (v) output resistance ( ? ) 3.5 5.5 4.5 30 20 25 15 max829 max828 50 10 output resistance vs. temperature 15 40 45 max828/829-02 temperature (?) output resistance ( ? ) 35 30 25 20 v in = 3.3v v in = 5.0v v in = 1.5v -40 -20 0 60 20 40 80 45 0 010 515 3540 max828 output current vs. capacitance 5 35 40 max828/829-03 capacitance ( f) output current (ma) 20 25 30 45 50 30 25 20 15 10 v in = 3.15v, v out = -2.5v v in = 1.9v, v out = -1.5v v in = 4.75v, v out = -4.0v 45 0 0 5 20 25 max829 output current vs. capacitance 5 35 40 max828/829-04 capacitance ( f) output current (ma) 15 10 30 30 25 20 15 10 v in = 3.15v, v- = -2.5v v in = 1.9v, v- = -1.5v v in = 4.75v, v- = -4.0v 200 0 1.5 2.5 supply current vs. supply voltage 25 50 175 max828/829-07 supply voltage (v) supply current ( a) 3.5 5.5 4.5 150 100 125 75 max829 max828 500 450 0 0 5 20 25 max828 output voltage ripple vs. capacitance 50 350 400 max828/829-05 capacitance ( f) output voltage ripple (mvp-p) 15 10 30 300 250 200 150 100 v in = 4.75v, v out = -4.0v v in = 3.15v, v out = -2.5v v in = 1.9v, v out = -1.5v 450 0 0 5 20 25 max829 output voltage ripple vs. capacitance 50 350 400 max828/829-06 capacitance ( f) output voltage ripple (mvp-p) 15 10 30 300 250 200 150 100 v in = 4.75v, v out = -4.0v v in = 3.15v, v out = -2.5v v in = 1.9v, v out = -1.5v 60 55 45 35 25 15 10 -40 -20 0 60 max828 pump frequency vs. temperature 20 50 max828/829-08 temperature ( c) pump frequency (khz) 20 40 80 40 30 v in = 3.3v v in = 5.0v v in = 1.5v __________________________________________typical operating characteristics (circuit of figure 1, v in = +5v, c1 = c2 = c3, t a = +25?, unless otherwise noted.) 55 30 max829 pump frequency vs. temperature 35 50 max828/829-9 temperature ( c) pump frequency (khz) 45 40 v in = 3.3v v in = 5.0v v in = 1.5v -40 -20 0 60 20 40 80
_____________________pin description max828/max829 switched-capacitor voltage inverters 4 _______________________________________________________________________________________ typical operating characteristics (continued) (circuit of figure 1, v in = +5v, c1 = c2 = c3, t a = +25?, unless otherwise noted.) 0.5 -5.5 05 15 10 35 output voltage vs. output current -4.5 -0.5 max828/829-10 output current (ma) output voltage (v) 20 30 25 45 50 40 -1.5 -2.5 -3.5 v in = 3.3v v in = 5.0v v in = 2.0v 100 0 0510 efficiency vs. output current 10 30 20 90 max828/829-11 output current (ma) efficiency ( % ) 20 15 30 25 45 40 50 35 70 80 50 60 40 v in = 2.0v v in = 3.3v v in = 5.0v v out 20mv/div max828 output noise and ripple max828/829-12 v in = 3.3v, v out = -3.2v, i out = 5ma, ac coupled 20 s/div flying capacitor? positive terminal c1+ 5 ground gnd 4 flying capacitor? negative terminal c1- 3 pin positive power-supply input in 2 inverting charge-pump output out 1 function name voltage inverter out in c1+ v in r l c1 3.3 f* *10 f (max828) c2 3.3 f* c3 3.3 f* 5 1 2 3 4 v out gnd c1- max828 max829 figure 1. test circuit v out 20mv/div max829 output noise and ripple max828/829-13 v in = 3.3v, v out = -3.2v, i out = 5ma, ac coupled 10 s/div
_______________detailed description the max828/max829 capacitive charge pumps invert the voltage applied to their input. for highest performance, use low equivalent series resistance (esr) capacitors. during the first half-cycle, switches s2 and s4 open, switches s1 and s3 close, and capacitor c1 charges to the voltage at in (figure 2). during the second half- cycle, s1 and s3 open, s2 and s4 close, and c1 is level shifted downward by v in volts. this connects c1 in par- allel with the reservoir capacitor c2. if the voltage across c2 is smaller than the voltage across c1, then charge flows from c1 to c2 until the voltage across c2 reaches - v in . the actual voltage at the output is more positive than -v in , since switches s1?4 have resistance and the load drains charge from c2. charge-pump output the max828/max829 are not voltage regulators: the charge pump? output source resistance is approxi- mately 20 ? at room temperature (with v in = +5v), and v out approaches -5v when lightly loaded. v out will droop toward gnd as load current increases. the droop of the negative supply (v droop- ) equals the cur- rent draw from out (i out ) times the negative convert- er? source resistance (rs-): v droop- = i out x rs- the negative output voltage will be: v out = -(v in - v droop- ) efficiency considerations the efficiency of the max828/max829 is dominated by its quiescent supply current (i q ) at low output current and by its output impedance (r out ) at higher output current; it is given by: where the output impedance is roughly approximated by: the first term is the effective resistance of an ideal switched-capacitor circuit (figures 3a and 3b), and r sw is the sum of the charge pump? internal switch resistances (typically 8 ? to 9 ? at v in = +5v). the typical output impedance is more accurately determined from the typical operating characteristics . applications information capacitor selection to maintain the lowest output resistance, use capacitors with low esr (table 1). the charge-pump output resis- tance is a function of c1? and c2? esr. therefore, minimizing the charge-pump capacitor? esr minimizes the total output resistance. r 1 f x c1 2r 4esr esr out osc sw c1 c2 ? () ++ + i ii 1 i x r v out out q out out in ? + ? ? ? ? ? ? ? max828/max829 switched-capacitor voltage inverters _______________________________________________________________________________________ 5 s1 in s2 s3 s4 c1 c2 v out = -(v in ) figure 2. ideal voltage inverter v+ c1 f c2 r l v out figure 3a. switched-capacitor model r equiv = r equiv v out r l 1 v+ f c1 c2 figure 3b. equivalent circuit
max828/max829 switched-capacitor voltage inverters 6 _______________________________________________________________________________________ flying capacitor (c1) increasing the flying capacitor? size reduces the output resistance. small c1 values increase the output resis- tance. above a certain point, increasing c1? capaci- tance has a negligible effect, because the output resistance becomes dominated by the internal switch resistance and capacitor esr. output capacitor (c2) increasing the output capacitor? size reduces the output ripple voltage. decreasing its esr reduces both output resistance and ripple. smaller capacitance values can be used with light loads if higher output ripple can be tolerated. use the following equation to calculate the peak-to-peak ripple: input bypass capacitor bypass the incoming supply to reduce its ac impedance and the impact of the max828/max829? switching noise. the recommended bypassing depends on the circuit configuration and on where the load is connected. when the inverter is loaded from out to gnd, current from the supply switches between 2 x i out and zero. therefore, use a large bypass capacitor (e.g., equal to the value of c1) if the supply has a high ac impedance. when the inverter is loaded from in to out, the circuit draws 2 x i out constantly, except for short switching spikes. a 0.1? bypass capacitor is sufficient. voltage inverter the most common application for these devices is a charge-pump voltage inverter (figure 1). this application requires only two external components?apacitors c1 and c2?lus a bypass capacitor, if necessary. refer to the capacitor selection section for suggested capacitor types and values. cascading devices two devices can be cascaded to produce an even larger negative voltage (figure 4). the unloaded output voltage is normally -2 x v in , but this is reduced slightly by the output resistance of the first device multiplied by the quiescent current of the second. when cascading more than two devices, the output resistance rises dra- matically. for applications requiring larger negative voltages, see the max864 and max865 data sheets. paralleling devices paralleling multiple max828s or max829s reduces the output resistance. each device requires its own pump capacitor (c1), but the reservoir capacitor (c2) serves all devices (figure 5). increase c2? value by a factor of n, where n is the number of parallel devices. the equation for calculating output resistance is also shown in figure 5. combined doubler/inverter in the circuit of figure 6, capacitors c1 and c2 form the inverter, while c3 and c4 form the doubler. c1 and c3 are the pump capacitors; c2 and c4 are the reservoir capacitors. because both the inverter and doubler use part of the charge-pump circuit, loading either output causes both outputs to decline toward gnd. make sure the sum of the currents drawn from the two outputs does not exceed 40ma. v = i f x c2 ripple out osc + 2 2 x i x esr out c table 1. low-esr capacitor manufacturers matsuo avx manufacturer (714) 969-2491 (803) 946-0690 (800) 282-4975 phone (603) 224-1961 (619) 661-6835 sprague sanyo (603) 224-1430 (619) 661-1055 (714) 960-6492 (803) 626-3123 fax surface-mount, 595d series through-hole, os-con series surface-mount, 267 series surface-mount, tps series device type usa japan 81-7-2070-6306 81-7-2070-1174
max828/max829 switched-capacitor voltage inverters _______________________________________________________________________________________ 7 heavy output current loads when under heavy loads, where higher supply is sourcing current into out, the out supply must not be pulled above ground. applications that sink heavy current into out require a schottky diode (1n5817) between gnd and out, with the anode connected to out (figure 7). layout and grounding good layout is important, primarily for good noise perfor- mance. to ensure good layout, mount all components as close together as possible, keep traces short to mini- mize parasitic inductance and capacitance, and use a ground plane. shutting down the max828/max829 for a similar device with logic-controlled shutdown, please refer to the max1719/max1720/max1721. to add manual shutdown control to the max828/max829, use the circuit in figure 8. the output resistance of the max828/max829 will typically be 20 ? plus two times the output resistance of the buffer driving in. the 0.1? capacitor at the in pin absorbs the transient input cur- rents of the max828/max829. the output resistance of the buffer driving the in pin can be reduced by connecting multiple buffers in parallel. the polarity of the shutdown signal can also be changed by using a noninverting buffer to drive in. max828 max829 ? max828 max829 ? 2 1 v out c2 2 +v in c1 c2 c1 33 44 55 1 v out = -nv in figure 4. cascading max828s or max829s to increase output voltage max828 max829 n max828 max829 1 2 1 v out c2 2 +v in c1 c1 3 3 44 5 5 1 v out = -v in r out = r out of single device number of devices figure 5. paralleling max828s or max829s to reduce output resistance max828 max829 2 1 v out = (2v in ) - (v fd1 ) - (v fd2 ) c2 +v in c1 3 4 5 v out = -v in c4 d1 d1, d2 = 1n4148 c3 d2 figure 6. combined doubler and inverter max828 max829 4 1 gnd out figure 7. high v- load current
max828/max829 switched-capacitor voltage inverters max828 max829 2 c1- in out c1+ gnd 1 c2 c in 0.1 f c1 3 5 4 output input off on shutdown logic signal figure 8. shutdown control maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 1999 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information sot5l.eps chip information transistor count: 58 substrate connected to in
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