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general description the MAX8614A/max8614b dual-output step-up dc-dc converters generate both a positive and negative sup- ply voltage that are each independently regulated. the positive output delivers up to 50ma while the inverter supplies up to 100ma with input voltages between 2.7v and 5.5v. the MAX8614A/max8614b are ideal for pow- ering ccd imaging devices and displays in digital cameras and other portable equipment. the MAX8614A/max8614b generate an adjustable positive output voltage up to +24v and a negative out- put down to 16v below the input voltage. the max8614b has a higher current limit than the MAX8614A. both devices operate at a fixed 1mhz fre- quency to ease noise filtering in sensitive applications and to reduce external component size. additional features include pin-selectable power-on sequencing for use with a wide variety of ccds, true shutdown, overload protection, fault flag, and internal soft-start with controlled inrush current. the MAX8614A/max8614b are available in a space- saving 3mm x 3mm 14-pin tdfn package and are specified over the -40? to +85? extended temperature range. applications ccd bias supplies and oled displays digital cameras camcorders and portable multimedia pdas and smartphones features ? dual output voltages (+ and -) ? adjustable up to +24v and down to -10v at 5.5v in ? output short/overload protection ? true shutdown on both outputs ? controlled inrush current during soft-start ? selectable power-on sequencing ? up to 90% efficiency ? 1? shutdown current ? 1mhz fixed-frequency pwm operation ? fault-condition flag ? thermal shutdown ? small, 3mm x 3mm, 14-pin tdfn package MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd ________________________________________________________________ maxim integrated products 1 19-4014; rev 0; 3/06 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. 14 13 12 11 10 9 8 1 + 23 4567 lxn v cc pvp pgnd ref av cc fbn onbst top view MAX8614A max8614b lxp oninv seq fbp flt gnd tdfn pin configuration lxn v cc input (2.7v to 5.5v) ref av cc av cc fbn oninv v inv -7.5v MAX8614A max8614b gnd pgnd onbst pvp lxp fbp v bst +15v ref seq flt typical operating circuit ordering information part temp range pin- package top mark ilim bst/inv MAX8614A etd+ -40? to +85? 14 tdfn 3mm x 3mm (t1433-2) abg 0.44/0.33 max8614b etd+ -40? to +85? 14 tdfn 3mm x 3mm (t1433-2) abh 0.8/0.75 true shutdown is a trademark of maxim integrated products, inc. + denotes lead-free package.
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd 2 _______________________________________________________________________________________ absolute maximum ratings 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. v cc , av cc to gnd...................................................-0.3v to +6v lxn to v cc ............................................................. -18v to +0.3v lxp to pgnd ..........................................................-0.3v to +33v ref, oninv, onbst, seq, fbn, fbp flt to gnd ..........................................-0.3v to (av cc + 0.3)v pvp to gnd ................................................-0.3v to (v cc + 0.3)v av cc to v cc ..........................................................-0.3v to +0.3v pgnd to gnd .......................................................-0.3v to +0.3v continuous power dissipation (t a = +70? multilayer board) 14-pin 3mm x 3mm tdfn (derate 18.2mw/? above t a = +70?) ............................................................1454.4mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? electrical characteristics (v cc = v avcc = v oninv = v onbst = 3.6v, pgnd = seq = gnd, c6 = 0.22?, c1 = 2.2?, c2 = 4.7?, figure 1, t a = 0? to +85? , unless otherwise noted. typical values are at t a = +25?.) parameter conditions min typ max units av cc and v cc voltage range (note 1) 2.7 5.5 v uvlo threshold v cc rising 2.42 2.55 2.66 v uvlo hysteresis 25 mv step-up output voltage adjust range v avcc 24 v inverter output voltage adjust range v inv - v cc (note 2) -16 0 v max8614b 0.7 0.8 0.9 lxp current limit MAX8614A 0.34 0.44 0.52 a max8614b 0.90 1.05 1.20 lxp short-circuit current limit MAX8614A 0.52 0.61 0.70 a max8614b 0.65 0.75 0.85 lxn current limit MAX8614A 0.28 0.33 0.38 a lxn on-resistance v cc = 3.6v 0.6 1.1 ? lxp on-resistance v cc = 3.6v 0.625 ? pvp on-resistance v cc = 3.6v 0.15 0.3 ? maximum duty cycle step-up and inverter 82 90 % i avcc 0.75 1.4 quiescent current (switching, no load) i vcc 23 ma i avcc 400 800 quiescent current (no switching, no load) i v cc 815 ? t a = +25? 0.1 5 shutdown supply current t a = +85? 0.1 ? fbp line regulation v cc = 2.7v to 5.5v -20 mv/d fbn line regulation v cc = 2.7v to 5.5v 20 mv/ (d - 0.5)
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = v avcc = v oninv = v onbst = 3.6v, pgnd = seq = gnd, c6 = 0.22?, c1 = 2.2?, c2 = 4.7?, figure 1, t a = 0? to +85? , unless otherwise noted. typical values are at t a = +25?.) parameter conditions min typ max units i lxp = i ilimmin , max8614b -15 fbp load regulation i lxp = i ilimmin , MAX8614A -35 mv/a i lxn = i ilimmin , max8614b 17.5 fbn load regulation i lxn = i ilimmin , MAX8614A 65 mv/a oscillator frequency 0.93 1 1.07 mhz soft-start interval step-up and inverter 10 ms overload-protection fault delay 100 ms fbp, fbn, reference ref output voltage no load 1.24 1.25 1.26 v ref load regulation 0? < i ref < 50? 10 mv ref line regulation 3.3v < v avcc < 5.5v 2 5 mv fbp threshold voltage no load 0.995 1.010 1.025 v fbn threshold voltage no load -10 0 +10 mv t a = +25? -50 +5 +50 fbp input leakage current v fbp = 1.025v t a = +85? +5 na t a = +25? -50 +5 +50 fbn input leakage current fbn = -10mv t a = +85? +5 na t a = +25? -5 +0.1 +5 lxn input leakage current v lxn = -12v t a = +85? +0.1 ? t a = +25? -5 +0.1 +5 lxp input leakage current v lxp = 23v t a = +85? +0.1 ? t a = +25? -5 +0.1 +5 pvp input leakage current v pvp = 0v t a = +85? +0.1 ? t a = +25? -1 +0.1 +1 flt input leakage current v flt = 3.6v t a = +85? +0.1 ? flt input resistance fault mode, t a = +25? 10 20 ? oninv, onbst, seq logic inputs logic-low input 2.7v < v avcc < 5.5v 0.5 v logic-high input 2.7v < v avcc < 5.5v 1.6 v bias current t a = +25? 0.1 1 a
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd 4 _______________________________________________________________________________________ electrical characteristics (v cc = v avcc = v oninv = v onbst = v en = 3.6v, pgnd = seq = gnd, c6 = 0.22?, c1 = 2.2?, c2 = 6.7?, figure 1, t a = -40? to +85? , unless otherwise noted.) (note 3) parameter conditions min typ max units a vcc = v cc voltage range (note 1) 3 5.5 v uvlo threshold v cc rising 2.42 2.82 v step-up output voltage adjust range v avcc 24 v inverter output voltage adjust range v inv - v cc (note 2) -16 0 v max8614b 0.7 0.9 lxp current limit MAX8614A 0.34 0.52 a max8614b 0.9 1.2 lxp short-circuit current limit MAX8614A 0.52 0.70 a max8614b 0.65 0.85 lxn current limit MAX8614A 0.28 0.38 a lxn on-resistance v cc = 3.6v 1.1 ? pvp on-resistance v cc = 3.6v 0.3 ? maximum duty cycle step-up and inverter 82 % i avcc 1.4 quiescent current (switching, no load) i vcc 3 ma i avcc 800 quiescent current (no switching, no load) i vcc 15 ? oscillator frequency 0.93 1.07 mhz fbp, fbn, reference ref output voltage no load 1.235 1.260 v fbp threshold voltage no load 0.995 1.025 v fbn threshold voltage no load -10 +10 mv oninv, onbst seq logic inputs logic-low input 2.7v < v avcc < 5.5v 0.5 v logic-high input 2.7v < v avcc < 5.5v 1.6 v note 1: output current and on-resistance are specified at 3.6v input voltage. the ic operates to 2.7v with reduced performance. note 2: the specified maximum negative output voltage is referred to v cc , and not to gnd. with v cc = 3.3v, the maximum negative output is then -12.7v. note 3: specifications to -40? are guaranteed by design, not production tested.
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd _______________________________________________________________________________________ 5 maximum output current vs. input voltage input voltage (v) maximum output current (ma) MAX8614A/b toc01 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0 50 100 150 200 250 300 350 v out = 20v v out = 15v v out = 10v maximum output current vs. input voltage input voltage (v) maximum output current (ma) . MAX8614A/b toc02 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0 50 100 150 200 250 300 v inv = -10v v inv = -7.5v v inv = -5v positive output efficiency vs. output current output current (ma) efficiency (%) MAX8614A/b toc03 0.1 1 10 100 l = 2.2 h, c = 2.2 f 0 10 20 30 40 50 60 70 80 90 100 v cc = 3v v cc = 3.6v v cc = 4.2v v cc = 5v positive output efficiency vs. output current output current (ma) efficiency (%) MAX8614A/b toc04 0 10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 l = 10 h, c = 10 f v cc = 3v v cc = 3.6v v cc = 4.2v v cc = 5v negative output efficiency vs. output current output current (ma) efficiency (%) MAX8614A/b toc05 0 10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 l = 4.7 h, c = 4.7 f v cc = 3v v cc = 3.6v v cc = 4.2v v cc = 5v negative output efficiency vs. output current output current (ma) efficiency (%) MAX8614A/b toc06 0 10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 l = 10 h, c = 10 f v cc = 3v v cc = 3.6v v cc = 4.2v v cc = 5v output efficiency vs. output current output current (ma) efficiency (%) MAX8614A/b toc07 0 10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 both outputs loaded equally l1 = 2.2 h, c1 = 2.2 f, l2 = 4.7 h, c2 = 4.7 f v cc = 3v v cc = 3.6v v cc = 4.2v v cc = 5v output efficiency vs. output current output current (ma) efficiency (%) MAX8614A/b toc08 0 10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 both outputs loaded equally l1 = 10 h, c1 = 10 f, l2 = 10 h, c2 = 10 f v cc = 3v v cc = 3.6v v cc = 4.2v v cc = 5v typical operating characteristics (t a = +25?, v cc = v avcc = 3.6v, seq = gnd, figure 1, unless otherwise noted.)
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd 6 _______________________________________________________________________________________ change in output voltage vs. output current (negative output) output current (ma) change in output voltage (%) MAX8614A/b toc10 0 25 50 75 100 125 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0 v in = 5v v out - = -7.5v v in = 4.2v v in = 3v v in = 3.6v no-load supply current vs. input voltage input voltage (v) supply current ( a) MAX8614A/b toc11 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0 100 200 300 400 500 600 700 800 900 1000 av cc v cc soft-start waveforms MAX8614A/b toc12 v oninv 5v/div 0v 10v/div 5v/div 100ma/div 0v 0v v onbst v bst v inv i in 4ms/div seq = gnd soft-start waveforms MAX8614A/b toc13 v oninv 5v/div 0v 10v/div 5v/div 100ma/div 0v 0v v onbst v bst v inv i in 4ms/div seq = av cc line transient MAX8614A/b toc14 50mv/div ac-coupled 50mv/div ac-coupled 3.5v v bst v in 3.5v to 4.5v to 3.5v v inv 40 s/div typical operating characteristics (continued) (t a = +25?, v cc = v avcc = 3.6v, seq = gnd, figure 1, unless otherwise noted.) change in output voltage vs. load current (positive output) load current (ma) change in output voltage (%) MAX8614A/b toc09 0 25 50 75 100 125 150 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0 v cc = 3v v cc = 5v v cc = 4.2v v cc = 3.6v
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd _______________________________________________________________________________________ 7 load transient (negative output) MAX8614A/b toc16 50mv/div ac-coupled 100mv/div ac-coupled 50ma/div 0v v bst i inv v inv 4 s/div 20ma to 100ma to 20ma switching waveforms (positive output) MAX8614A/b toc17 50mv/div ac-coupled 10v/div 500ma/div 0a 0v v bst i lx v lx 400ns/div i bst = 20ma switching waveforms (positive output) MAX8614A/b toc18 50mv/div ac-coupled 10v/div 500ma/div 0a 0v v bst i lx v lx 400ns/div i bst = 50ma switching waveforms (negative output) MAX8614A/b toc19 50mv/div ac-coupled 10v/div 500ma/div 0a 0v v inv i lx v lx 400ns/div i inv = 20ma switching waveforms (negative output) MAX8614A/b toc20 50mv/div ac-coupled 10v/div 500ma/div 0a 0v v inv i lx v lx 400ns/div i inv = 100ma load transient (positive output) MAX8614A/b toc15 20mv/div ac-coupled 100mv/div ac-coupled 20ma/div 0v v bst i bst v inv 4 s/div 20ma to 50ma to 20ma typical operating characteristics (continued) (t a = +25?, v cc = v avcc = 3.6v, seq = gnd, figure 1, unless otherwise noted.)
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd 8 _______________________________________________________________________________________ typical operating characteristics (continued) (t a = +25?, v cc = v avcc = 3.6v, seq = gnd, figure 1, unless otherwise noted.) reference voltage vs. temperature temperature ( c) reference voltage (v) MAX8614A/b toc21 -40 -15 10 35 60 85 1.2450 1.2455 1.2460 1.2465 1.2470 1.2475 1.2480 1.2485 1.2490 switching frequency vs. temperature temperature ( c) frequency (khz) MAX8614A/b toc22 -40 -15 10 35 60 85 0.996 0.997 0.998 0.999 1.000 1.001 1.002 1.003 1.004 1.005 1.006 v bst = +15v i out = 50ma v inv = -7.5v i out = 100ma pin name function 1 onbst enable logic input. connect onbst to av cc for automatic startup of the step-up converter, or use onbst as an independent control of the step-up converter. 2 fbn negative output feedback input. connect a resistor-divider between the negative output and ref with the center to fbn to set the negative output voltage. 3 av cc bias supply. av cc powers the ic. av cc must be connected to v cc . 4 ref 1.25v reference voltage output. bypass with a 0.22? ceramic capacitor to gnd. 5 gnd ground. connect gnd to pgnd with a short trace. 6 flt fault open-drain output. connect a 100k ? resistor from flt to av cc . flt is active low during a fault event and is high impedance in shutdown. 7 fbp positive output-voltage feedback input. connect a resistor-divider between the positive output and gnd with the center to fbp to set the positive output voltage. fbp is high impedance in shutdown. 8 seq sequence logic input. when seq = low, power-on sequence can be independently controlled by onbst and oninv. when seq = high, the positive output powers up before the negative output. 9 oninv enable logic input. connect oninv to av cc for automatic startup of the inverter, or use oninv as an independent control of the inverter. 10 lxp positive output switching inductor node. lxp is high impedance in shutdown. 11 pgnd power ground. connect pgnd to gnd with a short trace. 12 pvp true-shutdown load disconnect switch. connect one side of the inductor to pvp and the other side to lxp. pvp is high impedance in shutdown. 13 v cc power input supply. v cc supplies power for the step-up and inverting dc-dc converters. v cc must be connected to av cc . 14 lxn negative output switching inductor node. lxn is high impedance in shutdown. ep exposed pad. connect exposed paddle to ground. pin description
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd _______________________________________________________________________________________ 9 detailed description the MAX8614A/max8614b generate both a positive and negative output voltage by combining a step-up and an inverting dc-dc converter on one ic. both the step-up converter and the inverter share a common clock. each output is independently regulated. each output is separately controlled by a pulse-width- modulated (pwm) current-mode regulator. this allows the converters to operate at a fixed frequency (1mhz) for use in noise-sensitive applications. the 1mhz switching rate allows for small external components. both converters are internally compensated and are optimized for fast transient response (see the load- transient response/voltage positioning section). step-up converter the step-up converter generates a positive output volt- age up to 24v. an internal power switch, internal true- shutdown load switch (pvp), and external catch diode allow conversion efficiencies as high as 90%. the inter- nal load switch disconnects the battery from the load by opening the battery connection to the inductor, pro- viding true shutdown. the internal load switch stays on at all times during normal operation. the load switch is used in the control scheme for the converter and can- not be bypassed. lxn v cc pvp ref fbn onbst MAX8614A max8614b lxp seq oninv av cc gnd pgnd fbp 1mhz oscillator reference 1.25v step-up current sense inverter current sense soft-start error amplifier pwm comparator inverter control logic bias and control block 1.01v error amplifier pwm comparator step-up control logic flt functional diagram
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd 10 ______________________________________________________________________________________ inverter the inverter generates output voltages down to -16v below v cc . an internal power switch and external catch diode allow conversion efficiencies as high as 85%. control scheme both converters use a fixed-frequency, pwm current- mode control-scheme. the heart of the current-mode pwm controllers is a comparator that compares the error-amp voltage-feedback signal against the sum of the amplified current-sense signal and a slope-com- pensation ramp. at the beginning of each clock cycle, the internal power switch turns on until the pwm com- parator trips. during this time the current in the inductor ramps up, storing energy in the inductor? magnetic field. when the power switch turns off, the inductor releases the stored energy while the current ramps down, providing current to the output. fault protection the MAX8614A/max8614b have robust fault and over- load protection. after power-up the device is set to detect an out-of-regulation state that could be caused by an overload or short condition at either output. if either output remains in overload for more than 100ms, both converters turn off and the flt flag asserts low. during a short-circuit condition longer than 100ms on the positive output, foldback current limit protects the output. during a short-circuit condition longer than 100ms on the nega- tive output, both converters turn off and the flt flag asserts low. the converters then remain off until the device is reinitialized by resetting the controller. the MAX8614A/max8614b also have thermal shutdown. when the device temperature reaches +170? (typ) the device shuts down. when it cools down by 20? (typ), the converters turn on. enable (onbst/oninv) applying a high logic-level signal to onbst/oninv turns on the converters using the soft-start and power- on sequencing described below. pulling onbst/ oninv low puts the ic in shutdown mode, turning off the internal circuitry. when onbst/oninv goes high (or if power is applied with onbst/oninv high), the power-on sequence is set by seq. in shutdown, the device consumes only 0.1? and both output loads are disconnected from the input supply. soft-start and inrush current the step-up converter and inverter in the MAX8614A/ max8614b feature soft-start to limit inrush current and minimize battery loading at startup. this is accom- plished by ramping the reference voltage at the input of each error amplifier. the step-up reference is ramped from 0 to 1v (where 1v is the desired feedback voltage for the step-up converter) while the inverter reference is ramped down from 1.25v to 0 (where 0 is the desired feedback voltage for the inverter). during startup, the step-up converter true-shutdown load switch turns on before the step-up-converter refer- ence voltage is ramped up. this effectively limits inrush current peaks to below 500ma during startup. undervoltage lockout (uvlo) the MAX8614A/max8614b feature undervoltage-lock- out (uvlo) circuitry, which prevents circuit operation and mosfet switching when av cc is less than the uvlo threshold (2.55v, typ). the uvlo comparator has 25mv of hysteresis to eliminate chatter due to the source supply output impedance. power-on sequencing (seq) the MAX8614A/max8614b have pin-selectable inter- nally programmed power-on sequencing. this sequencing covers all typical sequencing options required by ccd imagers. when seq = 0, power-on sequence can be indepen- dently controlled by oninv and onbst. when seq = 0 and oninv and onbst are pulled high, both outputs reach regulation simultaneously. the inverter is held off while the step-up true-shutdown switch slowly turns on to pull pvp to v cc . the positive output rises to a diode drop below v cc . once the step-up output reaches this voltage, the step-up and the inverter then ramp their respective references over a period of 7ms. this brings the two outputs into regulation at approximately the same time. when seq = 1 and onbst and oninv are pulled high, the step-up output powers on first. the inverter is held off until the step-up completes its entire soft-start cycle and the positive output is in regulation. then the invert- er starts its soft-start cycle and achieves regulation in about 7ms. true shutdown the MAX8614A/max8614b completely disconnect the loads from the input when in shutdown mode. in most step-up converters the external rectifying diode and inductor form a dc current path from the battery to the output. this can drain the battery even in shutdown if a load is connected at the step-up converter output. the MAX8614A/max8614b have an internal switch between the input v cc and the inductor node, pvp. when this switch turns off in shutdown there is no dc path from the input to the output of the step-up converter. this load disconnect is referred to as ?rue shutdown.?at
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd ______________________________________________________________________________________ 11 the inverter output, load disconnect is implemented by turning off the inverter? internal power switch. current-limit select the max8614b allows an inductor current limit of 0.8a on the step-up converter and 0.75a on the inverter. the MAX8614A allows an inductor current limit of 0.44a on the step-up converter and 0.33a on the inverter. this allows flexibility in designing for higher load-current applications or for smaller, more compact designs when less power is needed. note that the currents list- ed above are peak inductor currents and not output currents. the max8614b output current is 50ma at +15v and 100ma at -7.5v. the MAX8614A output cur- rent is 25ma at +15v and 50ma at -7.5v. load transient/voltage positioning the MAX8614A/max8614b match the load regulation to the voltage droop seen during load transients. this is sometimes called voltage positioning. this results in min- imal overshoot when a load is removed and minimal volt- age drop during a transition from light load to full load. the use of voltage positioning allows superior load- transient response by minimizing the amplitude of over- shoot and undershoot in response to load transients. dc-dc converters with high control-loop gains maintain tight dc load regulation but still allow large voltage drops of 5% or greater for several hundred microsec- onds during transients. load-transient variations are seen only with an oscilloscope (see the typical operating characteristics ). since dc load regulation is read with a voltmeter, it does not show how the power supply reacts to load transients. applications information adjustable output voltage the positive output voltage is set by connecting fbp to a resistive voltage-divider between the output and gnd (figure 1). select feedback resistor r2 in the 30k ? to 100k ? range. r1 is then given by: where v fbp = 1.01v. the negative output voltage is set by connecting fbn to a resistive voltage-divider between the output and ref (figure 1). select feedback resistor r4 in the 30k ? to 100k ? range. r3 is then given by: where v ref = 1.25v and v fbn = 0v. inductor selection the MAX8614A/max8614b high switching frequency allows for the use of a small inductor. the 4.7? and 2.2? inductors shown in the typical operating circuit is recommended for most applications. larger inductances reduce the peak inductor current, but may result in skip- ping pulses at light loads. smaller inductances require less board space, but may cause greater peak current due to current-sense comparator propagation delay. use inductors with a ferrite core or equivalent. powder iron cores are not recommended for use with high switch- ing frequencies. the inductor? incremental saturation rat- ing must exceed the selected current limit. for highest efficiency, use inductors with a low dc resistance (under 200m ? ); however, for smallest circuit size, higher resis- tance is acceptable. see table 1 for a representative list of inductors and table 2 for component suppliers. diode selection the MAX8614A/max8614b high switching frequency demands a high-speed rectifier. schottky diodes, such as the cmhsh5-2l or mbr0530l, are recommended. make sure that the diode? peak current rating exceeds the selected current limit, and that its breakdown volt- age exceeds the output voltage. schottky diodes are preferred due to their low forward voltage. however, ultrahigh-speed silicon rectifiers are also acceptable. table 2 lists component suppliers. capacitor selection output filter capacitor the primary criterion for selecting the output filter capacitor is low effective series resistance (esr). the product of the peak inductor current and the output fil- ter capacitor? esr determines the amplitude of the high-frequency ripple seen on the output voltage. these requirements can be balanced by appropriate selection of the current limit. for stability, the positive output filter capacitor, c1, should satisfy the following: c1 > (6l i bstmax ) / ( r cs d+ v bst 2 ) where r cs = 0.015 (max8614b), and 0.035 (MAX8614A). d+ is 1 minus the step-up switch duty cycle and is: d+ = v cc / v bst r vv vv fbn imv ref fbn 34 = ? ? ? ? ? ? ? ? r r v v bst fbp 12 1 =? ? ? ? ? ? ? r
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd 12 ______________________________________________________________________________________ for stability, the inverter output filter capacitor, c2, should satisfy the following: c2 > (6l v ref i invmax ) / (r cs d- (v ref - v inv ) v inv ) where r cs = 0.0175 (max8614b), and 0.040 (MAX8614A). d- is 1 minus the inverter switch duty cycle and is: d- = v cc / v inv table 2 lists representative low-esr capacitor suppliers. input bypass capacitor although the output current of many MAX8614A/ max8614b applications may be relatively small, the input must be designed to withstand current transients equal to the inductor current limit. the input bypass capacitor reduces the peak currents drawn from the voltage source, and reduces noise caused by the MAX8614A/max8614b switching action. the input source impedance determines the size of the capacitor required at the input. as with the output filter capacitor, a low-esr capacitor is recommended. a 4.7?, low- esr capacitor is adequate for most applications, although smaller bypass capacitors may also be acceptable with low-impedance sources or if the source supply is already well filtered. bypass av cc separately from v cc with a 0.1? ceramic capacitor placed as close as possible to the av cc and gnd pins. pc board layout and routing proper pc board layout is essential due to high-current levels and fast-switching waveforms that radiate noise. breadboards or protoboards should never be used when prototyping switching regulators. table 1. inductor selection guide output voltages and load current inductor l ( h) dcr (m ? )i sat (a) size (mm) toko db3018c, 1069as-2r0 2.0 72 1.4 3 x 3 x 1.8 toko db3018c, 1069as-4r3 4.3 126 0.97 3 x 3 x 1.8 toko s1024as-4r3m 4.3 47 1.2 4 x 4 x 1.7 sumida cdrh2d14-4r7 4.7 170 1 3.2 x 3.2 x 1.55 15v, 50ma -7.5v, 100ma toko s1024as-100m 10 100 0.8 4 x 4 x 1.7 sumida cdrh2d11-100 10 400 0.35 3.2 x 3.2 x 1.2 sumida cdrh2d14-100 10 295 0.46 3.2 x 3.2 x 1.55 15v, 20ma -7.5v, 40ma murata lqh32cn100k33 10 300 0.45 3.2 x 2.5 x 2 table 2. component suppliers supplier phone website inductors murata 770-436-1300 www.murata.com sumida 847-545-600 www.sumida.com toko 847-297-0070 www.tokoam.com diodes central semiconductor (cmhsh5-2l) 631-435-1110 www.centralsemi.com motorola (mbr0540l) 602-303-5454 www.motorola.com capacitors taiyo yuden 408-573-4150 www.t-yuden.com tdk 888-835-6646 www.tdk.com
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd ______________________________________________________________________________________ 13 it is important to connect the gnd pin, the input bypass-capacitor ground lead, and the output filter capacitor ground lead to a single point (star ground configuration) to minimize ground noise and improve regulation. also, minimize lead lengths to reduce stray capacitance, trace resistance, and radiated noise, with preference given to the feedback circuit, the ground circuit, and lx_. place feedback resistors r1?4 as close to their respective feedback pins as possible. place the input bypass capacitor as close as possible to av cc and gnd. chip information process: bicmos lxn v cc pvp c5 0.1 f c6 0.22 f c4 4.7 f c2 4.7 f c3 1 f c1 2.2 f v batt (2.7v ~ 5v) fault v batt ref fbn 14 12 10 8 r3 187k ? 1% r4 30.9k ? 1% r5 100k ? r1 1.4m ? 1% r2 100k ? 1% v inv v bst 13 511 1 9 2 3 4 6 7 onbst oninv ref v inv -7.5v at 100ma d2 cmhsh5-21 d1 cmhsh5-21 MAX8614A max8614b lxp seq gnd pgnd v bst +15v at 50ma l2 4.7 h l1 2.2 h fbp flt av cc figure 1. typical application circuit
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd 14 ______________________________________________________________________________________ MAX8614A/max8614b package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) 6, 8, &10l, dfn thin.eps l c l c pin 1 index area d e l e l a e e2 n g 1 2 21-0137 package outline, 6,8,10 & 14l, tdfn, exposed pad, 3x3x0.80 mm -drawing not to scale- k e [(n/2)-1] x e ref. pin 1 id 0.35x0.35 detail a b d2 a2 a1
MAX8614A/max8614b dual-output (+ and -) dc-dc converters for ccd 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 15 2006 maxim integrated products printed usa is a registered trademark of maxim integrated products, inc. MAX8614A/max8614b package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) common dimensions symbol min. max. a 0.70 0.80 d 2.90 3.10 e 2.90 3.10 a1 0.00 0.05 l 0.20 0.40 pkg. code n d2 e2 e jedec spec b [(n/2)-1] x e package variations 0.25 min. k a2 0.20 ref. 2.300.10 1.500.10 6 t633-1 0.95 bsc mo229 / weea 1.90 ref 0.400.05 1.95 ref 0.300.05 0.65 bsc 2.300.10 8 t833-1 2.00 ref 0.250.05 0.50 bsc 2.300.10 10 t1033-1 2.40 ref 0.200.05 - - - - 0.40 bsc 1.700.10 2.300.10 14 t1433-1 1.500.10 1.500.10 mo229 / weec mo229 / weed-3 0.40 bsc - - - - 0.200.05 2.40 ref t1433-2 14 2.300.10 1.700.10 t633-2 6 1.500.10 2.300.10 0.95 bsc mo229 / weea 0.400.05 1.90 ref t833-2 8 1.500.10 2.300.10 0.65 bsc mo229 / weec 0.300.05 1.95 ref t833-3 8 1.500.10 2.300.10 0.65 bsc mo229 / weec 0.300.05 1.95 ref -drawing not to scale- g 2 2 21-0137 package outline, 6,8,10 & 14l, tdfn, exposed pad, 3x3x0.80 mm downbonds allowed no no no no yes no yes no

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