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mic2296 high power density 1.2a boost regulator mlf and micro leadframe are registered trademarks of amkor technology, inc. micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 ( 408 ) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com january 2010 m9999-011310 general description the mic2296 is a 600khz, pwm dc/dc boost switching regulator available in a 2mm x 2mm mlf ? package option. high power density is achieved with the mic2296?s internal 34v / 1.2a switch, allowing it to power large loads in a tiny footprint. the mic2296 is a version of the mic2295 1.2mhz, pwm dc/dc boost switching regulator, that offers improved effici ency resulting from 600khz operation. the mic2296 implements cons tant frequency 600khz pwm current mode control. the mic2296 offers internal compensation that offers excellent transient response and output regulation performanc e. the high frequency operation saves board space by allowing small, low-profile external components. the fixed frequency pwm scheme also reduces spurious switching noise and ripple to the input power source. the mic2296 is available in a low-profile thin sot23 5- pin package and a 2mm x2mm 8-pin mlf ? leadless package. the 2mm x 2mm mlf ? package option has an output over-voltage pr otection feature. the mic2296 has an operating junction temperature range of ?40 c to +125 c features ? 2.5v to 10v input voltage range ? output voltage adjustable to 34v ? 1.2a switch current ? 600khz pwm operation ? stable with small size ceramic capacitors ? high efficiency ? low input and output ripple ? <1a shutdown current ? uvlo ? output over-voltage protection (MIC2296BML) ? over temperature shutdown ? 2mm x 2mm leadless 8-pin mlf ? package option ? ?40 o c to +125 o c junction temperature range applications ? organic el power supplies ? 3.3v to 5v/500ma conversion ? tft-lcd bias supplies ? positive and negative output regulators ? sepic converters ? positive to negative cuk converters ? 12v supply for dsl applications ? multi-output dc/dc converters 10h r2 901 r1 10k MIC2296BML vin v in 1-cell li ion 3v to 4.2v v out 15v/100ma en fb agnd c1 2.2f 2.2f pgnd sw ovp l1 10h r2 3.3k r1 10k mic2296 bd5 vin 1-cell li ion v out 5v/400ma en sw fb gnd v in c1 2.2f 10f 1000 pf
micrel, inc. mic2296 january 2010 2 m9999-011310 ordering information part number marking code standard lead-free output over voltage protection standard lead-free junction temp. range package MIC2296BML mic2296yml 34v wda w da -40 c to 125 c 8-pin 2mm x2mm mlf ? mic2296bd5* mic2296yd5* - wdaa w daa -40 c to 125 c 5-pin thin sot-23 * contact factory for availability. pin configuration fb gnd en vin sw 3 1 5 2 4 tsot-23-5 (bd5) 1 ovp vin en a gnd 8 pgnd sw fb nc 7 6 5 2 3 4 ep 8-pin mlf ? (bml) pin description mic2296bd5 thin sot-23-5 MIC2296BML 2x2 mlf-8l pin name pin function ? 1 ovp output over-voltage protection (input): tie this pin to v out to clamp the output voltage to 34v maximum in fault conditions. tie this pin to ground if ovp function is not required. 5 2 vin supply (input): 2.5v to 10v input voltage. 4 3 en enable (input): logic high enables regulator. logic low shuts down regulator. ? 4 agnd analog ground ? 5 n/c no connect. no internal connection to die. 3 6 fb feedback (input): 1.24v ou tput voltage sense node. v out = 1.24v ( 1 + r1/r2) 1 7 sw switch node (input): internal power bipolar collector. ? 8 pgnd power ground 2 ? gnd ground (return): ground. ? ep gnd ground (return). exposed backside pad.
micrel, inc. mic2296 january 2010 3 m9999-011310 absolute maximum rating (1) supply voltage (v in )........................................................12v switch voltage (v sw ) ........................................ -0.3v to 34v enable pin voltage (v en )....................................... -0.3 to v in fb voltage (v fb )...............................................................6v switch current (i sw ) ......................................................2.5a ambient storage temperature (t s )............-65 c to +150 c esd rating (3) ................................................................. 2kv operating range (2) supply voltage (v in ).......................................... 2.5v to 10v junction temperature range (t j )..............-40 c to +125 c package thermal impedance ja 2x2 mlf-8l ..................................................93 c/w electrical characteristics (4) t a =25 o c, v in =v en = 3.6v, v out = 15v, i out = 40ma, unless otherwise noted. bold values indicate -40 c t j 125 c. symbol parameter condition min typ max units v in supply voltage range 2.5 10 v v uvlo under-voltage lockout 1.8 2.1 2.4 v i vin quiescent current v fb = 2v (not switching) 2.8 5 ma i sd shutdown current v en = 0v (5) 0.1 1 a (1%) 1.227 1.24 1.252 v fb feedback voltage (2%) (over temp) 1.215 1.265 v i fb feedback input current v fb = 1.24v -450 na line regulation 3v v in 5v 0.04 1 % load regulation 5ma i out 40ma 0.5 % d max maximum duty cycle 90 95 % i sw switch current limit note 5 1.2 1.7 2.5 a v sw switch saturation voltage i sw = 0.5a 250 mv i sw switch leakage current v en = 0v, v sw = 10v 0.01 1 a v en enable threshold turn on turn off 1.5 0.4 v i en enable pin current v en = 10v 20 40 a f sw oscillator frequency v in = 3.6v 525 600 675 khz v ovp output over-voltage protecti on MIC2296BML only 30 32 34 v 150 c t j over-temperature threshold shutdown hysteresis 10 c notes: 1. absolute maximum ratings indicate limits beyond which damage to the component may occur. electr ical specifications do not ap ply when operating the device outside of its operating ratings. the maximum allowable power dissi pation is a function of the maximum jun ction temperature, t j(max) , the junction-to-ambient thermal resistance, ja , and the ambient temperature, t a . the maximum allowable power dissipation will result in excessive die temperatur e, and the regulator will go into thermal shutdown. 2. this device is not guaranteed to oper ate beyond its specified operating rating. 3. ic devices are inherently esd sensitive. handling precautions required. human body model rating: 1.5k in series with 100pf. 4. specification for packaged product only. 5. i sd = i vin .
micrel mic2296 january 2010 4 m9999-011310 typical characteristics 72 74 76 78 80 82 84 0 50 100 150 200 250 output current (ma) 12v output with l = 4.7h v in = 3.2v v in = 3.6v v in = 4.2v 70 72 74 76 78 80 82 84 86 88 90 0 200 400 600 800 1000 output current (ma) 5v output with l = 4.7h v in = 3.2v v in = 3.6v v in = 4.2v 200 210 220 230 240 250 260 270 280 290 300 10 input voltage (v) switch saturation voltage vs. input voltage 0 200 400 600 800 2.5 5 7.5 10 input voltage (v) frequency vs. input voltage 90 92 94 96 98 100 2.5 5 7.5 10 input voltage (v) max duty cycle vs. input voltage 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.5 5 7.5 10 input voltage (v) current limit vs. input voltage 11.8 11.85 11.9 11.95 12 12.05 12.1 12.15 12.2 0 25 50 75 100 125 150 output voltage (v) load (ma) load regulation v in = 3.6v 1.10 1.12 1.14 1.16 1.18 1.20 1.22 1.24 1.26 1.28 1.30 -40 -20 0 20 40 60 80 100 120 feedback voltage (v) temperature (c) feedback voltage vs. temperature 0 100 200 300 400 500 600 700 -40 -20 0 20 40 60 80 100 120 feedback current (na) temperature (c) fb pin current vs. temperature
micrel mic2296 january 2010 5 m9999-011310 functional characteristics enable characteristics enable volta g e (2v/div) time (2s/div) v in = 3.6v v out = 12v i out = 150ma outpu t volta g e (5v/div) step load response output volta g e (50mv/div) load current (100ma/div) time (100s/div) v in = 3.6v v out = 12v i out = 50ma to 150ma
micrel mic2296 january 2010 6 m9999-011310 functional description the mic2296 is a high power density, pwm dc/dc boost regulator. the block diagram is shown in figure 1. the mic2296 is composed of an oscillator, slope compensation ramp generator, current amplifier, gm error amplifier, pwm generator, and a 1.2a bipolar output transistor. the oscillator generates a 600khz clock. the clock?s two functions are to trigger the pwm generator that turns on the output transist or, and to reset the slope compensation ramp generator. the current amplifier is used to measure the switch current by amplifying the voltage signal from the internal sense resistor. the output of the current amplifier is summed with the output of the slope compensation ramp generator. this summed current-loop signal is fed to one of the inputs of the pwm generator. the g m error amplifier measures the feedback voltage through the external feedback resistors and amplifies the error between the detected signal and the 1.24v reference voltage. the output of the g m error amplifier provides the voltage-loop signal that is fed to the other input of the pwm generator. when the current-loop signal exceeds the voltage-loop signal, the pwm generator turns off the bipolar output transistor. the next clock period initiates the next switching cycle, maintaining constant frequency current-mode pwm control gnd ca pwm generator ramp generator 600khz oscillator sw en fb ovp* vin 1.24v * ovp available on mlf tm package option only. g m ovp* v r e f mic2296 figure 1. mic2296 block diagram
micrel mic2296 january 2010 7 m9999-011310 application information dc to dc pwm boost conversion the mic2296 is a constant frequency boost converter. it operates by taking a dc input voltage and regulating a higher dc output voltage. figure 2 shows a typical circuit. en vin sw fb gnd c2 10f gnd l1 10h r1 r2 gnd v in u1 mic2296-bml ovp v out figure 2 boost regulation is achieved by turning on an internal switch, which draws current through the inductor (l1). when the switch turns off, the inductor?s magnetic field collapses. this causes the current to be discharged into the output capacitor through an external schottkey diode (d1). voltage regulation is achieved my modulating the pulse width or pulse width modulation (pwm). duty cycle considerations duty cycle refers to the switch on-to-off time ratio and can be calculated as follows for a boost regulator; d = 1 ? v in v out the duty cycle required for voltage conversion should be less than the maximum duty cycle of 90%. also, in light load conditions where the input voltage is close to the output voltage, the minimum duty cycle can cause pulse skipping. this is due to the energy stored in the inductor causing the output to overshoo t slightly over the regulated output voltage. during the next cycle, the error amplifier detects the output as being high and skips the following pulse. this effect can be reduced by increasing the minimum load or by increasing the inductor value. increasing the inductor value reduces peak current, which in turn reduces energy transfer in each cycle. over voltage protection for mlf package of mic2296, there is an over voltage protection function. if t he feedback resistors are disconnected from the circuit or the feedback pin is shorted to ground, the feedback pin will fall to ground potential. this will cause the mic2296 to switch at full duty-cycle in an attempt to maintain the feedback voltage. as a result the output voltage w ill climb out of control. this may cause the switch node voltage to exceed its maximum voltage rating, possibly damaging the ic and the external components. to ensure the highest level of protection, the mic2296 ovp pin will shut the switch off when an over- voltage condition is detected saving itself and other sensitive circuitry downstream. component selection inductor inductor selection is a balance between efficiency, stability, cost, size and rated current. for most applications a 10h is the recommended inductor value. it is usually a good balance between these considerations. efficiency is affected by inductance value in that larger inductance values reduce the peak to peak ripple current. this has an effect of reducing both the dc losses and the transition losses. there is also a secondary effect of an inductors dc resistance (dcr). the dcr of an inductor will be higher for more inductance in the same package size. this is due to the longer windings required for an increase in inductance. since the majority of input current (minus the mic2296 operating current) is passed through the inductor, higher d cr inductors will reduce efficiency. also, to maintain stability, increasing inductor size will have to be met with an increase in output capacitance. this is due to the unavoidable ?right half plane zero? effect for the continuous current boost converter topology. the frequency at which the right half plane zero occurs can be calculated as follows; frhpz = v in 2 v out l i out 2 the right half plane zero has the undesirable effect of increasing gain, while decreasing phase. this requires that the loop gain is rolled off before this has significant effect on the total loop response. this can be accomplished by either reducing inductance (i ncreasing rhpz frequency) or increasing the output capacitor value (decreasing loop gain). output capacitor output capacitor selection is also a trade-off between performance, size and cost. increasing output capacitance will lead to an improved tran sient response, but also an increase in size and cost. x5r or x7r dielectric ceramic capacitors are recommended for designs with the mic2296. y5v values may be used, but to offset their tolerance over temperature, more capacitance is required. the following table shows the recommended ceramic (x5r) output capacitor value vs. output voltage. output voltage recommended output capacitance <6v 10f <16v 4.7f <34v 2.2f
micrel mic2296 january 2010 8 m9999-011310 diode selection the mic2296 requires an external diode for operation. a schottkey diode is recommended for most applications due to their lower forward voltage drop and reverse recovery time. ensure the diode selected can deliver the peak inductor current and the maximum reverse voltage is rated greater than the output voltage. input capacitor a minimum 1f ceramic capa citor is recommended for designing with the mic2296. increasing input capacitance will improve performance and greater noise immunity on the source. the input capacitor should be as close as possible to the inductor and t he mic2296, with short traces for good noise performance. feedback resistors the mic2296 utilizes a feedback pin to compare the output to an internal reference. the output voltage is adjusted by selecting the appr opriate feedback resistor values. the desired output voltage can be calculated as follows; v out = v ref r1 r2 + 1 ? ? ? ? ? ? where v ref is equal to 1.24v. duty-cycle the mic2296 is a general-purpose step up dc-dc converter. the maximum difference between the input voltage and the output voltage is limited by the maximum duty-cycle (d max ) of the converter. in the case of mic2296, d max = 85%. the actual duty cycle for a given application can be calculated as follows: d = 1 ? v in v out the actual duty-cycle, d, cannot surpass the maximum rated duty-cycle, d max . output voltage setting the following equation can be used to select the feedback resistors r1 and r2 (see figure 1). r 1 = r 2 ? v out 1.24v ? 1 ? ? ? ? ? ? a high value of r2 can increase the whole system efficiency, but the feedba ck pin input current (i fb ) of the gm operation amplifier will affect the output voltage. the r2 resistor value must be less than or equal to 5k ? (r2 5k ? ). inductor selection in mic2296, the switch current limit is 1.2a. the selected inductor should handle at least 1.2a current without saturating. the inductor should have a low dc resistor to minimize power losses. the inductor?s value can be 4.7h to 10h for most applications. capacitor selection multi-layer ceramic capacitors are the best choice for input and output capacitors. they offer extremely low esr, allowing very low ripple, and are available in very small, cost effective packages. x5r dielectrics are preferred. a 4.7f to 10f output capacitor is suitable for most applications. diode selection for maximum efficiency, schottky diode is recommended for use with mic2296. an optimal component selection can be made by choosing the appropriate reverse blocking voltage rating and the average forward current rating for a given application. for the case of maximum output voltage (34v) and maximum output current capability, a 40v / 1a schottky diode should be used. open-circuit protection for mlf ? package option of mic2296, there is an output over-voltage protection function that clamps the output to below 34v in fault conditions. possible fault conditions may include: if the device is configured in a constant current mode of operation and the load opens, or if in the standard application the feedback resistors are disconnected from the circuit. in these cases the fb pin will pull to ground, causing the mic2296 to switch with a high duty-cycle. as a result, the output voltage will climb out of regulation, causing the sw pin to exceed its maximum voltage rating and possibly damaging the ic and the external components. to ensure the highest level of safety, the mic2296 has a dedicated pin, ovp, to monitor and clamp the output voltage in over-voltage conditions. the ovp function is offered in the 2mm x 2mm mlf - 8l package option only. to disable ovp function, tie the ovp pin to ground
micrel mic2296 january 2010 9 m9999-011310 l1 4.7h c2 22f 6.3v r2 1.87k r1 5.62k MIC2296BML vin v in 3v to 4.2v v out 5v @ 400ma en sw fb gnd gnd ovp gnd c1 4.7f 6.3v d1 470 pf 3v in to 4.2v out @ 400ma l1 4.7h c2 4.7f 16v r2 5k r1 31.6k MIC2296BML vin v in 3v to 4.2v v out 9v @ 180ma en sw fb gnd gnd ovp gnd c1 2.2f 10v d1 560 pf 3v in - 4.2v in to 9v out @ 180ma l1 15h c2 4.7f 16v r2 5k r1 43.2k MIC2296BML vin v in 3v to 4.2v v out 12v @ 120ma en sw fb gnd gnd ovp gnd c1 2.2f 10v d1 1200 pf 3v in - 4.2vin to 12v out @ 120ma l1 15h c2 2.2f 25v r2 2.32k r1 43.2k MIC2296BML vin v in 5v v out 24v @160ma en sw fb gnd gnd ovp gnd c1 2.2f 10v d1 5v in to 24v out @ 160ma l1 15h c2 2.2f 25v r2 2.32k r1 43.2k MIC2296BML vin v in 3v to 4.2v v out 24v@80ma en sw fb gnd gnd ovp gnd c1 2.2f 10v d1 1200 pf 3v in to 4.2v in to 24v out @ 80ma
micrel mic2296 january 2010 10 m9999-011310 package information 8-pin package mlf (ml) 5-pin thin sot-23 (d5)
micrel mic2296 january 2010 11 m9999-011310 recommended land pattern 8-pin package mlf (ml) 5-pin thin sot-23 (d5)
micrel mic2296 january 2010 12 m9999-011310 micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944-0800 fax +1 (408) 474-1000 web http:/www.micrel.com the information furnished by micrel in this data sheet is belie ved to be accurate and reliable. however, no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. micrel products are not designed or authori zed for use as components in life support app liances, devices or systems where malfu nction of a product can reasonably be expected to result in pers onal injury. life support devices or system s are devices or systems that (a) are in tended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significan t injury to the user. a purchaser?s use or sale of micrel produc ts for use in life support app liances, devices or systems is a purchaser?s own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2005 micrel, incorporated.

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