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MIC22200 2a integrated switch synchronous buck regulator with frequency programmable from 800khz to 4mhz micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com general description the micrel MIC22200 is a high-efficiency, 2a integrated switch synchronous buck (step-down) regulator. the MIC22200 switching frequency is programmable from 800khz to 4mhz, allowing the customer to optimize their designs either for efficiency or for the smallest footprint. the regulator achieves efficiencies as high as 95% while still switching at 1mhz over a broad load range. the ultra high-speed control loops keep the output voltage within regulation even under the extreme transient load swings commonly found in fpgas and low-voltage asics. the output voltage can be adjusted down to 0.7v to address all low-voltage power needs. the MIC22200 offers a full range of sequencing and tracking options. the en/dly pin, combined with the power-on-reset (por) pin, allows multiple outputs to be sequenced in many ways during turn on and turn off. the rc (ramp control) pin allows the device to be connected to another device in the mic22x00 family of products to keep the output voltages within a certain delta v on start up. the MIC22200 is available in a 3mm 3mm 12-pin mlf ? package with a junction operating range from ?40 c to +125 c. data sheets and support documentation can be found on micrel?s web site at www.micrel.com . features ? input voltage range: 2.6v to 5.5v ? adjustable output voltage option down to 0.7v ? output load current to 2a ? full sequencing and tracking capability ? easy rc compensation ? power-on-reset (por) output ? efficiency >90% across a broad load range ? operating frequency: programmable from 800 khz up to 4mhz ? ultra-fast transient response ? 100% maximum duty cycle ? fully integrated mosfet switches ? micropower shutdown ? thermal-shutdown and cu rrent-limit protection ? available in pb-free 3mm 3mm mlf-12-pin mlf ? package ? ?40 c to +125 c junction temperature range applications ? high power density point-of-load conversion ? servers/routers ? dvd recorders and multimedia players ? computing peripherals ? base stations ? fpgas, dsp and low voltage asic devices _________________________________________________________________________________________________________________________ typical application december 2010 m9999-120310-c
micrel, inc. MIC22200 december 2010 2 m9999-120310-c ordering information part number nominal output voltage junction temperature range (1) package lead finish MIC22200yml adjustable ? 40c to +125 c 3mm 3mm 12-pin mlf ? lead free (1) note : mlf ? is a green rohs-compliant package. lead fini sh is nipdau. mold compound is halogen free. pin configuration 12-pin mlf ? (ml) pin description pin number pin name pin function 1 por power-on-reset (output): open drai n output device indicates when t he output is out of regulation and is active after the delay set by the delay pin. 2 rc ramp control. capacitor to gnd from this pin determines the slew rate of output voltage during start-up. this can be used for tracking capability as well as for soft start. 3 cf external capacitor to adjust switching frequency. 4 sgnd signal ground (signal): ground (gnd) 5 comp compensation pin (input): placing an rc to g nd will compensate the devic e. see applications section. 6 fb feedback (input): input to the erro r amplifier; connected to the external resistor divider network to set the output voltage. 7 svin signal power supply voltage (input ): requires bypass capacitor to gnd. 8 pvin power supply voltage (input): requires bypass capacitor to gnd. 9 sw switch (output): from internal power mosfet output switches. 10 pgnd power ground (power): ground (gnd) 11 delay delay (input) 12 en/dly enable (input): when this pin is pulled higher t han the enable threshold, the part will start up. below this voltage the device is in its low quie scent current mode. the pin has a 1a current source charging it to vin. by adding a capacitor to this pin a delay may easily be generated. the enable function will not operate with an input voltage lower than the min specified. epad gnd exposed pad (power): you must make a full con nection to a gnd plane for full output power to be released.
micrel, inc. MIC22200 december 2010 3 m9999-120310-c absolute maximum ratings (1) supply voltage (p vin , s vin ) ............................................+6v output switch (sw)..........................................................6v logic voltage (en/dly, por, delay) ............vin to -0.3v control voltage (cf, rc, comp, fb) ..............vin to -0.3v lead temperature (sol dering 10 s)............................. 260c storage temperatur e range (ts) ............. ? 65c to +150c eds rating (3) .................................................................. 2kv operating ratings (2) supply voltage (v in )..................................... +2.6v to +5.5v junction temperature range (t j )....... ? 40 c t j +125 c thermal resistance 3mm 3mm mlf-12l ( ja ) ...............................40c/w electrical characteristics (4) t a = 25c with v in = v en = 3.3v, unless otherwise specified. bold values indicate ? 40 c t j +125 c parameter condition min. typ. max. units supply voltage range 2.6 5.5 v under-voltage lockout threshold (turn-on) 2.4 2.5 2.6 v uvlo hysteresis 280 mv quiescent current, pwm mode v en 1.34v; v fb = 0.9v 1.2 2 ma shutdown current v en = 0v 3.7 10 a feedback voltage 2% (over temperature) 0.686 0.7 0.714 v oscillator frequency 0.8 1 1.2 mhz fb pin input current 1 na current limit v fb = 0.9*vnom 2 5.5 8 a output voltage line regulation v in = 2.6v to 5.5v 0.2 % output voltage load regulation 100ma < i load < 2a, v in = 3.3v 0.2 % maximum duty cycle vfb 0.5v 100 % switch on-resistance pfet switch on-resistance nfet i sw = 1000ma v fb =0.5v i sw = -1000ma v fb =0.9v 0.18 0.10 ? en/dly threshold voltage v in =3.3v 1.14 1.24 1.34 v en/dly hysteresis 12 mv delay threshold voltage v in =3.3v 1.14 1.24 1.34 v delay hysteresis 6 mv en/dly source current v in = 2.6 to v in = 5.5v 0.7 1 1.3 a rc source current ramp control current 0.7 1 1.3 a por ipg(leak) v porh = 5.5v; por = high 1 2 a por vpg(lo) output logic-low voltage (undervoltage condition), i por = 5ma 135 mv notes: 1. exceeding the absolute maximum rating may damage the device. 2. the device is not guaranteed to function outside its operating rating. 3. devices are esd sensitive. hand ling precautions recommended. human body model, 1.5k in series with 100pf. 4. specification for packaged product only.
micrel, inc. MIC22200 december 2010 4 m9999-120310-c electrical characteristics (4) (continued) t a = 25c with v in = v en = 3.3v, unless otherwise specified. bold values indicate ? 40 c t j +125 c parameter condition min. typ. max. units threshold, % of v out below nominal 7.5 10 12.5 % por vpg hysteresis 1 % over-temperature shutdown 160 c over-temperature shutdown hysteresis 25 c
micrel, inc. MIC22200 december 2010 5 m9999-120310-c typical characteristics 0 2 4 6 8 10 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) shutdown current vs. input voltage t a = 25c 0 2 4 6 8 10 02 55 07 5 100 125 temperature (c) shutdown current vs. temperature 1000 1100 1200 1300 1400 1500 1600 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) quiescent current vs. input voltage no switching fb = 0.9v t a = 25c 1000 1050 1100 1150 1200 1250 1300 02 55 07 5 100 125 temperature (c) quiscent current vs. temperature v in = 3.3v no switching fb = 0.9v t a = 25c 0.69 0.695 0.7 0.705 0.71 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) reference voltage vs. input voltage t a = 25c 0.69 0.695 0.7 0.705 0.71 02 55 07 5 100 125 temperature (c) reference voltage vs. temperature v in = 3.3v 1.1 1.14 1.18 1.22 1.26 1.3 02 55 07 5 100 125 temperature (c) v in = 3.3v enable voltage vs. temperature 8 9 10 11 12 13 14 15 16 02 55 07 5 100 125 temperature (c) enable hysterisis vs. temperature v in = 3.3v 950 975 1000 1025 1050 1075 1100 02 55 07 5 100 125 temperature (c) frequency vs. temperature c f = 220pf v in = 3.3v
micrel, inc. MIC22200 december 2010 6 m9999-120310-c typical characteristics (continued) 145 155 165 175 185 195 205 215 225 02 55 07 5 100 125 temperature (c) channel rdson vs. temperature 90 95 100 105 110 115 120 125 130 135 140 02 55 07 5 100 125 temperature (c) channel rdson vs. temperature 70 75 80 85 90 95 100 0 0.5 1 1.5 2 output current (a) efficiency vout=3.3v v in = 5v 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 50 cf capicitor (pf) frequency vs. cf 60 65 70 75 80 85 90 95 100 0 0.5 1 1.5 2 output current (a) efficiency vout=1.8v v in = 3.3v v in = 5.0v 60 65 70 75 80 85 90 95 100 0 0.5 1 1.5 2 output current (a) efficiency vout=1.2v v in = 3.3v v in = 5.0v
micrel, inc. MIC22200 december 2010 7 m9999-120310-c functional characteristics
micrel, inc. MIC22200 december 2010 8 m9999-120310-c functional diagram figure 1. MIC22200 functional diagram
micrel, inc. MIC22200 december 2010 9 m9999-120310-c functional description pvin, svin pvin is the input supply to the internal 180m ? p-channel power mosfet. th is should be connected externally to the svin pin. the supply voltage range is from 2.6v to 5.5v. a 10f ceramic is recommended for bypassing the pvin supply. en/dly this pin is internally fed with a 1a current source to vin. a delayed turn on is implemented by adding a capacitor to this pin. the delay is proportional to the capacitor value. the internal circuits are held off until en/dly reaches the enable threshold of 1.24v. rc rc allows the slew rate of the output voltage to be programmed by the addition of a capacitor from rc to ground. rc is internally fed with a 1a current source and v out slew rate is proportional to the capacitor and the 1a source. delay adding a capacitor to this pin allows the delay of the por signal. when v out reaches 90% of its nominal voltage, the delay pin current source (1a) starts to charge the external capacitor. at 1.24v , por is asserted high. comp the MIC22200 uses an internal compensation network containing a fixed-frequency zero (phase lead response) and pole (phase lag response) which allows the external compensation network to be mu ch simplified for stability. the addition of a single capacitor and resistor will add the necessary pole and zero for voltage mode loop stability using low-value, lo w-esr ceramic capacitors. fb the feedback pin provides the control path to control the output. a resistor divider connecting the feedback to the output is used to adjust the desired output voltage. refer to the feedback section in the applications information section for more detail. por this is an open drain output. a 47k resistor can be used for a pull up to this pin. por is asserted high when output voltage reaches 90% of nominal set voltage and after the delay set by c delay . por is asserted low without delay when enable is set low or when the output goes below the -10% threshold. for a power good (pg) function, the delay can be set to a minimum. this can be done by removing the delay pin capacitor. sw this is the connection to the drain of the internal p-channel mosfet and drain of the n-channel mosfet. this is a high-frequency, high-power connection; therefore traces should be kept as short and as wide as practical. cf adding a capacitor to this pin can adjust switching frequency from 800khz to 4mhz. the cf capacitor must be connected between the cf pin and power ground. sgnd internal signal ground for all low-power sections. pgnd internal ground connection to the source of the internal n-channel mosfets.
micrel, inc. MIC22200 december 2010 10 m9999-120310-c application information the MIC22200 is a 2a synchronous step-down regulator ic with an adjustable switching frequency from 800khz to 4mhz, voltage mode pwm control scheme. the other features include tracking and sequencing control for controlling multiple output power systems, por. component selection input capacitor a minimum 10f ceramic is recommended on each of the pvin pins for bypassing. x5r or x7r dielectrics are recommended for the input capacitor. y5v dielectrics, aside from losing most of their capacitance over temperature, they also be come resistive at high frequencies. this reduces their ability to filter out high- frequency noise. output capacitor the MIC22200 was designed spec ifically for the use of ceramic output capacitors and 22f is optimum output capacitor. 22f can be increased to 100f to improve transient performance. since the MIC22200 is in voltage mode, the control loop relies on the inductor and output capacitor for compensation. for this reason, do not use excessively large output capacitors. the output capacitor requires either an x7r or x5r dielectric. y5v and z5u dielectric capacitors, aside fr om the undesirable effect of their wide variation in capacitance over temperature, become resistive at high frequencies. using y5v or z5u capacitors can cause instability in the MIC22200. inductor selection inductor selection will be determined by the following (not necessarily in the order of importance): ? inductance ? rated current value ? size requirements ? dc resistance (dcr) the MIC22200 is designed for use with a 0.47h to 4.7h inductor. maximum current ratings of the inductor are generally given in two methods: permissible dc current and saturation current. permissible dc current can be rated either for a 40c temperature rise or a 10% loss in inductance. ensure the inductor selected can handle the maximum operating current. when saturation current is specified, make sure that there is enough margin that the peak current will not saturate the inductor. the ripple can add as much as 1.2a to the output current level. the rms rating should be chosen to be equal or greater than the current limit of the mi c22200 to prevent overheating in a fault condition. for best electrical performance, the inductor should be placed very close to the sw nodes of the ic. for this reason, the heat of the inductor is somewhat coupled to the ic, so it offers some level of protection if the inductor gets too hot. it is important to test all operating limits before settling on the final inductor choice. the size requirements refer to the area and height requirements that are necessary to fit a particular design. please refer to the inductor dimensions on their datasheet. dc resistance is also important. while dcr is inversely proportional to size, dcr can represent a significant efficiency loss. refer to the efficiency considerations below for a more detailed description. en/dly capacitor en/dly pin sources 1a out of the ic to allow a startup delay to be implemented. the delay time is simply the time it takes 1a to charge c en/dly to 1.25v. therefore: 6 1.10 c1.24 t en/dly en/dly ? = cf capacitor adding a capacitor to this pin can adjust switching frequency from 800khz to 4mhz. cf sources 400a out of the ic to charge the cf capacitor to set up the switching frequency. the switch period is simply the time it takes 400a to charge cf to 1.0v (2%). therefore: capacitor cf frequency 56pf 4.4mhz 68pf 4mhz 82pf 3.4mhz 100pf 2.8mhz 150pf 2.1mhz 180pf 1.7mhz 220pf 1.4mhz 270pf 1.2mhz 330pf 1.1mhz 390pf 1.05mhz 470pf 1mhz table 1. cf vs. frequency it is necessary to connect the cf capacitor between the cf pin and power ground.
micrel, inc. MIC22200 december 2010 11 m9999-120310-c efficiency considerations efficiency is defined as the amount of useful output power, divided by the amount of power consumed: 100 iv iv % efficiency inin out out ? ? ? ? ? ? = maintaining high efficiency serves two purposes. it decreases power dissipation in the power supply, reducing the need for heat sinks and thermal design considerations and it decreas es consumption of current for battery-powered applications. reduced current draw from a battery increases the devices operating time, critical in hand held devices. there are mainly two loss terms in switching converters: static losses and switching losses. static losses are simply the power losses due to vi or i 2 r. for example, power is dissipated in the high-side switch during the on cycle. power loss is equal to the high-side mosfet rds(on) multiplied by the rms switch current squared (isw 2 ). during the off cycle, the low-side n-channel mosfet conducts, also dissipating power. similarly, the inductor?s dcr and capacitor?s esr also contribute to the i 2 r losses. device operating current also reduces efficiency by the product of the quiescent (operating) current and the supply voltage. the current required to drive the gates on and in the frequency range from 800khz to 4mhz and the switching transitions make up the switching losses. figure 2 shows an efficiency curve. the portion, from 0a to 0.2a, efficiency losses are dominated by quiescent current losses, gate drive and transition losses. in this case, lower supply voltages yield greater efficiency in that they require less current to drive the mosfets and have reduced input power consumption. figure 2. efficiency curve the region, 0.2a to 2a, efficiency loss is dominated by mosfet rdson and inductor dc losses. higher input supply voltages will increase the gate-to-source voltage on the internal mosfets, reducing the internal rdson. this improves efficiency by reducing dc losses in the device. all but the inductor losses are inherent to the device. in which case, inductor selection becomes increasingly critical in efficiency calculations. as the inductors are reduced in si ze, the dc resistance (dcr) can become quite significant. the dcr losses can be calculated as follows: dcr il 2 out pd = from that, the loss in efficiency due to inductor resistance can be calculated as follows: () 100 li v iv 1% efficiency pd out out out out ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ?= efficiency loss due to dcr is minimal at light loads and gains significance as the load is increased. inductor selection becomes a trade-o ff between efficiency and size in this case. alternatively, under lighter loads, the ripple current due to the inductance becomes a significant factor. when light load efficiencies become more critical, a larger inductor value may be desired. larger inductances reduce the peak-to-peak inductor ripple current, which minimize losses. the following graph in figure 3 illustrates the effects of inductance value at light load: 76 78 80 82 84 86 88 90 92 94 0 0.2 0.4 0.6 0.8 1 1.2 output current (a) efficiency vs. inductance 1h 4.7h figure 3. efficiency vs. inductance
micrel, inc. MIC22200 december 2010 12 m9999-120310-c compensation the MIC22200 has a combination of internal and external stability compensation to simplify the circuit for small, high efficiency designs. in such designs, voltage mode conversion is often the optimum solution. voltage mode is achieved by creating an internal 1mhz ramp signal and using the output of the error amplifier to modulate the pulse width of the switch node, thereby maintaining output voltage regulation. with a typical gain bandwidth of 100 ? 200khz, the MIC22200 is capable of extremely fast transient responses. the MIC22200 is designed to be stable with a typical application using a 1h inductor and a 47f ceramic (x5r) output capacitor. these values can be varied dependant upon the tradeoff between size, cost and efficiency, keeping the lc natural frequency ( ( ) cl 2 1 ) ideally less than 26khz to ensure stability can be achieved. the minimum recommended inductor value is 0.47h and minimum recommended output capacitor value is 22f. the tradeoff between changing these values is that with a larger inductor, there is a reduced peak-to-peak current which yields a greater efficiency at lighter loads. a larger output capacitor will improve transient response by providing a larger hold up reservoir of energy to the output. the integration of one pole-zero pair within the control loop greatly simplifies compensation. the optimum values for c comp (in series with a 20k resistor) are shown in table 2: c ? l 22-47f 47f- 100f 100f- 470f 0.47h 0*-10pf 22pf 33pf 1h 0 ? -15pf 15-22pf 33pf 2.2h 15-33pf 33-47pf 100-220pf * vout > 1.2v, ? vout > 1v table 2. compensation capacitor selection note : for compensation values for various output voltages and inductor values refer to table 4. feedback the MIC22200 provides a feedback pin to adjust the output voltage to the desired level. this pin connects internally to an error amplifier. the error amplifier then compares the voltage at the feedback to the internal 0.7v reference voltage and adjusts the output voltage to maintain regulation. the resistor divider network for a desired v out is given by: ? ? ? ? ? ? ? = 1 v v r1 r2 ref out where v ref is 0.7v and v out is the desired output voltage. a 10k ? or lower resistor value from the output to the feedback is recommended since large feedback resistor values increase the impedance at the feedback pin, making the feedback node more susceptible to noise pick-up. a small capacitor (50pf ? 100pf) across the lower resistor can reduce noise pick-up by providing a low impedance path to ground. pwm operation the MIC22200 is a voltage-mode, pulse-width modulation (pwm) controller. by controlling the ratio of on-to-off time, or duty cycle, a regulated dc output voltage is achieved. as load or supply voltage changes, so does the duty cycle to maintain a constant output voltage. in cases where the input supply runs into a dropout condition, the mic 22200 will run at 100% duty cycle. the MIC22200 provides constant switching from 800khz to 4mhz with synchronous internal mosfets. the internal mosfets include a 180m ? high-side p- channel mosfet from the input supply to the switch pin and a 100m ? n-channel mosfet from the switch pin- to-ground. since the low-side n-channel mosfet provides the current during the off cycle, a freewheeling schottky diode from the switch node-to-ground is not required. pwm control provides fixed-frequency operation. by maintaining a constant switching frequency, predictable fundamental and harmonic frequencies are achieved. other methods of regulation, such as burst and skip modes, have frequency spectrums that change with load that can interfere with sensitive communication equipment. sequencing and tracking the MIC22200 provides additional pins to provide up/down sequencing and tracking capability for connecting multiple voltage regulators together. en/dly pin the en/dly pin contains a trimmed, 1a current source which can be used with a capacitor to implement a fixed desired delay in some sequenced power systems. the threshold level for power on is 1.24v with a hysteresis of 20mv.
micrel, inc. MIC22200 december 2010 13 m9999-120310-c delay pin the delay pin also has a 1a trimmed current source and a 1a current sink which acts with an external capacitor to delay the operation of the por output. this can be used also in sequencing outputs in a sequenced system, but with the addition of a conditional delay between supplies; allowing a first up, last down power sequence. after en/dly pin is driven high, v out will start to rise (rate determined by rc capacitor). as the fb voltage goes above 90% of its nominal set voltage, delay pin begins to rise as the 1a source charges the external capacitor. when the threshold of 1.24v is crossed, por is asserted high and delay pin continues to charge to a voltage v dd . when fb falls below 90% of nominal, por is asserted low immediately. however, if en/dly pin is driven low, por will fall immediately to the low state and delay pin will begin to fall as the external capacitor is discharged by the 1a current sink. when the threshold of v dd -1.24v is crossed, v out will begin to fall at a rate determined by the rc capacitor. as the voltage change in both cases is 1.24v, both rising and falling delays are matched at 6 1.10 c1.24 t delay por ? = . rc pin the rc pin provides a trimmed 1a current source/sink similar to the delay pin for ac curate ramp up (soft start) and ramp down control. this allows the MIC22200 to be used in systems requiring voltage tracking or ratio-metric voltage tracking at startup. there are two ways of using the rc pin: ? externally driven from a voltage source ? externally attached capacitor sets output ramp up/down rate in the first case, driving rc with a voltage from 0v to v ref will program the output voltage between 0 and 100% of the nominal set voltage. in the second case, the external capacitor sets the ramp up and ramp down time of the output voltage. the time is given by 6 1.10 c0.7 t rc ramp ? = where t ramp is the time from 0 to 100% nominal output voltage. sequencing and tracking examples there are four distinct variations which are easily implemented using the MIC22200. the two sequencing variations are windowed and delayed. the two tracking variants are normal and ratio metric. figures 5 thru 10 illustrate methods for connecting two MIC22200?s to achieve these requirements. sequencing : figure 4. sequencing MIC22200 circuit figure 5. window sequencing example figure 6. delayed sequencing example
micrel, inc. MIC22200 december 2010 14 m9999-120310-c normal tracking : figure 7. normal tracking circuit figure 8. normal tracking example radio metric tracking : figure 9. radio metric tracking circuit figure 10. radio metric tracking example
micrel, inc. MIC22200 december 2010 15 m9999-120310-c an alternative method here shows an example of a v ddq and v tt solution for a ddr memory power supply. note that por is taken from vo1 as por2 will not go high. this is because por is set high when fb > 0.9 ? v ref . in this example, fb2 is regulated to ? ? v ref . figure 11. ddr memory tracking circuit figure 12. ddr memory tracking example current limit the MIC22200 is protected against overload in two stages. the first is to limit the current in the p-channel switch; the second is over temperature shutdown. current is limited by measuring the current through the high-side mosfet during its power stroke and immediately switching off the driver when the preset limit is exceeded. figure 13 describes the operat ion of the current-limit circuit. since the actual rdson of the p-channel mosfet varies part-to-part, over temperature and with input voltage, simple ir voltage detection is not employed. instead, a smaller copy of the power mosfet (reference fet) is fed with a constant current which is a directly proportional to the factory set current limit. this sets the current limit as a current ratio and thus, is not dependant upon the rdson value. current limit is set to 5.5a nominal. variations in the scale factor k between the power pfet and the reference pfet used to generate the limit threshold account for a relatively small inaccuracy. figure 13. current-limit detail thermal considerations the MIC22200 is packaged in the mlf ? 3mm x 3mm, a package that has excellent thermal performance equaling that of the larger tssop packages. this maximizes heat transfer from the junction to the exposed pad (epad) which connects to the ground plane. the size of the ground plane attached to the exposed pad determines the overall thermal resistance from the junction to the ambient air surrounding the printed circuit board. the junction temperature for a given ambient temperature can be calculated using: ja daj r ptt + = where: p d is the power dissipated within the mlf ? package and is typically 0.8w at 2a for v in = 5v and v out = 1.8v load. this has been calculated for a 1h inductor and details can be found in table 3.
micrel, inc. MIC22200 december 2010 16 m9999-120310-c r ja is a combination of junction-to-case thermal resistance (r jc ) and case-to-ambient thermal resistance (r ca ), since thermal resistance of the solder connection from the epad to the pcb is negligible; r ca is the thermal resistance of the ground plane to ambient, so r ja = r jc + r ca . t a is the operating ambient temperature. example: to calculate the junction temperature for a 50c ambient: t j = t a + p di . r ja t j = 50 + 0.8 x 40 t j = 82c vout @2a vin 3v vin 3.5v vin 4v vin 4.5v vin 5v 1 0.86822 0.81512 0. 7836 0.77014 0.76194 1.2 0.87796 0.8247 0. 79362 0.77956 0.76842 1.8 0.93972 0.86722 0. 82568 0.8095 0.80076 2.5 0.91848 0.90504 0. 85466 0.83296 0.81846 3.3 ? ? 0.8764 0.842 0.8326 this is below the maximum of 125c. table 3. power dissipation (w) for 2a output v in = 5v v out l c out c comp r comp c ff r ff c fb r fb 1.1v 3.3h 2 x 47f 100pf 5k ? n.u. 4.7k ? 100pf 8.2k ? 1.3v 1.5h 2 x 47f 100pf 5k ? 1nf 4.7k ? 100pf 5.49k ? 1.8v 2.2h 2 x 47f 100pf 5k ? 1nf 4.7k ? 100pf 3.0k ? 4.2v 1.5h 2 x 47f 100pf 20k ? 1nf 4.7k ? 100pf 953 ? table 4. compensation selection figure 14. table 4 schematic reference
micrel, inc. MIC22200 december 2010 17 m9999-120310-c design example MIC22200yml evaluation board schematic bill of materials item part number manufacturer description qty. c2012x5r0j106k tdk (1) grm2196r60j106k murata (2) c1 08056d106kat2a avx (3) capacitor, 10f, 6.3v, x5r, size 0805 1 c1608x5r0j105k tdk (1) grm188r60j105ka01d murata (2) c2 06036d105kat2a avx (3) capacitor, 1f, 6.3v, x5r, size 0603 1 c1608c0g1h102j tdk (1) grm1885c1h102ja01d murata (2) c3, c7, c8 06035a102kat2a avx (3) capacitor, 1nf, 50v, npo, size 0603 3 c1608x7r1h332k tdk (1) grm188r71h332ka01d murata (2) c4 06035c332kat2a avx (3) capacitor, 3.3nf, 50v, x7r, size 0603 1 c1608c0g1h470j tdk (1) gqm1885c1h470jb01d murata (2) c5 06035a470jat2a avx (3) capacitor, 47pf, 50v, npo, size 0603 1 c1608c0g1h221j tdk (1) grm1885c1h221ja01d murata (2) c6 06035a221jat2a avx (3) capacitor, 220pf, 50v, npo, size 0603 1 notes: 1. tdk: www.tdk.com . 2. murata: www.murata.com . 3. avx: www.avx.com . 4. vishay: www.vishay.com 5. micrel, inc.: www.micrel.com .
micrel, inc. MIC22200 december 2010 18 m9999-120310-c bill of materials (continued) item part number manufacturer description qty. c3216x5r0j476m tdk (1) grm31cr60j476me19l murata (2) c9, c10 1206d476mat2a avx (3) capacitor, 47f, 6.3v, x5r, size 1206 2 c1608c0g1h101j tdk (1) grm1885c1h101ja01d murata (2) c11 06035a101jat2a avx (3) capacitor, 100pf, 50v, npo size 0603 1 l1 ihlp1616bzer1r0m11 vishay (4) inductor , 1h, 5a 1 r1 crcw06031602fkea avx (3) resistor, 16k, 1%, size 0603 1 r2, r3 crcw06031002fkea avx (3) resistor, 10k, 1%, size 0603 2 r4 crcw060320k0fkea avx (3) resistor, 20k, 1%, size 0603 1 r5 crcw06032r20fkea avx (3) resistor, 2.2 ? , 1%, size 0603 1 r6 crcw060349r9fkea avx (3) resistor, 49.9 ? , 1%, size 0603 1 u1 MIC22200yml micrel (5) integrated 2a synchronous buck regulator 1 notes: 1. tdk: www.tdk.com . 2. murata: www.murata.com . 3. avx: www.avx.com . 4. vishay: www.vishay.com 5. micrel, inc.: www.micrel.com .
micrel, inc. MIC22200 december 2010 19 m9999-120310-c pcb layout recommendations top silk top layer
micrel, inc. MIC22200 december 2010 20 m9999-120310-c pcb layout recommendations (continued) bottom layer
micrel, inc. MIC22200 december 2010 21 m9999-120310-c package information 12-pin mlf ? (ml)
micrel, inc. MIC22200 december 2010 22 m9999-120310-c recommended land pattern fo r 32-pin 3mm x 3mm mlf? 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 micrel makes no representations or warranties with respect to the accuracy or comple teness of the information furnished in this data sheet. this information is not intended as a warranty and micrel does not assume responsibility for it s use. micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. no license, whether express, implied, arising by estoppel or other wise, to any intellectual property rights is granted by this document. except as provided in micrel?s terms and conditions of sale for such products, mi crel assumes no liability whatsoever, and micrel disclaims any express or implied warranty relating to the sale and/or use of micrel products including l iability or warranties relating to fitness for a particular purpose, merchantability, or infringement of an y patent, copyright or other intellectual p roperty right. micrel products are not designed or authorized for use as components in life suppor t appliances, devices or systems where malfu nction of a product reasonably be expected to result in pers onal injury. life support devices or system s are devices or systems that (a) are intended for surgical impla into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant 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 re sulting from such use or sale. can nt ? 2008 micrel, incorporated.

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