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mic68400 4a sequencing ldo with tracking and ramp control? ramp control is a trademark of micrel, inc. mlf and micro leadframe is a registered trademark 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 june 2007 m9999-061907-b general description the mic68400 is a high peak current ldo regulator designed specifically for powering applications such as fpga core voltages that requi re high start up current with lower nominal operating current. capable of sourcing 4a of current for start-up, the mi c68400 provides high power from a small mlf ? leadless package. the mic68400 can also implement a variety of power-up and power-down protocols such as sequencing, tracking, and ratiometric tracking. the mic68400 operates from a wide input range of 1.65v to 5.5v, which includes all of the main supply voltages commonly available today. it is designed to drive digital circuits requiring low voltage at high currents (i.e. plds, dsp, microcontroller, etc.). the mic68400 incorporates a delay pin (delay) for control of power on reset output (por) at turn-on and power- down delay at turn-off. in addition there is a ramp control pin (rc) for either tracking applications or output voltage slew rate adjustment at turn- on and turn-off. this is important in applications where the load is highly capacitive and in-rush currents can cause supply voltages to fail and microprocessors or other complex logic chips to hang up. multiple mic68400s can be daisy chained in two modes. in tracking mode the output voltage of the master drives the rc pin of a slave so that the slave tracks the main regulator during turn-on and turn-off. in sequencing mode the por of the master drives the enable (en) of the slave so that it turns on after the master and turns off before (or after) the master. this behavior is critical for power-up and power-down control in multi- output power supplies. the mic68400 is fully protected offering both thermal, current limit protection, and reverse current protection. the mic68400 has a junction temperature range of ?40c to +125c and is available in fixed as well as an adjustable option. the mic68400 is offered in the tiny 16-pin 4mm x 4mm mlf ? package. features ? stable with 10f ceramic capacitor ? input voltage range: 1.65v to 5.5v ? 0.5v reference ? 2.0% output tolerance over temperature ? 4a maximum output current ? peak start up ? 3a continuous operating current ? tracking on turn-on and turn-off with pin strapping ? timing controlled sequencing on/off ? programmable ramp control? for in-rush current limiting and slew rate control of the output voltage during turn-on and turn-off ? power-on reset (por) supervisor with programmable delay time ? single master can control multiple slave regulators with tracking output voltages ? tiny 4mm x 4mm mlf ? package ? maximum dropout (v in ? v out ) of 500mv over temperature at 3a output current ? fixed and adjustable output voltages ? excellent line and load regulation specifications ? logic controlled shutdown ? thermal shutdown and current limit protection applications ? fpga/pld power supply ? networking/telecom equipment ? microprocessor core voltage ? high efficiency linear post regulator ? sequenced or tracked power supply
micrel, inc. mic68400 june 2007 2 m9999-061907-b typical application sequenced dual power supply for i/o and core voltage of processor
micrel, inc. mic68400 june 2007 3 m9999-061907-b tracking dual power supply for i/o and core voltage of processor
micrel, inc. mic68400 june 2007 4 m9999-061907-b block diagram bandgap reference output error holdoff thermal shutdown low voltage holdoff sequencing timer/controller bgstart bgdis ramp control rcdis in rc en dly bgstart: bandgap startup bgdis: bandgap shutdown rcdis: ramp control discharge gnd por sns out rc buffer error amp current driver current limit external on adjustable part amp min ordering information part number output current voltage junction temperature range package mic68400-1.8yml 4.0a 1.8v ?40c to +125c pb-free 16-pin 4x4 mlf ? mic68400yml 4.0a adj ?40c to +125c pb-free 16-pin 4x4 mlf ? note: for additional voltage options, c ontact micrel marketing.
micrel, inc. mic68400 june 2007 5 m9999-061907-b pin configuration 16-pin 4mm 4mm mlf ? (ml) fixed voltages 16-pin 4mm 4mm mlf ? (ml) adjustable voltages pin description (pin numbering may change depending on layout considerations) pin number mic68400yml pin name pin function 1, 2, 15, 16 vin input: input voltage supply pin. place a capacitor to ground to bypass the input supply. 3 delay delay: capacitor to ground sets internal delay timer. timer delays power-on reset (por) output at turn-on, and ramp down at turn-off. 4 rc ramp control: may be voltage driven for tracking applications or a capacitor to ground will set the slew rate of output voltage during start-up. 5 en enable (input): cmos compatible input. logic high = enable, logic low = shutdown. 6, 14 nc not internally connected. 7, 8, tab gnd ground. 9 por power-on reset: open-drain output device indicates when the output is in regulation. high (open) means device is regulating within 10%. por onset can be delayed using a single capacitor from delay to ground. 10 (fixed) sns output voltage sense pi n: connect directly to output pin. 10 (adj) adj adjustable regulators: feedback input. connect to resistor voltage divider. 11, 12, 13 vout output voltage: output of voltage re gulator. place capacitor to ground to bypass the output voltage. minimum load current is 100a. nominal bypass capacitor is 10f.
micrel, inc. mic68400 june 2007 6 m9999-061907-b absolute maximum ratings (1) supply voltage (v in ) .........................................................6v enable input voltage (v en )...............................................6v por (v por )........................................................... v in + 0.3v rc ....................................................................... v in + 0.3v power dissipation .................................. in ternally limited (3) junction temper ature .........................?40c t j +125c storage temperature (t s )...................?65c t j +150c esd rating (4) ................................................................. 2kv operating ratings (2) supply voltage (v in ) ....................................... 1.65v to 5.5v enable input voltage (v en )..................................... 0v to v in ramp control (v rc )............................................. 0v to 5.5v junction temperat ure ran ge ............?40c t j +125c package thermal resistance 4x4 mlf-16 ( ja ) ..............................................30c/w electrical characteristics (5) t a = 25c with v in = v out + 1v; v en = v in ; i out = 10ma; bold values indicate ?40c t j +125c, unless noted. parameter conditions min typ max units output voltage accuracy 10ma < i out < i l(max) , v out + 1 v in 5.5v -2 +2 % feedback voltage adjustable version only 0.49 0.50 0.51 v feedback current adjustable version only 20 na output voltage line regulation v in = v out + 1v to 5.0v 0.06 0.5 % output voltage load regulation i l = 10ma to 3a 0.5 1 % v in ? v o ; dropout voltage i l = 1.5a i l = 3.0a i l = 4.0a 300 360 400 500 800 mv mv mv ground pin current i l = 10ma i l = 1.5a i l = 3.0a i l = 4.0a 1.2 20 55 90 130 ma ma ma ma shutdown current v en = 0v; v out = 0v 0.01 10 a current limit v out = 0v; v in = 3.0v 4.0 6.0 a start-up time v en = v in ; c rc = open 35 150 s enable input enable input threshold regulator enable regulator shutdown 1 0.2 v v enable hysteresis 20 120 200 mv enable input current v il 0.2v (regulator shutdown) v ih 1v (regulator enable) 0.02 3 a a por output i por(leak) v por = 5.5v; por = high 1 2 a a v por(lo) output logic-low voltage (undervoltage condition), i por = 1ma 60 90 mv 7.5 10 12.5 % threshold, % of v out below nominal 10 12.5 15 % v por : v out ramping up v out ramping down hysteresis 3 % delay current v delay = 0.75v 0.7 1 1.3 a delay voltage ( note 6 ) v por = high 1.185 1.235 1.285 v
micrel, inc. mic68400 june 2007 7 m9999-061907-b parameter conditions min typ max units ramp control i rc ramp control current (v rc = 0.75v) 0.7 1 1.3 a i discharge(output) ( note 7 ) v out = 0.5v nom , v ramp =0v 25 45 70 ma tracking accuracy: fixed ( note 8 ) 200mv < v rc < v target ; measure (vout ? v rc ) -50 25 100 mv tracking accuracy: adjustable ( note 8 ) measure (vout - v rc x (v target / 500mv)) -10 15 50 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. the maximum allowable power dissipation of any t a (ambient temperature) is p d(max) = t j(max) ? t a ) / ja . exceeding the maximum allowable power dissipation will result in excessive die te mperature, and the regulator will go into thermal shutdown. 4. devices are esd sensitive. handl ing precautions recommended. human body model, 1.5k in series with 100pf. 5. specification for packaged product only. 6. timer high voltage along with delay pin current (1a nom) det ermines the delay per f of capacitance. typical delay is 1. 1sec/f. 7. discharge current is the current drawn from the output to ground to actively discharge the output capacitor during the shut down process. 8. v target is the output voltage of an adjustable with cu stomer resistor divider installed between v out and adj/sns pin, or the rated output voltage of a fixed device.
micrel, inc. mic68400 june 2007 8 m9999-061907-b typical characteristics
micrel, inc. mic68400 june 2007 9 m9999-061907-b functional characteristics
micrel, inc. mic68400 june 2007 10 m9999-061907-b applications information enable input the mic68400 features a ttl/cmos compatible positive logic enable input for on/off control of the device. high (>1v) enables the regulator while low (<.2v) disables the regulator. in shutdown the regulator consumes very little current (only a few microamperes of leakage). fo r simple applications the enable (en) can be connected to v in (in). while mic68400 only requires a few a?s of enable current to turn on, actual enable pin current will depend on the overdrive (enable voltage exceeding 1v) in each particular application. control logic high > 1v enable connections for logic driven input enable connection for v in -driven and/or slow rise-time inputs input capacitor an input capacitor of 0.1f or greater is recommended when the device is more than 4 inches away from the bulk supply capacitance, or when the supply is a battery. small, surface mount chip capac- itors can be used for the bypassing. the capacitor should be place within 1 inch of the device for optimal performance. larger values will help to improve ripple rejection by bypassing the regulator input, further improving the integrity of the output voltage. output capacitor the mic68400 requires an output capacitor for stable operation. as a cap ld o, the mic68220 can operate with ceramic output capacitors of 10f or greater with esr?s ranging from a 3m ? to over 300m ? . values of greater than 10f improve trans- ient response and noise r eduction at high frequency. x7r/x5r dielectric-type ceramic capacitors are recommended because of their superior temperature performance. x7r-type capacitors change capaci- tance by 15% over their operating temperature range and are the most stable type of ceramic capacitors. larger output capacitances can be achieved by placing tantalum or aluminum electrolytics in parallel with the ceramic capacitor. for example, a 100f electrolytic in parallel with a 10f ceramic can provide the transient and high frequency noise performance of a 100f ceramic at a significantly lower cost. specific undershoot/overshoot performance will depend on both the values and esr/esl of the capacitors.
micrel, inc. mic68400 june 2007 11 m9999-061907-b adjustable regulator design adjustable regulator with resistors the adjustable mic68400 output voltage can be programmed from 0.5v to 5.5v using a resistor divider from output to the sns pin. resistors can be quite large, up to 1m ? because of the very high input impedance and low bias current of the sense amplifier. typical sense input currents are less than 30na which causes less than 0.3% error with r1 and r2 less than or equal to 100k ? . for large value resistors (>50k ? ) r1 should be bypassed by a small capacitor (c ff = 0.1f bypass capacitor) to avoid instability due to phase la g at the adj/sns input. the output resistor divider values are calculated by: ? ? ? ? ? ? + = 1 r2 r1 0.5v v out power on reset (por) and delay (dly) the power-on reset output (por) is an open-drain n-channel device requiring a pull-up resistor to either the input voltage or output voltage for proper voltage levels. por is driven by the internal timer so that the release of por at turn-on can be delayed for as much as 1 second. por is always pulled low when enable (en) is pulled low or the output goes out of regulation by more than 10% due to loading conditions. the internal timer is controlled by the dly pin which has a bidirectional current source and two limiting comparators. a capacitor connected from dly to gnd sets the delay time for two functions. on start up, dly sets the time from the nominal output voltage is reached to the release of the por. at shut down, the delay sets the time fr om disable (en pin driven low) to actual ramp down of the output voltage. the current source is 1a, which charges the capacitor from ~150mv (nominal disabled dly voltage) to ~1.25v. at turn on, the dly cap begins to charge when the output voltage reaches 90% of the target value. when the capacitor reaches 1.25v, the output of the por is released to go high. at turn off, the dly cap begins to discharge when the en is driven low. when the cap reaches ~150mv the output is ramped down. both delays are nominally the same, and are calculated by the same formula: () ? ? ? ? ? ? ? ? = a 1 c 1.1 t dly dly scale factor is: 1.1 seconds/microfarad, 1.1 milliseconds/nanofarad, or 1.1 microseconds/picofarad. t dlyoff is the time from lowering of en to the start of ramp down on the off cycle. t por is the time from the rising of en to the release (low to high edge) of the por. this behavior means that a p or other complex logic system is guaranteed that the nominal output voltage is stable for a known time before the por is released, and they are further guaranteed that once por is pulled low, they have a known time to ?tidy up? memory or other registers for a well controlled shutdown. in master/slave configurations the timers can be used to assure that the master is always accurately regulating when the slave is on. ramp control the ramp control (rc) has a bidirectional current source and a sense amplifier, which together are used to control the voltage at the output. when rc is below the target voltage (nominal output voltage for fixed voltage parts, 0.5v for ad justable parts) the rc pin controls the output voltage. when rc is at or above the target voltage, the ou tput is controlled by the internal regulator. tracking applications: driving rc from a voltage source fixed parts: if rc is driven from another (master) regulator the two outputs will track each other until the master exceeds the target voltage of the slave regulator. typically the out put of the mic68400 will track above the rc input by 30mv to 70mv. this offset is designed to allow master/slave tracking of same-voltage regulators. wi thout the offset, same- voltage master/slave configurations could suffer poor regulation. adjustable parts: the rc pi n on adjustable versions operates from 0v to 0.5v. to implement tracking on an adjustable version, an external resistor divider must be used. this divider is the nearly same ratio as the voltage setting divider used to drive the sense/adjustable pin. it is recommended that the ratio be adjusted to track ~50mv (2% to 3%) above the target voltage if the master and slave are operating at the same target voltage.
micrel, inc. mic68400 june 2007 12 m9999-061907-b ramp up: cap controlled slew rate if a capacitor is connected to rc, the bidirectional current source will charge the cap during startup and discharge the cap during shutdown. the size of the capacitor and the rc current (1a nom) control the slew rate of the output voltage during startup. for example, to ramp up a 1.8v regulator from zero to full output in 10msec requires a 5.6nf capacitor. for fixed versions: ? ? ? ? ? ? ? ? = a 1 c v t rc out rc ? ? ? ? ? ? ? ? = rc on c a 1 sr similarly, to slew an adjus table (any output voltage) from 0 to full output in 10msec requires a 20nf cap. for adjustable versions: ? ? ? ? ? ? ? ? = a 1 c v 5 . 0 t rc rc ? ? ? ? ? ? ? ? = rc out on c a 1 2v sr ramp down: turn off slew rate when en is lowered and the dly pin has discharged, the rc pin and the out pin slew toward zero. for fixed voltage devices, the rc pin slew rate is 2 to 3 times the sr on defined above. for adjustable voltage devices the rc pin slew is much higher. in both cases, turn off slew rate may be determined by the rc pin for low values of output capacitor, or by the maximum discharge current available at the output for large values of output capaci tor. turn off slew rate is not a specified characteristic of the mic68400. sequencing configurations sequencing refers to timing based master/slave control between regulators. it allows a master device to control the start and st op timing of a single or multiple slave devices. in typical sequencing the master por drives the slave en. the sequence begins with the master en driven high. the master output ramps up and triggers the master dly when the master output reaches 90%. the master dly then determines when the por is released to enable the slave device. when the master en is driven low, the master por is immediately pulled low causing the slave to ramp down. however, the master output will not ramp down until the master dly has fully discharged. in this way, the master power can remain good after the slave has been ramped down. in sequencing configurations the master dly controls the turn-on time of the slave and the slave dly controls the turn-off time of the slave. sequencing connections cdlys > cdlym [cdlys=2nf; cdlym=1nf] delayed sequencing cdlys < cdlym [cdlys=1nf; cdlym=2nf] windowed sequencing
micrel, inc. mic68400 june 2007 13 m9999-061907-b tracking configurations normal tracking in normal tracking the slave rc pin is driven from the master output. the internal control buffering assures that the output of the slav e is always slightly above the master to guarantee that the slave properly regulates (based on its own internal reference) if master and slave are both fi xed voltage devices of the same output voltage. the schematic and plot below show a 1.2 volt device tracking a 1.8 volt device through the entire turn-on / turn-off sequence. note that since the rc pin will ov erdrive the target voltage (to assure proper regulation) the ramp down delay is longer than the por delay during turn-on. fixed voltage devices fixed voltage versions of mic68400 have two internal voltage dividers: one for setting the output voltage and the other for driving the tracking circuitry. adjustable parts have up to two external dividers: one from output to sns (to set the output voltage) and one from the output to the slave rc pin (in tracking configurations). also, the rc pin in fixed parts operates at the same voltage as the output, whereas the rc pin in adjustable parts operates at the 0.5v reference. to setup a normal tracking configuration, the divider driving the slave rc pin is the same ratio (or nearly the same ? if both master and slave are set to the same output voltage, the slave rc divider should be adjusted 2% to 4% higher) as the divider driving the slave sns pin. this is shown below. adjustable voltage devices
micrel, inc. mic68400 june 2007 14 m9999-061907-b ratiometric tracking ratiometric tracking allows independent ramping speeds for both regulators so that the regulation voltage is reached at the same time. this is accomplished by adding a resistor divider between the master output pin and the slave rc pin. the divider should be scaled such that the slave rc pin reaches or exceeds the target output voltage of the slave as the master reaches its target voltage. fixed voltage devices ratiometric tracking may be used with adjustable parts by simply connecting the rc pins of the master and slave. use a single rc capacitor of twice the normal value (since twice the current is injected into the single rc cap). alternatively, fixed parts may use ratiometric tracking in a manner similar to adjustable normal tracking, with the tracking divider changed to the same resistor ratio driving the master adj/sns pin. adjustable voltage devices final note on tracking the mic68400 does not fully shutdown unt il the output load is discharged to near zero. if rc is driven from an external source in a tracking configurat ion, and the external source does not go to zero on shutdown it may prevent complete shutdown of the mic68400. this will cause no damage, but some q current will rema in and may cause concern in battery operated portable eq uipment. also, when rc is driven in tracking mode, pulling en low will not cause the output to drop. maintainin g low en in tracking mode simply mean s that the mic68400 will shutdown when the tracking voltage gets near zero. in no case can the mi c68400 enter the tracking mode unless en is pulled high.
micrel, inc. mic68400 june 2007 15 m9999-061907-b package information 16-pin 4mm x 4mm mlf (ml) 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 personal injury. life suppo rt devices or systems are devic es 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 re sulting from such use or sale. ? 2007 micrel, incorporated.

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