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august 2005 1 mic5156/5157/5158 mic5156/5157/5158 micrel, inc. mic5156/5157/5158 super ldo? regulator controller either 3.3v, 5.0v, or 12v. the mic5158 can be con?gured as a ?xed 5v controller or programmed to any voltage from 1.3v to 36v using two external resistors. the mic5156 is available in an 8-pin dip or soic. the mic5157 and mic5158 are available in a 14-pin dip or soic which operate from C40c to +85c. features ? 4.5ma typical operating current ? <1a typical standby current ? low external parts count ? optional current limit (35mv typical threshold) ? 1% initial output voltage tolerance in most con?gurations ? 2% output voltage tolerance over temperature ? fixed output voltages of 3.3v, 5.0v (mic5156) ? fixed output voltages of 3.3v, 5.0v, 12v (mic5157) ? programmable (1.3 to 36v) with 2 resistors (mic5156/8) ? internal charge pump voltage tripler (mic5157/8) ? enable pin to activate or shutdown the regulator ? internal gate-to-source protective clamp ? all versions available in dip and soic applications ? ultrahigh current ultralow dropout voltage regulator ? constant high-current source ? low parts count 5.0v to 3.3v computer supply ? low noise/low-dropout smps post regulator ? high-current, current-limited switch 10a 5v to 3.3v desktop computer regulator general description the mic5156, mic5157, and mic5158 super low-dropout (ldo) regulator controllers are single ic solutions for high- current low-dropout linear voltage regulation. super ldo? regulators have the advantages of an external n-channel power mosfet as the linear pass element. the mic5156/7/8 family features a dropout voltage as low as the r ds(on) of the external power mosfet multiplied by the output current. the output current can be as high as the largest mosfets can provide. the mic5156/7/8 family operates from 3v to 36v. the mic5156 requires an external gate drive supply to provide the higher voltage needed to drive the gate of the external mosfet. the mic5157 and mic5158 each have an inter - nal charge pump tripler to produce the gate drive voltage. the tripler is capable of providing enough voltage to drive a logic-level mosfet to 3.3v output from a 3.5v supply and is clamped to 17.5v above the supply voltage. the tripler requires three external capacitors. the regulator output is constant-current limited when the controller detects 35mv across an optional external sense resistor. an active-low open-collector ?ag indicates a low voltage of 8% or more below nominal output. a shutdown (low) signal to the ttl-compatible enable control reduces controller supply current to less than 1a while forcing the output voltage to ground. the mic5156-3.3 and mic5156-5.0 controllers have inter - nally ?xed output voltages. the mic5156 [adjustable] output is con?gured using two external resistors. the mic5157 is a ?xed output controller which is externally con?gured to select 1 2 3 4 14 13 12 11 5 6 7 10 9 8 mic5157 c 2+ c 2C v c p g nd f lag 3 .3v 5 v c 1+ c 1 C v d d g d s e n v ou t 3.3v, 10a v in (3.61vmin.) 0.1f 1.0f 0.1f r s r s = 0.035v / i limit 3m ? irlz44 (logic level mosfet) c l * 47f *i m proves transient response to load changes enable shutdown 47 f 10a low-dropout voltage regulator 1 2 3 8 7 6 4 5 mic5156-3.3 v p g nd f lag e n v d d g d s v ou t 3.3v, 10a v in 5v 0.1f r s r s = 0.035v / i limit 3m ? smp60n03-10l c l * 47f *i m proves transient response to load changes +12v enable shutdown 47f typical applications super ldo is a trademark of micrel, 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
mic5156/5157/5158 micrel, inc. mic5156/5157/5158 2 august 2005 pin con?guration ordering information mic5156 part number temperature standard pb-free voltage range package mic5156-3.3bn mic5156-3.3yn 3.3v C40c to +85c 8-pin dip mic5156-5.0bn mic5156-5.0yn 5.0v C40c to +85c 8-pin dip mic5156bn mic5156 yn adj C40c to +85c 8-pin dip mic5156-3.3bm mic5156-3.3ym 3.3v C40c to +85c 8-pin soic mic5156-5.0bm mic5156-5.0ym 5.0v C40c to +85c 8-pin soic mic5156bm mic5156ym adj C40c to +85c 8-pin soic ordering information mic5157 part number temperature standard pb-free voltage range package mic5157bn mic5157yn selectable C40c to +85c 14-pin dip mic5157bm mic5157ym selectable C40c to +85c 14-pin soic ordering information mic5158 part number temperature standard pb-free voltage range package mic5158bn MIC5158YN 5.0v/adj C40c to +85c 14-pin dip mic5158bm mic5158ym 5.0v/adj C40c to +85c 14-pin soic 1 2 3 4 e n f l a g s (source) gnd v p d (drain) v d d g (gate) 8 7 6 5 mic5156-x.x 1 2 3 4 e a 5v fb e n f l a g gnd s (source) g (gate) d (drain) 14 13 12 11 mic5158 5 6 7 v c p c2C c2+ v d d c1+ c1 C 10 9 8 1 2 3 4 5v 3.3v e n f l a g gnd s (source) g (gate) d (drain) 14 13 12 11 mic5157 5 6 7 v c p c2C c2+ v d d c1+ c1 C 10 9 8 1 2 3 4 e n f l a g gnd v p d (drain) v d d g (gate) 8 7 6 5 mic5156 e a
august 2005 3 mic5156/5157/5158 mic5156/5157/5158 micrel, inc. pin description mic5156 pin number pin name pin function 1 en enable (input): ttl high enables regulator; ttl low shuts down regulator. 2 flag output flag (output): open collector output is active (low) when v out is more than 8% below nominal output. circuit has 3% hysteresis. 3 gnd circuit ground. 4 v p n-channel gate drive supply voltage: user supplied voltage for driving the gate of the external mosfet. 5 v dd supply voltage (input): supply voltage connection. connect sense resis - tor (r s ) to v dd if current limiting used. connect supply bypass capacitor to ground near device. 6 g gate (output): drives the gate of the external mosfet. 7 d drain and current limit (input): connect to external mosfet drain and ex - ternal sense resistor (current limit), or connect to v dd and external mosfet drain (no current limit). 8 (3.3v, 5v) s source (input): top of internal resistive divider chain. connect directly to the load for best load regulation. 8 (adjustable) ea error ampli?er (input): connect to external resistive divider. pin description mic5157, mic5158 pin number pin name pin function 1 (mic5157) 5v 5v con?guration (input): connect to s (source) pin for 5v output. 1 (mic5158) ea error ampli?er (input): connect to external resistive divider to obtain adjust - able output. 2 (mic5157) 3.3v 3.3v con?guration (input): connect to s (source) pin for 3.3v output. 2 (mic5158) 5v fb 5v feedback (input): connect to ea for ?xed 5v output. 3 flag output voltage flag (output): open collector is active (low) when v out is 8% or more below its nominal value. 4 gnd circuit ground. 5 v cp voltage tripler output [filter capacitor]. connect a 1 to 10f capacitor to ground. 6 c2C charge pump capacitor 2: second stage of internal voltage tripler . connect a 0.1f capacitor from c2+ to c2C. 7 c2+ charge pump capacitor 2: see c2C pin 6. 8 c1+ charge pump capacitor 1: first stage of internal voltage tripler . connect a 0.1f capacitor from c1+ to c1C. 9 c1C charge pump capacitor 1: see c1+ pin 8. 10 v dd supply voltage (input): supply voltage connection. connect sense resis - tor (r s ) to v dd if current limiting used. connect supply bypass capacitor to ground near device. 11 g gate (output): connect to external mosfet gate. 12 d drain and current limit (input): connect to external mosfet drain and ex - ternal sense resistor (current limit), or connect to v dd and external mosfet drain (no current limit). 13 (mic5157) s source and 3.3v/5v con?guration: top of internal resistor chain. connect to source of external mosfet for 3.3v, 5v, and 12v operation. also see 3.3v and 5v pin descriptions. 13 (mic5158) s source (input): top of internal resistor chain. connect to top of external resis - tive divider and source of external mosfet. 14 en enable (input): ttl high enables regulator; ttl low shuts down regulator.
mic5156/5157/5158 micrel, inc. mic5156/5157/5158 4 august 2005 electrical characteristics (note 5) v dd = 5v, v en = 5v; t a = 25c; unless noted. symbol parameter condition min typ max units v dd supply voltage 3 36 v i dd(on) supply current mic5156 operating, v en = 5v 2.7 10 ma i dd(off) shutdown, v en = 0v 0.1 5 a i dd(on) supply current mic5157/8 operating, v en = 5v 4.5 10 ma i dd(off) shutdown, v en = 0v 0.1 5 a v ih enable input threshold high 2.4 1.3 v v il low 1.3 0.8 v en i b enable input bias current v en = 2.4v 20 25 a v cp max. charge pump voltage v cp C v dd , v dd > 10v 17.5 18.5 v f cp charge pump frequency 160 khz v out max maximum gate drive voltage v source = 0v (mic5157/8) v dd = 3.5v 5 7.0 9 v v dd = 5v 9 11.3 15 v v dd = 12v 24 28 30 v v out min minimum gate drive voltage v source > v out(nom) 1.0 v v lim current limit threshold v dd C v d @ i lim 28 35 42 mv v s source voltage short g (gate) to (s) source, note 4 mic5156-3.3 3.267 3.3 3.333 v mic5156-5.0 4.950 5.0 5.050 v mic5157, 3.3v pin to s pin (3.3v con?g.) 3.250 3.3 3.350 v mic5157, 5v pin to s pin (5v con?g.) 4.950 5.0 5.050 v mic5157, v dd = 7v, (12v con?g.) 11.70 12 12.30 v mic5158, 5v fb pin to ea pin (5v con?g.) 4.925 5.0 5.075 v v bg bandgap reference voltage mic5156 [adjustable] and mic5158 1.222 1.235 1.248 v v lr output voltage line regulation 5v < v dd < 15v, v out = 3.3v 2 7 mv v gs max gate to source clamp 14 16.6 20 v v ft flag comparator threshold % of nominal v source 92 % v fh flag comparator hysteresis % of nominal v source 3 % v sat flag comparator sat. voltage i flag = 1ma 0.09 0.2 v note 1. exceeding the absolute maximum rating may damage the device. note 2. the device is not guaranteed to function outside its operating rating. note 3. devices are esd sensitive. handling precautions recommended. note 4. test con?guration. external mosfet not used. note 5. speci?cation for packaged product only. absolute maximum ratings (note 1) supply input (v dd ) ....................................................... +38v enable input (v en ) .......................................... C0.3v to 36v gate output (v g ) mic5156 ......................................... +55v charge pump node (v cp ) mic5157/8 ........................ +55v source connection (v s ) ................................... 1.3 to +36v flag (v flag ) .................................................... C0.3 to +40v storage temperature (t s ) ........................ C65c to +150c lead temperature (soldering 10 sec.) ....................... 300c operating ratings (note 2) ambient temperature range (t a ) mic515xbm/bn ...................................... C40c to +85c junction temperature (t j ) ....................................... +150c thermal resistance ( ja ) package mic5156 mic5157/8 dip ................................ 100c/w ..................... 90c/w soic ............................. 160c/w ................... 120c/w
august 2005 5 mic5156/5157/5158 mic5156/5157/5158 micrel, inc. typical characteristics 3.26 3.27 3.28 3.29 3.30 3.31 3.32 3.33 3.34 -60 -30 0 3 0 6 0 9 0 120 150 output voltage (v) temperature (c) 3.3v regulator output voltage vs. temperature 4.96 4.97 4.98 4.99 5.00 5.01 5.02 5.03 5.04 -60 -30 0 3 0 6 0 9 0 120 150 output voltage (v) temperature (c) 5.0v regulator output voltage vs. temperature 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 0 5 10 15 20 25 30 on-state supply current (ma) supply voltage (v) mic5157/8 on-state supply current vs. supply voltage 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 -60 -30 0 3 0 6 0 9 0 120 150 on-state supply current (ma) temperature (c) mic5157/8 on-state supply current vs. temperature v dd = 5v 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 -60 -30 0 3 0 6 0 9 0 120 150 off-state supply current (a) temperature (c) off-state supply current vs. temperature v dd = 5v 0 10 20 30 40 50 60 0 5 10 15 20 25 30 charge pump voltage (v) supply voltage (v) charge-pump output voltage vs. supply voltage 0 25 50 75 100 125 150 175 200 -60 -30 0 3 0 6 0 9 0 120 150 flag voltage (mv) temperature (c) flag output voltage vs. temperature v dd = 5v i f l ag = 1ma 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 -60 -30 0 3 0 6 0 9 0 120 150 enable threshold voltage (v) temperature (c) enable threshold voltage vs. temperature 0 10 20 30 40 50 60 70 -60 -30 0 3 0 6 0 9 0 120 150 current limit threshold (mv) temperature (c) current limit threshold vs. temperature -2 0 2 4 6 8 10 12 -0.2 0.0 0.2 0.4 0.6 voltage (v) time (ms) mic5157/8 turn-on response time for 3.3v c c p = 1 f c l = 50 f logic input 3.3v output mosfet = irf540 v in = 5v , i l = 0.5a c c 1 = c c 2 = 0. 1 f 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 2 4 6 8 10 flag voltage (v) flag sink current (ma) flag output voltage vs. flag current v dd = 5v 0 20 40 60 80 100 120 0 2 4 6 8 1 0 1 2 1 4 1 6 enable bias current (a) enable voltage (v) enable input bias current vs. enable voltage
mic5156/5157/5158 micrel, inc. mic5156/5157/5158 6 august 2005 block diagram mic5156 e n enable shutdown 1.235v bandgap reference internal bias error amp 75m v 35m v gnd s* (source) 16.6v i limit comparator d (drain) [ i limit ] g (gate) f l a g v p v dd v ou t comparator 10k to all internal blocks e a ? 17k ? regulated +3.3v output +12v input +5v input +5v input r s 3m ? 0.1f q2 q1 smp60n03-10l switched 5v load 12k * fixed version only ? 3.3v = 17k, 5v = 32k ? adjustable version only c l block diagram mic5157 block diagram with external components fixed 3.3v power supply with 5.0v load switch block diagram with external components fixed 3.3v 10a power supply 1.235v bandgap reference v c p clamp internal bias error amp 75mv 35m v gnd s (source)* i limit comparator d (drain) [ i limit ] g (gate) v c p v dd v ou t comparator to all i nternal blocks 3.3v regulated +3.3v output +5v input q1 irfz44 r s 3m ? 1f 16.6v 10k 58k 15k 17k 5v oscillator charge pump tripler c1+ c1C c2+ c2 C 0.1f 0.1f c1 c2 c3 f l a g e n enable shutdown c l
august 2005 7 mic5156/5157/5158 mic5156/5157/5158 micrel, inc. functional description a super ldo regulator is a complete regulator built around micrels super ldo regulator controller . refer to block diagrams mic5156, mic5157, and mic5158. version differences the mic5156 requires an external voltage for mosfet gate drive and is available in 3.3v ?xed output, 5v ?xed output, or adjustable output versions. with 8-pins, the mic5156 is the smallest of the super ldo regulator controllers. the mic5157 and mic5158 each have an internal charge pump which provides mosfet gate drive voltage. the mic5157 has a selectable ?xed output of 3.3v, 5v, or 12v. the mic5158 may be con?gured for a ?xed 5v or adjustable output. enable (en) with at least 3.0v on v dd , applying a ttl low to en places the controller in shutdown mode. a ttl high on en enables the internal bias circuit which powers all internal circuitry. en must be pulled high if unused. the voltage applied to en may be as high as 36v. the controller draws less than 1a in shutdown mode. gate enhancement the super ldo regulator controller manages the gate- 1.235v bandgap reference v c p clamp internal bias error amp 75mv 35m v e a s (source) i limit comparator d (drain) [ i limit ] g (gate) v c p v dd v ou t comparator to all internal blocks gnd regulated +3.6v output +5v input q1 irfz44 r s 3m ? 1f 16.6v 32k 10k 5v f b oscillator charge pump tripler c1+ c1C c2+ c2 C 0.1f 0.1f c1 c2 c3 f l a g 19.1k 10.0k e n enable shutdown c l block diagram mic5158 block diagram with external components adjustable power supply, 3.6v con?guration to-source enhancement voltage for an external n-channel mosfet (regulator pass element) placed between the supply and the load. the gate-to-source voltage may vary from 1v to 16v depending upon the supply and load conditions. because the source voltage (output) approaches the drain voltage (input) when the regulator is in dropout and the mosfet is fully enhanced, an additional higher supply voltage is required to produce the necessary gate-to-source enhancement. this higher gate drive voltage is provided by an external gate drive supply (mic5156) or by an internal charge pump (mic5157 and mic5158). gate drive supply voltage (mic5156 only) the gate drive supply voltage must not be more than 14v above the supply voltage (v p C v dd < 14v). the minimum necessary gate drive supply voltage is: v p = v out + v gs + 1 where: v p = gate drive supply voltage v out = regulator output voltage v gs = gate-to-source voltage for full mosfet gate enhancement the error ampli?er uses the gate drive supply voltage to drive the gate of the external mosfet. the error ampli?er output can swing to within 1v of v p .
mic5156/5157/5158 micrel, inc. mic5156/5157/5158 8 august 2005 charge pump (mic5157/5158 only) the charge pump tripler creates a dc voltage across reservoir capacitor c3. external capacitors c1 and c2 provide the nec - essary storage for the stages of the charge pump tripler. the triplers approximate dc output voltage is: v cp 3 (v dd C 1) where: v cp = charge pump output voltage v dd = supply voltage the v cp clamp circuit limits the charge pump voltage to 16v above v dd by gating the charge pump oscillator on or off as required. the charge pump oscillator operates at 160khz. the error ampli?er uses the charge pump voltage to drive the gate of the external mosfet. it provides a constant load of about 1ma to the charge pump. the error ampli?er output can swing to within 1v of v cp . although the mic5157/8 is designed to provide gate drive using its internal charge pump, an external gate drive sup - ply voltage can be applied to v cp . when using an external gate drive supply, v cp must not be forced more than 14v higher than v dd . when constant loads are driven, the on/off switching of the charge pump may be evident on the output waveform. this is caused by the charge pump switching on and rapidly increasing the supply voltage to the error ampli?er. the period of this small charge pump excitation is determined by a number of factors: the input voltage, the 1ma op-amp load, any dc leakage associated with the mosfet gate circuit, the size of the charge pump capacitors, the size of the charge pump reservoir capacitor, and the characteristics of the input voltage and load. the period is lengthened by increasing the charge pump reservoir capacitor (c3). the amplitude is reduced by weakening the charge pumpthis is accomplished by reduc - ing the size of the pump capacitors (c1 and c2). if this small burst is a problem in the application, use a 10f reservoir capacitor at c3 and 0.01f pump capacitors at c1 and c2. note that the recovery time to repetitive load transients may be affected with small pump capacitors. gate-to-source clamp a gate-to-source protective voltage clamp of 16.6v protects the mosfet in the event that the output voltage is suddenly forced to zero volts. this prevents damage to the external mosfet during shorted load conditions. refer to charge pump for normal clamp circuit operation. the source connection required by the gate-to-source clamp is not available on the adjustable version of the mic5156. output regulation at start-up, the error ampli?er feedback voltage (ea), or internal feedback on ?xed versions, is below nominal when compared to the internal 1.235v bandgap reference. this forces the error ampli?er output high which turns on exter - nal mosfet q1. once the output reaches regulation, the controller maintains constant output voltage under changing input and load conditions by adjusting the error ampli?er output voltage (gate enhancement voltage) according to the feedback voltage. out-of-regulation detection when the output voltage is 8% or more below nominal, the open-collector flag output (normally high) is forced low to signal a fault condition. the flag output can be used to signal or control external circuitry. the flag output can also be used to shut down the regulator using the en control. current limiting super ldo regulators perform constant-current limiting (not foldback). to implement current limiting, a sense resistor (r s ) must be placed in the power path between v dd and d (drain). if the voltage drop across the sense resistor reaches 35mv, the current limit comparator reduces the error ampli?er out - put. the error ampli?er output is decreased only enough to reduce the output current, keeping the voltage across the sense resistor from exceeding 35mv. application information mosfet selection standard n-channel enhancement-mode mosfets are ac - ceptable for most super ldo regulator applications. logic-level n-channel enhancement-mode mosfets may be necessary if the external gate drive voltage is too low (mic5156), or the input voltage is too low, to provide adequate charge pump voltage (mic5157/8) to enhance a standard mosfet. circuit layout for the best voltage regulation, place the source, ground, and error ampli?er connections as close as possible to the load. see ?gures (1a) and (1b). gnd s g mic515x v in figure 1a. connections for fixed output
august 2005 9 mic5156/5157/5158 mic5156/5157/5158 micrel, inc. adjustable con?gurations micrels mic5156 [adjustable] and mic5158 require an ex - ternal resistive divider to set the output voltage from 1.235v to 36v. for best results, use a 10k resistor for r2. see equation (1) and ?gure (2). 1) r 1 = 1 1 0 4 ( - 1 ) v o u t 1 . 2 3 5 gnd s ea* mic5157/8 r 1 r 2 10k v ou t g figure 2. typical resistive divider input filter capacitor the super ldo requires an input bypass capacitor for accom - modating wide changes in load current and for decoupling the error ampli?er and charge pump. a medium to large value low-esr (equivalent series resistance) capacitor is best, mounted close to the device. output filter capacitor an output ?lter capacitor may be used to reduce ripple and improve load regulation. stable operation does not require a large capacitor, but for transient load regulation the size of the output capacitor may become a consideration. common aluminum electrolytic capacitors perform nicely; very low-esr capacitors are not necessary. increased capacitance (rather than reduced esr) is preferred. the capacitor value should be large enough to provide suf?cient i = c dv/dt current consistent with the required transient load regulation quality. for a given step increase in load current, the output voltage will drop by about dv = i dt/c, where i represents the increase in load current over time t. this relationship assumes that all output current was being supplied via the mosfet pass device prior to the load increase. small (0.01f to 10f) ?lm capacitors parallel to the load will further improve response to transient loads. some linear regulators specify a minimum required output ?lter capacitance because the capacitor determines the dominant pole of the system, and thereby stabilizes the system. this is not the situation for the mic5156/7/8; its dominant pole is determined within its error ampli?er. gnd s e a mic5157 or mic5158 g v in figure 1b. connections for adjustable output gnd mic5156 g v in e a * optional 16v zener diode recommended in applications where v g is greater than 18v * figure 1c. mic5156 connections for adjustable output mosfet gate-to-source protection when using the adjustable version of the mic5156, an external 16v zener diode placed from gate-to-source is recommended for mosfet protection. all other versions of the super ldo regulator controller use the internal gate-to-source clamp. output voltage con?guration fixed con?gurations the mic5156-3.3 and mic5156-5.0 are preset for 3.3v and 5.0v respectively. the mic5157 operates at 3.3v when the 3.3v pin is connected to the s (source) pin; 5.0v when the 5.0v pin is connected to the s pin; or 12v if the 3.3v and 5.0v pins are open. the mic5158 operates at a ?xed 5v (without an external resistive divider) if the 5v fb pin is connected to ea.
mic5156/5157/5158 micrel, inc. mic5156/5157/5158 10 august 2005 current limiting current sensing requires a low-value series resistance (r s ) between v dd and d (drain). refer to the typical applications. the internal current-limiting circuit limits the voltage drop across the sense resistor to 35mv. equation (2) provides the sense resistor value required for a given maximum current. 2) r s = 3 5 m v i l i m where: r s = sense resistor value i lim = maximum output current most current-limited applications require low-value resistors. see application hints 21 and 25 for construction hints. non-current-limited applications for circuits not requiring current limiting, do not use a sense resistor between v dd and d (drain). see ?gure (3). the con - troller will not limit current when it does not detect a 35mv drop from v dd to d. s g mic5156 d v dd v in figure 3. no current limit 3.3v microprocessor applications for computer designs that use 3.3v microprocessors with 5v logic, the flag output can be used to suppress the 5v sup - ply until the 3.3v output is in regulation. refer to the external components shown with the mic5156 block diagram. smps post regulator application a super ldo regulator can be used as a post regulator for a switch-mode power supply. the super ldo regulator can pro - vide a signi?cant reduction in peak-to-peak ripple voltage. high-current switch application all versions of the mic5156/7/8 may be used for current-lim - ited, high-current, high-side switching with or without voltage regulation. see ?gure (4a). simply leave the s terminal open. a 16v zener diode from the gate to the source of the mosfet protects the mosfet from overdrive during fault conditions. g mic5156-x.x d v dd v in v g gate supply enable shutdown en gnd r s s figure 4a. high-side switch if a mic5157 or mic5158 is used and is shutdown for a given time, the charge pump reservoir v cp will bleed off. if recharging the reservoir causes an unacceptable delay in the load reaching its operating voltage, do not use the en pin for on/off control. instead, use the mic5158, hold en high to keep the charge pump in continuous operation, and switch the mosfet on or off by overriding the error ampli?er input as shown in ?gure (4b). gnd s e a mic5158 g e n output off output on 1n4148 v in v dd figure 4b. fast high-side switch battery charger application the mic5158 may be used in constant-current applications such as battery chargers. see ?gure (5). the regulator supplies a constant-current (35mv r3) until the battery approaches the ?oat voltage: v f l = 1 . 2 3 5 ( 1 + ) r 1 r 2 where: v fl = ?oat voltage at ?oat voltage, the mosfet is shut off. a trickle charge is supplied by r4.
august 2005 11 mic5156/5157/5158 mic5156/5157/5158 micrel, inc. gnd s e a mic5158 g e n v in r 1 r 2 d r 3 r 4 v dd figure 5. battery charger concept uninterruptible power supply the mic5157 and two n-channel mosfets provide battery switching for uninterruptible power as shown in ?gure (6). two mosfets are placed source-to-source to prevent cur - rent ?ow through their body diodes when switched off. the super ldo regulator is continuously enabled to achieve fast battery switch-in. careful attention must be paid to the ac-line monitoring circuitry to ensure that the output voltage does not fall below design limits while the battery is being switched in. line battery s g mic5158 d v dd en gnd e a 1n4148 uninterruptable d c d s d g s g mosfet body diodes shown for clarity off-line power supply a c line q1 q2 40v max. figure 6. ups power supply concept
mic5156/5157/5158 micrel, inc. mic5156/5157/5158 12 august 2005 package information 0.380 (9.65) 0.370 (9.40) 0.135 (3.43) 0.125 (3.18) pin 1 dimensions: inch (mm) 0.018 (0.57) 0.100 (2.54) 0.013 (0.330) 0.010 (0.254) 0.300 (7.62) 0.255 (6.48) 0.245 (6.22) 0.380 (9.65) 0.320 (8.13) 0.0375 (0.952) 0.130 (3.30) 8-pin dip (n) 8-pin soic (m)
august 2005 13 mic5156/5157/5158 mic5156/5157/5158 micrel, inc. .080 (1.524) .015 (0.381) .023 (.5842) .015 (.3810) .310 (7.874) .280 (7.112) .770 (19.558) max .235 (5.969) .215 (5.461) .060 (1.524) .045 (1.143) .160 max (4.064) .160 (4.064) .100 (2.540) .110 (2.794) .090 (2.296) .400 (10.180) .330 (8.362) .015 (0.381) .008 (0.2032) .060 (1.524) .045 (1.143) pin 1 14-pin dip (n) 45 3C6 0.244 (6.20) 0.228 (5.80) 0.344 (8.75) 0.337 (8.55) 0.006 (0.15) seating plane 0.026 (0.65) max ) 0.016 (0.40) typ 0.154 (3.90) 0.057 (1.45) 0.049 (1.25) 0.193 (4.90) 0.050 (1.27) typ pin 1 dimensions: inches (mm) 14-pin soic (m) 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 this information furnished by micrel in this data sheet is believed to be accurate and reliable. however no responsibility is assumed by micrel for its use. micrel reserves the right to change circuitry and speci?cations at any time without noti?cation to the customer. micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are intended 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 signi? cant injury to the user. a purchaser's use or sale of micrel products for use in life support appliances, 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. ? 1999 micrel , inc.

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