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| ? 2014-2015 microchip technology inc. ds20005315b-page 1 MCP1661 features ?36v, 800m ? integrated switch ? up to 92% efficiency ? high output voltage range: up to 32v ? 1.3a peak input current limit: -i out > 200 ma @ 5.0v v in , 12v v out -i out > 125 ma @ 3.3v v in , 12v v out -i out > 100 ma @ 4.2v v in , 24v v out ? input voltage range: 2.4v to 5.5v ? undervoltage lockout (uvlo): -uvlo@v in rising: 2.3v, typical -uvlo@v in falling: 1.85v, typical ? no load input current: 250 a, typical ? sleep mode with 200 na typical quiescent current ? pwm operation with skip mode: 500 khz ? feedback voltage reference: v fb = 1.227v ? cycle-by-cycle current limiting ? internal compensation ? inrush current limiting and internal soft start ? output overvoltage protection (ovp) in the event of: - feedback pin shorted to gnd - disconnected feedback divider ? overtemperature protection ? easily configurable for sepic or flyback topologies ? available packages: - 5-lead sot-23 - 8-lead 2x3 tdfn applications ? two and three-cell alkaline, lithium ultimate and nimh/nicd portable products ? single-cell li-ion to 5v, 12v or 24v converters ? lcd bias supply for portable applications ? camera phone flash ? portable medical equipment ? hand-held instruments ? single-cell li-ion to 3.0v or 3.3v sepic applications (see figure 6-3 ) general description the MCP1661 device is a compact, high-efficiency, fixed-frequency, non-synchronous step-up dc-dc converter which integrates a 36v, 800 m ? nmos switch. it provides a space-efficient high-voltage step-up power supply solution for applications powered by either two-cell or three-cell alkaline, ultimate lithium, nicd, nimh, one-cell li-ion or li-polymer batteries. the integrated switch is protected by the 1.3a cycle-by-cycle inductor peak current limit operation. there is an output overvoltage protection which turns off switching in case the feedback resistors are accidentally disconnected or the feedback pin is short-circuited to gnd. low-voltage technology allows the regulator to start-up without high inrush current or output voltage overshoot from a low-voltage input. the device features a uvlo which avoids start-up and operation with low inputs or discharged batteries for two cell-powered applications. for standby applications (en = gnd), the device stops switching, enters sleep mode and consumes 200 na (typical) of input current. MCP1661 is easy to use and allows creating classic boost, sepic or flyback dc-dc converters within a small printed circuit board (pcb) area. all compensation and protection circuitry is integrated to minimize the number of external components. ceramic input and output capacitors are used. package types * includes exposed thermal pad (ep); see ta b l e 3 - 1 . sw en v in gnd MCP1661 sot-23 v fb MCP1661 2x3 tdfn* 1 2 3 5 4 sw s gnd nc p gnd nc 1 2 3 4 8 7 6 5 v in en v fb ep 9 high-voltage integrated switch pwm boost regulator with uvlo
MCP1661 ds20005315b-page 2 ? 2014-2015 microchip technology inc. typical applications v in gnd v fb v out 12v, 75 ma-125 ma c out 4.7-10 f c in 4.7-10 f l 4.7 h sw 1.05 m 120 k en + - alkaline on off + - alkaline r top r bot v in 2.4v -3.0v d MCP1661 pmeg2005 d v = 1.227v fb v in gnd v fb v out 24v, 50 ma-125 ma c out 10 f c in 10 f l 10 h sw 1.05 m 56 k en + - alkaline + - alkaline r top r bot v in 3.0v - 4.2v d MCP1661 mbr0540 d 0 50 100 150 200 250 300 2.4 2.8 3.2 3.6 4 4.4 4.8 i out (ma) v in (v) v out = 12v v out = 24v maximum output current vs. v in ? 2014-2015 microchip technology inc. ds20005315b-page 3 MCP1661 1.0 electrical characteristics absolute maximum ratings ? v sw ? gnd .....................................................................+36v en, v in ? gnd...............................................................+6.0v v fb .................................................................................+1.3v power dissipation ....................................... internally limited storage temperature .................................... -65 c to +150 c ambient temperature with power applied .... -40 c to +125 c operating junction temperature................... -40 c to +150 c esd protection on all pins: hbm ................................................................. 4 kv mm ..................................................................300v ? notice: stresses above those listed under ?maximum ratings? may cause permanent damage to the device. this is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational sections of this specification is not intended. exposure to maximum rating conditions for extended periods may affect device reliability. dc and ac characteristics electrical specifications: unless otherwise specified, all limits apply for typical values at ambient temperature t a =+25c, v in = 3.3v, i out =20ma, v out =12v, c in =c out = 10 f, x7r ceramic, l = 4.7 h. boldface specifications apply over the controlled t a range of -40c to +125c. parameters sym. min. typ. max. units conditions input voltage range v in 2.4 ? 5.5 v note 1 undervoltage lockout (uvlo) uvlo start ?2.3? vv in rising, i out =1ma resistive load uvlo stop ?1.85? vv in falling, i out =1ma resistive load output voltage adjust range v out ??32 v note 1 maximum output current i out ?125? ma3.3v v in , 12v v out 200 ? ma 5.0v v in , 12v v out 100 ? ma 4.2v v in , 24v v out feedback voltage v fb 1.190 1.227 1.264 v v fb accuracy -3 ? 3 % feedback input bias current i vfb ?0.005? a no load input current i in0 ? 250 ? a device switching, no load, 3.3v v in , 12v v out ( note 2 ) shutdown quiescent current i qshdn ? 200 ? na en = gnd, feedback divider current not included ( note 3 ) peak switch current limit i n(max) ?1.3? a note 4 nmos switch leakage i nlk ?0.4? av in =v sw =5v; v out =5.5v v en =v fb =gnd nmos switch on resistance r ds(on) ?0.8? ? v in =5v, v out = 12v, i out =100ma ( note 4 ) note 1: minimum input voltage in the range of v in (v in <5.5v MCP1661 ds20005315b-page 6 ? 2014-2015 microchip technology inc. note: unless otherwise indicated, v in =3.3v, i out =20ma, v out =12v, c in =c out = 10 f, x7r ceramic, l=4.7h, t a = 25c, 5-lead sot-23 package. figure 2-7: inductor peak current limit vs. ambient temperature. figure 2-8: no load input current, i in0 vs. v in (en = v in ). figure 2-9: shutdown quiescent current, i qshdn vs. v in (en = gnd). figure 2-10: no load input current, i in0 vs. ambient temperature. figure 2-11: f sw vs. ambient temperature. figure 2-12: pwm pulse skipping mode threshold. 0.5 0.7 0.9 1.1 1.3 1.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 inductor peak current (a) ambient temperature (c) v in = 5.0v v out = 12.0v 150 175 200 225 250 275 300 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 i in0 no load input current (a) input voltage (v) v out = 6.0v v out = 12.0v 0.00 0.05 0.10 0.15 0.20 0.25 0.30 1.8 2.2 2.6 3 3.4 3.8 4.2 4.6 5 i q shutdown mode (a) input voltage (v) note: without fb resistor divider current 0 200 400 600 800 1000 1200 1400 1600 1800 2000 -40 -25 -10 5 20 35 50 65 80 95 110 125 i in0 no load input current (a) ambient temperature (c) v in = 3.0v v in = 5.5v v out = 12v v in = 2.3v 425 450 475 500 525 550 575 -40 -25 -10 5 20 35 50 65 80 95 110 125 switching frequency (khz) ambient temperature (c) v in = 3.0v i out = 100 ma 0 1 2 3 4 5 6 0 5 10 15 20 25 30 v in (v) i out (ma) v out = 24.0v v out = 12.0v v out = 6.0v ? 2014-2015 microchip technology inc. ds20005315b-page 7 MCP1661 note: unless otherwise indicated, v in =3.3v, i out =20ma, v out =12v, c in =c out = 10 f, x7r ceramic, l=4.7h, t a = 25c, 5-lead sot-23 package. figure 2-13: enable threshold vs. input voltage. figure 2-14: n-channel switch r dson vs. v in . figure 2-15: 12.0v v out light load pwm mode waveforms. figure 2-16: high load pwm mode waveforms. figure 2-17: 12.0v start-up by enable. figure 2-18: 12.0v start-up (v in =v enable ). 0 10 20 30 40 50 60 70 80 90 100 2.3 2.6 2.9 3.2 3.5 3.8 4.1 4.4 4.7 5 enable thresholds (% of v in ) input voltage (v) en v il en v ih i out = 1 ma 0 0.2 0.4 0.6 0.8 1 2.6 2.9 3.2 3.5 3.8 4.1 4.4 4.7 5 switch r ds(on) ( ) input voltage (v) i out =100ma 2 s/div v out 20 mv/div, ac coupled 20 mhz bw i out =5ma v sw 5v/div i l 100 ma/div 1 s/div v out 50 mv/div, ac coupled 20 mhz bw i out =100ma v sw 5v/div i l 400 ma/div v out 3v/div i out =15ma v en 3v/div i l 300 ma/div 500 s/div v in 3v/div v out 3v/div i out =15ma v sw 5v/div v in 3v/div 500 s/div MCP1661 ds20005315b-page 8 ? 2014-2015 microchip technology inc. note: unless otherwise indicated, v in =3.3v, i out =20ma, v out =12v, c in =c out = 10 f, x7r ceramic, l=4.7h, t a = 25c, 5-lead sot-23 package. figure 2-19: 12.0v v out load transient waveforms. figure 2-20: 12.0v v out line transient waveforms. 2ms/div v out 200 mv/div, ac coupled i out 30 ma/div step from 20 ma to 50 ma 1ms/div v out 100 mv/div, ac coupled v in 1v/div step from 3.3v to 5.0v i out =60ma ? 2014-2015 microchip technology inc. ds20005315b-page 9 MCP1661 3.0 pin descriptions the descriptions of the pins are listed in tab l e 3 - 1 . 3.1 feedback voltage pin (v fb ) the v fb pin is used to provide output voltage regulation by using a resistor divider. the v fb voltage is 1.227v typical. 3.2 signal ground pin (s gnd ) the signal ground pin is used as a return for the integrated reference voltage and error amplifier. the signal ground and power ground must be connected externally in one point. 3.3 switch node pin (sw) connect the inductor from the input voltage to the sw pin. the sw pin carries inductor current, which can be as high as 1.3a peak. the integrated n-channel switch drain is internally connected to the sw node. 3.4 not connected (nc) this is an unconnected pin. 3.5 power supply input voltage pin (v in ) connect the input voltage source to v in . the input source must be decoupled from gnd with a 4.7 f minimum capacitor. 3.6 power ground pin (p gnd ) the power ground pin is used as a return for the high-current n-channel switch. the signal ground and power ground must be connected externally in one point. 3.7 enable pin (en) the en pin is a logic-level input used to enable or disable device switching and lower quiescent current while disabled. a logic high (>85% of v in ) will enable the regulator output. a logic low (<7.5% of v in ) will ensure that the regulator is disabled. 3.8 exposed thermal pad (ep) there is no internal electrical connection between the exposed thermal pad (ep) and the s gnd and p gnd pins. they must be connected to the same potential on the pcb. 3.9 ground pin (gnd) the ground or return pin is used for circuit ground connection. the length of the trace from the input cap return, the output cap return and the gnd pin must be as short as possible to minimize noise on the gnd pin. the 5-lead sot-23 package uses a single ground pin. table 3-1: pin function table MCP1661 sot-23 MCP1661 2x3 tdfn symbol description 31v fb feedback voltage pin ?2s gnd signal ground pin (tdfn only) 1 3 sw switch node, boost inductor input pin ? 4, 6 nc not connected 55v in input voltage pin ?7p gnd power ground pin (tdfn only) 4 8 en enable control input pin ? 9 ep exposed thermal pad (ep); must be connected to ground. (tdfn only) 2 ? gnd ground pin (sot-23 only) MCP1661 ds20005315b-page 10 ? 2014-2015 microchip technology inc. notes: ? 2014-2015 microchip technology inc. ds20005315b-page 11 MCP1661 4.0 detailed description 4.1 device overview MCP1661 is a constant frequency pwm boost (step-up) converter, based on a peak current mode architecture which delivers high efficiency over a wide load range from two-cell and three-cell alkaline, ultimate lithium, nimh, nicd and single-cell li-ion battery inputs. a high level of integration lowers total system cost, eases implementation and reduces board area. the device features controlled start-up voltage (uvlo), adjustable output voltage, 500 khz pwm operation with skipping mode, 36v integrated switch, internal compensation, inrush current limit, soft start, and overvoltage protection in case the v fb connection is lost. the 800 m ? , 36v integrated switch is protected by the 1.3a cycle-by-cycle inductor peak current operation. when the enable pin is pulled to ground (en = gnd), the device stops switching, enters in shutdown mode and consumes approximately 200 na of input current (the feedback current is not included). MCP1661 can be used to build classic boost, sepic or flyback dc-dc converters. MCP1661 ds20005315b-page 12 ? 2014-2015 microchip technology inc. 4.2 functional description the MCP1661 device is a compact, high-efficiency, fixed-frequency, step-up dc-dc converter that provides an easy-to-use high-output power supply solution for applications powered by either two-cell or three-cell alkaline or lithium energizer, three-cell nicd or nimh or one-cell li-ion or li-polymer batteries. figure 4-1 depicts the functional block diagram of the MCP1661 device. it incorporates a current mode control scheme, in which the pwm ramp signal is derived from the nmos power switch current (v sense ). this ramp signal adds slope ramp compensation signal (v ramp ) and is compared to the output of the error amplifier (v error ) to control the on-time of the power switch. a proper slope rate will be designed to improve circuit stability. figure 4-1: MCP1661 simplified block diagram. en + - + - + - s + - 1.227v sw v fb ea gnd + - ovp_ref v fb v fb_fault cc rc v ramp v error v pwm clk qn v ext v fb v in_ok en v bias v uvlo_ref v in_ok 1.227v ovp_ref v uvlo_ref v sense v limit v out_ok v in internal bias and uvlo comparator gate drive and shutdown control logic overcurrent comparator oscillator slope compensation logic sr latch overvoltage comparator thermal shutdown power good comparator and delay band gap ? 2014-2015 microchip technology inc. ds20005315b-page 13 MCP1661 4.2.1 internal bias the MCP1661 device gets its bias from v in . the v in bias is used to power the device and drive circuits over the entire operating range. 4.2.2 start-up voltage and soft start the MCP1661 device starts at input voltages that are higher than or equal to a predefined set uvlo value. MCP1661 starts switching at approximately 2.3v for 12.0v output and 1 ma resistive load. once started, the device will continue to operate under normal load conditions down to 1.85v typical. there is a soft start feature which provides a way to limit the inrush current drawn from the input (batteries) during start-up. the soft start has an important role in applications where the switch will reach 32v. during start-up, excessively high switch current, together with the presence of high voltage, can overstress the nmos switch. when the device is powered (en = v in and v in rises from zero to its nominal value), the output capacitor charges to a value close to the input voltage (or v in minus a schottky diode voltage drop). the overshoot on output is limited by slowly increasing the reference of the error amplifier. there is an internal reference voltage which charges an internal capacitor with a weak current source. the voltage on this capacitor slowly ramps the reference voltage. the soft-start capacitor is completely discharged in the event of a commanded shutdown or a thermal shutdown. due to the direct path from input to output, in the case of start-up by enable (en voltage switches from low-to- high), the output capacitor is already charged and the output starts from a value close to the input voltage. the internal oscillator has a delayed start to let the output capacitor be completely charged to the input voltage value. 4.2.3 undervoltage lockout (uvlo) MCP1661 features an uvlo which prevents fault operation below 1.85v, which corresponds to the typical value of two discharged batteries. the device starts its normal operation at 2.3v input. the upper limit is set to avoid any input transients (temporary v in drop), which might trigger the lower uvlo threshold and restart the device. usually, these voltage transients (overshoots and undershoots) have up to a few hundred mv. MCP1661 is a non-synchronous boost regulator. due to this fact, there is a direct path from v in to v out through the inductor and the diode. this means that, while the device is not switching (v in below uvlo stop threshold), v out is not zero but equal to v in ?v f (where v f is the voltage drop on the rectifier diode). when the input voltage is below the 2.3v uvlo start threshold, the device is operating with limited specification. 4.2.4 pwm mode operation MCP1661 operates as a fixed-frequency, non-synchronous converter. the switching frequency is maintained at 500 khz with a precision oscillator. lossless current sensing converts the peak current signal to a voltage (v sense ) and adds it to the internal slope compensation (v ramp ). this summed signal is compared to the voltage error amplifier output (v error ) to provide a peak current control signal (v pwm ) for the pwm control block. the slope compensation signal depends on the input voltage. therefore, the converter provides the proper amount of slope compensation to ensure stability. the peak current is set to 1.3a. the MCP1661 device will operate in pwm even during periods of light load operation by skipping pulses. by operating in pwm mode, the output ripple is low and the frequency is constant. 4.2.5 adjustable output voltage the MCP1661 output voltage is adjustable with a resistor divider over the v out range. high value resistors are recommended to minimize power loss and keep efficiency high at light loads. the device integrates a transconductance-type error amplifier and the values of the feedback resistors do not influence the stability of the system. 4.2.6 minimum input voltage and maximum output current the maximum output current for which the device can supply the load is dependent upon the input and output voltage. the minimum input voltage necessary to reach the value of the desired output depends on the maximum duty cycle (approximately 90%) in accordance with the mathematical relation v out =v inmin /(1 ? d max ). as there is a 1.3a inductor peak current limit, v out can go out of regulation before reaching the maximum duty cycle. (for boost converters, the average inductor current is equal to the input current.) for example, to ensure a 100 ma load current for v out = 12.0v, a minimum of 2.8v input voltage is necessary. if an application is powered by one li-ion battery (v in from 3.3v to 4.2v), the minimum load current the MCP1661 device can deliver is close to 50 ma at 24.0v output (see figure 2-3 ). MCP1661 ds20005315b-page 14 ? 2014-2015 microchip technology inc. 4.2.7 enable pin the MCP1661 device is enabled when the en pin is set high. the device is put into shutdown mode when the en pin is set low. to enable the boost converter, the en voltage level must be greater than 85 % of the v in voltage. to disable the boost converter, the en voltage must be less than 7.5 % of the v in voltage. in shutdown mode, the MCP1661 device stops switching and all internal control circuitry is switched off. on boost configuration, the input voltage will be bypassed to output through the inductor and the schottky diode. in the sepic converter, shutdown mode acts as output disconnect. 4.2.8 internal compensation the error amplifier, with its associated compensation network, completes the closed-loop system by comparing the output voltage to a reference at the input of the error amplifier and by feeding the amplified and inverted error voltage to the control input of the inner current loop. the compensation network provides phase leads and lags at appropriate frequencies to cancel excessive phase lags and leads of the power circuit. all necessary compensation components and slope compensation are integrated. 4.2.9 output overvoltage protection (ovp) an internal v fb fault signal turns off the pwm signal (v ext ) and prevents the output from going out of regulation in the event of: ? short circuit of the feedback pin to gnd ? disconnection of the feedback divider from v out in any of the above events, for a regular integrated boost circuit (ic) without any protection implemented, if the v fb voltage drops to ground potential, its n-channel transistor will be forced to switch at full duty cycle and v out rises. this fault event may cause the sw pin to exceed its maximum voltage rating and may damage the boost regulator ic, the external components and the load. to avoid all these, MCP1661 has implemented an overvoltage protection (ovp) which turns off pwm switching when an overvoltage condition is detected. there is an overvoltage comparator with 80 mv reference which monitors the v fb voltage. the ovp comparator is disabled during start-up sequences and thermal shutdown. if ovp occurs with the input voltage below the uvlo start threshold and v fb remains under 80 mv due to a low input voltage or overload condition, the device latches its output and resumes after restart. 4.2.10 overcurrent limit the MCP1661 device uses a 1.3a cycle-by-cycle inductor peak current limit to protect the n-channel switch. there is an overcurrent comparator which resets the drive latch when the peak of the inductor current reaches the limit. in current limitation, the output voltage starts dropping. 4.2.11 output short circuit condition like all non-synchronous boost converters, the MCP1661 inductor current will increase excessively during a short circuit on the converter?s output. short circuit on the output will cause the diode rectifier to fail and the inductor?s temperature to rise. when the diode fails, the sw pin becomes a high-impedance node, it remains connected only to the inductor and the excessive resulted ringing will damage the MCP1661 device. 4.2.12 overtemperature protection overtemperature protection circuitry is integrated into the MCP1661 device. this circuitry monitors the device junction temperature and shuts the device off if the junction temperature exceeds the typical +150c threshold. if this threshold is exceeded, the device will automatically restart when the junction temperature drops by 15c. the output overvoltage protection (ovp) is reset during an overtemperature condition. ? 2014-2015 microchip technology inc. ds20005315b-page 15 MCP1661 5.0 application information 5.1 typical applications the MCP1661 nonsynchronous boost regulator operates over a wide output voltage range up to 32v. the input voltage ranges from 2.4v to 5.5v. the device operates down to 1.85v input with limited specification. the uvlo thresholds are set to 2.3v when v in is ramping and to 1.85v when v in is falling. the power efficiency conversion is high for several decades of load range. output current capability increases with the input voltage and decreases with the increasing output voltage. the maximum output current is based on the n-channel switch peak current limit, set to 1.3a, and on a maximum duty cycle of 90%. typical characterization curves in this data sheet are presented to display the typical output current capability. 5.2 adjustable output voltage calculations to calculate the resistor divider values for the MCP1661, the following equation can be used. where r top is connected to v out , r bot is connected to gnd and both are connected to the v fb input pin. equation 5-1: the values of the two resistors, r top and r bot , affect the no load input current and quiescent current. in shutdown mode (en = gnd), the device consumes approximately 0.2 a. with 24v output and 1 m ? feedback divider, the current which this divider drains from input is 2.4 a. this value is much higher than what the device consumes. keeping r top and r bot high will optimize efficiency conversion at very light loads. there are some potential issues with higher value resistors, as in the case of small surface mount resistors; environment contamination can create leakage paths on the pcb that significantly change the resistor divider and may affect the output voltage tolerance. 5.2.1 overvoltage protection the MCP1661 features an output overvoltage protection (ovp) in case r top is disconnected from the v out line. a typical 80 mv ovp reference is compared to v fb voltage. if voltage on the v fb pin drops below the reference value, the device stops switching and prevents v out from rising up to a dangerous value. ovp is not enabled during start-up and thermal shutdown events. example 5-1: v out =12.0v v fb = 1.227v r bot =120k ? r top = 1053.6 k ? (v out = 11.96v with a standard value of 1050 k ? ) example 5-2: v out =24.0v v fb = 1.227v r bot =53k ? r top = 983.67 k ? (v out = 23.82v with a standard value of 976 k ? ) r top r bot v out v fb ------------- 1 ? ?? ?? ? = MCP1661 ds20005315b-page 16 ? 2014-2015 microchip technology inc. 5.3 input capacitor selection the boost input current is smoothened by the boost inductor, reducing the amount of filtering necessary at the input. some capacitance is recommended to provide decoupling from the input source. because MCP1661 is rated to work up to 125c, low esr x7r ceramic capacitors are well suited, since they have a low temperature coefficient and are small-sized. for limited temperature range use at up to 85c, a x5r ceramic capacitor can be used. for light load applications, 4.7 f of capacitance is sufficient at the input. for high-power applications that have high source impedance or long leads, using a 20-30 f input capacitor is recommended to sustain high input boost currents. additional input capacitance can be added to provide a stable input voltage. table 5-1 contains the recommended range for the input capacitor value. 5.4 output capacitor selection the output capacitor helps provide a stable output voltage during sudden load transients and reduces the output voltage ripple. as with the input capacitor, x7r ceramic capacitor is recommended for this application. using other capacitor types (aluminum or tantalum) with large esr has impact on the converter's efficiency (see an1337), maximum output power and stability. for limited temperature range (up to 85c), x5r ceramic capacitors can be used. the dc rating of the output capacitor should be greater than the v out value. generally, ceramic capacitors lose up to 50% of their capacity when the voltage applied is close to the maximum dc rating. choosing a capacitor with a safe higher dc rating or placing two capacitors in parallel assure enough capacity to correctly filter the output voltage. the MCP1661 device is internally compensated so output capacitance range is limited. see table 5-1 for the recommended output capacitor range. an output capacitance higher than 10 f adds a better load step response and high-frequency noise attenuation, especially while stepping from light to heavy current loads. in addition, 2 x 10 f output capacitors ensure a better recovery of the output after a short period of overloading. while the n-channel switch is on, the output current is supplied by the output capacitor c out . the amount of output capacitance and equivalent series resistance will have a significant effect on the output ripple voltage. while c out provides load current, a voltage drop also appears across its internal esr that results in ripple voltage. peak-to-peak output ripple voltage also depends on the equivalent series inductance (esl) of the output capacitor. there are ceramic capacitors with special internal architecture which minimize the esl. consult the ceramic capacitor's manufacturer portfolio for more information. ta b l e 5 - 1 contains the recommended range for the input and output capacitor value. 5.5 inductor selection the MCP1661 device is designed to be used with small surface mount inductors; the inductance value can range from 4.7 h to 10 h. an inductance value of 4.7 h is recommended for output voltages below 15v. for higher output voltages, up to 32v, an inductance value of 10 h is optimum. while the device operates at low inputs, below 3.0v, a low value inductor (2.2 h or 3.3 h) ensures better stability but limited output power capability. usually, this is a good trade-off as boost converters powered from two-cell batteries are low-power applications. table 5-1: capacitor value range c in c out minimum 4.7 f 10 f maximum ? 47 f ? 2014-2015 microchip technology inc. ds20005315b-page 17 MCP1661 several parameters are used to select the correct inductor: maximum rated current, saturation current and copper resistance (dcr). for boost converters, the inductor current is much higher than the output current. the average inductor current is equal to the input current. the inductor?s peak current is 30-40% higher than the average. the lower the inductor dcr, the higher the efficiency of the converter: a common trade-off in size versus efficiency. the saturation current typically specifies a point at which the inductance has rolled off a percentage of the rated value. this can range from a 20% to 40% reduction in inductance. as inductance rolls off, the inductor ripple current increases, as does the peak switch current. it is important to keep the inductance from rolling off too much, causing switch current to reach the peak limit. 5.6 rectifier diode selection schottky diodes are used to reduce losses. the diode?s current rating has to be equal or higher than the maximum output current. the diode?s reverse breakdown voltage must be higher than the internal switch rating voltage of 36v. the converter?s efficiency will be improved if the voltage drop across the diode is lower. the forward voltage rating is forward-current dependent, which is equal in particular to the load current. for high currents and high ambient temperatures, use a diode with good thermal characteristics. 5.7 sepic converter considerations one of the advantages of using MCP1661 in sepic topology is the usage of an output disconnect feature. also, the output voltage may be lower or higher than the input voltage, resulting in buck or boost operation. input voltage is limited to the 2.4-5.5v range. one major advantage is that the sepic converter allows 3.0v or 3.3v buck-boost application from a li-ion battery with load disconnect. also, sepic is recommended for higher output voltages where an input-to-output isolation is necessary (due to the coupling capacitor). an application example is shown in figure 6-3 . the maximum output voltage, v outmax , must be limited to the sum of (v in +v out ) < 36v, which is the maximum internal switch dc rating. v in must be 5.5v. some extra aspects need to be taken into account when choosing the external components: ? the dc voltage rating of the coupling capacitor should be at least equal to the maximum input voltage ? the average current rating of the rectifier diode?s is equal to the output load current ? the peak current of the rectifier diode is the same as the internal switch current, i sw =i in +i out . see the notes on figure 6-3 in section 6.0 ?typical application circuits? for some recommended 1:1 coupled inductors. 5.8 thermal calculations the MCP1661 device is available in two different packages (5-lead sot-23 and 8-lead 2x3 tdfn). by calculating the power dissipation and applying the package thermal resistance ( ? ja ), the junction temperature is estimated. the maximum continuous junction temperature rating for the MCP1661 device is +125c. to quickly estimate the internal power dissipation for the switching boost regulator, an empirical calculation using measured efficiency can be used. given the measured efficiency, the internal power dissipation is estimated by equation 5-2 . table 5-2: MCP1661 recommended inductors for boost converters part number value (h) dcr ? (typ.) i sat (a) size wxlxh (mm) coilcraft mss5131-472 4.7 0.038 1.42 5.1x5.1x3.1 xfl4020-472 4.7 0.057 2.7 4.2x4.2x2.1 lps5015-562 5.6 0.175 1.6 5.0x5.0x1.5 lps6235-103 10 0.065 1.5 6.2x6.2x3.5 xal4040-103 10 0.092 1.9 4.3x4.3x4.1 wrth elektronik 744025004 we-tpc 4.7 0.1 1.7 2.8x2.8x2.8 744043004 we-tpc 4.7 0.05 1.7 4.8x4.8x2.8 744773112 we-pd2 10 0.156 1.6 4.0x4.5x3.2 74408943100 we-spc 10 0.082 2.1 4.8x4.8x3.8 tdk corporation b82462g4472 4.7 0.04 1.8 6.3x6.3x3.0 b82462g4103 10 0.062 1.3 6.3x6.3x3.0 vlcf4024t-4r7 4.7 0.087 1.43 4.0x4.0x2.4 table 5-3: recommended schottky diodes type v outmax t a pmeg2005 18v < 85c pmeg4005 36v < 85c mbr0520 18v < 125c mbr0540 36v < 125c MCP1661 ds20005315b-page 18 ? 2014-2015 microchip technology inc. equation 5-2: the difference between the first term, input power, and the second term, power delivered, is the power dissipated when using the MCP1661 device. this is an estimate, assuming that most of the power lost is internal to the MCP1661 and not c in , c out , the diode and the inductor. there is some percentage of power lost in the boost inductor and rectifier diode, with very little loss in the input and output capacitors. for a more accurate estimation of the internal power dissipation, subtract the i inrms 2 xl dcr and i out xv f power dissipation (where i nrms is the average input current, l dcr is the inductor series resistance and v f is the diode voltage drop). 5.9 pcb layout information good printed circuit board layout techniques are important to any switching circuitry, and switching power supplies are no different. when wiring the switching high-current paths, short and wide traces should be used. therefore, it is important that the input and output capacitors be placed as close as possible to the MCP1661 to minimize the loop area. the feedback resistors and feedback signal should be routed away from the switching node and the switching current loop. when possible, ground planes and traces should be used to help shield the feedback signal and minimize noise and magnetic interference. figure 5-1: 5-lead sot-23 recommended layout. v out i out ? efficiency ------------------------------------- ?? ?? v out i out ? ?? ? p dis = c out l c in +v in gnd gnd +v out en MCP1661 r top 1 gnd vias to gnd bottom plane r bot vias to gnd bottom plane d a k gnd bottom plane ? 2014-2015 microchip technology inc. ds20005315b-page 19 MCP1661 figure 5-2: 8-lead tdfn recommended layout. c out l c in +v in +v out MCP1661 routed to bottom side r bot gnd vias to gnd bottom plane 1 r top a k d en via to gnd en routed on bottom side gnd gnd bottom plane MCP1661 ds20005315b-page 20 ? 2014-2015 microchip technology inc. 6.0 typical application circuits figure 6-1: two alkaline cells to 12v boost converter. v in gnd v fb v out 12v, 75 ma c out 10 f c in 10 f l 4.7 h sw 1.05 m ? 120 k ? en + - alkaline on off + - alkaline r top r bot v in 2.4v -3.0v d MCP1661 schottky d component value manufacturer part number comment c in 10 f tdk corporation c2012x7r1a106k125ac cap. ceramic 10 f 10v 10% x7r 0805 c out 10 f tdk corporation c3216x7r1c106k160ac cap. ceramic 10 f 16v 10% x7r 1206 l 4.7 h coilcraft xfl4020-472meb inductor power 4.7 h 2a smd r top 1.05 m ? yageo corporation rc0805fr-071m05l res. 1.05 m ? 1/8w 1% 0805 smd r bot 120 k ? yageo corporation rc0805fr-07120kl res. 120 k ? 1/8w 1% 0805 smd d ? nxp semiconductor pmeg2005eh,115 diode schottky 20v 0.5a sod123f ? 2014-2015 microchip technology inc. ds20005315b-page 21 MCP1661 figure 6-2: single li-ion cell to 24v output boost converter. gnd v fb v out 24v, 50 ma c out 10 f c in 10 f l 10 h sw 1.05 m ? 56 k ? en + - li-ion r top r bot v in 3.0v-4.2v d component value manufacturer part number comment c in 10 f tdk corporation c2012x7r1a106k125ac cap. ceramic 10 f 10v 10% x7r 0805 c out 10 f tdk corporation c3216x7r1v106k160ac cap. ceramic 10 f 35v 10% x7r 1206 l 10 h epcos ag b82462g4103m000 inductor power 10 h 1.5a smd r top 1.05 m ? yageo corporation rc0805fr-071m05l res. 1.05 m ? 1/8w 1% 0805 smd r bot 56 k ? yageo corporation rc0805fr-0756kl res. 56 k ? 1/8w 1% 0805 smd d ? micro commercial components mbr0540-tp diode schottky 40v 0.5a sod123 v in MCP1661 schottky MCP1661 ds20005315b-page 22 ? 2014-2015 microchip technology inc. figure 6-3: single li-ion cell to 3.3v output buck-boost (sepic) converter with 1:1 coupled inductors and load disconnect. v in gnd v fb v out 3.3v, 250 ma c out 4.7-10 f c in 4.7-10 f l1a ( 1 ) 4.7 h sw 2.2 k ? 1.3 k ? en + - li-ion on off r top r bot l1b ( 1 ) 4.7 h v in 3.0v-4.2v d c c 1f MCP1661 component value manufacturer part number comment c in 10 f tdk corporation c2012x7r1a106k125ac cap. ceramic 10 f 10v 10% x7r 0805 c out 10 f tdk corporation c3216x7r1v106k160ac cap. ceramic 10 f 35v 10% x7r 1206 c c 1 f tdk corporation c2012x7r1e105k125ab cap. ceramic 1 f 25v 10% x7r 0805 l 4.7 h wrth elektronik 744878004 inductor array 2 coil 4.7 h smd r top 2.2 k ? yageo corporation rc0805fr-072k2l res. 2.2 k ? 1/8w 1% 0805 smd r bot 1.3 k ? yageo corporation rc0805fr-071k3l res. 1.3 k ? 1/8w 1% 0805 smd d ? nxp semiconductors pmeg2020aea,115 diode schottky 20v 2a sod323 schottky note 1: recommended 1:1 coupled inductors. ? 2014-2015 microchip technology inc. ds20005315b-page 23 MCP1661 figure 6-4: single li-ion cell to 12v flyback converter for low load currents application example. v in gnd v fb v out 12v c out 10 f c in 10 f sw 1.05 m ? 120 k ? en on off r top r bot d + - li-ion v in 3.3v-4.2v c ff 22-33 p f tr schottky MCP1661 component value manufacturer part number comment c in 10 f tdk corporation c2012x7r1a106k125ac cap. ceramic 10 f 10v 10% x7r 0805 c out 10 f tdk corporation c3216x7r1v106k160ac cap. ceramic 10 f 35v 10% x7r 1206 c ff 27 pf tdk corporation c1608np02a270j080aa cap. ceramic 27 pf 100v 5% np0 0603 tr 25 h wrth elektronik 750310799 trans. flyback lt3573 25 h smd r top 1.05 m ? yageo corporation rc0805fr-071m05l res. 1.05 m ? 1/8w 1% 0805 smd r bot 120 k ? yageo corporation rc0805fr-07120kl res. 120 k ? 1/8w 1% 0805 smd d ? micro commercial components mbr0540-tp diode schottky 40v 0.5a sod123 25 h MCP1661 ds20005315b-page 24 ? 2014-2015 microchip technology inc. figure 6-5: two alkaline cells to 12v boost converter with load disconnect application example. v in gnd v fb v out 12v, 50 ma c out 10 f c in 10 f l 4.7 h sw 1.05 m ? 120 k ? en + - alkaline on off r top r bot v in 2.4v-3.0v d r bot schottky r bot v out i out ---------------- 1 0 0 ? ? + - alkaline MCP1661 c1 0.1 f component value manufacturer part number comment c in 10 f tdk corporation c2012x7r1a106k125ac cap. ceramic 10 f 10v 10% x7r 0805 c out 10 f tdk corporation c3216x7r1v106k160ac cap. ceramic 10 f 35v 10% x7r 1206 c1 0.1 f tdk corporation c1608x7r1e104k080aa cap. ceramic 0.1 f 25v 10% x7r 0603 l 4.7 h wrth elektronik 744043004 inductor power 4.7 h 1.55a smd r top 1.05 m ? yageo corporation rc0805fr-071m05l res. 1.05 m ? 1/8w 1% 0805 smd r bot 120 k ? yageo corporation rc0805fr-07120kl res. 120 k ? 1/8w 1% 0805 smd d ? micro commercial components mbr0540-tp diode schottky 40v 0.5a sod123 q ? micro commercial components mmbt3906-tp trans. ss pnp 40v 300mw sot-23 ? 2014-2015 microchip technology inc. ds20005315b-page 25 MCP1661 7.0 packaging information 7.1 package marking information 8-lead tdfn (2x3x0.75 mm) example 5-lead sot-23 example legend: xx...x customer-specific information y year code (last digit of calendar year) yy year code (last 2 digits of calendar year) ww week code (week of january 1 is week ?01?) nnn alphanumeric traceability code pb-free jedec ? designator for matte tin (sn) * this package is pb-free. the pb-free jedec designator ( ) can be found on the outer packaging for this package. note : in the event the full microchip part number cannot be marked on one line, it will be carried over to the next line, thus limiting the number of available characters for customer-specific information. 3 e 3 e abz 525 25 aaal5 25256 MCP1661 ds20005315b-page 26 ? 2014-2015 microchip technology inc. n b e e1 d 1 2 3 e e1 a a1 a2 c l l1 ? 2014-2015 microchip technology inc. ds20005315b-page 27 MCP1661 note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging MCP1661 ds20005315b-page 28 ? 2014-2015 microchip technology inc. note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging ? 2014-2015 microchip technology inc. ds20005315b-page 29 MCP1661 note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging MCP1661 ds20005315b-page 30 ? 2014-2015 microchip technology inc. ? 2014-2015 microchip technology inc. ds20005315b-page 31 MCP1661 appendix a: revision history revision b (february 2015) the following is the list of modifications: 1. updated section 6.0 ?typical application circuits? . 2. added legend tables for figures 6-3 to 6-5 . 3. minor typographical corrections. revision a (june 2014) ? original release of this document. MCP1661 ds20005315b-page 32 ? 2014-2015 microchip technology inc. product identification system to order or obtain information, e. g., on pricing or delivery, refer to the factory or the listed sales office . examples: a) MCP1661t-e/mny: tape and reel, extended temperature, 8ld tfdn package b) MCP1661t-e/ot: tape and reel, extended temperature, 5ld sot-23 package device: MCP1661: high-voltage step-up led driver with uvlo and olp tape and reel option: t = tape and reel (1) temperature range: e=-40 ? c to +125 ? c (extended) package: mn* = plastic dual flat, no lead ? 2x3x0.75 mm body (tdfn) ot = plastic small outline transistor (sot-23) *y = nickel palladium gold manufacturing designator. only available on the tdfn package. note 1: tape and reel identifier only appears in the catalog part number description. this identifier is used for ordering purposes and is not printed on the device package. check with your microchip sales office for package availability with the tape and reel option. part no. x /xx package temperature range device [x] (1) tape and reel option ? 2014-2015 microchip technology inc. ds20005315b-page 33 information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. it is your responsibility to ensure that your application meets with your specifications. microchip makes no representations or warranties of any kind whether express or implied, written or oral, statutory or otherwise, related to the information, including but not limited to its condition, quality, performance, merchantability or fitness for purpose . microchip disclaims all liability arising from this information and its use. use of microchip devices in life support and/or safety applications is entirely at the buyer?s risk, and the buyer agrees to defend, indemnify and hold harmless microchip from any and all damages, claims, suits, or expenses resulting from such use. no licenses are conveyed, implicitly or otherwise, under any microchip intellectual property rights. trademarks the microchip name and logo, the microchip logo, dspic, flashflex, flexpwr, jukeblox, k ee l oq , k ee l oq logo, kleer, lancheck, medialb, most, most logo, mplab, optolyzer, pic, picstart, pic 32 logo, righttouch, spynic, sst, sst logo, superflash and uni/o are registered trademarks of microchip tec hnology incorporated in the u.s.a. and other countries. the embedded control solutions company and mtouch are registered trademarks of microchip technology incorporated in the u.s.a. analog-for-the-digital age, bodycom, chipkit, chipkit logo, codeguard, dspicdem, dspicdem.net, ecan, in-circuit serial programming, icsp, inter-chip connectivity, kleernet, kleernet logo, miwi, mpasm, mpf, mplab certified logo, mplib, mplink, multitrak, netdetach, omniscient code generation, picdem, picdem.net, pickit, pictail, righttouch logo, real ice, sqi, serial quad i/o, total endurance, tsharc, usbcheck, varisense, viewspan, wiperlock, wireless dna, and zena are trademarks of microchip technology incorporated in the u.s.a. and other countries. sqtp is a service mark of microchip technology incorporated in the u.s.a. silicon storage technology is a registered trademark of microchip technology inc. in other countries. gestic is a registered trademar ks of microchip technology germany ii gmbh & co. kg, a subsidiary of microchip technology inc., in other countries. all other trademarks mentioned herein are property of their respective companies. ? 2014-2015, microchip technology incorporated, printed in the u.s.a., all rights reserved. isbn: 978-1-63277-121-6 note the following details of the code protection feature on microchip devices: ? microchip products meet the specification cont ained in their particular microchip data sheet. ? microchip believes that its family of products is one of the most secure families of its kind on the market today, when used i n the intended manner and under normal conditions. ? there are dishonest and possibly illegal methods used to breach the code protection feature. all of these methods, to our knowledge, require using the microchip produc ts in a manner outside the operating specif ications contained in microchip?s data sheets. most likely, the person doing so is engaged in theft of intellectual property. ? microchip is willing to work with the customer who is concerned about the integrity of their code. ? neither microchip nor any other semiconduc tor manufacturer can guarantee the security of their code. code protection does not mean that we are guaranteeing the product as ?unbreakable.? code protection is constantly evolving. we at microchip are co mmitted to continuously improvin g the code protection features of our products. attempts to break microchip?s code protection feature may be a violation of the digital millennium copyright act. if such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that act. microchip received iso/ts-16949:2009 certification for its worldwide headquarters, design and wafer fabrication facilities in chandler and tempe, arizona; gresham, oregon and design centers in california and india. the company?s quality system processes and procedures are for its pic ? mcus and dspic ? dscs, k ee l oq ? code hopping devices, serial eeproms, microperipherals, nonvolatile memory and analog products. in addition, microchip?s quality system for the design and manufacture of development systems is iso 9001:2000 certified. quality management s ystem certified by dnv == iso/ts 16949 == ds20005315b-page 34 ? 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