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| ? 2003-2013 microchip technology inc. ds21762b-page 1 mcp1601 features ? input range of 2.7v to 5.5v ? 3 operating modes: pwm, pfm and ldo ? integrated buck and synchronous switches ? ceramic or electrolytic input/output filtering capacitors ? 750 khz fixed switching frequency ? oscillator synchronization to 1 mhz pwm mode ? auto-switching from pwm/pfm operation ? 100% duty cycle capable for low input voltage ? 500 ma continuous output current capability ? integrated under-voltage lock-out protection ? integrated over-temperature protection ? integrated soft start circuitry ? low output voltage capability to 0.9v ? temperature range: -40c to +85oc ? small 8-pin msop package applications ? low power handheld cpus and dsps ? cellular phones ? organizers and pdas ?digital cameras ? +5v or +3.3v distributed voltages ? usb powered devices package type description the mcp1601 is a fully integrated synchronous buck (step down) dc/dc converter for battery powered sys- tems. with an input operating range of 2.7v to 5.5v, the mcp1601 is ideal for applications being powered by one single cell li-ion, 2 to 3 cell nimh, nicd or alkaline sources. output voltages can range from 0.9v to v in to accommodate a wide range of applications. efficiency can exceed 92% while operating at 750 khz with load current capability up to 500 ma. the mcp1601 is used to minimize space, cost and wasted energy. the pwm mode switching frequency is internally set to a fixed 750 khz allowing the use of low profile, surface mount inductors and ceramic capacitors while maintaining a typical efficiency of 92%. the mcp1601 is capable of three distinct operating modes: pwm, pfm and low drop out. when operating in pwm (pulse width modulation) mode, the dc/dc converter switches at a single high frequency determined by either the internal 750 khz oscillator or external synchronization frequency. for applications that operate at very light to no load for extended periods of time, the mcp1601 is capable of operating in pfm (pulse frequency modulation mode) to reduce the number of switching cycles/sec and consume less energy. the third mode of operation (ldo mode) occurs when the input voltage approaches the output voltage and the buck duty cycle approaches 100%. the mcp1601 will enter a low drop out mode and the high-side p-channel buck switch will saturate, providing the output with the maximum voltage possible. the mcp1601 has integrated over-current protection, over-temperature protection and uvlo (under voltage lockout) to provide for a fail safe solution with no external components. the mcp1601 is available in the 8-pin msop package, with an operating temperature range of -40c to +85c. 8-pin msop v in shdn fb a gnd l x p gnd v out sync/pwm 1 2 3 4 8 7 6 5 mcp1601 500 ma synchronous buck regulator
mcp1601 ds21762b-page 2 ? 2003-2013 microchip technology inc. typical application functional block diagram v out p gnd l x shdn v in 1 2 3 4 8 7 6 5 mcp1601 fb sync/ a gnd input voltage 2.7v-4.2v c in 10 f 10 h c out 10 f r 1 250 k ? (for 1.8v) r 2 200 k ? typical application (2.7v to 4.2v) i out = 0 ma to 400 ma c out range 10 f to 47 f l range 10 h to 22 h c 1 47 pf v out range 1.2v to 3.3v pwm + - ea c comp fb r comp feedforward oscillator k*v in duty clamp 10% - 90% pwm latch r out inset timing 0.8v i sense p v ref s sqw v in shdn internal circuit uvlo enable out a gnd a gnd a gnd pfm comparator internal band gap reference buffered 0.8v output v ref sync/pwm v ref i sense p i sense n pfm mode timing l x v out p gnd p gnd soft start i sense n duty clamp 800 k ? 12 pf 10 pf 3m ? - - + v ref - - + - + enable cycle cycle ? 2003-2013 microchip technology inc. ds21762b-page 3 mcp1601 1.0 electrical characteristics absolute maximum ratings ? v in - a gnd ......................................................................6.0v shdn , fb, sync/pwm, v out ..... (a gnd -0.3v) to (v in +0.3v) l x to p gnd ................................................ -0.3v to (v in +0.3v) p gnd to a gnd .................................................. -0.3v to +0.3v output short circuit current .................................continuous storage temperature .....................................-65c to +150c ambient temp. with power applied ................-40c to +85c operating junction temperature...................-40c to +125c esd protection on all pins ???????????????????????????????????????????????????? 4kv ? notice: stresses above those listed under ?maximum rat- ings? 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 listings of this spec ification is not implied. expo- sure to maximum rating conditions for extended periods may affect device reliability. pin function table name function v in input source voltage shdn device shutdown pin fb output voltage feedback input a gnd analog ground v out sensed output voltage sync/pwm synchronous clock input or pwm/ pfm select p gnd power ground l x output inductor node electrical specifications electrical specifications: unless otherwise indicated, v in =4.2v, v out =1.8v, i load = 10 ma, t a =-40c to +85c. parameters sym min typ max units conditions power input requirements voltage v in 2.7 ? 5.5 v i load = 0 ma to 500 ma shutdown current i(v in ) ? 0.05 1.0 a shutdown mode (shdn = gnd) pfm mode current i(v in ) ? 119 180 a sync/pwm = gnd, pfm mode (i load = 0 ma) oscillator section internal oscillator frequency f osc 650 750 850 khz sync/pwm = v in external oscillator capture range f sync 850 ? 1000 khz f sync > f osc external oscillator duty cycle f syn-fall 10 ? 90 % f sync = 1 mhz internal power switches r dson p-channel r dson-p ? 500 ? m ? i p =100 ma, t a =+25c, v in =4.2v r dson n-channel r dson-n ? 500 ? m ? i n =100 ma, t a =+25c, v in =4.2v dropout voltage v dropout ? 250 ? mv v out = 2.7v, i load = 300 ma, t a =+25c, v dropout =97%v out pin leakage current i lx -1.0 ? 1.0 a shdn = 0v, v in = 5.5v, l x = 0v, l x = 5.5v output pwm mode peak current limit i peak-pwm ? 1.0 ? a pwm mode, sync/pwm = v in, t a = +25c output voltage output voltage range v out 0.9 ? v in v reference feedback voltage v fb 0.78 0.8 0.82 v feedback input bias current i vfb ?0.1?na line regulation v line-reg ?0.1?%/vv in =2.7v to 5.5v, i load =10 ma load regulation v load-reg ?1.5? %v in = 3.6v, i load = 0 ma to 300 ma start-up time t start ? 0.5 ? ms pwm mode, sync/pwm=v in mcp1601 ds21762b-page 4 ? 2003-2013 microchip technology inc. temperature specifications protection features average short circuit current ? 890 ? ma r load < 1 ohm under-voltage lockout uvlo 2.4 ? 2.7 v for v in decreasing under-voltage lockout hysteresis uvlo- hys ? 190 ? mv thermal shutdown t shd ? 160 ? c thermal shutdown hysteresis t shd-hys ?10?c interface signals (shdn , sync/pwm) logic low input v in-high ? ? 15 % of v in logic high input v in-high 45 ? ? % of v in input leakage current i in-lk ??0.1a electrical specifications: unless otherwise noted, all parameters apply at v dd = 2.7v to 5.5v parameters symbol min typ max units conditions temperature ranges specified temperature range t a -40 ? +85 c operating junction temperature range t j -40 ? +125 c storage temperature range t a -65 ? +150 c thermal package resistances thermal resistance, 8 pin msop ? ja ? 208 ? c/w single-layer semi g42-88 board, natural convection electrical specifications (continued) electrical specifications: unless otherwise indicated, v in =4.2v, v out =1.8v, i load = 10 ma, t a =-40c to +85c. parameters sym min typ max units conditions ? 2003-2013 microchip technology inc. ds21762b-page 5 mcp1601 2.0 typical performance curves note: unless otherwise indicated, v in = 4.2v, v out = 1.8v, l = 10 h, c out = 10 f (x5r ceramic), c in = 10 f (x5r ceramic), sync/pwm=v in . figure 2-1: efficiency vs. load current (v out = 1.2v). figure 2-2: efficiency vs. load current (v out = 1.8v). figure 2-3: efficiency vs. load current (v out = 3.3v). figure 2-4: pfm mode quiescent current vs. input voltage. figure 2-5: oscillator frequency vs. input voltage. figure 2-6: output voltage vs. load current. note: the graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. the performance characteristics listed herein are not tested or guaranteed. in some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. 40 50 60 70 80 90 100 0 100 200 300 400 500 load current (ma) efficiency (%) v out = 1.2v auto pwm/pfm v in = 2.7v v in = 3.6v v in = 4.2v 50 60 70 80 90 100 110 0 100 200 300 400 500 load current (ma) efficiency (%) v out = 1.8v auto pwm/pfm v in = 2.7v v in = 3.6v v in = 4.2v 50 60 70 80 90 100 110 0 100 200 300 400 500 load current (ma) efficiency (%) v out = 3.3v auto pwm/pfm v in = 5.0v v in = 4.5v v in = 5.5v 100 110 120 130 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 input voltage (v) pfm mode quiescent current (a) v out = 1.8v pfm mode i load = 0 t a = - 40c t a = + 0c t a = + 85c t a = + 25c 680.0 700.0 720.0 740.0 760.0 780.0 2.73.13.53.94.34.75.15.5 input voltage (v) internal oscillator frequency (khz) t a = + 125c t a = - 40c t a = + 25c t a = 0c i load = 10 ma forced pwm mode 1.100 1.125 1.150 1.175 1.200 1.225 1.250 1.275 1.300 0 100 200 300 400 500 load current (ma) output voltage (v) v out = 1.2v auto pwm/pfm v in = 2.7v v in = 3.6v v in = 4.2v mcp1601 ds21762b-page 6 ? 2003-2013 microchip technology inc. note: unless otherwise indicated, v in = 4.2v, v out = 1.8v, l = 10 h, c out = 10 f (x5r ceramic), c in = 10 f (x5r ceramic), sync/pwm=v in . figure 2-7: output voltage vs. load current. figure 2-8: output voltage vs. load current. figure 2-9: input to output voltage differential for 100% duty cycle vs. load current. figure 2-10: switch leakage vs. temperature. figure 2-11: typical pwm mode of operation waveforms. figure 2-12: typical pfm mode of operation waveforms. 1.700 1.720 1.740 1.760 1.780 1.800 1.820 0 100 200 300 400 500 load current (ma) output votlage (v) v out = 1.8v auto pwm/pfm v in = 2.7v v in = 3.6v v in = 4.2v 3.10 3.13 3.15 3.18 3.20 3.23 3.25 3.28 3.30 3.33 3.35 0 100 200 300 400 500 load current (ma) output voltage (v) v out = 3.3v auto pwm/pfm v in = 4.5v v in = 5.0v v in = 5.5v 0 50 100 150 200 250 300 350 400 450 0 100 200 300 400 500 load current (ma) dropout voltage (mv) v out = 3.3v v out = 2.7v dropout = (v in -v out ) in mv @ 97% of v out 0.0 1.5 3.0 4.5 -40 -15 10 35 60 85 ambient temperature (c) l x leakage current (na) v in = 5.0v synchronous n channel buck switch p channel ? 2003-2013 microchip technology inc. ds21762b-page 7 mcp1601 note: unless otherwise indicated, v in = 4.2v, v out = 1.8v, l = 10 h, c out = 10 f (x5r ceramic), c in = 10 f (x5r ceramic), sync/pwm=v in . figure 2-13: typical startup from shutdown waveform. figure 2-14: startup from 0v input. figure 2-15: load step response (forced pwm). figure 2-16: load step response (pfm to pwm). figure 2-17: line step response (forced pwm). figure 2-18: line step response (pfm mode). mcp1601 ds21762b-page 8 ? 2003-2013 microchip technology inc. note: unless otherwise indicated, v in = 4.2v, v out = 1.8v, l = 10 h, c out = 10 f (x5r ceramic), c in = 10 f (x5r ceramic), sync/pwm=v in . figure 2-19: typical output ripple voltage (forced pwm mode). figure 2-20: typical output ripple voltage (pfm mode). figure 2-21: external oscillator synchronization. ? 2003-2013 microchip technology inc. ds21762b-page 9 mcp1601 3.0 pin functions table 3-1: pin function table 3.1 input voltage (v in ) connect the unregulated input voltage source to v in . if the input voltage source is located more than several inches away, or is a battery, a typical input capacitor of 10 f is recommended. 3.2 shutdown input (shdn ) connect shdn to a logic low input to force the device into a shutdown low quiescent current mode. when in shutdown, both the p-channel and n-channel switches are turned off, in addition to the internal oscil- lator and other circuitry. when connected to a logic high input, the device will operate in the selected mode. 3.3 feedback input (fb) connect fb to an external resistor divider to set output voltage regulation. the feedback pin is typically equal to 0.8v. see section 5.0, ?applications information?, for details in selecting feedback resistors. 3.4 analog ground return (a gnd ) tie all small signal ground returns to a gnd . (see section 5.6, ?printed circuit board layout?, for details). 3.5 oscillator synchronization or pwm/ pfm select mode input (sync/pwm) connect an external oscillator to sync/pwm to syn- chronize. with an external oscillator present, the device is forced into a pwm-only mode of operation. for inter- nal oscillator operation, the sync/pwm pin is tied high to operate in a forced pwm-only mode and low for a pwm/pfm mode of operation. 3.6 output voltage sense (v out ) connect the output voltage directly to v out for sensing. 3.7 power ground return (p gnd ) connect all large signal ground returns to p gnd . (see section 5.6, ?printed circuit board layout?, for details). 3.8 buck inductor connection (l x ) connect l x directly to the buck inductor. this pin car- ries large signal-level currents and all connections should be as short and wide as possible. (see section 5.6, ?printed circuit board layout?, for details). pin name function 1v in input voltage 2shdn shutdown input 3 fb feedback input 4a gnd analog ground return 5 sync/ pwm oscillator synchronization or pwm/ pfm select mode input 6v out sensed output voltage input 7p gnd power ground return 8l x buck inductor output mcp1601 ds21762b-page 10 ? 2003-2013 microchip technology inc. 4.0 device operation the mcp1601 is a synchronous dc/dc converter with integrated switches. developed to provide high effi- ciency across a wide line and load range, the mcp1601 integrates the three modes of operation described below. in addition to three operating modes, the mcp1601 also integrates many features that mini- mize external circuitry, saving board space and cost. with two external resistors used to set the output volt- age, the mcp1601 output is adjustable from 0.9v to v in . 4.1 operating modes the mcp1601 has three distinct modes of operation, with each one optimized for a specific operating condi- tion commonly encountered in handheld portable power applications. 4.1.1 feedforward voltage pulse width modulation (pwm) mode the pulse width modulation (pwm) mode of operation is desired when operating from typical to maximum out- put currents with the proper head room voltage at the input. this mode of operation optimizes efficiency and noise by switching at a fixed frequency. typical output ripple voltage is less than 10 mv when using a 10 h inductor and 10 f ceramic capacitor. the internal operating frequency of the mcp1601 is 750 khz, nom- inal. the duty cycle, or ?on? time, of the high-side, inte- grated, p-channel mosfet is determined by the continuous mode buck transfer function. for the con- tinuous inductor current case, the duty cycle can be approximated by v out /v in . the integrated high-side buck p-channel switch will conduct for the ?on? time. at the end of the ?on? time, the high-side p-channel switch is turned off and the integrated, low-side, n- channel synchronous switch is turned on to freewheel the inductor current. the pwm mode architecture employed in the mcp1601 is a feedforward voltage mode control and feeds the input voltage into the pwm oscillator ramp. this information is used to quickly change the operating duty cycle in the event of a sud- den input voltage change. the effects on the output voltage are minimized. to force the mcp1601 into pwm mode, the sync/pwm pin should be tied to a logic high. the forced pwm mode should be used for applications that require the fastest transient response from light load to heavy load or applications that require a single switching frequency independent of load. an external oscillator between 850 khz and 1 mhz can be connected to the sync/pwm pin for synchroniza- tion to an external clock source. the mcp1601 will always operate in the pwm mode when synchronized to an external oscillator. 4.1.2 pulse frequency modulation (pfm) mode the mcp1601 is also capable of operating in a pulse frequency modulation mode. this mode of operation is desired for applications that have very long periods of inactivity and the output current requirement placed on the mcp1601 is very low. by entering the pfm mode of operation, the switching frequency becomes mainly a function of load current and will decrease as the load current decreases. by switching slower, the energy used turning ?on? and ?off? the high-side p-channel and low-side n-channel is reduced, making the pfm mode more efficient with light output load currents. when load activity is encountered, the mcp1601 will auto- matically switch from the pfm mode to the fixed fre- quency pwm mode by sensing the increase in load current. the auto pwm/pfm mode is selected by plac- ing a logic low at the sync/pwm input pin. if an exter- nal clock is used to synchronize the mcp1601 switching frequency, the pfm mode is automatically disabled. to enter the pfm mode of operation, the sync/pwm pin must be held to a logic low level and the peak induc- tor current, sensed internal to the mcp1601, is below the internal pfm threshold for more than 1024 clock cycles. if both of these conditions are met, the mcp1601 will enter the pfm mode. while in the pfm mode, the mcp1601 will disable the low-side n-chan- nel switch to optimize efficiency at low operating cur- rents. a cycle will begin by turning on the high-side p-channel switch and will end when the output voltage exceeds a predetermined voltage set point. if the peak inductor current exceeds the internal pfm mode cur- rent threshold prior to the output voltage exceeding the voltage set point, the load current has increased and the mcp1601 will automatically switch to pwm opera- tion. the typical hysteresis on the pfm comparator is 6 mv. the typical output ripple voltage is below 40 mv when using a 10 h inductor and 10 f ceramic output capacitor when v in = 4.2v. for proper pfm mode oper- ation, the value of the external inductor and the exter- nal capacitor should be the same. for example, when using a 10 h inductor, a 10 f capacitor should be used. when using a 22 h inductor, a 22 f capacitor should be used. 4.1.3 low drop out (ldo) mode when the input voltage to the mcp1601 is decreasing and approaches the set output voltage level, the duty cycle increases to a maximum of 90% (typically). to continue to regulate the output to as high a voltage as possible, the mcp1601 enters the low drop out mode of operation. in this mode, the high-side p-channel mosfet acts like a saturated ldo. this mode allows the operation of the load circuitry down to the minimum input supply that is typical in battery-powered applications. ? 2003-2013 microchip technology inc. ds21762b-page 11 mcp1601 4.2 cross-conduction timing proper timing between turning on the p-channel, high- side mosfet and turning off the n-channel, low-side mosfet (and vice versa) is critical to obtaining high efficiency. this delay between transitions is what limits the maximum duty cycle obtainable by the mcp1601. the delay between transitions leads to more time when the external inductor current is freewheeling through the internal n-channel body diode and leads to a decrease in efficiency. if the timing delay is too short and both the internal p-channel mosfet and n- channel mosfet conduct, high peak currents will be observed shooting through the device. this will also reduce the operating efficiency. the mcp1601 inset timing is integrated to optimize efficiency for the entire line and load operating range of the device. 4.3 integrated protection features 4.3.1 shutdown by placing a logic low on the shdn pin of the mcp1601, the device will enter a low quiescent current shutdown mode. this feature turns off all of the internal bias and drivers within the mcp1601 in an effort to min- imize the quiescent current. this feature is popular for battery-operated, portable power applications. the shutdown low quiescent current is typically 1 a. 4.3.2 internal oscillator and synchronization capability the internal oscillator is completely integrated and requires no external components. the frequency is set nominally to 750 khz in an effort to minimize the exter- nal inductor and capacitor size needed for the buck topology. in addition to the internal 750 khz oscillator, the mcp1601 is capable of being synchronized to an external oscillator. the external oscillator frequency must be greater than 850 khz and less than 1 mhz. for proper synchronization, the duty cycle of the external synchronization clock must be between 10% and 90%. the minimum low voltage level should be below 15% of v in and the high level of the clock should be above 45% of v in . rise and fall time requirements for the external synchronization clock must be faster than 100 ns from 10% to 90%. when synchronizing to an external clock, the mcp1601 will always operate in the pwm mode in an effort to eliminate multiple switching frequency?s and their harmonics. 4.3.3 internal soft start the mcp1601 completely integrates the soft start func- tion and requires no external components. the soft start time is typically 0.5 ms and is reset during over- current and over-temperature shutdown. 4.3.4 over-temperature protection the mcp1601 protects the internal circuitry from over- temperature conditions by sensing the internal device temperature and shutting down when it reaches approximately 160 c. the device will shut down, the temperature will cool to approximately 150 c, soft start will be enabled and normal operation will resume with no external circuit intervention. 4.3.5 under-voltage lockout protection from operating at sustained input voltages that are out of range is prevented with the integrated under-voltage lockout feature. when the input voltage dips below 2.5v (typically), the mcp1601 will shutdown and the soft start circuit will be reset. normal operation will resume when the input voltage is elevated above 2.7v, maximum. this hysteresis is provided to prevent the device from starting with too low of an input voltage. mcp1601 ds21762b-page 12 ? 2003-2013 microchip technology inc. 5.0 applications information figure 5-1: typical application circuit. 5.1 setting output voltage the mcp1601 output voltage is set by using two exter- nal resistors for output voltages ? 1.2v. for output volt- ages < 1.2v, a third 1 m ? series resistor is necessary to compensate the control system. a 200 k ? resistor is recommended for r 2 , the lower end of the voltage divider. using higher value resistors will make the cir- cuit more susceptible to noise on the fb pin, causing unstable operation. lower value resistors can be used down to 20 k ? or below, if necessary. the feedback reference voltage for the mcp1601 is typically 0.8v. the equation used to calculate the output voltage is shown below. equation example: desired v out = 2.5v v fb = 0.8v r 2 = 200 k ? r 1 = 425 k ? 5.1.1 lead capacitor capacitor c 1 is used for applications that utilize ceramic output capacitors. to lower the pfm mode rip- ple voltage, a 47 pf capacitor for c 1 is used to couple the output ac ripple voltage to the internal pfm mode comparator. for pwm mode, only applications that use electrolytic capacitors that have 0.2 ?? or greater of esr (equivalent series resistance), c 1 is not necessary. 5.2 choosing external components 5.2.1 capacitors the mcp1601 was developed to take full advantage of the latest ceramic capacitor technology, though electro- lytic types can be used as well. when selecting the best capacitor for the application, the capacitance, physical size, esr, temperature coefficient, ripple current rat- ings (electrolytic) and cost are considered in making the best choice. when selecting ceramic capacitors for c out , the tem- perature coefficient of the dielectric should be evalu- ated. two dielectrics are recommended as they are stable over a wide temperature range (x5r and x7r). other dielectrics can be used, but their capacitance should stay within the recommended range over the entire operating temperature range. 1m ? for v out < 1.2v only v out p gnd l x shdn v in 1 2 3 4 8 7 6 5 mcp1601 fb sync/ a gnd input voltage 2.7v-4.2v c in 10 f 10 h c out 10 f r 1 250 k ? (for 1.8v) r 2 200 k ? mcp1601 application circuit i out = 0 ma to 400 ma c out range 10 f to 47 f l range 10 h to 22 h c 1 47 pf v out range 1.2v to 3.3v pwm r 1 r 2 v out v fb ? ?? 1 ? ?? ? = where: v out is the desired output voltage, v fb is the mcp1601 internal feedback reference voltage r 1 is the resistor connected to v out in the voltage divider r 2 is the resistor connected to ground in the voltage divider ? 2003-2013 microchip technology inc. ds21762b-page 13 mcp1601 5.2.1.1 input for all buck-derived topologies, the input current is pulled from the source in pulses, placing some burden on the input capacitor. for most applications, a 10 f ceramic capacitor connected to the mcp1601 input is recommended to filter the current pulses. less capaci- tance can be used for applications that have low source impedance. the ripple current ratings for ceramic capacitors are typically very high due to their low loss characteristics. lower-cost electrolytic capacitors can be used, but ripple current ratings should not be exceeded. 5.2.1.2 output for buck-derived topologies, the output capacitor fil- ters the continuous ac inductor ripple current while operating in the pwm mode. typical inductor ac ripple current for the mcp1601 is 120 ma peak-to-peak with a 3.6v input, 10 h inductor for a 1.8v output applica- tion. using an output capacitor with 0.3 ? of esr, the output ripple will be approximately 36 mv. the recommended range for the output capacitor is from 10 f (20%) to 47 f (20%). larger value capacitors can be used, but require evaluation of the control system stability. equation the above equation assumes that the output capaci- tance is large enough so that the ripple voltage (as a result of charging and discharging the capacitor) is negligible and can be used for applications that use electrolytic capacitors with esr > 0.3 ?? when using a 10 f ceramic x5r dielectric capacitor, the output ripple voltage is typically less than 10 mv. 5.2.2 buck inductor there are many suppliers and choices for selecting the buck inductor. the application, physical size require- ments (height vs. area), current rating, resistance, mounting method, temperature range, minimum induc- tance and cost all need to be considered in making the best choice. when choosing an inductor for the mcp1601 synchro- nous buck, there are two primary electrical specifications to consider. 1. current rating of the inductor. 2. resistance of the inductor. when selecting a buck inductor, many suppliers specify a maximum peak current. the maximum peak inductor current is equal to the maximum dc output current plus 1/2 the peak-to-peak ac ripple current in the inductor. the ac ripple current in the inductor can be calculated using the following relationship. equation solving for ? i l : equation example: the approximate ?on? time is equal to the duty cycle (v out / v in ) x 1/f sw . many suppliers of inductors rate the maximum rms (root mean square) current. the buck inductor rms current is dependent on the output current, inductance, input voltage, output voltage and switching frequency. for the mcp1601, the inductor rms current over the 2.7v to 5.5v input range, 0.9v to 5v output voltage range is no more than 15% higher than the average dc output current for the minimum recommended induc- tance of 10 h 20%. when selecting an inductor that has a maximum rms current rating, use a simple approximation that the rms current is 1.2 times the maximum output current. example: i out(max) = 300 ma, the inductor should have an rms rating > 360 ma (1.2 x i out(max) ). v ripple i lripple c outesr ? = v in =3.6v v out =1.8v f sw =750khz i out(max) =300ma t on = (1.8v/3.6v) x 1/(750 khz) t on = 667 ns v l = 3.6v - 1.8v = 1.8v ? i l = (1.8v/10 h) x 667 ns ? i l =120ma i l(peak) =i outmax + 1/2 ? i l i l(peak) = 300 ma + (120 ma) / 2 i l(peak) =360ma v l l t d di ? = ? i l v l l ? ??? t ? = where: ? t is equal to the ?on? time of the p-channel switch and, v l = the voltage across the inductor (v in - v out ) mcp1601 ds21762b-page 14 ? 2003-2013 microchip technology inc. dc resistance is another common inductor specifica- tion. the mcp1601 will work properly with inductor dc resistance down to 0 ? . the trade-off in selecting an inductor with low dc resistance is size and cost. to lower the resistance, larger wire is used to wind the inductor. the switch resistance in the mcp1601 is approximately 0.5 ? . inductors with dc resistance lower than 0.1 ? will not have a significant impact on the efficiency of the converter. 5.3 l and c out combinations when selecting the l-c out output filter components, the inductor value range is limited from 10 h to 22 h. however, when using the larger inductor values, larger capacitor values should be used. the following table lists the recommended combinations of l and c out . table 5-1: l-c out combinations 5.4 passive component suppliers table 5-2: ceramic capacitor suppliers table 5-3: electrolytic capacitor suppliers lc out 10 h 10 f to 47 f 15 h 15 f to 47 f 22 h 22f to 47 f note: for proper pfm mode operation, the value of the external inductor and the external capacitor should be the same. for exam- ple, when using a 10 h inductor, a 10 f capacitor should be used. when using a 22 h inductor, a 22 f capacitor should be used. supplier type description murata ? ceramic 10 f 0805 x5r 6.3v #grm21br60j106k murata ? ceramic 10 f 1206 x5r 6.3v #grm319r60j106k ta i y o yuden? ceramic 10 f 1210 x5r 6.3v jmk325bj106md avx? ceramic 10 f 0805 x5r 6.3v #08056d106mat4a avx? ceramic 10 f 1206 x5r 6.3v #12066d106mat4a kemet ? ceramic 10 f 1210 6.3v #c1210c106m9pac murata ? ceramic 22 f 1206 x5r 6.3v grm31cr60j226me20b ta i y o yuden? ceramic 22 f 1210 x5r 6.3v jmk325bj226my note: taiyo yuden 1210 is a low profile case (1.15 mm) supplier type description kemet ? tantalum 47 f d case 200 m ?? 10v #t495d476m010as avx? tantalum 47 f c case 300 m ? 6.3v #tpsc476m006s300 sprague ? tantalum 47 f c case 110 m ? 16v 594d47x0016c2t sprague ? tantalum 22 f b case 380 m ? 6.3v 594d226x06r3b2t sprague ? tantalum 15 f b case 500 m ? 10v 594d156x0010b2t ? 2003-2013 microchip technology inc. ds21762b-page 15 mcp1601 table 5-4: inductor suppliers 5.5 efficiency efficiency will be affected by the external component selection and the specific operating conditions for the application. in section 2.0, ?typical performance curves?, there are curves plotted using typical induc- tors that can be used to estimate the converter efficiency for 1.2v, 1.8v and 3.3v. 5.6 printed circuit board layout the mcp1601 is capable of switching over 500 ma at 750 khz. as with all high-frequency, switch mode, power supplies, a good board layout is essential to pre- venting the noise generated by the power train switch- ing from interfering with the sensing circuitry. the mcp1601 has not demonstrated a sensitivity to layout, but good design practice will prevent undesired results. figure 5-2: component placement. when designing a board layout for the mcp1601, the first thing to consider is the physical placement of the external components. in figure 5-2, sm0805 10 f ceramic capacitors are used for c in and c out . the sm0603 package is used for r 1 , r 2 and c 1 . the induc- tor used is the coilcraft ? lpo2506 series low profile (0.047? high). the board outline in this example is 1? x 1?. c in , l and c out are positioned around the mcp1601 to make the high current paths as short as possible. supplier l type area (mm) height (mm) dc resistance max. current series sumida ? 10 h unshielded 4.1 mm x 3.8 mm 3.0 mm 230 m ? 0.76a c32 sumida ? 10 h shielded 4.0 mm x 4.0 mm 1.8 mm 160 m ? 0.66a cdrh3d16 sumida ? 10 h shielded 5.7 mm x 5.7 mm 3.0 mm 65 m ? 1.3a cdrh5d28 ct* 10 h shielded 7.3 mm x 7.3 mm 3.5 mm 70 m ? 1.7a ctcdrh73 coilcraft ? 10 h shielded 6.6 mm x 4.5 mm 3.0 mm 75 m ? 1.0a ds1608 coilcraft ? 15 h shielded 6.6 mm x 4.5 mm 3.0 mm 90 m ? 0.8a ds1608 coilcraft ? 22 h shielded 6.6 mm x 4.5 mm 3.0 mm 110 m ? 0.7a ds1608 coilcraft ? 10 h unshielded wafer 6.0 mm x 5.4 mm 1.3 mm 300 m ? 0.60a lpo6013 coilcraft ? 15 h unshielded wafer 6.0 mm x 5.4 mm 1.3 mm 380 m ? 0.55a lpo6013 ta i y o yuden? 10 h shielded 5.0 mm x 5.0 mm 2.0 mm 66 m ? 0.7a np04sb100m note: ct* = central technologies mcp1601 c in c out r 1 c 1 r 2 p gnd p gnd a gnd a gnd silk mcp1601 ds21762b-page 16 ? 2003-2013 microchip technology inc. figure 5-3: top layer. the top layer of the board layout is shown in figure 5-3. the power conversion process is made up of two types of circuits. one circuit carries changing large signals (current, voltage), like c in , c out , l and the v in , l x p gnd pins of the mcp1601. the other cir- cuitry is much smaller in signal and is used to sense, regulate and control the high-power circuitry. these components are r 1 , r 2 , c 1 and pins fb, a gnd . the top layer is partitioned so that the larger signal connections are short and wide, while the smaller signals are routed away from the large signals. the mcp1601 utilizes two ground pins to separate the large signal ground current from the small signal circuit ground. the large signal (?power ground?) is labeled ?p gnd ?. the small signal is labeled ?analog ground? or ?a gnd ?. in figure 5-3, the p gnd and the a gnd are kept separate on the top layer. figure 5-4: bottom layer. in figure 5-4, the bottom layer is a partitioned ground plane that connects a gnd to p gnd near the input capacitor. the large signal current will circulate on the top p gnd partition. the lower partition is used for a ?quiet? ground, where a gnd is connected. m c p 1 6 0 1 p gnd a gnd p gnd a gnd bot ? 2003-2013 microchip technology inc. ds21762b-page 17 mcp1601 6.0 packaging information 6.1 package marking information 8-lead msop example: xxxxxx ywwnnn 1601i 344025 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 mcp1601 ds21762b-page 18 ? 2003-2013 microchip technology inc. 8-lead plastic micro small outline package (ms) (msop) d l c dimensions d and e1 do not include mold flash or protrusions. mold flash or protrusions shall not .037 .035 f footprint (reference) exceed .010" (0.254mm) per side. notes: drawing no. c04-111 *controlling parameter mold draft angle top mold draft angle bottom foot angle lead width lead thickness ? ? c b ? 7 7 .004 .010 0 .006 .012 (f) ? dimension limits overall height molded package thickness molded package width overall length foot length standoff overall width number of pins pitch a l e1 d a1 e a2 .016 .114 .114 .022 .118 .118 .002 .030 .193 .034 min p n units .026 nom 8 inches 1.00 0.95 0.90 .039 0.15 0.30 .008 .016 6 0.10 0.25 0 7 7 0.20 0.40 6 millimeters* 0.65 0.86 3.00 3.00 0.55 4.90 .044 .122 .028 .122 .038 .006 0.40 2.90 2.90 0.05 0.76 min max nom 1.18 0.70 3.10 3.10 0.15 0.97 max 8 ? e1 e b n 1 2 ? significant characteristic .184 .200 4.67 .5.08 p a a1 a2 note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging ? 2003-2013 microchip technology inc. ds21762b-page 19 mcp1601 7.0 revision history revision b (january 2013) added a note to each package outline drawing. mcp1601 ds21762b-page 20 ? 2003-2013 microchip technology inc. notes: ? 2003-2013 microchip technology inc. ds21762b-page21 mcp1601 product identification system to order or obtain information, e. g., on pricing or delivery, refer to the factory or the listed sales office . sales and support data sheets products supported by a preliminary data sheet may have an e rrata sheet describing minor operational differences and recom- mended workarounds. to determine if an erra ta sheet exists for a particular device, please contact one of the following: 1. your local microchip sales office 2. the microchip worldwide site (www.microchip.com) please specify which device, revision of silicon and data sheet (include literature #) you are using. customer notification system register on our web site (www.microchip.com/cn) to receive the most current information on our products. part no. x /xx package temperature range device device: mcp1601: 500 ma synchronous buck regulator mcp1601t: 500 ma synchronous buck regulator tape and reel temperature range: i = -40c to +85c package: ms = plastic micro small outline (msop), 8-lead examples: a) mcp1601-i/ms: 8ld msop package. b) mcp1601t-i/ms: tape and reel, 8ld msop package. mcp1601 ds21762b-page 22 ? 2003-2013 microchip technology inc. notes: ? 2003-2013 microchip technology inc. ds21762b-page 23 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, k ee l oq , k ee l oq logo, mplab, pic, picmicro, picstart, pic 32 logo, rfpic, sst, sst logo, superflash and uni/o are registered trademarks of microchip technology incorporated in the u.s.a. and other countries. filterlab, hampshire, hi-tech c, linear active thermistor, mtp, seeval and the embedded control solutions company are registered trademarks of microchip technology incorporated in the u.s.a. silicon storage technology is a registered trademark of microchip technology inc. in other countries. analog-for-the-digital age, app lication maestro, bodycom, chipkit, chipkit logo, codeguard, dspicdem, dspicdem.net, dspicworks, dsspeak, ecan, economonitor, fansense, hi-tide, in-circuit serial programming, icsp, mindi, miwi, mpasm, mpf, mplab certified logo, mplib, mplink, mtouch, omniscient code generation, picc, picc-18, picdem, picdem.net, pickit, pictail, real ice, rflab, select mode, sqi, serial quad i/o, total endurance, tsharc, uniwindriver, wiperlock, zena and z-scale 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. gestic and ulpp are registered trademarks 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. ? 2003-2013, microchip technology incorporated, printed in the u.s.a., all rights reserved. printed on recycled paper. isbn: 9781620768990 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 == ds21762b-page 24 ? 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