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? 2007 microchip technology inc. ds22061a-page 1 mcp1602 features over 90% typical efficiency output current: up to 500 ma power-good output with 262 ms delay low quiescent current: 45 a (typical) low shutdown current: 0.05 a (typical) automatic pwm to pfm mode transition adjustable output voltage: - 0.8v to 4.5v fixed output voltage: - 1.2v, 1.5v, 1.8v, 2.5v, and 3.3v 2.0 mhz fixed-frequency pwm (heavy load) internally compensated undervoltage lockout (uvlo) overtemperture protection overcurrent protection space saving packages: - 8-lead msop - 8-lead 3x3 dfn applications cellular telephones portable computers organizers / pdas usb powered devices digital cameras portable equipment +5v or +3.3v distributed systems general description the mcp1602 is a high efficient, fully integrated 500 ma synchronous buck regulator with a power- good monitor. the 2.7v to 5.5v input voltage range and low quiescent current (45 a, typical) makes the mcp1602 ideally suited for applications powered from 1-cell li-ion or 2-cell/3- cell nimh/nicd batteries. at heavy loads, the mcp1602 operates in the 2.0 mhz fixed frequency pwm mode which provides a low noise, low output ripple, small-size solution. when the load is reduced to light levels, the mcp1602 automatically changes operation to a pfm mode to minimize quiescent current draw from the battery. no intervention is necessary for a smooth transition from one mode to another. these two modes of operation allow the mcp1602 to achieve the highest efficiency over the entire operating current range. the open-drain power-good feature of the mcp1602 monitors the output voltage and provides indication when the output voltage is within 94% (typical) of the regulation value. the typical 2% hystereses in the power-good transition threshold as well as a 262 ms (typical) delay time ensures accurate power- good signaling. the mcp1602 is available in either the 8-pin dfn or msop package. it is also available with either an adjustable or fixed output voltage. the available fixed output voltage options are 1.2v, 1.5v, 1.8v, 2.5v, and 3.3v. additional protection features include: uvlo, overtemperature, and overcurrent protection. package types v in v in 8 76 5 4 3 2 1 shdn v cc pga gnd v out /v fb l x p gnd 8 76 5 4 3 2 1 shdn v cc pg a gnd v out /v fb l x p gnd 3x3 dfn-8 msop-8 2.0 mhz, 500 ma synchronous buck regulator with power-good downloaded from: http:///
mcp1602 ds22061a-page 2 ? 2007 microchip technology inc. typical application circuit shdn v cc pg a gnd v fb v in l x p gnd 1 2 3 4 8 7 6 5 on off mcp1602 v in 2.7v to 4.5v v out 1.5v @ 500 ma v in r pullup 4.7 f 4.7 h 4.7 f 0.1 f 10 processorreset downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 3 mcp1602 functional block diagram ilim pwm ilim pfm ipeak pwm ipeak pfm v in shdn v fb /v out p gnd l x band gap uvlo switch drive uvlo v ref logic and timing srq q soft start v ref pwm/pfm logic v ref slope comp osc -i pk limit thermal shutdown tsd ea poff noff pwm/pfm pfm error amp pwm error amp ov threshold uv threshold i pk limit -ilpk ipeak pwm ipeak pfm disable switcher -ilpk pg generator with delay v ref v cc v out a gnd pg v cc downloaded from: http:///
mcp1602 ds22061a-page 4 ? 2007 microchip technology inc. 1.0 electrical characteristics absolute maximum ratings ? v in - a gnd ......................................................................+6.0v all other i/o .............................. (a gnd - 0.3v) to (v in + 0.3v) lx to p gnd ............................................. -0.3v to (v in + 0.3v) output short circuit current..................................continuous power dissipation (note 6) ..........................internally limited storage temperature.................................... -65 o c to +150 o c ambient temp. with power applied................ -40 o c to +85 o c operating junction temperature.................. -40 o c to +125 o c esd protection on all pins: hbm..............................................................................3 kv mm...............................................................................200v ? notice: stresses above those listed under "maximum ratings" may cause permanent dam age 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 characteristics electrical characteristics: unless otherwise indicated, v in = 3.6v, c out = c in = 4.7 f, l = 4.7 h, v out (adj) = 1.8v, i out = 100 ma, t a = +25c. boldface specifications apply for the t a range of -40 o c to +85 o c . parameters sym min typ max units conditions input characteristics input voltage v in 2.7 5.5 v note 1 maximum output current i out 500 m a note 1 shutdown current i in_shdn 0.05 1 a shdn = gnd quiescent current i q 4 5 60 a shdn = v in , i out = 0 ma shutdown/uvlo/thermal shutdown characteristics shdn , logic input voltage low v il 15 %v in v in = 2.7v to 5.5v shdn , logic input voltage high v ih 45 % v in v in = 2.7v to 5.5v shdn , input leakage current v l_shnd -1.0 0.1 1.0 a v in = 2.7v to 5.5v, shdn =a gnd undervoltage lockout uvlo 2.40 2.55 2.70 vv in falling undervoltage lockout hystere- sis uvlo hys 200 mv thermal shutdown t shd 150 c note 5 , note 6 thermal shutdown hysteresis t shd-hys 1 0 c note 5 , note 6 output characteristics adjustable output voltage range v out 0.8 4.5 v note 2 reference feedback voltage v fb 0 . 8 v feedback input bias current i vfb -1.5 na note 1: the minimum v in has to meet two conditions: v in 2.7v and v in v out + 0.5v. 2: reference feedback voltage tolerance applies to adjustable output voltage setting. 3: v r is the output voltage setting. 4: regulation is measured at a constant junction te mperature using low duty cycle pulse testing. load regulation is tested over a load range of 0.1 ma to the maximum specified output current. changes in output voltage due to heating effects are cove red by the thermal regulation specification. 5: the maximum allowable power dissipation is a functi on of ambient temperature, the maximum allowable temperature and the thermal resistance from junction to air (i.e. t a , t j , ja ). exceeding the maximum allowable power dissipation causes the device to initiate thermal shutdown. 6: the internal mosfet switches have an integral diode from the l x pin to the v in pin, and from the l x pin to the gnd pin. in cases where these diodes are fo rward-biased, the package power dissipation limits must be adhered too. thermal protection is not ab le to limit the junction temperature for these cases. 7: the current limit threshold is a cycle-by-cycle current limit. downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 5 mcp1602 output voltage tolerance fixed v out -2.5 v r +2.5 % note 3 line regulation v line- reg 0 . 3% / vv in = v r + 1v to 5.5v, i out =100ma load regulation v load- reg 0 . 4 %v in =v r +1.5v, i load = 100 ma to 500 ma, note 1 internal oscillator frequency f osc 1.6 2.0 2.4 mhz start up time t ss 0 . 5 m st r = 10% to 90% r dson p-channel r dson-p 450 m i p =100ma r dson n-channel r dson-n 450 m i n = 100 ma l x pin leakage current i lx -1.0 0.01 1.0 a shdn =0v, v in = 5.5v, l x =0v, l x =5.5v positive current limit threshold +i lx(max) 700 ma note 7 power-good (pg) voltage range v pg 1.0 1.2 5 . 5 5.5 vt a = 0c to +70c t a = -40c to +85c v in 2.7v, i sink = 100 a pg threshold high v th_h 9 4 96 % of v out on rising v out pg threshold low v th_l 89 92 % of v out on falling v out pg threshold hysteresis v th_hys 2% o f v out pg threshold tempco v th / t 3 0 p p m / c pg delay t rpd 165 s v out =(v th_h + 100 mv) to (v th_l - 100 mv) pg active time-out period t rpu 140 262 560 ms v out =(v th_l -100mv) to (v th_h +100mv), i sink =1.2ma pg output voltage low pg_v ol 0.2 vv out =v th_l -100mv, i pg = 1.2 ma, v in >2.7v i pg = 100 a, 1.0 < v in <2.7v dc characteristics (continued) electrical characteristics: unless otherwise indicated, v in = 3.6v, c out = c in = 4.7 f, l = 4.7 h, v out (adj) = 1.8v, i out = 100 ma, t a = +25c. boldface specifications apply for the t a range of -40 o c to +85 o c . parameters sym min typ max units conditions note 1: the minimum v in has to meet two conditions: v in 2.7v and v in v out + 0.5v. 2: reference feedback voltage tolerance applies to adjustable output voltage setting. 3: v r is the output voltage setting. 4: regulation is measured at a constant junction te mperature using low duty cycle pulse testing. load regulation is tested over a load range of 0.1 ma to the maximum specified output current. changes in output voltage due to heating effects are cove red by the thermal regulation specification. 5: the maximum allowable power dissipation is a functi on of ambient temperature, the maximum allowable temperature and the thermal resistance from junction to air (i.e. t a , t j , ja ). exceeding the maximum allowable power dissipation causes the device to initiate thermal shutdown. 6: the internal mosfet switches have an integral diode from the l x pin to the v in pin, and from the l x pin to the gnd pin. in cases where these diodes are fo rward-biased, the package power dissipation limits must be adhered too. thermal protection is not ab le to limit the junction temperature for these cases. 7: the current limit threshold is a cycle-by-cycle current limit. downloaded from: http:///
mcp1602 ds22061a-page 6 ? 2007 microchip technology inc. temperature specifications electrical specifications: unless otherwise indicated, all limits are specified for: v in +2.7vto5.5v parameters sym min typ max units conditions temperature ranges operating junction temperature range t j -40 +125 c steady state storage temperature range t a -65 +150 c maximum junction temperature t j +150 c transient package thermal resistances thermal resistance, 8l-msop ja 211 c/w typical 4-layer board with internal ground plane thermal resistance, 8l-3x3 dfn ja 60 c/w typical 4-layer board with internal ground plane and 2-vias in thermal pad downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 7 mcp1602 2.0 typical performance curves note: unless otherwise indicated, v in = shdn =3.6v, c out =c in = 4.7 f, l = 4.7 h, v out (adj) = 1.8v, i load = 100 ma, t a = +25c. adjustable or fixed output voltage options can be used to generate the typical performance characteristics. figure 2-1: i q vs. ambient temperature. figure 2-2: efficiency vs. input voltage (v out = 1.2v). figure 2-3: efficiency vs. input voltage (v out = 1.8v). figure 2-4: i q vs. input voltage. figure 2-5: efficiency vs. output load (v out = 1.2v). figure 2-6: efficiency vs. output load (v out = 1.8v). note: the graphs and tables provided following this note ar e a statistical summary based on a limited number of samples and are provided for informational purposes onl y. the performance charac teristics listed herein are not tested or guaranteed. in some graphs or t ables, the data presented ma y be outside the specified operating range (e.g., outside specified power suppl y range) and therefore outs ide the warranted range. 30 35 40 45 50 55 60 -40 -25 -10 5 20 35 50 65 80 95 110 125 ambient temperature ( o c) quiescent current (a) v out = 1.8v v in = 5.5v v in = 3.6v v in = 4.2v 65 70 75 80 85 90 95 100 3.0 3.2 3.4 3.6 3.8 4.0 4.2 input voltage (v) efficiency (%) v out = 1.2v i out = 100 ma i out = 500 ma i out = 300 ma 70 75 80 85 90 95 100 3.0 3.2 3.4 3.6 3.8 4.0 4.2 input voltage (v) efficiency (%) v out = 1.8v i out = 100 ma i out = 500 ma i out = 300 ma 30 35 40 45 50 55 2.7 3.05 3.4 3.75 4.1 4.45 4.8 5.15 5.5 input voltage (v) quiescent current (a) t a = +90c t a = +25c t a = -40c 20 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 output current (ma) efficiency (%) v out = 1.2v v in = 3.0v v in = 3.6v v in = 4.2v 20 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 output current (ma) efficiency (%) v out = 1.8v v in = 3.0v v in = 3.6v v in = 4.2v downloaded from: http:///
mcp1602 ds22061a-page 8 ? 2007 microchip technology inc. typical performance curves (continued) note: unless otherwise indicated, v in = shdn =3.6v, c out =c in = 4.7 f, l = 4.7 h, v out (adj) = 1.8v, i load = 100 ma, t a = +25c. adjustable or fixed output voltage options can be used to generate the typical performance characteristics. figure 2-7: efficiency vs. input voltage (v out = 3.3v). figure 2-8: pg active time-out vs. ambient temperature. figure 2-9: feedback voltage vs. ambient temperature. figure 2-10: efficiency vs. output load (v out = 3.3v). figure 2-11: pg threshold voltage vs. ambient temperature. figure 2-12: output voltage vs. load current (v out = 1.8v). 85.0 87.5 90.0 92.5 95.0 97.5 100.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 input voltage (v) efficiency (%) v out = 3.3v i out = 100 ma i out = 500 ma i out = 300 ma 200 220 240 260 280 300 320 340 -40 -25 -10 5 20 35 50 65 80 95 110 125 ambient temperature (c) pg active time-out (ms) 0.812 0.816 0.820 0.824 0.828 0.832 -40 -25 -10 5 2035 50 65 80 95 110 125 ambient temperature (c) feedback voltage (v) 20 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 output current (ma) efficiency (%) v out = 3.3v v in = 5.5v v in = 4.2v 88 89 90 91 92 93 94 95 96 -40 -25 -10 5 20 35 50 65 80 95 110 125 ambient temperature (c) pg threshold (% of v out ) pg threshold high pg threshold low 1.81 1.82 1.83 1.84 1.85 0 50 100 150 200 250 300 350 400 450 500 output current (ma) output voltage (v) downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 9 mcp1602 typical performance curves (continued) note: unless otherwise indicated, v in = shdn =3.6v, c out =c in = 4.7 f, l = 4.7 h, v out (adj) = 1.8v, i load = 100 ma, t a = +25c. adjustable or fixed output voltage options can be used to generate the typical performance characteristics. figure 2-13: switching frequency vs. ambient temperature. figure 2-14: switch resistance vs. input voltage. figure 2-15: output voltage startup waveform. figure 2-16: switching frequency vs. input voltage. figure 2-17: switch resistance vs. ambient temperature. figure 2-18: heavy load switching waveform. 1.90 1.92 1.94 1.96 1.98 2.00 -40 -25 -10 5 20 35 50 65 80 95 110 125 ambient temperature (c) switching frequency (mhz) 0.2 0.3 0.4 0.5 0.6 2.70 3.05 3.40 3.75 4.10 4.45 4.80 5.15 5.50 input voltage (v) switch resistance ( ? ) n-channel p-channel 1.85 1.90 1.95 2.00 2.05 2.10 2.70 3.05 3.40 3.75 4.10 4.45 4.80 5.15 5.50 input voltage (v) switching frequency (mhz) 0.2 0.3 0.4 0.5 0.6 0.7 -40 -25 -10 5 20 35 50 65 80 95 110 125 ambient temperature (c) switch resistance ( ? ) n-channel p-channel downloaded from: http:///
mcp1602 ds22061a-page 10 ? 2007 microchip technology inc. typical performance curves (continued) note: unless otherwise indicated, v in = shdn =3.6v, c out =c in = 4.7 f, l = 4.7 h, v out (adj) = 1.8v, i load = 100 ma, t a = +25c. adjustable or fixed output voltage options can be used to generate the typical performance characteristics. figure 2-19: light load switching waveform. figure 2-20: output voltage load step response vs. time. figure 2-21: output voltage line step response vs. time. figure 2-22: power-good output timing. downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 11 mcp1602 3.0 pin descriptions the descriptions of the pins are listed in table 3-1 . table 3-1: pin function table 3.1 shutdown control input pin (shdn ) the shdn pin is a logic-level input used to enable or disable the device. a logic high (>45% of v in ) will enable the regulator output. a logic-low (<15% of v in ) will ensure that the regulator is disabled. 3.2 analog input supply voltage pin (v cc ) the v cc pin provides bias for internal analog functions. this voltage is derived by filtering the v in supply. 3.3 power-good output pin (pg) pg is an output level indicating that the output voltage is within 94% of regulation. the pg output is configured as an open-drain output. 3.4 analog ground pin (a gnd ) a gnd is the analog ground connection. tie a gnd to the analog portion of the ground plane (a gnd ). see the physical layout in formation in the section 5.8 pcb layout information section for ground recommenda- tions. 3.5 output voltage sense pin (v fb / v out ) for the adjustable output vo ltage options, connect the center of the output vo ltage divider to the v fb pin. for fixed-output voltage options, connect the output of the buck regulator to this pin (v out ). 3.6 power supply input voltage pin (v in ) v in is the buck regulator power input supply pin. connect a variable input voltage source to v in . 3.7 buck inductor output pin (l x ) connect l x directly to the buck inductor. this pin carries large signal-level current; all connections should be made as short as possible. 3.8 power ground pin (p gnd ) connect all large signal level ground returns to p gnd . these large signal level ground traces should have a small loop area and length to prevent coupling of switching noise to sensitive traces. 3.9 exposed metal pad (ep) for the dfn package, connect the exposed pad to a gnd , with vias into the a gnd plane. this connection to the a gnd plane will aid in heat removal from the package. msop dfn sym description 1 1 shdn shutdown input pin 22v cc analog input supply voltage pin 3 3 pg power good output pin 44a gnd analog ground pin 55v fb /v out feedback voltage (adjustable version) / output voltage (fixed version) pin 66v in input supply voltage pin 77 l x buck inductor output pin 88p gnd power ground pin exposed pad ep for the dfn package, the center exposed pad is a thermal path to remove heat from the device. electrically this pad is at ground potential and should be connected to a gnd downloaded from: http:///
mcp1602 ds22061a-page 12 ? 2007 microchip technology inc. 4.0 detailed description 4.1 device overview the mcp1602 is a synchronous buck regulator with a power-good signal. the device operates in a pulse frequency modulation (pfm) mode or a pulse width modulation (pwm) mode to maximize system efficiency over the entire operating current range. capable of operating from a 2. 7v to 5.5v input voltage source, the mcp1602 can deliver 500 ma of continuous output current. when using the mcp1602, the pcb area required for a complete step-down converter is minimized since both the main p-channel mosfet and the synchro- nous n-channel mosfet are integrated. also while in pwm mode, the device switches at a constant frequency of 2.0 mhz (typical) which allow for small fil- tering components. both fixed and adjustable output voltage options are available. the fixed voltage options (1.2v, 1.5v, 1.8v, 2.5v, 3.3v) do not require an external voltage divider which further reduces the required circuit board footprint. the adjustable output voltage options allow for more flexibility in the design, but require an external voltage divider. additionally the device features undervoltage lockout (uvlo), overtemperature shutdown, overcurrent protection, and enable/disable control. 4.2 synchronous buck regulator the mcp1602 has two distin ct modes of operation that allow the device to maintain a high level of efficiency throughout the entire operating current and voltage range. the device automatically switches between pwm mode and pfm mode depending upon the output load requirements. 4.2.1 fixed frequency, pwm mode during heavy load conditions, the mcp1602 operates at a high, fixed switching frequency of 2.0 mhz (typi- cal). this minimizes output ripple (10 - 15 mv typically) and noise while maintaining high efficiency (88% typi- cal with v in = 3.6v, v out = 1.8v, i out = 300 ma). during normal pwm operation, the beginning of a switching cycle occurs when the internal p-channel mosfet is turned on. the ramping inductor current is sensed and tied to one input of the internal high-speed comparator. the other input to the high-speed compar- ator is the error amplifier out put. this is the difference between the internal 0.8v reference and the sensed output voltage. when the sensed current becomes equal to the amplified error signal, the high-speed comparator switches st ates and the p-channel mosfet is turned off. the n-channel mosfet is turned on until the internal oscillator sets an internal rs latch initiating th e beginning of anot her switching cycle. pfm-to-pwm mode transition is initiated for any of the following conditions: continuous device switching output voltage has dropped out of regulation 4.2.2 light load, pfm mode during light load conditions, the mcp1602 operates in a pfm mode. when the mcp1602 enters this mode, it begins to skip pulses to minimize unnecessary quiescent current draw by reducing the number of switching cycles per seco nd. the typical quiescent current draw for this device is 45 a. pwm-to-pfm mode transition is initiated for any of the following conditions: discontinuous inductor current is sensed for a set duration inductor peak current falls below the transition threshold limit 4.3 power-good (pg) the open-drain power-good (pg) circuitry monitors the regulated output voltage. a fixed delay time of approximately 262 ms is generated once the output voltage is above the power-good high threshold, v th_h , (typically 94% of v out ). as the output voltage falls below the power-good low threshold, v th_l , (typically 92% of v out ) the pg signal transitions to a low state indicating that the output is out of regulation. the pg circuitry has a typical 165 s delay when detecting a falling output voltage. this helps to increase the noise immunity of the power-good output, avoiding false triggering of the pg signal during line and load transients. figure 4-1: power-good timing. v th_h v out pg t rpu t rpd v ol v oh v th_l downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 13 mcp1602 4.4 soft start the output of the mcp1602 is controlled during start- up. this control allows for a very minimal amount of v out overshoot during start-up from v in rising above the uvlo voltage or shdn being enabled. 4.5 overtemperature protection overtemperature protection circuitry is integrated in the mcp1602. this circuitry monitors the device junction temperature and shuts the device off if the junction tem- perature exceeds the typical 150 o c threshold. if this threshold is exceeded, the device will automatically restart once the junction temperature drops by approximately 10 o c. the soft start is reset during an overtemperture condition. 4.6 overcurrent protection cycle-by-cycle current limiti ng is used to protect the mcp1602 from being damaged when an external short circuit is applied. the typical peak current limit is 700 ma. if the sensed current reaches the 700 ma limit, the p-channel mosfet is turned off, even if the output voltage is not in regulation. the device will attempt to start a new switching cycle when the internal oscillator sets the internal rs latch. 4.7 enable/disable control the shdn pin is used to enable or disable the mcp1602. when the shdn pin is pulled low, the device is disabled. when pulled high the device is enabled and begins operation provided the input voltage is not below the uvlo threshold or a fault condition exists. 4.8 undervoltage lockout (uvlo) the uvlo feature uses a comparator to sense the input voltage (v in ) level. if the input voltage is lower than the voltage necessary to properly operate the mcp1602, the uvlo featur e will hold the converter off. when v in rises above the necessary input voltage, the uvlo is released and soft start begins. hysteresis is built into the uvlo circuit to compensate for input impedance. for example, if there is any resistance between the input voltage source and the device when it is operating, there will be a voltage drop at the input to the device equal to i in x r in . the typical hysteresis is 200 mv. downloaded from: http:///
mcp1602 ds22061a-page 14 ? 2007 microchip technology inc. 5.0 application information 5.1 typical applications the mcp1602 synchronous buck regulator with power- good operates over a wide input voltage range (2.7v to 5.5v) and is ideal for single-cell li-ion battery powered applications, usb powered applications, three cell nimh or nicd applications and 3v to 5v regulated input applications. 5.2 fixed output voltage applications the typical application circuit shows a fixed mcp1602 in a typical application used to convert three nimh batteries into a well regulated 1.5v @ 500 ma output. a 4.7 f input and output capacitor, a 4.7 h inductor, and a small rc filter make up the entire external component selectio n for this application. no external voltage divider or compensation is necessary. in addition to the fixed 1.5v option, the mcp1602 is also available in 1.2v, 1.8v, 2.5v, or 3.3v fixed voltage options. 5.3 adjustable output voltage applications when the desired output for a particular application is not covered by the fixed voltage options, an adjustable mcp1602 can be used. the circuit listed in figure 6-2 shows an adjustable mcp1602 being used to convert a 5v rail to 1.0v @ 500 ma. the output voltage is adjust- able by using two external resistors as a voltage divider. for adjustable output voltages, it is recom- mended that the top resistor divider value be 200 k . the bottom resistor value can be calculated using the following equation. equation 5-1: for adjustable output applic ations, an additional r-c compensation network is necessary for control loop stability. recommended values for any output voltage are: r comp = 4.99 k c comp = 33 pf refer to figure 6-2 for proper placement of r comp and c comp . 5.4 input capacitor selection the input current to a buck converter, when operating in continuous conduction mo de, is a squarewave with a duty cycle defined by the output voltage (v out ) to input voltage (v in ) relationship of v out /v in . to prevent undesirable input voltage trans ients, the input capacitor should be a low esr type with a rms current rating given by equation 5-2 . because of their small size and low esr, ceramic capacitors are often used. ceramic material x5r or x7r are well suited since they have a low temperature coefficient and acceptable esr. equation 5-2: table 5-1 contains the recommend range for the input capacitor value. 5.5 output capacitor selection the output capacitor helps provide a stable output voltage during sudden load transients, smooths the current that flows from the inductor to the load, and it also reduces the output voltage ripple. therefore, low esr capacitors are a desirable choice for the output capacitor. as with the input capacitor, x5r and x7r ceramic capacitors are well suited for this application. the output ripple voltage is often a design specifica- tion. a buck converters output ripple voltage is a function of the charging a nd discharging of the output capacitor and the esr of the capacitor. this ripple voltage can be calculated by equation 5-3 . equation 5-3: r bot r top v fb v out v fb C ---------------------------- - ?? ?? = example: r top = 200 k v out =1 . 0 v v fb 0.8v r bot = 200 k x (0.8v/(1.0v - 0.8v)) r bot = 800 k (standard value = 787 k ) i cin rms , i out max , v out v in v out C () v in ----------------------------------------------------- - ?? ?? ?? = v out i l esr i l 8 fc ------------ -------- - + = downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 15 mcp1602 table 5-1 contains the recommend range for the output capacitor value. 5.6 inductor selection for most applications an inductor value of 4.7 h is recommended to achieve a good balance between converter load transient response and minimized noise. there are many di fferent magnetic core materials and package options to select from. that decision is based on size, cost, and acceptable radiated energy levels. toroid and shielded ferrite pot cores will have low radiated energy, but tend to be larger and higher in cost. the value of inductance is selected to achieve a desired amount of ripple current. it is reasonable to assume a ripple current that is 20% of the maximum load current. the larger the amount of ripple current allowed, the larger the output capacitor value becomes to meet ripple voltage sp ecifications. the inductor ripple current can be calculated according to equation 5-4 . equation 5-4: when considering inductor ratings, the maximum dc current rating of the inductor should be at least equal to the maximum load current, plus one half the peak-to- peak inductor ripple current (1/2 * i l ). the inductor dc resistance adds to the total converter power loss. an inductor with a low dc resistance allows for higher converter efficiency. 5.7 thermal calculations the mcp1602 is available in two different packages (msop and 3x3 dfn). 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 mcp1602 is +125 o c. to quickly estimate the internal power dissipation for the switching buck regulator, an empirical calculation using measured efficiency can be used. given the measured efficiency, the internal power dissipation is estimated by: equation 5-5: the difference between the first term, input power dissipation, and the second term, power delivered, is the internal power dissipation. this is an estimate assuming that most of the power lost is internal to the mcp1602. there is some percentage of power lost in the buck inductor, with very little loss in the input and output capacitors. table 5-1: capacitor value range c in c out minimum 4.7 f 4.7 f maximum 22 f table 5-2: mcp1602 recommended inductors part number value (h) dcr (max) i sat (a) size wxlxh (mm) coiltronics? sd10 3.3 0.108 1. 31 5.2x5.2x1.0 sd10 4.7 0.154 1. 08 5.2x5.2x1.0 sd10 6.2 0.218 0. 92 5.2x5.2x1.0 sd12 3.3 0.104 1. 42 5.2x5.2x1.2 sd12 4.7 0.118 1. 29 5.2x5.2x1.2 sd12 6.2 0.170 1. 08 5.2x5.2x1.2 i l v out f sw l ------------------- 1 v out v in ------------ - C ?? ?? = where: f sw = switching frequency wurth elektronik? we-tpc type s 3.6 0.085 1.10 3.8x3.8x1.65 we-tpc type s 4.7 0.105 0.90 3.8x3.8x1.65 we-tpc type s 6.8 0.156 0.75 3.8x3.8x1.65 we-tpc type m 3.3 0.065 1.80 4.8x4.8x1.8 we-tpc type m 4.7 0.082 1.65 4.8x4.8x1.8 we-tpc type m 6.8 0.100 1.25 4.8x4.8x1.8 table 5-2: mcp1602 recommended inductors (continued) part number value (h) dcr (max) i sat (a) size wxlxh (mm) v out i out efficiency ------------------------------ - ?? ?? v out i out () C p dis = downloaded from: http:///
mcp1602 ds22061a-page 16 ? 2007 microchip technology inc. 5.8 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 high current paths, short and wide traces should be used. this high current path is shown with red connections in figure 5-1 . therefore, it is important that the components along the high current path should be placed as close as possible to the mcp1602 to minimize the loop area. the feedback resistors and feedback signal should be routed away from the switch ing node and this 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: pcb high current path. shdn v cc pg a gnd v fb v in l x p gnd 1 2 3 4 8 7 6 5 on off mcp1602 v in 2.7v to 4.5v v out 1.5v @ 500 ma v in r pullup 4.7 f 4.7 h 4.7 f 0.1 f 10 processor reset downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 17 mcp1602 6.0 typical application circuits l figure 6-1: single li-ion to 1.5v @ 500 ma application. figure 6-2: 5v to 1.0v @ 500 ma application. figure 6-3: 3 nimh batteries to 1.2v @ 500 ma application. shdn v cc pg a gnd v fb v in l x p gnd 1 2 3 4 8 7 6 5 on off mcp1602 v in 3.0v to 4.2v v out 1.5v @ 500 ma v in r pullup 4.7 f 4.7 h 4.7 f 0.1 f 10 processorreset shdn v cc pg a gnd v out v in l x p gnd 1 2 3 4 8 7 6 5 on off mcp1602 v in 5.0v v out 1.0v @ 500 ma v in r pullup 4.7 f 4.7 h 4.7 f 0.1 f 10 processor reset r top r comp c comp 200 k r bot 787 k 4.99 k 33 pf shdn v cc pg a gnd v fb v in l x p gnd 1 2 3 4 8 7 6 5 on off mcp1602 v in 2.7v to 4.5v v out 1.2v @ 500 ma v in r pullup 4.7 f 4.7 h 4.7 f 0.1 f 10 processor reset downloaded from: http:///
mcp1602 ds22061a-page 18 ? 2007 microchip technology inc. 7.0 packaging information 7.1 package marking information 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 nu mber 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 8-lead msop example: 8-lead dfn (3x3) example : part number code mcp1602-120i/mf caau mcp1602-150i/mf caav mcp1602-180i/mf caaw mcp1602-250i/mf caay mcp1602-330i/mf caaz mcp1602-adji/mf caas caau0733 256 xxxx xyww nnn xxxxxx ywwnnn 1602aj 733256 part number code mcp1602-120i/mf 160212 mcp1602-150i/mf 160215 mcp1602-180i/mf 160218 mcp1602-250i/mf 160225 mcp1602-330i/mf 160233 mcp1602-adji/mf 1602aj downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 19 mcp1602 8-lead plastic dual flat, no lead package (mf) C 3x3x0.9 mm body [dfn] notes: 1. pin 1 visual index feature may vary, but must be located within the hatched area. 2. package may have one or more exposed tie bars at ends. 3. package is saw singulated. 4. dimensioning and tolerancing per asme y14.5m. bsc: basic dimension. theoretically exact value shown without tolerances. ref: reference dimension, usually without tolerance, for information purposes only. note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging units millimeters dimension limits min nom max number of pins n 8 pitch e 0.65 bsc overall height a 0.80 0.90 1.00 standoff a1 0.00 0.02 0.05 contact thickness a3 0.20 ref overall length d 3.00 bsc exposed pad width e2 0.00 C 1.60 overall width e 3.00 bsc exposed pad length d2 0.00 C 2.40 contact width b 0.25 0.30 0.35 contact length l 0.20 0.30 0.55 contact-to-exposed pad k 0.20 C C bottom vie top vie d n e note 1 12 exposed pad b e n l e2 k note 1 d2 21 note 2 a a1 a 3 microchip technology drawing c04-062b downloaded from: http:///
mcp1602 ds22061a-page 20 ? 2007 microchip technology inc. 8-lead plastic micro small outline package (ms) [msop] notes: 1. pin 1 visual index feature may vary, but must be located within the hatched area. 2. dimensions d and e1 do not include mold flash or protrusions. mold flash or protrusions shall not exceed 0.15 mm per side. 3. dimensioning and tolerancing per asme y14.5m. bsc: basic dimension. theoretically exact value shown without tolerances. ref: reference dimension, usually without tolerance, for information purposes only. note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging units millimeters dimension limits min nom max number of pins n 8 pitch e 0.65 bsc overall height a C C 1.10 molded package thickness a2 0.75 0.85 0.95 standoff a1 0.00 C 0.15 overall width e 4.90 bsc molded package width e1 3.00 bsc overall length d 3.00 bsc foot length l 0.40 0.60 0.80 footprint l1 0.95 ref foot angle 0 C 8 lead thickness c 0.08 C 0.23 lead width b 0.22 C 0.40 d n e e1 note 1 1 2 e b a a1 a2 c l1 l microchip technology drawing c04-111b downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 21 mcp1602 appendix a: revision history revision a (october 2007) original release of this document. downloaded from: http:///
mcp1602 ds22061a-page 22 ? 2007 microchip technology inc. notes: downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 23 mcp1602 product identification system to order or obtain information, e.g., on pricing or de livery, refer to the factory or the listed sales office . device mcp1602: 2.0 mhz, 500 ma, buck reg w/power-good tape & reel t = tape and reel blank = tube standard fixed output voltage * 120 = 1.20v 150 = 1.50v 180 = 1.80v 250 = 2.50v 330 = 3.30v adj = adjustable voltage version (0.8v to 4.5v) * custom output voltages available upon request. contact your local microchip sales office for more information. temperature range i = -40 c to +85 c package * mf = plastic dual flat no lead, (3x3 mm body), 8-lead ms = plastic micro small outline, 8-lead part n o. x xx package temp. device examples: a) mcp1602-1202i/mf: 1.20v, 500 ma buck reg, 8ld dfn pkg. b) mcp1602-1202i/ms: 1.20v, 500 ma buck reg, 8ld msop pkg. c) mcp1602-1502i/mf: 1.50v, 500 ma buck reg, 8ld dfn pkg. d) mcp1602-1502i/ms: 1.50v, 500 ma buck reg, 8ld msop pkg. e) mcp1602-1802i/mf: 1.80v, 500 ma buck reg, 8ld dfn pkg. f) mcp1602-1802i/ms: 1.80v, 500 ma buck reg, 8ld msop pkg. g) mcp1602-2502i/mf: 2.50v, 500 ma buck reg, 8ld dfn pkg. h) mcp1602-2502i/ms: 2.50v, 500 ma buck reg, 8ld msop pkg. i) mcp1602t-3302i/mf: tape and reel, 3.30v, 500 ma buck reg, 8ld dfn pkg. j) mcp1602-3302i/ms: 3.30v, 500 ma buck reg, 8ld msop pkg. k) mcp1602-adji/mf: adjustable, 500 ma buck reg, 8ld dfn pkg. l) mcp1602-adji/ms: adjustable, 500 ma buck reg, 8ld msop pkg. range -xx x voltage output x tape & reel downloaded from: http:///
mcp1602 ds22061a-page 24 ? 2007 microchip technology inc. notes: downloaded from: http:///
? 2007 microchip technology inc. ds22061a-page 25 information contained in this publication regarding device applications and the like is prov ided only for your convenience and may be superseded by updates. it is your responsibility to ensure that your application me ets 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 safe ty applications is entirely at the buyers risk, and the buyer agrees to defend, indemnify and hold harmless microchip from any and all damages, claims, suits, or expenses resulting fr om such use. no licenses are conveyed, implicitly or ot herwise, under any microchip intellectual property rights. trademarks the microchip name and logo, the microchip logo, accuron, dspic, k ee l oq , k ee l oq logo, micro id , mplab, pic, picmicro, picstart, pro mate, rfpic and smartshunt are registered trademarks of microc hip technology incorporated in the u.s.a. and other countries. amplab, filterlab, linear active thermistor, migratable memory, mxdev, mxlab, seeval, smartsensor and the embedded control solutions company are registered trademarks of microchip te chnology incorporated in the u.s.a. analog-for-the-digital age, application maestro, codeguard, dspicdem, dspicdem.net, dspicworks, dsspeak, ecan, economonitor, fansense, flexrom, fuzzylab, in-circuit serial programming, icsp, icepic, mindi, miwi, mpasm, mplab certified logo, mplib, mplink, pickit, picdem, picdem.net, piclab, pictail, powercal, powerinfo, powermate, powertool, real ice, rflab, select mode, smart serial, smarttel, total endurance, uni/o, wiperlock and zena are trademarks of microchip technology incorporated in the u.s.a. and other countries. sqtp is a service mark of mi crochip technology incorporated in the u.s.a. all other trademarks mentioned herein are property of their respective companies. ? 2007, microchip technology incorporated, printed in the u.s.a., all rights reserved. printed on recycled paper. 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 mo st 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 meth ods used to breach the code protection fe ature. all of these methods, to our knowledge, require using the microchip products in a manner outside the operating specif ications contained in microchips 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 committed to continuously improving the code protection features of our products. attempts to break microchips c ode protection feature may be a violation of the digital millennium copyright act. if such acts allow unauthorized access to your softwa re or other copyrighted work, you may have a right to sue for relief under that act. microchip received iso/ts-16949:2002 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 companys quality system processes and procedures are for its pic ? mcus and dspic ? dscs, k ee l oq ? code hopping devices, serial eeproms, microperi pherals, nonvolatile memory and analog products. in addition, microchips quality system for the design and manufacture of development systems is iso 9001:2000 certified. downloaded from: http:///
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