View MIC2177-50BWM_2461960.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

april 1999 1 mic2177 mic2177 micrel mic2177 micrel mic2177 2.5a synchronous buck regulator general description the micrel mic2177 is a 200khz synchronous buck (step- down) switching regulator designed for high-efficiency, bat- tery-powered applications. the mic2177 operates from a 4.5v to 16.5v input and features internal power mosfets that can supply up to 2.5a output current. it can operate with a maximum duty cycle of 100% for use in low-dropout conditions. it also features a shutdown mode that reduces quiescent current to less than 5 m a. the mic2177 achieves high efficiency over a wide output current range by switching between pwm and skip mode. operating mode is automatically selected according to output conditions. switching frequency is preset to 200khz and can be synchronized to an external clock signal of up to 300khz. the mic2177 uses current-mode control with internal current sensing. current-mode control provides superior line regula- tion and makes the regulator control loop easy to compen- sate. the output is protected with pulse-by-pulse current limiting and thermal shutdown. undervoltage lockout turns the output off when the input voltage is less than 4.5v. the mic2177 is packaged in a 20-lead wide power so package with an operating temperature range of C40 c to +85 c. see the mic2178 for externally selected pwm or skip-mode operation. typical application features ? 4.5v to 16.5v input voltage range ? dual-mode operation for high efficiency (up to 96%) pwm mode for > 200ma load current skip mode for < 200ma load current ? 100m w internal power mosfets at 12v input ? 200khz preset switching frequency ? low quiescent current 1.0ma in pwm mode 500 m a in skip mode < 5 m a in shutdown mode ? 100% duty cycle for low dropout operation ? current-mode control simplified loop compensation superior line regulation ? current limit ? thermal shutdown ? undervoltage lockout applications ? high-efficiency, battery-powered supplies ? buck (step-down) dc-to-dc converters ? cellular telephones ? laptop computers ? hand-held instruments ? battery charger bias sgnd en comp pgnd fb out vin c3 220? 10v v out 5v/2.5a l1, 33? c5 10nf c4 0.01? mic2177-5.0 auto sync r7 15k v in 6v to 16.5v c1 22? 35v u1 20 18 11 13 14?7 19 12 4? 3,8 1,2,9 d1 mbrs140 sw 10 enable on c6 2.2nf auto mode pwm mode mode off c2 22? 35v c7 220? 10v 70 75 80 85 90 95 100 10 100 1000 2500 efficiency (%) output current (ma) 5v output efficiency v in = 6v skip pwm
mic2177 micrel mic2177 2 april 1999 ordering information part output switching temperature number voltage frequency range package mic2177-3.3bwm 3.3v 200khz C40 c to +85 c 20-lead wide sop mic2177-5.0bwm 5.0v 200khz C40 c to +85 c 20-lead wide sop mic2177bwm adj. 200khz C40 c to +85 c 20-lead wide sop pin description pin number pin name pin function 1, 2, 9 vin supply input: controller and switch supply. unregulated supply input to internal regulator, output switches, and control circuitry. requires bypass capacitor to pgnd. all three pins must be connected to v in . 3,8 sw switch (output): internal power mosfet switch output. both pins must be externally connected together. 4,5,6,7 pgnd power ground: output stage ground connections. connect all pins to a common ground plane. 10 out output voltage sense (input): senses output voltage to determine minimum switch current for pwm operation. connect directly to v out . 11 auto automatic mode: connect 2.2nf timing capacitor for automatic pwm-/skip- mode switching. regulator operates exclusively in pwm mode when pin is pulled low. 12 fb feedback (input): error amplifier inverting input. for adjustable output version, connect fb to external resistive divider to set output voltage. for 3.3v and 5v fixed output versions, connect fb directly to output. 13 comp compensation: internal error amplifier output. connect to capacitor or series rc network to compensate the regulator control loop. 14,15,16,17 sgnd signal ground: ground connection of control section. connect all pins to common ground plane. 18 sync frequency synchronization (input): optional clock input. connect to external clock signal to synchronize oscillator. leading edge of signal above 1.7v terminates switching cycle. connect to sgnd if not used. 19 bias bias supply: internal 3.3v bias supply output. decouple with 0.01 m f bypass capacitor to sgnd. do not apply any external load. 20 en enable (input): logic high enables operation. logic low shuts down regulator. do not allow pin to float. pin configuration 2 vin 3 sw 4 pgnd 5 pgnd 6 pgnd 7 pgnd 1 vin 8 sw 9 vin en 20 bias 19 sync 18 sgnd 17 sgnd 16 sgnd 15 10 out 14 13 12 11 auto fb comp sgnd 20-lead wide sop
april 1999 3 mic2177 mic2177 micrel absolute maximum ratings supply voltage [100ms transient] (v in ) ......................... 18v output switch voltage (v sw ) ........................................ 18v output switch current (i sw ) ......................................... 6.0a enable, output-sense voltage (v en , v out ) ................. 18v sync voltage (v sync ) ..................................................... 6v operating ratings supply voltage (v in ) ..................................... 4.5v to 16.5v junction temperature range (t j ) ........... C40 c to +125 c electrical characteristics v in = 7.0v; t a = 25 c, bold indicates C40 c t a 85 c; unless noted. symbol parameter condition min typ max units i ss input supply current pwm mode, output not switching, 1.0 1.5 ma 4.5v v in 16.5v skip mode, output not switching, 500 650 m a 4.5v v in 16.5v v en = 0v, 4.5v v in 16.5v 1 25 m a v bias bias regulator output voltage v in = 16.5v 3.10 3.30 3.4 v v fb feedback voltage mic2177 [adj.]: v out = 3.3v, i load = 0 1.22 1.245 1.27 v v out output voltage mic2177 [adj.]: v out = 3.3v, 3.20 3.3 3.40 v 5v v in 16v, 10ma i load 2a 3.14 3.46 v mic2177-5.0: i load = 0 4.85 5.0 5.15 v mic2177-5.0: 4.85 5.0 5.15 6v v in 16v, 10ma i load 2a 4.75 5.25 v mic2177-3.3: i load = 0 3.20 3.3 3.40 v mic2177-3.3: 3.20 3.3 3.40 v 5v v in 16v, 10ma i load 2a 3.14 3.46 v v th undervoltage lockout upper threshold 4.25 4.35 v v tl lower threshold 3.9 4.15 v i fb feedback bias current mic2177 [adj.] 60 150 na mic2177-5.0, mic2177-3.3 20 40 m a a vol error amplifier gain 0.6v v comp 0.8v 15 18 20 error amplifier output swing upper limit 0.9 1.5 v lower limit 0.05 0.1 v error amplifier output current source and sink 15 25 35 m a f o oscillator frequency 160 200 240 khz d max maximum duty cycle v fb = 1.0v 100 % t on min minimum on-time v fb = 1.5v 300 400 ns sync frequency range 220 300 khz sync threshold 0.8 1.6 2.2 v sync minimum pulse width 500 ns i sync sync leakage v sync = 0v to 5.5v C1 0.01 1 m a i lim current limit pwm mode, v in = 12v 3.8 4.7 5.7 a skip mode 600 ma r on switch on-resistance high-side switch, v in = 12v 90 250 m w low-side switch, v in = 12v 110 250 m w i sw output switch leakage v sw = 16.5v 1 10 m a
mic2177 micrel mic2177 4 april 1999 symbol parameter condition min typ max units enable threshold 0.8 1.6 2.2 v i en enable leakage v en = 0v to 5.5v C1 0.01 1 m a auto threshold 0.8 1.6 v auto source current v fb = 1.5v, v auto < 0.8v 7 11 15 m a minimum switch current v in C v out = 0v 220 ma for pwm operation v in C v out = 3v 420 ma general note: devices are esd sensitive. handling precautions recommended.
april 1999 5 mic2177 mic2177 micrel typical characteristics 175 180 185 190 195 200 205 -60 -30 0 30 60 90 120 150 frequency (khz) temperature ( c) oscillator frequency vs. temperature 1.238 1.240 1.242 1.244 1.246 1.248 1.250 1.252 -60 -30 0 30 60 90 120 150 reference voltage (v) temperature ( c) reference voltage vs. temperature mic2177 [adj.] 3.280 3.285 3.290 3.295 3.300 3.305 3.310 3.315 3.320 -60 -30 0 30 60 90 120 150 reference voltage (v) temperature ( c) reference voltage vs. temperature mic2177-3.3 4.970 4.980 4.990 5.000 5.010 5.020 5.030 -60 -30 0 30 60 90 120 150 reference voltage (v) temperature ( c) reference voltage vs. temperature mic2177-5.0 16.0 16.5 17.0 17.5 18.0 18.5 19.0 -60 -30 0 30 60 90 120 150 amplifier voltage gain temperature ( c) error-amplifier gain vs. temperature 0 20 40 60 80 100 120 -60 -30 0 30 60 90 120 150 bias current (na) temperature ( c) feedback input bias current vs. temperature 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 -60 -30 0 30 60 90 120 150 current limit (a) temperature ( c) current limit vs. temperature 0 50 100 150 200 250 24681012141618 on-resistance (m w ) input voltage (v) high-side switch on-resistance 125 c 85 c 25 c 0 c 0 50 100 150 200 250 300 350 24681012141618 on-resistance (m w ) input voltage (v) low-side switch on-resistance 125 c 85 c 25 c 0 c 0 2 4 6 8 10 12 24681012141618 supply current (ma) input voltage (v) pwm-mode supply current output switching 60 65 70 75 80 85 90 95 100 10 100 1000 2500 efficiency (%) output current (ma) v in = 5v 8v 12v 3.3v output efficiency skip pwm 70 75 80 85 90 95 100 10 100 1000 2500 efficiency (%) output current (ma) 8v 12v 5v output efficiency v in = 6v skip pwm
mic2177 micrel mic2177 6 april 1999 block diagram v out 1.245 r1 r2 1 sw pgnd i sense amp. pwm/ skip-mode select logic v ref 1.245v fb 100m w n-channel 100m w p-channel comp vin error amp. skip-mode comp. i min comp. i limit comp. output control logic i min thrshld. low output comp. 40mv r s q 200khz oscillator pwm comp. 3.3v regulator uvlo, thermal shutdown v out l1 out sgnd 2.2nf c c auto 0.01? en bias v in 4.5v to 16.5v c in sync c out mic2177 [adjustable] internal supply voltage enable shutdown auto-mode pwm 20 19 18 11 13 2 1 3 8 d 4 5 6 7 r1 r2 12 10 14 15 16 17 bold lines indicate high current traces r c corrective ramp reset pulse 10? 3.3v 9
april 1999 7 mic2177 mic2177 micrel functional description micrels mic2177 is a synchronous buck regulator that oper- ates from an input voltage of 4.5v to 16.5v and provides a regulated output voltage of 1.25v to 16.5v. it has internal power mosfets that supply up to 2.5a of load current and operates with up to 100% duty cycle to allow low-dropout operation. to optimize efficiency, the mic2177 operates in pwm and skip mode. skip mode provides the best efficiency when load current is less than 200ma, while pwm mode is more efficient at higher current. a patented technique allows the mic2177 to automatically select the correct operating mode as the load current changes. during pwm operation, the mic2177 uses current-mode control which provides superior line regulation and makes the control loop easier to compensate. the pwm switching frequency is set internally to 200khz and can be synchro- nized to an external clock frequency up to 300khz. other features include a low-current shutdown mode, current limit, undervoltage lockout, and thermal shutdown. see the follow- ing sections for details. switch output the switch output (sw) is a half h-bridge consisting of a high- side p-channel and low-side n-channel power mosfet. these mosfets have a typical on-resistance of 100m w when the mic2177 operates from a 12v supply. antishoot- through circuitry prevents the p-channel and n-channel from turning on at the same time. current limit the mic2177 uses pulse-by-pulse current limiting to protect the output. during each switching period, a current limit comparator detects if the p-channel current exceeds 4.7a. when it does, the p-channel is turned off until the next switching period begins. undervoltage lockout undervoltage lockout (uvlo) turns off the output when the input voltage (v in ) is too low to provide sufficient gate drive for the output mosfets. it prevents the output from turning on until v in exceeds 4.3v. once operating, the output will not shut off until v in drops below 4.2v. thermal shutdown thermal shutdown turns off the output when the mic2177 junction temperature exceeds the maximum value for safe operation. after thermal shutdown occurs, the output will not turn on until the junction temperature drops approximately 10 c. shutdown mode the mic2177 has a low-current shutdown mode that is controlled by the enable input (en). when a logic 0 is applied to en, the mic2177 is in shutdown mode and its quiescent current drops to less than 5 m a. internal bias regulator an internal 3.3v regulator provides power to the mic2177 control circuits. this internal supply is brought out to the bias pin for bypassing by an external 0.01 m f capacitor. do not connect any external load to the bias pin. it is not designed to provide an external supply voltage. frequency synchronization the mic2177 operates at a preset switching frequency of 200khz. it can be synchronized to a higher frequency by connecting an external clock to the sync pin. the sync pin is a logic level input that synchronizes the oscillator to the rising edge of an external clock signal. it has a frequency range of 220khzC300khz, and can operate with a minimum pulse-width of 500ns. if synchronization is not required, connect sync to ground. low-dropout operation output regulation is maintained in pwm or skip mode even when the difference between v in and v out decreases below 1v. as v in C v out decreases, the duty cycle increases until it reaches 100%. at this point, the p-channel is kept on for several cycles at a time, and the output stays in regulation until v in C v out falls below the dropout voltage (dropout voltage = p-channel on resistance load current). pwm-mode operation refer to pwm-mode functional diagram which is a simpli- fied block diagram of the mic2177 operating in pwm mode with its associated waveforms. when operating in pwm mode, the output p-channel and n- channel mosfets are alternately switched on at a constant frequency and variable duty cycle. a switching period begins when the oscillator generates a reset pulse. this pulse resets the rs latch which turns on the p-channel and turns off the n-channel. during this time, inductor current (i l1 ) increases and energy is stored in the inductor. the current sense amplifier (i sense amp) measures the p-channel drain-to- source voltage and outputs a voltage proportional to i l1 . the output of i sense amp is added to a sawtooth waveform (corrective ramp) generated by the oscillator, creating a composite waveform labeled i sense on the timing diagram. when i sense is greater than the error amplifier output, the pwm comparator will set the rs latch which turns off the p- channel and turns on the n-channel. energy is then dis- charged from the inductor and i l1 decreases until the next switching cycle begins. by varying the p-channel on-time (duty cycle), the average inductor current is adjusted to whatever value is required to regulate the output voltage. the mic2177 uses current-mode control to adjust the duty cycle and regulate the output voltage. current-mode control has two signal loops that determine the duty cycle. one is an outer loop that senses the output voltage, and the other is a faster inner loop that senses the inductor current. signals from these two loops control the duty cycle in the following way: v out is fed back to the error amplifier which compares the feedback voltage (v fb ) to an internal reference voltage (v ref ). when v out is lower than its nominal value, the error amplifier output voltage increases. this voltage then inter- sects the current-sense waveform later in switching period which increases the duty cycle and average inductor current. if v out is higher than nominal, the error amplifier output voltage decreases, reducing the duty cycle. the pwm control loop is stabilized in two ways. first, the inner signal loop is compensated by adding a corrective ramp to the output of the current sense amplifier. this allows the regulator to remain stable when operating at greater than
mic2177 micrel mic2177 8 april 1999 50% duty cycle. second, a series resistor-capacitor load is connected to the error amplifier output (comp pin). this places a pole-zero pair in the regulator control loop. one more important item is synchronous rectification. as mentioned earlier, the n-channel output mosfet is turned on after the p-channel turns off. when the n-channel turns on, its on-resistance is low enough to create a short across the output diode. as a result, inductor current flows through the n-channel and the voltage drop across it is significantly lower than a diode forward voltage. this reduces power dissipation and improves efficiency to greater than 95% under certain operating conditions. to prevent shoot through current, the output stage employs break-before-make circuitry that provides approximately 50ns of delay from the time one mosfet turns off and the other turns on. as a result, inductor current briefly flows through the output diode during this transition. skip-mode operation refer to skip-mode functional diagram which is a simpli- fied block diagram of the mic2177 operating in skip mode and its associated waveforms. skip-mode operation turns on the output p-channel at a frequency and duty cycle that is a function of v in , v out , and the output inductor value. while in skip mode, the n-channel is kept off to optimize efficiency by reducing gate charge dissipation. v out is regulated by skipping switching cycles that turn on the p-channel. to begin analyzing mic2177 skip-mode operation, assume the skip-mode comparator output is high and the latch output has been reset to a logic 1. this turns on the p-channel and causes i l1 to increase linearly until it reaches a current limit of 600ma. when i l1 reaches this value, the current limit comparator sets the rs latch output to logic 0, turning off the p-channel. the output switch voltage (v sw ) then swings from v in to 0.4v below ground, and i l1 flows through the schottky diode. l1 discharges its energy to the output and i l1 de- creases to zero. when i l1 = 0, v sw swings from C0.4v to v out , and this triggers a one-shot that resets the rs latch. resetting the rs latch turns on the p-channel, which begins another switching cycle. the skip-mode comparator regulates v out by controlling when the mic2177 skips cycles. it compares v fb to v ref and has 10mv of hysteresis to prevent oscillations in the control loop. when v fb is less than v ref C 5mv, the comparator output is logic 1, allowing the p-channel to turn on. con- versely, when v fb is greater than v ref + 5mv, the p-channel is turned off. note that this is a self-oscillating topology which explains why the switching frequency and duty cycle are a function of v in , v out , and the value of l1. it has the unique feature (for a pulse-skipping regulator) of supplying the same value of maximum load current for any value of v in , v out , or l1. this allows the mic2177 to always supply up to 300ma of load current (i load ) when operating in skip mode. changing from pwm to skip mode refer to block diagram for circuits described in the following sections. the mic2177 automatically changes from pwm to skip mode operation when i load drops below a minimum value. i min is determined indirectly by detecting when the peak inductor current (i l(peak) ) is less than 420ma. this is done by the minimum current comparator which detects if the output p- channel current equals 420ma during each switching cycle. if it does not, the pwm/skip-mode select logic places the mic2177 into skip-mode operation. the value of i min that corresponds to i l1(peak) = 420ma is given by the following equation: i 420ma i min l1 = -d 2 where: d i l1 = inductor ripple current this equation shows i min varies as a function of d i l . there- fore, the user must select an inductor value that results in i min = 200ma when i l(peak) = 420ma. the formulas for cal- culating the correct inductor value are given in the applica- tions information section. note that d i l varies as a function of input voltage, and this also causes i min to vary. in applica- tions where the input voltage changes by a factor of two, i min will typically vary from 130ma to 250ma. during low-dropout operation, the minimum current thresh- old circuit reduces the minimum value of i l1(peak) for pwm operation. this compensates for d i l1 decreasing to almost zero when the difference between v in and v out is very low. changing from skip to pwm mode the mic2177 will automatically change from skip to pwm mode when i load exceeds 300ma. during skip-mode opera- tion, it can supply up to 300ma, and when i load exceeds this limit, v out will fall below its nominal value. at this point, the mic2177 begins operating in pwm mode. note that the maximum value of i load for skip mode is greater than the minimum value required for pwm mode. this current hyster- esis prevents the mic2177 from toggling between modes when i load is in the range of 100ma to 300ma. the low output comparator determines when v out is low enough for the regulator to change operating modes. it detects when the feedback voltage is 3% below nominal, and pulls the auto pin to ground. when auto is less than 1.6v, the pwm/skip-mode select logic places the mic2177 into pwm operation. the external 2.2nf capacitor connected to auto is charged by a 10 m a current source after the regulator begins operating in pwm mode. as a result, auto stays below 1.6v for several switching cycles after pwm operation begins, forcing the mic2177 to remain in pwm mode during this transition. external pwm-mode selection the mic2177 can be forced to operate in only pwm mode by connecting auto to ground. this prevents skip-mode opera- tion in applications that are sensitive to switching noise.
april 1999 9 mic2177 mic2177 micrel pwm-mode functional diagram sw pgnd i sense amp. v ref 1.245v 100m w n-channel 100m w p-channel comp vin error amp. r s q 200khz oscillator pwm comp. v out l1 fb sgnd c c v in 4.5v to 16.5v c in sync c out mic2177 [adjustable] pwm-mode signal path stop 18 13 2 1 3 8 d 4 5 6 7 r1 r2 12 14 15 16 17 r c corrective ramp reset pulse i l1 v out 1.245 r1 r2 1 9 v sw i l1 reset pulse i sense i load d i l1 error amp. output
mic2177 micrel mic2177 10 april 1999 skip-mode functional diagram s r q one shot sw pgnd i sense amp. v ref 1.245v 100m w p-channel vin skip-mode comp. i limit comp. v out l1 fb sgnd v in 4.5v to 16.5v c in c out mic2177 [adjustable] skip-mode signal path 2 1 3 8 d 4 5 6 7 r1 r2 12 14 15 16 17 i limit thresh. voltage output control logic i l1 v out 1.245 r1 r2 1 9 v sw i l1 one-shot pulse v fb v ref + 5mv v ref ?5mv 0 i lim 0 v out v in
april 1999 11 mic2177 mic2177 micrel application information feedback resistor selection (adjustable version) the output voltage is configured by connecting an external resistive divider to the fb pin as shown in mic2177 block diagram. the ratio of r1 to r2 determines the output voltage. to optimize efficiency during low output current operation, r2 should not be less than 20k w . however, to prevent feedback error due to input bias current at the fb pin, r2 should not be greater than 100k w . after selecting r2, calculate r1 using the following formula: r1 = r2 v 1.245v 1 out ? ? ? ? - ? ? input capacitor selection the input capacitor is selected for its rms current and voltage rating and should be a low esr (equivalent series resistance) electrolytic or tantalum capacitor. as a rule-of- thumb, the voltage rating for a tantalum capacitor should be twice the value of v in , and the voltage rating for an electrolytic should be 40% higher than v in. the rms current rating must be equal or greater than the maximum rms input ripple current. a simple, worst-case formula for calculating this rms current is: i = i rms(max) load(max) 2 tantalum capacitors are a better choice for applications that require the most compact layout or operation below 0 c. the input capacitor must be located very close to the vin pin (within 0.2 inches, 5mm). also place a 0.1 m f ceramic bypass capacitor as close as possible to vin. inductor selection the inductor must be at least a minimum value in order for the mic2177 to change from pwm to skip mode at the correct value of output current. this minimum value ensures the inductor ripple current never exceeds 600ma, and is calcu- lated using the following formula: l = v 1 v v 8.3 h/v min out out in(max) ? ? ? ? m where: v in(max) = maximum input voltage in general, a value at least 20% greater than l min should be selected because inductor values have a tolerance of 20%. two other parameters to consider in selecting an inductor are winding resistance and peak current rating. the inductor must have a peak current rating equal or greater than the peak inductor current. otherwise, the inductor may saturate, causing excessive current in the output switch. also, the inductors core loss may increase significantly. both of these effects will degrade efficiency. the formula for peak inductor current is: i i 300ma l(peak) load(max) =+ to maximize efficiency, the inductors resistance must be less than the output switch on-resistance (preferably 50m w or less). output capacitor selection select an output capacitor that has a low value of esr. this parameter determines a regulators output ripple voltage (v ripple ) which is generated by d i l esr. as mentioned in inductor selection, the maximum value for d i l is 600ma. therefore, the maximum value of esr is: esr = 600ma v max ripple where: v ripple < 1% of v out typically, capacitors in the range of 100 m f to 220 m f have esr less than this maximum value. the output capacitor can be either a low esr electrolytic or tantalum capacitor, but tantalum is a better choice for compact layout and operation at temperatures below 0 c. the voltage rating of a tantalum capacitor must be 2 v out , and the voltage rating of an electrolytic must be 1.4 v out . output diode selection in pwm operation, inductor current flows through the output diode approximately 50ns during the dead time when one output mosfet turns off and the other turns on. in skip mode, the inductor current flows through the diode during the entire p-channel off time. the correct diode for both of these conditions is a 1a diode with a reverse voltage rating greater than v in . it must be a schottky or ultrafast-recovery diode (t r < 100ns) to minimize power dissipation from the diodes reverse-recovery charge. compensation compensation is provided by connecting a series rc load to the comp pin. this creates a pole-zero pair in the regulator control loop, allowing the regulator to remain stable with enough low frequency loop-gain for good load and line regulation. at higher frequencies, pole-zero reduces loop- gain to a level referred to as the mid-band gain. the mid-band gain is low enough so that the loop gain crosses 0db with sufficient phase margin. typical values for the rc load are 4.7nf C 10nf for the capacitor and 5k w C 20k w for the resistor. printed circuit board layout a well designed pc board will prevent switching noise and ground bounce from interfering with the operation of the mic2177. a good design takes into consideration component placement and routing of power traces. the first thing to consider is the locations of the input capacitor, inductor, output diode, and output capacitor. the input capacitor must be placed very close to the vin pin, the inductor and output diode very close to the sw pin, and the output capacitor near the inductor. these components pass large high-frequency current pulses, so they must use short, wide power traces. in addition, their ground pins and pgnd are connected to a ground plane that is nearest the power supply ground bus.
mic2177 micrel mic2177 12 april 1999 the feedback resistors, rc compensation network, and bias pin bypass capacitor should be located near their respective pins. to prevent ground bounce, their ground traces and sgnd should not be in the path of switching currents returning to the power supply ground bus. sgnd and pgnd should be tied together by a ground plane that extends under the mic2177. bias sgnd auto comp pgnd fb sw vin c2 100? 10v v out 3.3v/1a l1, 50? c4 6.8nf c3 0.01? mic2177 sync en r4 10k v in 4.5v to 16.5v c1 22? 35v u1 20 18 10 11 13 14?7 19 12 4? 3,8 1,2,9 d1 mbrs130l u1 micrel mic2177-3.3bwm c1 avx tpse226m035r0300, esr = 0.3 w c2 avx tpsd107m010r0100, esr = 0.1 w c3 z5uorx7r ceramic dielectric material c4 x7rornp0 ceramic dielectric material d1 motorola mbrs130lt3 l1 coiltronics ctx50-4p, dcr = 0.097 w l1 coilcraft do3316p-473, dcr = 0.12 w l1 bi hm77-11003, dcr = 0.073 w c5 0.01 ? out figure 1. mic2177 4.5vC16.5v to 3.3/1a regulator suggested manufacturers list inductors capacitors diodes transistors coilcraft avx corp. general instruments (gi) siliconix 1102 silver lake rd. 801 17th ave. south 10 melville park rd. 2201 laurelwood rd. cary, il 60013 myrtle beach, sc 29577 melville, ny 11747 santa clara, ca 96056 tel: (708) 639-2361 tel: (803) 448-9411 tel: (516) 847-3222 tel: (800) 554-5565 fax: (708) 639-1469 fax: (803) 448-1943 fax: (516) 847-3150 coiltronics sanyo video components corp. international rectifier corp. 6000 park of commerce blvd. 2001 sanyo ave. 233 kansas st. boca raton, fl 33487 san diego, ca 92173 el segundo, ca 90245 tel: (407) 241-7876 tel: (619) 661-6835 tel: (310) 322-3331 fax: (407) 241-9339 fax: (619) 661-1055 fax: (310) 322-3332 bi technologies sprague electric motorola inc. 4200 bonita place lower main st. ms 56-126 fullerton, ca 60005 sanford, me 04073 3102 north 56th st. tel: (714) 447-2345 tel: (207) 324-4140 phoenix, az 85018 fax: (714) 447-2500 tel: (602) 244-3576 fax: (602) 244-4015
april 1999 13 mic2177 mic2177 micrel package information 0.022 (0.559) 0.018 (0.457) 5 typ 0.408 (10.363) 0.404 (10.262) 0.509 (12.929) 0.505 (12.827) 0.103 (2.616) 0.099 (2.515) seating plane 0.027 (0.686) 0.031 (0.787) 0.016 (0.046) typ 0.301 (7.645) 0.297 (7.544) 0.094 (2.388) 0.090 (2.286) 0.297 (7.544) 0.293 (7.442) 10 typ 0.032 (0.813) typ 0.330 (8.382) 0.326 (8.280) 7 typ 0.050 (1.270) typ 0.015 (0.381) r 0.015 (0.381) min pin 1 dimensions: inches (mm) 20-lead wide sop (wm)
mic2177 micrel mic2177 14 april 1999
april 1999 15 mic2177 mic2177 micrel
mic2177 micrel mic2177 16 april 1999 micrel inc. 1849 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 web http://www.micrel.com this information is believed to be accurate and reliable, however no responsibility is assumed by micrel for its use nor for an y infringement of patents or other rights of third parties resulting from its use. no license is granted by implication or otherwise under any patent or pat ent right of micrel inc. ? 1999 micrel incorporated

▲Up To Search▲

Price & Availability of MIC2177-50BWM

	To Download MIC2177-50BWM Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .