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  august 2012 ? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan56310 ? rev. 1.0.0 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator fan53600 / fan53610 3 mhz, 600 ma / 1a synchronous buck regulator features ? 600 ma or 1 a output current capability ? 26 a typical quiescent current ? 3 mhz fixed-frequency operation ? best-in-class load transient response ? best-in-class efficiency ? 2.3 v to 5.5 v input voltage range ? 0.8 v to 3.3 v fixed output voltage ? low ripple light-load pfm mode ? forced pwm and external clock synchronization ? internal soft-start ? input under-voltage lockout (uvlo) ? thermal shutdown and overload protection ? optional output discharge ? 6-bump wlcsp, 0.4 mm pitch applications ? 3g, 4g, wifi ? , wimax?, and wibro ? data cards ? tablets ? dsc, dvc ? netbooks ? , ultra-mobile pcs all trademarks are the property of their respective owners. description the fan53600/10 is a 3 mhz step-down switching voltage regulator, available in 600 ma or 1 a options, that delivers a fixed output from an input voltag e supply of 2.3 v to 5.5 v. using a proprietary architecture with synchronous rectification, the fan53600/1 0 is capable of delivering a peak efficiency of 92%, while maintaining efficiency over 80% at load currents as low as 1 ma. the regulator operates at a nominal fixed frequency of 3 mhz, which reduces the value of the external components to as low as 1 h for the output inductor and 4.7 f for the output capacitor. in addition, the pulse-width modulation (pwm) modulator can be synchronized to an external frequency source. at moderate and light loads, pulse frequency modulation (pfm) is used to operate the device in power-save mode with a typical quiescent current of 26 a. even with such a low quiescent current, the part exhibits excellent transient response during large load swings. at higher loads, the system automatically switches to fixed-frequency control, operating at 3 mhz. in shutdown mode, the supply current drops below 1 a, reducing power consumption. for applications that require minimu m ripple or fixed frequency, pfm mode can be disabled using the mode pin. the fan53600/10 is available in 6-bump, 0.4 mm pitch, wafer-level chip-scale package (wlcsp). figure 1. typical application ordering information part number output voltage (1) max. output current active discharge (2) package temperature range packing FAN53600AUC33X 3.3 v 600 ma yes wlcsp-6, 0.4 mm pitch ?40 to +85c tape and reel fan53610auc29x 2.9 v 1 a yes notes: 1. other voltage options available on requ est. contact a fairchild representative. 2. all voltage and output current options are available with or without active discharge. contact a fairchild representative.
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 2 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator pin configurations c1 b1 a1 c2 b2 a2 mode sw fb vin en gnd figure 2. bumps facing down figure 3. bumps facing up pin definitions pin # name description a1 mode mode . logic 1 on this pin forces the ic to stay in pwm mode. logic 0 allows the ic to automatically switch to pfm mode during light loads. the regulator also synchronizes its switching frequency to two times the frequency provided on this pin. do not leave this pin floating. b1 sw switching node . connect to output inductor. c1 fb feedback . connect to output voltage. c2 gnd ground . power and ic ground. all signals are referenced to this pin. b2 en enable . the device is in shutdown mode when voltage to this pin is <0.4 v and enabled when >1.2 v. do not leave this pin floating. a2 vin input voltage . connect to input power source.
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 3 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator absolute maximum ratings stresses exceeding the absolute maximum ratings may damage the device. the device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. in addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. the absolute maximum ratings are stress ratings only. symbol parameter min. max. unit v in input voltage ?0.3 7.0 v v sw voltage on sw pin ?0.3 v in + 0.3 (3) v v ctrl en and mode pin voltage ?0.3 v in + 0.3 (3) v other pins ?0.3 v in + 0.3 (3) v esd electrostatic discharge protection level human body model per jesd22-a114 3.5 kv charged device model per jesd22-c101 1.5 t j junction temperature ?40 +150 c t stg storage temperature ?65 +150 c t l lead soldering temperature, 10 seconds +260 c note: 3. lesser of 7 v or v in +0.3 v. recommended operating conditions the recommended operating conditions table defines the conditions for actual device operation. recommended operating conditions are specified to ensure optimal performance to the datasheet specifications . fairchild does not recommend exceeding them or designing to absolute maximum ratings. symbol parameter min. typ. max. unit v cc supply voltage range 2.3 5.5 v i out output current fan53600 0 600 ma fan53610 0 1 a l inductor 1 h c in input capacitor 2.2 f c out output capacitor v out <2.7 v 1.6 4.7 12.0 f v out 2.7 v 10 t a operating ambient tem perature ?40 +85 c t j operating junction temperature ?40 +125 c thermal properties junction-to-ambient thermal resistance is a function of applicat ion and board layout. this data is measured with two-layer 1s2p boards in accordance to jedec standard jesd51. special attention must be paid not to exceed junction temperature t j(max) at a given ambient temperature t a . symbol parameter typical unit ja junction-to-ambient thermal resistance 150 c/w
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 4 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator electrical characteristics minimum and maximum values are at v in = v en = 2.3 v to 5.5 v, v mode = 0v (auto mode), and t a = -40c to +85 c; circuit of figure 1, unless otherwise noted. typical values are at t a = 25c, v in = v en = 3.6 v, v out =2.9 v. symbol parameter conditions min. typ. max. unit power supplies i q quiescent current no load, not switching 26 a pwm mode 3 ma i (sd) shutdown supply current v in = 3.6 v, en = gnd 0.25 1.00 a v uvlo under-voltage lockout threshold rising v in 2.15 2.27 v v uvhyst under-voltage lockout hysteresis 200 mv logic inputs: en and mode pins v ih enable high-level input voltage 1.2 v v il enable low-level input voltage 0.4 v v lhyst logic input hysteresis voltage 100 mv i in enable input leakage current pin to v in or gnd 0.01 1.00 a switching and synchronization f sw switching frequency (4) v in = 3.6 v, t a = 25c 2.7 3.0 3.3 mhz f sync mode synchronization range (4) square wave at mode input 1.3 1.5 1.7 mhz regulation v o output voltage accuracy 1.233v i load = 0 to 600 ma 1.207 1.233 1.272 v pwm mode 1.207 1.233 1.259 v 1.820v i load = 0 to 600 ma 1.784 1.820 1.875 v pwm mode 1.784 1.820 1.856 v 2.900v i load = 0 to 400 ma, v in v out + 150mv 2.755 (-5%) 2.900 2.987 (+3%) v i load = 0 to 600 ma, v in v out + 300 mv 2.813 (-3%) 2.900 2.987 (+3%) v t ss soft-start from en rising edge 180 300 s output driver r ds(on) pmos on resistance v in = v gs = 3.6 v 175 m nmos on resistance v in = v gs = 3.6 v 165 m i lim(ol) pmos peak current limit open-loop for fan53600 900 1100 1250 ma open-loop for fan53610 1500 1750 2000 ma r dis output discharge resistance en = gnd 230 t tsd thermal shutdown ccm only 150 c t hys thermal shutdown hysteresis 15 c notes: 4. limited by the effect of t off minimum (see operation description section) . 5. the electrical characteristics table reflects open-loop data .
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 5 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator typical performance characteristics unless otherwise noted, v in = v en = 3.6 v, v mode = 0 v (auto mode), and t a = 25c. 80% 83% 86% 89% 92% 95% 98% 0 200 400 600 800 1000 efficiency load current (ma) 3.6 vin 4.2 vin 5.0 vin 5.5 vin 70% 75% 80% 85% 90% 95% 100% 0 200 400 600 800 1000 efficiency load current (ma) - 40c, auto +25c, auto +85c, auto - 40c, pwm +25c, pwm +85c, pwm figure 4. efficiency vs. load current and input voltage, v out =3.3 v, dotted for decreasing load figure 5. efficiency vs. load current and temperature v in =5 v, v out =3.3 v, dotted for fpwm 80% 83% 86% 89% 92% 95% 98% 0 200 400 600 800 1000 efficiency load current (ma) 3.2 vin 3.6 vin 4.2 vin 5.0 vin 70% 75% 80% 85% 90% 95% 100% 0 200 400 600 800 1000 efficiency load current (ma) - 40c, auto +25c, auto +85c, auto - 40c, pwm +25c, pwm +85c, pwm figure 6. efficiency vs. load current and input voltage, v out =2.9 v, dotted for decreasing load figure 7. efficiency vs. load current and temperature, v out =2.9 v, dotted for fpwm 75% 77% 79% 81% 83% 85% 87% 89% 91% 93% 95% 0 200 400 600 800 1000 efficiency load current (ma) 2.7 vin 3.6 vin 4.2 vin 5.0 vin 65% 70% 75% 80% 85% 90% 95% 0 200 400 600 800 1000 efficiency load current (ma) -40c, auto +25c, auto +85c, auto -40c, pwm +25c, pwm +85c, pwm figure 8. efficiency vs. load current and input voltage, v out =1.82 v, dotted for decreasing load figure 9. efficiency vs. load current and temperature, v out =1.82 v, dotted for fpwm
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 6 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator typical performance characteristics (continued) unless otherwise noted, v in = v en = 3.6 v, v mode = 0 v (auto mode), and t a = 25c. 70% 73% 76% 79% 82% 85% 88% 91% 0 200 400 600 800 1000 efficiency load current (ma) 2.7 vin 3.6 vin 4.2 vin 5.0 vin 60% 65% 70% 75% 80% 85% 90% 0 200 400 600 800 1000 efficiency load current (ma) -40c, auto +25c, auto +85c, auto -40c, pwm +25c, pwm +85c, pwm figure 10. efficiency vs. load current and input voltage, v out =1.23 v, dotted for decreasing load figure 11. efficiency vs. load current and temperature, v out =1.23 v, dotted for fpwm -2 -1 0 1 2 3 0 200 400 600 800 1000 output regulation (%) load current (ma) 2.7vin, auto 3.6vin, auto 4.2vin, auto 5.0vin, auto 2.7vin, pwm 3.6vin, pwm 4.2vin, pwm 5.0vin, pwm -2 -1 0 1 2 3 0 200 400 600 800 1000 output regulation (%) load current (ma) 2.7vin, auto 3.6vin, auto 4.2vin, auto 5.0vin, auto 2.7vin, pwm 3.6vin, pwm 4.2vin, pwm 5.0vin, pwm figure 12. ? v out (%) vs. load current and input voltage, v out =1.82 v, normalized to 3.6 v in , 500ma load, fpwm, dotted for auto mode figure 13. ? v out (%) vs. load current and input voltage, v out =1.23 v, normalized to 3.6 v in , 500 ma load, fpwm, dotted for auto mode 0 100 200 300 400 500 3.33.84.34.85.3 load current (ma) input voltage (v) pwm pfm 100% d.c. 0 100 200 300 400 500 2.9 3.4 3.9 4.4 4.9 5.4 load current (ma) input voltage (v) pwm pfm 100% d.c. figure 14. pfm / pwm /100% duty cycle boundary vs. input voltage, v out =3.3 v figure 15. pfm / pwm /100% duty cycle boundary vs. input voltage, v out =2.9 v
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 7 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator typical performance characteristics (continued) unless otherwise noted, v in = v en = 3.6 v, v mode = 0 v (auto mode), and t a = 25c. 0 100 200 300 400 500 2.5 3.0 3.5 4.0 4.5 5.0 5.5 load current (ma) input voltage (v) pwm pfm 0 100 200 300 400 500 2.5 3.0 3.5 4.0 4.5 5.0 5.5 load current (ma) input voltage (v) pwm pfm figure 16. pfm / pwm boundary vs. input voltage, v out =1.82 v figure 17. pfm / pwm boundary vs. input voltage, v out =1.23 v 10 15 20 25 30 35 40 2.53.03.54.04.55.05.5 input current ( a) input voltage (v) - 40c, en=vin +25c, en=vin +85c, en=vin - 40c, en=1.8v +25c, en=1.8v +85c, en=1.8v 10 15 20 25 30 35 40 2.5 3.0 3.5 4.0 4.5 5.0 5.5 input current ( a) input voltage (v) - 40c, en=vin +25c, en=vin +85c, en=vin - 40c, en=1.8v +25c, en=1.8v +85c, en=1.8v figure 18. quiescent current vs. input voltage and temperature, v out =2.9 v, en=v in solid, dotted for en=1.8 v figure 19. quiescent current vs. input voltage and temperature, v out =1.82 v, en=v in solid, dotted for en=1.8 v 0 5 10 15 20 25 2.53.03.54.04.55.05.5 input current (ma) input voltage (v) - 40c +25c +85c 0 5 10 15 20 25 2.5 3.0 3.5 4.0 4.5 5.0 5.5 input current (ma) input voltage (v) - 40c +25c +85c figure 20. quiescent current vs. input voltage and temperature, v out =2.9 v, mode=en=v in (fpwm) figure 21. quiescent current vs. input voltage and temperature, v out =1.82 v, mode=en=v in (fpwm)
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 8 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator typical performance characteristics (continued) unless otherwise noted, v in = v en = 3.6 v, v mode = 0 v (auto mode), and t a = 25c. 0 20 40 60 80 100 0 200 400 600 800 1000 output ripple (mvpp) load current (ma) 3.2vin, auto 3.6vin, auto 5.0vin, auto 3.2vin, pwm 3.6vin, pwm 5.0vin, pwm 0 10 20 30 40 50 0 200 400 600 800 1000 output ripple (mvpp) load current (ma) 2.7vin, auto 3.6vin, auto 5.0vin, auto 2.7vin, pwm 3.6vin, pwm 5.0vin, pwm figure 22. output ripple vs. load current and input voltage, v out =2.9 v, fpwm, dotted for auto mode figure 23. output ripple vs. load current and input voltage, v out =2.9 v, fpwm, dotted for auto mode 0 500 1,000 1,500 2,000 2,500 3,000 3,500 0 200 400 600 800 1000 switching frequency (khz) load current (ma) 3.2vin, auto 3.6vin, auto 5.0vin, auto 3.2vin, pwm 3.6vin, pwm 5.0vin, pwm 0 500 1,000 1,500 2,000 2,500 3,000 3,500 0 200 400 600 800 1000 switching frequency (khz) load current (ma) 2.7vin, auto 3.6vin, auto 5.0vin, auto 2.7vin, pwm 3.6vin, pwm 5.0vin, pwm figure 24. . frequency vs. load current and input voltage, v out =2.9 v, auto mode, dotted for fpwm figure 25. frequency vs. load current and input voltage, v out =1.82 v, auto mode, dotted for fpwm figure 26. load transient, v in =5 v, v out =3.3 v, 10-200-10 ma, 100 ns edge figure 27. load transient, v in =5 v, v out =3.3 v, 200- 800-200 ma, 100 ns edge
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 9 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator typical performance characteristics (continued) unless otherwise noted, v in = v en = 3.6 v, v mode = 0 v (auto mode), and t a = 25c. figure 28. load transient, v in =5 v, v out =2.9 v, 10-200-10 ma, 100 ns edge figure 29. load transient, v in =5 v, v out =2.9 v, 200-800-200 ma, 100 ns edge figure 30. line transient, 3.3-3.9-3.3 v in , 10 s edge, v out =2.9 v, 58 ma load figure 31. line transient, 3.3-3.9-3.3 v in , 10 s edge, v out =2.9 v, 600 ma load figure 32. combined line / load transient, v out =2.9v, 3.9-3.3-3.9 v in , 10 s edge, 58-500-58 ma load, 100 ns edge figure 33. startup, 50 ? load
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 10 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator typical performance characteristics (continued) unless otherwise noted, v in = v en = 3.6 v, v mode = 0 v (auto mode), and t a = 25c. figure 34. startup, 4.7 ? load figure 35. over-current, load increasing past current limit, fan53600 figure 36. 250 m ? fault, rapid fault, fan53600
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 11 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator operation description the fan53600/10 is a 3 mhz, step-down switching voltage regulator, available in 600 ma or 1 a options, that delivers a fixed output from an input volt age supply of 2.3 v to 5.5 v. using a proprietary architecture with synchronous rectification, the fan53600/10 is capable of delivering a peak efficiency of 92%, while maintaining efficiency over 80% at load currents as low as 1 ma. the regulator operates at a nominal fixed frequency of 3 mhz, which reduces the value of the external components to as low as 1 h for the output inductor and 4.7 f for the output capacitor. in addition, the pwm modulator can be synchronized to an external frequency source. control scheme the fan53600/10 uses a proprietary, non-linear, fixed- frequency pwm modulator to deliver a fast load transient response, while maintaining a constant switching frequency over a wide range of operating conditions. the regulator performance is independent of the output capacitor esr, allowing the use of ceramic output capacitors. although this type of operation normally results in a switching frequency that varies with input voltage and load current, an internal frequency loop holds the switching frequency constant over a large range of input voltages and load currents. for very light loads, the fan53600/10 operates in discontinuous current (dcm), single-pulse, pfm mode; which produces low output ripple compared with other pfm architectures. transition between pwm and pfm is seamless, with a glitch of less than 18 mv at v out during the transition between dcm and ccm modes. combined with exceptional transient response characteristics, the very lo w quiescent current of the controller (26 a) maintains high efficiency, even at very light loads, while preserving fast transient response for applications requiring tigh t output regulation. 100% duty cycle operation when v in approaches v out , the regulator increases its duty cycle until 100% duty cycle is reached. as the duty cycle approaches 100%, the switchi ng frequency declines due to the minimum off-time (t off(min) ) of about 50 ns imposed by the control circuit. when 100% duty cycle is reached, v out follows v in with a drop-out voltage (v dropout ) determined by the total resistance between v in and v out as calculated by: ( ) ) ( + ? = (1) enable and soft-start when en is low, all circuits are off and the ic draws ~50 na of current. when en is high and v in is above its uvlo threshold, the regulator begins a soft-start cycle. the output ramp during soft-start is a fixed slew rate of 50 mv/ s from 0 to 1 v out , then 12.5 mv/ s until the output reaches its setpoint. regardless of the st ate of the mode pin, pfm mode is enabled to prevent current from being discharged from c out if soft-start begins when c out is charged. all voltage options can be order ed with a feature that actively discharges fb to ground through a 230 path when en is low. raising en above its threshold voltage activates the part and starts the soft-start cycle. during soft-start, the internal reference is ramped using an exponential rc shape to prevent overshoot of the output voltage. current limiting minimizes inrush during soft-start. the ic may fail to start if heavy load is applied during startup and/or if excessive c out is used. this is due to the current- limit fault response, which protec ts the ic in the event of an over-current condition present during soft-start. the current required to charge c out during soft-start, commonly referred to as ?displacement current,? is given as: dt dv c i out disp ? = (2) where the dt dv term refers to the soft-start slew rate above. to prevent shutdown during so ft-start, the following condition must be met: ) ( dc max load disp i i i < + (3) where i max(dc) is the maximum load current the ic is guaranteed to support. startup into large c out multiple soft-start cycles are required for no-load startup if c out is greater than 15 f. large c out requires light initial load to ensure the fan53600/10 starts appropriately. the ic shuts down for 1.3 ms when i disp exceeds i limit for more than 210 s of current limit. the ic then begins a new soft- start cycle. since c out retains its charge when the ic is off, the ic reaches regulation after multiple soft-start attempts. mode pin logic 1 on this pin forces the ic to stay in pwm mode. logic 0 allows the ic to automatically switch to pfm during light loads. if the mode pin is toggled, with a frequency between 1.3 mhz and 1.7 mhz, the converter synchronizes its switching frequency to two times the frequency on the mode pin (f mode ). the mode pin is internally buffered with a schmitt trigger, which allows the mode pin to be driven with slow rise and fall times. an asymmetric duty cycle for frequency synchronization is also permitted as long as the minimum time below v il(max) or above v ih(max) is 100 ns.
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 12 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator current limit, fault shutdown, and restart a heavy load or short circuit on the output causes the current in the inductor to increase until a maximum current threshold is reached in the high-side switch. upon reaching this point, the high-side switch turns off, preventing high currents from causing damage. the regulator continues to limit the current cycle by cycle. after 16 cycles of current limit, the regulator triggers an over-current fault, causing the regulator to shut down for about 1.3 ms before attempting a restart. if the fault was caused by short circuit, the soft-start circuit attempts to restart and produces an over-current fault after about 250 s, which results in a duty cycle of less than 0%, limiting power dissipation. the closed-loop peak-current limit, i lim(pk) , is not the same as the open-loop tested current limit, i lim(ol) , in the electrical characteristics table. this is primarily due to the effect of propagation delays of the ic current-limit comparator. under-voltage lockout (uvlo) when en is high, the under-voltage lockout keeps the part from operating until the input supply voltage rises high enough to properly operate. this ensures no misbehavior of the regulator during startup or shutdown. thermal shutdown (tsd) when the die temperature increases, due to a high load condition and/or a high ambient temperature, the output switching is disabled until the temperature on the die has fallen sufficiently. the junction temperature at which the thermal shutdown activates is nominally 150c with a 15c hysteresis. minimum off-time and switching frequency t off(min) is 50 ns. this imposes constraints on the maximum in out v v that the fan53600/10 can provide, or the maximum output voltage it can provide at low v in while maintaining a fixed switching frequency in pwm mode. when v in is low, fixed switching frequency is maintained as long as: 85 . 0 1 ) ( ? ? sw min off in out f t v v . the switching frequency drops when the regulator cannot provide sufficient duty cycle at 3 mhz to maintain regulation. this occurs when v out >0.85 v in at high load currents. the calculation for switching frequency is given by: ? ? ? ? ? ? ? ? = mhz t f max sw sw 3 , 1 min ) ( (4) where: ? ? ? ? ? ? ? ? ? ? ? ? + + ? = out on out in off out out max sw v r i v r i v ns t 1 50 ) ( (5) where: off r = l n dson dcr r + _ on r = l p dson dcr r + _ .
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 13 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator applications information selecting the inductor the output inductor must meet both the required inductance and the energy handling capability of the application. the inductor value affects average current limit, the pwm-to- pfm transition point, output voltage ripple, and efficiency. the ripple current ( ? i) of the regulator is: ? ? ? ? ? ? ? ? ? ? ? sw out in in out f l v v v v i (6) the maximum average load current, i max(load), is related to the peak current limit, i lim(pk) , by the ripple current, given by: 2 ) ( ) ( i i i pk lim load max ? = (7) the transition between pfm and pwm operation is determined by the point at which the inductor valley current crosses zero. the regulator dc current when the inductor current crosses zero, i dcm , is: 2 i i dcm = (8) the fan53600/10 is optimized for operation with l = 1 h, but is stable with inductances up to 2.2 h (nominal). the inductor should be rated to maintain at least 80% of its value at i lim(pk) . efficiency is affected by inductor dcr and inductance value. decreasing the inductor value for a given physical size typically decreases dcr; but since ? i increases, the rms current increases, as do the core and skin effect losses: 12 i i i 2 2 ) dc ( out rms + = (9) the increased rms current produces higher losses through the r ds(on) of the ic mosfets, as well as the inductor dcr. increasing the inductor value produces lower rms currents, but degrades transient response. for a given physical inductor size, increased inductance usually results in an inductor with lower saturation current and higher dcr. table 1 shows the effects of inductance higher or lower than the recommended 1 h on regulator performance. output capacitor table 2 suggests 0402 capacitors. 0603 capacitors may further improve performance in that the effective capacitance is higher. this improves transient response and output ripple. increasing c out has no effect on loop stability and can therefore be increased to reduce output voltage ripple or to improve transient response. output voltage ripple, ? v out , is: () ? ? ? ? ? ? ? ? ? ? + ? ? ? ? ? = out sw 2 out sw l out c f 8 1 d 1 d 2 esr c f i v (10) input capacitor the 2.2 f ceramic input capacitor should be placed as close as possible between the vin pin and gnd to minimize parasitic inductance. if a long wire is used to bring power to the ic, additional ?bulk? capacitance (electrolytic or tantalum) should be placed between c in and the power source lead to reduce ringing that can occur between the inductance of the power source leads and c in . the effective capacitance value decreases as v in increases due to dc bias effects. table 1. effects of changes in inductor value ( 470 nh recommended value) on regulator performance inductor value i max(load) ? v out transient response increase increase decrease degraded decrease decrease increase improved table 2. recommended passive components and variation due to dc bias component description vendor min. typ. comment l1 1 h, 2012, 190 m , 0.8 a murata lqm21pn1r0mc0 1 h not recommended for 1a load 1 h, 1.4 a, 85 m , 2016 murata lqm2mpn1r0m 1 h utilized to generate graphs, figure 4 ? figure 36 c in 2.2 f, 6.3 v, x5r, 0402 murata or equivalent grm155r60j225me15 grm188r60j225ke19d 1.0 f 2.2 f decrease primarily due to dc bias (v in ) and elevated temperature c out 4.7 f, x5r 0603 murata or equivalent grm188r60g106me47d 1.6 f 4.7 f decrease primarily due to dc bias (v out ) and elevated temperature
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 14 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator pcb layout guidelines there are only three external components: the inductor and the input and output capacitors. for any buck switcher ic, including the fan53600/10, it is important to place a low-esr input capacitor very close to the ic, as shown in figure 37. the input capacitor ensures good input decoupling, which helps reduce noise at the output terminals and ensures that the control sections of the ic do not behave erratically due to excessive noise. this reduces switching cycle jitter and ensures good overall performance. it is important to place the common gnd of c in and c out as close as possible to the c2 terminal. there is some flexibility in moving the inductor further away from the ic; in that case, v out should be considered at the c out terminal. figure 37. 3 mhz pcb layout guidance
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 15 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator physical dimensions figure 38. 6-bump wlcsp, 0.4mm pitch product-specific dimensions product d e x y FAN53600AUC33X 1.160 0.030 0.860 0.030 0.230 0.180 fan53610auc29x 1.160 0.030 0.860 0.030 0.230 0.180 fan53610uc33x 1.160 0.030 0.860 0.030 0.230 0.180 package drawings are provided as a service to customers considering fairchild component s. drawings may change in any manner wit hout notice. please note the revision and/or date on the drawing and contact a fairchild semi conductor representative to verify or o btain the most recent revision. package specifications do not expand the terms of fairchild?s worldwide terms and conditions, specifically the warranty therein, which covers fairchild products. always visit fairchild semiconductor?s online packagi ng area for the most recent package drawings: http://www.fairchildsemi.com/packaging/ .
? 2010 fairchild semiconductor corporation www.fairchildsemi.com fan53600 / fan53610 ? rev. 1.0.0 16 fan53600 / fan53610 ? 3mhz, 600ma / 1a synchronous buck regulator


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