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wd101 5 1.5mhz, 1.0a, step - down dc - dc converter descriptions the WD1015 is a high efficiency, synchronous step down dc - dc converter optimized for battery powered portable applications . i t supports up to 1.0a output current. with a wide input voltage range of 2.7v to 5.5v, the device supports applications powered by single li - ion battery with extended voltage range, two and three alkaline cell, 3.3v and 5v input voltage range. the WD1015 operates at 1.5mhz fixed switching frequency with pulse - width - modulati on ( pwm) and enters pulse - skipping - modulation (psm) operation at light load current to maintain high efficiency over the entire load current range. 100% duty cycle capability provides low dropout operation, extending battery life in portable systems. the switching frequency is internally set at 1.5 mhz, allowing the use of tiny surface mount inductor and input/output capacitors. low output voltage is easily supported with the 0.6v feedback reference voltage. the WD1015 is available in sot - 23 - 5l package. s tandard product is pb - free and halogen - free. features ? input voltage range : 2.7~5.5v ? continue output current : 1.0a ? switch ing frequency : 1.5mhz (typ.) ? efficiency : up to 92% ? feedback reference voltage : 0.6v ? 100% duty cycle for low dropout operatio n ? adjustable output voltage applications ? c ellphones ? pads ? stbs ? dscs sot - 23 - 5l pin configuration (top view) wd1 5 = device code yy = year code ww = week code marking order i nformation devi ce package shipping WD1015 ea - 5/tr sot - 23 - 5l 3000/reel&tape 1 2 3 5 4 v i n g n d e n f b s w 1 2 3 5 4 w d 1 5 y y w w 1 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification 1 2 3 5 4 v i n g n d e n f b s w 1 2 3 5 4 w d 1 5 y y w w
typical applications block diagram pin descriptions symbol sot - 23 - 5l descriptions en 1 enable , active high gnd 2 ground sw 3 switching signal out put vin 4 power input fb 5 feedback v i n g n d e n f b s w v i n 1 . 8 v v o u t 4 . 7 u f 1 0 u f 2 2 p f 3 0 0 k 1 5 0 k 2 . 2 u h currrent limit & feedback logic buffer driver ramp wave generator pwm \ psm selector phase compesation enable logic verf 0 . 6 v with soft start u . v . l . o u . v . l . o comp . pwm comp . error amp . vref 0 . 6 v fb otp vin gnd en sw wd101 5 2 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification v i n g n d e n f b s w v i n 1 . 8 v v o u t 4 . 7 u f 1 0 u f 2 2 p f 3 0 0 k 1 5 0 k 2 . 2 u h currrent limit & feedback logic buffer driver ramp wave generator pwm \ psm selector phase compesation enable logic verf 0 . 6 v with soft start u . v . l . o u . v . l . o comp . pwm comp . error amp . vref 0 . 6 v fb otp vin gnd en sw
absolute maximum ratings these are stress ratings only. stresses exceeding the range specified under absolute maximum ratings may cause substantial damage to the device. functional operation of this device at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability. note 1: surface mounted on fr - 4 board using 1 square inch pad size , dual side , 1oz copper parameter symbol value unit vin pin voltage r ange v in - 0.3 6.5 v en, fb pin voltage range - - 0.3 v in v sw pin voltage range (dc) - - 0.3 v in v power dissipation C sot - 23 - 5l (not e 1) p d 0.5 w junction to ambient thermal resistance C sot - 23 - 5l (note 1) r ja 250 o c/w junction temperature t j 150 o c lead temperature(soldering, 10s) t l 260 o c operating ambient temperature topr - 40 ~ 85 o c storage temperature tstg - 55 ~ 150 o c esd ratings hbm 2000 v mm 200 v wd101 5 3 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
electronics characteristics (ta=25 o c, v in =3.6v, v en =v in , unless otherwise noted) parameter symbol conditions min. typ. max. units input voltage range v in 2.7 5.5 v operating supply current i q v fb = 60%, i out = 0a 150 200 ua standby supply current i q v fb = 105%, i out = 0a 65 85 u a shutd own supply current i shdn v en = 0v, v in =4.2v 1 ua feedback reference voltage v fb i load =200ma 0.588 0.60 0.612 v line regulation line v in = 2.7 v to 5 .5 v 0.5 1 %/v load regulation load i out = 200 ma to 1.0a 0.5 % inductor limit current i lim v in = 3 .6 v, v out = 90% *v out 1.8 2.4 3.0 a oscillator frequency f osc v fb or v out in regulation 1.2 1.5 1.8 mhz v fb or v out to gnd 225 280 335 khz r ds(on) of p - channel fet r pfet i sw = 100ma 0.23 0.35 r ds(on) of n - channel fet r nfet i sw = ? 100ma 0.20 0.30 feedback leakage current i fb 30 na sw leakage current i lsw v in = 5 .5 v, v sw = 0v or 5 .5 v 1 ua en rising threshold v enh 1.4 v en falling threshold v enl 0.4 v en leakage current i en v in = 5.5v, v en = 0v or vin 1 ua over temperature prote ction t otp 165 o c otp hysteresis 20 o c wd101 5 4 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
typical characteristics (ta=25 o c, v in =3.6v, unless otherwise noted) efficiency vs. output current output voltage vs. load current output volta ge vs. temperature efficiency vs. output current output voltage vs. load current output voltage vs. temperature -25 0 25 50 75 100 125 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 v out (v) temperature ( o c) v in = 3.6v i o = 300ma -25 0 25 50 75 100 125 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 v out (v) temperature ( o c) v in = 3.6v i o = 300ma 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 1.26 output voltage vs. load current output voltage ( v ) load current ( a ) v out = 1.2 v vin = 2.7 v vin = 3.6 v vin = 5 v 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 output voltage ( v ) load current ( a ) v out = 2.5 v vin = 3.6v vin = 5.0v 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 60 65 70 75 80 85 90 efficiency vs. load current efficiency ( % ) load current ( a ) v out = 1.2 v vin = 2.7 v vin = 3.6 v vin = 5 v 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 45 50 55 60 65 70 75 80 85 90 95 100 efficiency vs. load current efficiency ( % ) load current ( a ) v out = 2.5 v vin = 2.7 v vin = 3.6 v vin = 5 v wd101 5 5 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification -25 0 25 50 75 100 125 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 v out (v) temperature ( o c) v in = 3.6v i o = 300ma -25 0 25 50 75 100 125 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 v out (v) temperature ( o c) v in = 3.6v i o = 300ma 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 1.26 output voltage vs. load current output voltage ( v ) load current ( a ) v out = 1.2 v vin = 2.7 v vin = 3.6 v vin = 5 v 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 output voltage ( v ) load current ( a ) v out = 2.5 v vin = 3.6v vin = 5.0v 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 60 65 70 75 80 85 90 efficiency vs. load current efficiency ( % ) load current ( a ) v out = 1.2 v vin = 2.7 v vin = 3.6 v vin = 5 v 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 45 50 55 60 65 70 75 80 85 90 95 100 efficiency vs. load current efficiency ( % ) load current ( a ) v out = 2.5 v vin = 2.7 v vin = 3.6 v vin = 5 v
feedback voltage vs. temperature frequency vs. temperature start - up from en en threshold vs. supply voltage frequency vs. supply voltage shutdown from en -25 0 25 50 75 100 125 0.56 0.57 0.58 0.59 0.60 0.61 0.62 0.63 0.64 v fb (v) temperature ( o c) v in = 3.6v i o = 300ma 3.0 3.5 4.0 4.5 5.0 5.5 0.2 0.4 0.6 0.8 1.0 1.2 1.4 v en falling en threshold (v) input voltage (v) v en rising -25 0 25 50 75 100 125 1.2 1.3 1.4 1.5 1.6 1.7 1.8 v in = 3.6v v out = 1.8v i out = 300ma oscillator frequency (mhz) temperature ( o c) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 1.2 1.3 1.4 1.5 1.6 v in = 3.6v v out = 1.2v i out = 300ma oscillator frequency(mhz) supply voltage(v) wd101 5 6 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification -25 0 25 50 75 100 125 0.56 0.57 0.58 0.59 0.60 0.61 0.62 0.63 0.64 v fb (v) temperature ( o c) v in = 3.6v i o = 300ma 3.0 3.5 4.0 4.5 5.0 5.5 0.2 0.4 0.6 0.8 1.0 1.2 1.4 v en falling en threshold (v) input voltage (v) v en rising -25 0 25 50 75 100 125 1.2 1.3 1.4 1.5 1.6 1.7 1.8 v in = 3.6v v out = 1.8v i out = 300ma oscillator frequency (mhz) temperature ( o c) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 1.2 1.3 1.4 1.5 1.6 v in = 3.6v v out = 1.2v i out = 300ma oscillator frequency(mhz) supply voltage(v)
load transient response load transient response load transie nt response load transient response wd101 5 7 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
operation informations pwm control mode the WD1015 step - down converter operates with typically 1.5mhz fixed - frequency pulse width modulation (pwm) at moderate to heavy load currents. both the main p - channel mosfet and synchronous n - channel mosfet switches are internal. during pwm operation, the converter uses a current - mode control scheme to achieve good line and load transient response . a t the beginning of each clock cycle initiated by the clock signal, the main switch is turned on. t he current flows from the input capacitor via the main switch through the inductor to the output capacitor and load. d uring this phase, the current ramps up until the pwm comparator trips and the control logic turn off the switch. a fter a dead time, which prevents shoot - through current, the synchronous switch is turned on and the inductor current ramps down. t he current flows from the inductor and the output capacitor to the load. i t returns back to the induct or through the synchronous switch. t he next cycle is initiated by the clock signal again turning off the synchronous switch and turning on the main switch. pulse skipping mode (psm) at light loads, the inductor current may reach zero or reverse on each pul se. the synchronous switch is turned off by the current reversal comparator, i rcmp , and the switch voltage will ring. this is discontinuous mode operation, and is normal behavior for the switching regulator. at very light loads, the WD1015 will automatical ly skip pulses in pulse skipping mode (psm) operation to maintain output regulation. short - circuit protection when the output is shorted to ground, the frequency of the oscillator is reduced to about 280k hz. this frequency fold - back ensures that the induc tor current has more time to decay, thereby preventing runaway. the oscillators frequency will progressively increase to 1.5 mhz when v fb rises above 0v. dropout operation t he device starts to enter 100% duty - cycle mode once the input voltage comes close to the nominal output voltage. i n order to maintain the output voltage, the main switch is turned on 100% for one or more cycles . the output voltage will then be determined by the input voltage minus the voltage drop across the p - channel mosfet and the ind uctor . shutdown mode drive en to gnd to place the WD1015 in shutdown mode. i n shutdown mode, the reference, control circuit , main switch, and synchronous switch turn off and the output becomes high impedance. i nput current falls to 0.1 a (typ.) during shu tdown mode. over temperature protection (otp) as soon as the junction temperature (t j ) exceeds 165 o c (typ.), the device goes into thermal shutdown. in this mode, the high - side and low - side mosfet are turned off. wd101 5 8 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
application informations e xternal component selection for the application circuit depends on the load current requirements . c ertain tradeoffs between different performance parameters can also be made. output voltage setting the output voltage can be calculated as : ? ? ? ? ? ? ? ? ? 2 r 1 r 1 6 . 0 v out the external resistive divider is connected to the output . to minimize the current through the feedback divider network, r1 should be larger than 100k . t he sum of r1 and r2 should not exceed 1 m , to keep the network robust against noise. a n external feed forward capacitor c fwd , is required for optimum load transient response. t he value of c fwd should be in the range between 22pf and 33pf. r oute the fb line away from noise sources, such as the inductor or the sw line. inductor selection t he WD1015 h igh switching frequency allows the use of a physically small inductor. t he inductor ripple current is determined by 1 ( )( ) out out l in vv i f l v ?? ? ? ? ?? ?? w here i l is the peak - to - peak inductor ripple current and f is the switching frequency. t he inductor peak - to - pea k current ripple is typically set to be 40% of the maximum dc load current. u sing this guideline and solving for l, () 1 (40% ) out out load max in vv l f i v ?? ?? ?? ?? i t is important to ensure that the inductor is capable of handling the maximum peak inductor current, i lpk , dete rmined by () 2 l lpk load max i ii ? ?? i nductor core selection different core materials and shapes will change the size/current and price/current relationship of an inductor. toroid or shielded pot cores in ferrite or permalloy materials are small and dont radiate much energy, but generally cost more than powdered iron core inductors with similar electrical characteristics. the choice of which style inductor to use often depend s more on the price vs . size requirements and any radiated field emi requirements than on what the WD1015 requires to operate. input capacitor selection c apacitor esr is a major contributor to input ripple in high - frequency dc - dc converters. o rdinary aluminum electrolytic capacitors have high esr and should be avoided. low - esr tantalu m or polymer capacitors are better and provide a compact solution for space constrained surface mount designs. c eramic capacitors have the lowest overall esr. t he input filter capacitor reduces peak currents and noise at the input voltage source. c onnect a low esr bulk capacitor (2.2 f to 10 f) to the input. s elect this bulk capacitor to meet the input ripple requirements and voltage rating rather than capacitance value. u se the following equation to calculate the maximum rms input current: ? ? out rms out in out in i i v v v v ? ? ? o utput capacitor selection c eramic capacitors with low - esr values have the lowest output voltage ripple and are recommended. a t nominal load current, the device operates in pwm mode, and the rms ripple current is calculated as: wd101 5 9 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification ? 1 ? u 2 r 1 r 1 6 . 0 v out 1 ( )( ) out out l in vv i f l v ' ? ?1 () 1 (40% ) out out load max in vv l f i v ? ?1 () 2 l lpk load max i ii ' out rms out in out in i i v v v v u
1 1 23 out in rmscout out v v iv lf ? ? ? ? ? ? at nominal load current, the device operates in pwm mode, and the overall output voltage ripple is the sum of the voltage spike caused by the output capacitor esr plus the voltage ripple caused by charging and discharging the output capacitor: 1 1 8 out in out out v v v v esr l f c f ? ?? ? ? ? ? ? ?? ? ? ? ?? a t light load currents, the converter operates in pulse skipping mode, and the output voltage ripple is dependent on the capacitor and inductor values. l arger output capacitor and inductor values minimize the voltage ripple in p sm operation and tighten dc output accuracy in psm operation. pc board layout considerations a good circuit board layout aids in extracting the most performance from the WD1015 . p oor circuit layout degrades the output ripple and the electromagnetic interf erence (emi) or electromagnetic compatibility (emc) performance. t he evaluation board layout is optimized for the WD1015 . u se this layout for best performance. i f this layout needs changing, use the following guidelines: 1. use separate analog and power groun d planes. c onnect the sensitive analog circuitry (such as voltage divider components) to analog ground; connect the power components (such as input and output bypass capacitors) to power ground. c onnect the two ground planes together near the load to reduc e the effects of voltage dropped on circuit board traces. locate c in as close to the v in pin as possible, and use separate input bypass capacitors for the analog. 2. route the high current path from c in , through l, to the sw and pgnd pins as short as possible . 3. keep high current traces as short and as wide as possible. 4. place the feedback resistors as close as possible to the fb pin to prevent noise pickup. 5. avoid routing high impedance traces, such as fb, near the high current traces and components or near the s witch node (sw). 6. if high impedance traces are routed near high current and/or the sw node, place a ground plane shield between the traces. WD1015 ea pcb suggest layout (demo) WD1015 ea demo schematic v i n g n d e n f b s w v i n v o u t c i n c o u t c f w d r 1 r 2 w d 1 0 1 5 l 1 4 . 7 u f 1 8 0 k 3 6 0 k 1 0 u f 2 . 2 u h 2 2 p f wd101 5 10 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification 1 1 23 out in rmscout out v v iv lf u u u u 1 1 8 out in out out v v v v esr l f c f ' u u ? u u u ?1 v i n g n d e n f b s w v i n v o u t c i n c o u t c f w d r 1 r 2 w d 1 0 1 5 l 1 4 . 7 u f 1 8 0 k 3 6 0 k 1 0 u f 2 . 2 u h 2 2 p f
package outline dimensions sot - 23 - 5l symbol dimensions in millimeters min. typ. max. a 1.050 - 1.250 a1 0.000 - 0.100 a2 1.050 - 1.150 b 0.300 0.400 0.500 c 0.100 - 0.200 d 2.820 2.900 3.020 e 1.500 1.600 1.700 e1 2.650 2.800 2.950 e 0.950 typ. e1 1.800 1.900 2.000 l 0.300 - 0.600 0 o - 8 o wd101 5 11 of 11 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification

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