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________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 1/11 UM3501 600ma, 1.2mhz, synchronous step-down dc-dc converter UM3501 sot23-5 UM3501da dfn6 2.02.0 general description UM3501 is a high-efficiency pulse-width-modulated (pwm) step-down dc-dc converter, capable of delivering 600ma output current over a wide input voltage range from 2.5v to 5.5v. the target application of UM3501 is for portable electronic devices that are powered from 1-cell li-ion battery or from other power sources within the range such as cellular phones, pdas and handy-terminals. internal synchronous rectifier with low r ds(on) dramatically reduces conduction loss at pwm mode. no external schottky diode is required in practical application. the UM3501 automatically turns off the synchronous rectifier while the inductor current is low and enters discontinuous pwm mode. this can increase efficiency at light load condition. UM3501 enter shutdown mode and consumes less than 0.1ua when en pin is pulled low. the operation frequency is set to 1.2mhz. this along with small sot23-5 package and dfn6 2.02.0 package provides small pcb area application. ot her features include lower internal reference voltage with 2% accuracy, over temperature protection, and over current protection. applications features z cellular and smart phones z microprocessors and dsp core supplies z wireless and dsl modems z pdas, gps z mp3 player z portable instruments z high efficiency: up to 90% z 1.2mhz constant switching frequency z 600ma output current z integrated main switch and synchronous rectifier. no schottky diode required z 2.5v to 5.5v input voltage range z low quiescent current: 50a z thermal fault protection z <1a shutdown current z lead free sot23-5 package and dfn6 2.02.0 package typical application circuit UM3501 v in c1 4.7uf c3 10uf vin en gnd fb sw v out 1.8v l1 2.2uh r2 634k r1 316k 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 y( ) vin=2.5v vin=3.6v vin=4.2v vin=5.5v efficiency vs load current output current (ma) efficiency (%)
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 2/11 UM3501 pin configurations top view UM3501da m: month code dfn6 2.02.0 pin description pin number sot23-5 dfn6 2.02.0 symbol function 1 3 vin supply input pin. must be closely decoupled to gnd, pin2, with a 4.7 f or greater ceramic capacitor. 2 5 gnd ground. 3 2 en regulator enable control input. drive en above 1.0v to turn on the part. drive en below 0.4v to turn it off. in shutdown, all functions are disabled drawing <1 a supply current. do not leave en floating. 4 6 fb feedback input pin. connect fb to the center point of the external resistor divider. 5 4 sw p ower switch output. it is the switch node connection to inductor. this pin connects to the drains of the internal p-ch and n-ch mosfet switches. - 1 nc not connected. ordering information part number packaging type marking code shipping qty UM3501 sot23-5 5ca 3000pcs/7inch tape & reel UM3501da dfn6 2.02.0 aae 3000pcs/7inch tape & reel UM3501 m: month code sot23-5
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 3/11 UM3501 absolute maximum ratings (note 1) symbol parameter value unit v in input voltage -0.3 to +6.0 v v en ,v fb en, fb voltages -0.3 to v in +0.3 v v sw sw voltage -0.3 to v in +0.3 v i sw peak sw sink and source current 1.5 a t o operating temperature -40 to +85 c t stg storage temperature range -65 to +150 c note 1: stresses greater than those listed unde r maximum ratings may cause permanent damage to the device. this is a stress rating only a nd functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. exposure to absolute ma ximum rating conditions for extended periods may affect reliability. electrical characteristics (note 2) (v in =v en =3.6v, t a =+25 , unless otherwise noted) symbol parameter test conditions min typ max unit v in input voltage range 2.5 5.5 v i q (active) input dc supply current (active mode) v fb =0.6v, iload=0a 50 a i q (shutdown) input dc supply current (shutdown mode) v fb =0v, v in =4.2v 0.08 1.0 a t a = +25oc 0.5880 0.6000 0.6120 0oc t a 85oc 0.5865 0.6000 0.6135 v fb regulated feedback voltage -40oc t a 85oc 0.5850 0.6000 0.6150 v i fb fb input bias current v fb =0.65v 30 na reference voltage line regulation 2.5v v in 5.5v, v out =v fb (r2=0) 0.11 0.40 %/v output voltage line regulation 2.5v v in 5.5v, i out =10ma 0.11 0.40 %/v output voltage load regulation 100ma i out 600ma 0.0015 %/ma i o(max ) maximum output current v in =3.6v, v out =1.8v 600 ma f oscillator frequency v fb =0.6v or v out =100% 1.2 mhz r ds(on) of p-ch mosfet v in =3.6v, i sw =100ma 0.40 0.50 ? r ds(on) r ds(on) of n-ch mosfet v in =3.6, i sw = -100ma 0.35 0.45 ? i p peak induct or current v in =3.0v, v fb =0.5v or v out =90%, duty cycle<35% 1.20 a
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 4/11 UM3501 electrical characteristics (continued) (v in =v en =3.6v, t a =+25 , unless otherwise noted) symbol parameter test conditions min typ max unit i swl sw leakage v en =0v, v in =5v ; v sw =0v or 5v 0.01 1 a v h en high-level threshold -40oc t a 85oc 1.0 v v l en low-level threshold -40oc t a 85oc 0.4 v i enl en leakage current 0.1 1 a (max) max. efficiency v in =3.6v, v out =2.5v 90 % thermal shutdown temperature 160 oc note2: 100% production test at +25oc. specifica tions over the temperature range are guaranteed by design and characterization. typical performance characteristics (v in = 3.6 v, v out = 1.8v, l1 = 2.2h, c1 = 4.7f, c3 = 10f, t a = +25c, unless otherwise noted.) efficiency vs load current efficiency vs load current efficiency vs input voltage output voltage vs load current 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current (ma) efficiency (%) vout=1.2v vout=1.8v vout=1.8v vin=3.6v vout=1.8v 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current (ma) efficiency (%) vin=2.5v vin=3.6v vin=4.2v vin=5.5v 1.75 1.76 1.77 1.78 1.79 1.80 1.81 1 10 100 1000 output current (ma) output voltage(v) vin=2.5v vin=3.6v vin=4.2v 0 10 20 30 40 50 60 70 80 90 100 2.5 3.5 4.5 5.5 input voltage (v) efficiency (%) iload=200ma iload=400ma iload=600ma
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 5/11 UM3501 typical performance characteristics (continued) (v in = 3.6v, v out = 1.8v, l1 = 2.2h, c1 = 4.7f, c3 = 10f, t a = +25c, unless otherwise noted.) output voltage vs input voltage output voltage vs temperature supply current vs input voltage frequency vs input voltage line transient response load transient response (vout=1.8v, iout=300ma) (vin=3.6 v, vout=1.8v) 200 400 600 800 1000 1200 1400 1600 2.5 3 3.5 4 4.5 5 5.5 6 supply voltage(v) frequency(khz ) 10 20 30 40 50 60 70 80 2.533.544.555.5 supply voltage(v) supply current(ua) iload=100ma 1.750 1.755 1.760 1.765 1.770 1.775 1.780 1.785 1.790 1.795 1.800 1.805 1.810 -50 -25 0 25 50 75 100 125 temperature( ) output voltage(v) vin=3.5v to 4.5v vout 50mv/div 50 s/div iout=100ma to 600ma vout 100mv/div 50 s/div vin=3.6v, iload=100ma iload=100ma vout=1.8v 1.770 1.775 1.780 1.785 1.790 1.795 1.800 1.805 1.810 2.5 3.5 4.5 5.5 input voltage(v) output voltage(v) iload=200ma iload=400ma iload=600ma
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 6/11 UM3501 typical performance characteristics (continued) (v in = 3.6v, v out = 1.8v, l1 = 2.2h, c1 = 4.7f, c3 = 10f, t a = +25c, unless otherwise noted.) light load operation heavy load operation (vout=1.8v, io=0ma) (vout=1.8v, io=200ma) block diagram function description UM3501 is a monolithic switching mode step-d own dc-dc converter. it utilizes internal mosfets to achieve high efficiency and can genera te very low output voltage by using internal reference at 0.6v. it operates at a fixed switc hing frequency, and uses the slope compensated current mode architecture. this step-down dc -dc converter supplies 600ma output current at v in =3.6v with input voltage range from 2.5v to 5.5v. sw vout 20mv/div 5ms/div sw vout 20mv/div 500ns/div
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 7/11 UM3501 current mode pwm control slope compensated current mode pwm control provides stable switching and cycle-by-cycle current limit for excellent load and line responses a nd protection of the internal main switch (p-ch mosfet) and synchronous rectifier (n-ch mos fet). during normal operation, the internal p-ch mosfet is turned on for a certain time to ra mp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. the current comparator, i comp , limits the peak inductor current. when the main switch is off, the synchronous rectifier will be turned on immediatel y and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, i zero , or the beginning of the next clock cycle. pulse skipping mode operation at very light loads, the UM3501 automatically ente rs pulse skipping mode. in the pulse skipping mode, the inductor current may reach zero or reverse on each pulse. the pwm control loop will automatically skip pulses to maintain output regul ation. the bottom mosfet is turned off by the current reversal comparator, i zero , and the switch voltage will ring. this is discontinuous mode operation, and is normal behavior for the switching regulator. maximum load current the UM3501 will operate with input supply volta ge as low as 2.5v, however, the maximum load current decreases at lower input due to large ir drop on the main switch and synchronous rectifier. the slope compensation signal reduces the peak induc tor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. conversely the current limit increases as the duty cycle decreases. applications information output voltage setting the external resistor divider sets the output vol tage.the feedback resistor r1 also sets the feedback loop bandwidth with the internal compensation capacitor. choose r1 around 300k ? for optimal transient response. r2 is then given by: 1 6 . 0 1 2 ? = v v r r out inductor selection a 1h to 10h inductor with dc current rati ng at least 25% higher than the maximum load current is recommended for most applications. fo r best efficiency, the inductor dc resistance shall be<200m ? . for most designs, the inductance value can be derived from the following equation: osc l in out in out f i v v v v l ? = ) ( where ? i l is the inductor ripple current. choose inducto r ripple current approximately 30% of the maximum load current, 600ma. the maximum inductor peak current is: 2 ) ( l load max l i i i + = under light load conditions below 100ma, larg er inductance is recommended for improved efficiency. input capacitor selection the input capacitor reduces the surge current draw n from the input and switching noise from the
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 8/11 UM3501 device. the input capacitor impedance at the switc hing frequency shall be less than input source impedance to prevent high frequency switching curre nt passing to the input. ceramic capacitors with x5r or x7r dielectrics are highly recomme nded because of their low esr and small temperature coefficients. for most applications, a 4.7f capacitor is sufficient. output capacitor selection the output capacitor keeps output voltage ripple small and ensures regulation loop stable. the output capacitor impedance shall be low at the switching frequency. ceramic capacitor with x5r or x7r dielectrics are recommended. the output ripple ? v out is approximately: ? ? ? ? ? ? ? ? + ? 3 8 1 ) ( c f esr l f v v v v v osc osc in out in out out layout guidance when laying out the pc board, the following su ggestions should be taken to ensure proper operation of the UM3501. 1. the power traces, including the gnd trace, the sw trace and the vin trace should be kept short, direct and wide to allow large current flow. 2. connect the input capacitor c1 to the vin pin as closely as possible to get good power filter effect. 3. keep the switching node, sw, away from the sensitive fb node. 4. do not trace signal line under inductor.
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 9/11 UM3501 package information UM3501: sot23-5 outline drawing dimensions millimeters inches symbol min max min max a 1.050 1.250 0.041 0.049 a1 0.000 0.100 0.000 0.004 a2 1.050 1.150 0.041 0.045 b 0.300 0.500 0.012 0.020 c 0.100 0.200 0.004 0.008 d 2.820 3.020 0.111 0.119 e 1.500 1.700 0.059 0.067 e1 2.650 2.950 0.104 0.116 e 0.950ref 0.037ref e1 1.800 2.000 0.071 0.079 l 0.300 0.600 0.012 0.024 0 8 0 8 land pattern notes: 1. compound dimension: 2.921.60; 2. unit: mm; 3. general tolerance 0.05mm unless otherwise specified; 4. the layout is just for reference. tape and reel orientation
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 10/11 UM3501 UM3501da: dfn6 2.02.0 outline drawing dimensions millimeters symbol min typ max a 0.57 0.60 0.63 a1 0 0.03 0.05 a3 0.15typ b 0.20 0.25 0.30 d 1.95 2.00 2.075 e 1.95 2.00 2.075 d2 1.45 1.55 1.65 e2 0.76 0.86 0.96 e 0.65typ l 0.30 0.35 0.40 land pattern notes: 1. compound dimension: 2.02.0; 2. unit: mm; 3. general tolerance 0.05mm unless otherwise specified; 4. the layout is just for reference. tape and reel orientation
________________________________________________________________________ http://www.union-ic.com rev.03 may.2013 11/11 UM3501 important notice the information in this document has been ca refully reviewed and is believed to be accurate. nonetheless, this document is subjec t to change without notice. union assumes no responsibility for any inaccuracies that may be contained in this document, and makes no commitment to update or to keep current the contained information, or to notify a person or organization of any update. union rese rves the right to make changes, at any time, in order to improve reliability, function or design and to attempt to supply the best product possible. union semiconductor, inc add: 2f, no. 3, lane 647 songtao road, shanghai 201203 tel: 021-51093966 fax: 021-51026018 website: www.union-ic.com

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