www.reactor-micro.com 1 description RM1410 consists of step-down switching regulator with pwm control. these devices include a reference voltage source, oscillation circuit, error amplifier, internal pmos and etc. RM1410 provides low-ripple power, high efficiency, and excellent tr ansient characteristics. the pwm control circuit is able to vary the duty ratio linearly from 0 up to 100%. an enable function, an over current protect f unction and a short circuit protect function are built inside, and when ocp or scp happens, the operation frequency will be reduced from 380khz to 35khz. also, an internal compensation block is built in to minimum external component count. with the addition of an internal p-channel power mos, a coil, capacitors, and a diode connected externally, thes e ics can function as step-down switching regulators. they serve as ideal power supply units for portable devices when coupled with the sop?8l mini-package, providing such outstanding features as low current consumption. since this converter can accommodate an input voltage up to 15v, it is also suitable for the operation via an ac adapter. features input voltage: 3.6v to 15v output voltage: 0.8v to v cc duty ratio: 0% to 100% pwm control oscillation frequency: 380khz typ current limit, enable function thermal shutdown function built-in internal sw p-channel mos sop-8l pb-free package compatible with td1410/mp1410 applications battery charger adapter pc motherboard lcd monitor graphic card dvd-video player telecom equipment adsl modem printer and other peripheral equipment microprocessor core supply networking power supply typical application u2 RM1410 nc 1 nc 6 nc 8 vcc 2 sw 3 vss 4 fb 5 en 7 + ec1 470uf r3 10k +12v l1 33uh_3a d1 in5822 + ec2 470uf_10v rb 2k_1% ra 10.5k_1% c1 22nf +5v_2a RM1410 pwm control 2a step-down converter free datasheet http://
RM1410 2 www.reactor-micro.com package information top view u2 RM1410 nc 1 nc 6 nc 8 vcc 2 sw 3 vss 4 fb 5 en 7 sop-8l pin functions pin symbol function description 1,6,8 nc not connect. 2 vcc ic power supply pin 3 output switch pin.output is t he switch node that supplies power to the output. connect external inductor/diode here. minimize trace area at this pin to reduce emi. 4 vss gnd pin. 5 fb feedback pin.through an external resistor divider network, fb senses the ou tput voltage and regulates it. 7 en power-off pin h:normal operation(step-down operation). l: step-down operation stopped(all circuits deactivated). free datasheet http://
RM1410 www.reactor-micro.com 3 absolute maximum ratings symbol parameter rating unit v cc v cc pin voltage v ss -0.3 to v ss +18 v v fb feedback pin voltage v ss -0.3 to v cc v v en en pin voltage v ss -0.3 to v cc +0.3 v v output switch pin voltage v ss -0.3 to v cc +0.3 v p d power dissipation internally limited mw t opr operating temperature range -20 to +125 t stg storage temperature range -40 to +150 caution: the absolute maximum ratings are rated values e xceeding which the product could suffer physical damage. these values must therefore not be exceeded under any conditions. electrical characteristics the specifications are applied at t=25 , vcc=12v, unless otherwise noted. symbol parameter conditions min. typ. max. unit v in input voltage - 3.6 - 15 v v fb feedback voltage i out =0.2a 0.784 0.8 0.824 v i fb feedback bias current i out =0.2a - 0.1 0.5 ua i sw switch current - 2.5 - - a i sss current consumption during power off v en =0v - 0.1 - ua i q quiescent current v fb =2v - 4.0 6.0 ma v out /v out line regulation v in =7v 15v - 2 4 % v out /v out load regulation i out =0.2 to 2a - 0.2 0.5 % f osc oscillation frequency meas ure waveform at sw pin 340 380 420 khz f osc1 frequency of current limit or short circuit protect measure waveform at sw pin - 35 - khz v sh evaluate oscillation at sw pin 2.0 - - v sl en pin input voltage evaluate oscillation stop at sw pin - - 0.8 v i sh - - 20 - ua i sl en pin input leakage current - - -10 - ua t ss soft-start time - 0.3 2 5 ms v in =5v v fb =0v - 100 150 r dson internal mosfet rdson v in =12v v fb =0v 65 100 m ? effi efficiency v in =12v v out =5v i out =2a - 90 - % free datasheet http://
RM1410 4 www.reactor-micro.com block diagram operation (refer to block diagram) pwm control the RM1410 consists of dc/dc converters that employ a pulse-width modulation (pwm) system. in converters of the RM1410, t he pulse width varies in a range from 0 to 100%, according to the load current. the ripple voltage produced by the switching can easily be removed through a filter because the switching fre quency remains constant. therefore, these converte rs provide a low-ripple power over broad ranges of input voltage and load current. pin functions vcc this is the positive input supply for the ic switching regulator. a suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. vss circuit ground. sw internal switch. the voltage at this pin switches between (vcc ? vds) and approximately ? 0.5v, with a duty cycle of approximately vout / vcc. to minimize coupling to sens itive circuitry, the pc board copper area connected to this pin should be kept a minimum. fb senses the regulated output voltage to complete the feedback loop. en allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply cu rrent to approximately 0.1ua. pulling this pin below a threshold voltage of approximately 0.8 v turns the regulator down, and pulling this pin above 2v le ts the regulator on. free datasheet http://
RM1410 www.reactor-micro.com 5 typical operating characteristics thermal 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 0.20 0.4 0 0.6 0 0.8 0 1 . 00 1 . 20 1 . 40 1 . 60 1 . 80 2.0 0 2.2 0 2.6 0 3 . 00 thermal efficiency 40.00 50.00 60.00 70.00 80.00 90.00 100.00 0.20 0 . 40 0 . 60 0 . 80 1 .0 0 1 .2 0 1 .4 0 1 . 60 1 . 80 2.00 2 .2 0 2 .4 0 2 .6 0 2.80 3.00 efficiency thermal vs. output current efficiency vs. output current soft-start output current=0.5a soft-start output current=2a turn off output current=0.5a turn off output current=2a free datasheet http://
RM1410 6 www.reactor-micro.com frequency output current=0.5a frequency output current=2a short output protect free datasheet http://
RM1410 www.reactor-micro.com 7 application information inductor selection the selection of output inductor is based on the considerations of eddici ency, output power and operating frequency. low inductance value has smaller size, but results in low efficiency, large ripple current and high eddi ciency, large ripple current and high output ripple voltage . generally, an inductor and 50% of output current is appropriate. ; t i l v v l out in = ? in out s v v d f d t = = ; ; l=(vin-vout) l s in out i f v v ; where: t =d1 turn on time l i =inductor current ripple (approximately equal 0.3 times of max output current) output capacitor selection the selection of output capacitor depends on the output ripple voltage requirement.practically, the output ripple voltage is a function of both capacitance value and t he equivalent series resistance.the ac impedanc e of output capacitor at operating frequency is quite smaller than the load impedance, so the ripple current of the inductor current flows mainly through output capacitor. the output rippl e voltage is described as: out l each l l out v i esr n esr i esl t i v = + = ) ( where: out v =max ripple voltage in output input capacitor selection the selection of input capacitor is mainly based on its maximum ripple current capability. the rms value of ripple current flowing through the input capacitor is described as: ( ) d d i i out rms ? = 1 the input capacitor must be cable of handling this ripple current. sometimes, for higher efficiency the low esr capacitor is necessarily. free datasheet http://
RM1410 8 www.reactor-micro.com package information package type: sop-8l dimensions dimensions in millimeters dimensions in inches symbol min. nom. max. min. nom. max. a 1.40 1.60 1.75 0.055 0.063 0.069 a1 0.10 - 0.25 0.040 - 0.100 a2 1.30 1.45 1.50 0.051 0.057 0.059 b 0.33 0.41 0.51 0.013 0.016 0.020 c 0.19 0.20 0.25 0.0075 0.008 0.010 d 4.80 5.05 5.30 0.189 0.199 0.209 e 3.70 3.90 4.10 0.146 0.154 0.161 e - 1.27 - - 0.050 - h 5.79 5.99 6.20 0.228 0.236 0.244 l 0.38 0.71 1.27 0.015 0.028 0.050 y - - 0.10 - - 0.004 0 - 8 0 - 8 free datasheet http://
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