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rev.01 1 EP3003 2-ch, 600ma synchronous step-down converter description the EP3003 is a dual channel, 1.5mhz constant frequency, slope compensated current mode pwm step-down converter. the EP3003 can supply 600ma of load current from a 2.5v to 5.5v input voltage. each output voltage is adjustable from 0.6v to 5v. it is ideal for powering portable equipment that runs from a single cell lithium-ion (li+) battery. internal synchronous 0.35 ? , 1a power switches provide high efficiency without the need for external schottky diodes. the EP3003 can also run at 100% duty cycle for low dropout operation, extending battery life in portable system. pulse skipping mode operation at light loads provides very low output ripple voltage for noise sensitive applications. burst mode operation provides higher efficiency at light loads. applications ? cellular and smart phones ? microprocessors and dsp core supplies ? wireless and dsl modems ? pdas ? portable instruments / media players ? digital cameras ? pc cards features ? high efficiency: up to 96% ? 1.5mhz constant switching frequency ? 600ma output current ? integrated main switch and synchronous rectifier ? high switch current: 1a on each channel ? 2.5v to 5.5v input voltage range ? output voltage as low as 0.6v ? 100% duty cycle in dropout ? low quiescent current: 50 a slope compensated current mode co ? ntrol for excellent line and load transient response ? can be synchronized to an external oscillator short circuit protection ? ? power-on reset output thermal fault protection ? ? <1ua shutdown current ? small thermally enhanced 10-pin msop and 3mm 3mm dfn packages typical application figure 1. basic application circuit for 2.5v and 1.8v output voltages
rev.01 2 EP3003 package/order information msop: dfn: eorex power management buck regulator series number e p 30 03 absolute maximum rating (note1) input supply voltage........ ... ............... .... -0.3v to +6v run, v fb voltages ............. .... ..... -0.3v to vin+0.3v sw voltages................ ............?... .-0.3v to vin+0.3v mode/sync voltages....................-0.3v to vin+0.3v /por voltages.......... ........... .. ..?... ...... -0 .3v to +6v p-channel switch source current (dc).?.......800ma n-channel switch sink current (dc).....??....800ma operating temperat ure range............ -40c to +85c junction temperature???. ................. ...........+125c storage temperature range (msop) -65c to +150c storage temperature range (dfn) .. -65c to +125c lead temperature (solderi ng, 10s) ............?..+300c note 1. absolute maximum ratings are those values beyond which the life of a device may be impaired.
rev.01 3 EP3003 electrical characteristics (note 2) : (v in =v run = 3.6v, t a = 25c, unless otherwise noted.) parameter conditions min typ max unit input voltage range 2.5 5.5 v input dc supply current active mode shutdown mode v fb =0.5v run=0v, v in =5.5v, mode/sync=0v 600 0.1 800 1.0 a a t a = +25c 0.588 0.600 0.612 v t a = 0c Q t a Q 85c 0.586 0.600 0.613 v regulated feedback voltage t a = -40c Q t a Q 85c 0.582 0.600 0.618 v v fb input bias current 30 na reference voltage line regulation v in = 2.5v to 5.5v 0.3 0.5 %/v threshold: v fbx ramping up, mode/sync = 0v v fbx ramping down, mode/sync = 0v 8.5 -8.5 % % power-on reset on-resistance 100 200 ? power-on reset (por) power-on reset delay 270k cycles output voltage load regulation 0.5 % peak inductor current v in =3v, v fb =0.5v duty cycle < 35% 0.75 1.00 1.25 a oscillator frequency v fbx =0.6v 1.2 1.5 1.8 mhz synchronization frequency 1.5 mhz r ds(on) top switch on-resistance bottom switch on-resistance 0.35 0.30 0.45 0.45 ? ? sw leakage v run = 0v, v fbx = 0v, v in = 5v 0.01 1 a run threshold -40c Q t a Q 85c 0.3 1.0 1.50 v run leakage current 0.01 1 a note 2. 100% production test at + 25c. specifications over the temperature range are guaranteed by design and characterization.
rev.01 4 EP3003 typical performance characteristics (tbd)
rev.01 5 EP3003 functional block diagram
rev.01 6 EP3003 pin description pin name function 1 v fb1 output voltage feedback pin. an internal re sistive divider divides the output voltage down for comparison to the internal reference voltage. nominal voltage for this pin is 0.6v. 2 run1 regulator 1 enable control input. forcing th is pin to vin enables regulator 1, while forcing it to gnd causes regulator 1 to shut down. in shutdown, all functions are disabled drawing <1a supply current. do not leave run floating. 3 v in main power supply. must be closely decoupled to gnd with a ceramic capacitor. 4 sw1 regulator 1 power switch output. switch node connection to the inductor. this pin swings from vin to gnd. 5 gnd ground 6 mode/sync combination of mode selection and oscillator synchronization. this pin controls the operation of the device. when tied to v in or gnd, burst mode operation or pulse skipping mode is selected, respectively. do not float this pin. the oscillation frequency can be synchronized to an external oscillator applied to this pin and pulse skipping mode is automatically selected. 7 sw2 regulator 2 power switch output. switch no de connection to the inductor. this pin swings from v in to gnd. 8 /por power-on reset. this common-drain logic out put is pulled to gnd when the output voltage is not within 8.5% of regulatio n and goes high after 175ms when both channels are within regulation. 9 run2 regulator 2 enable control input . forcing this pin to v in enables regulator 2, while forcing it to gnd causes regulator 2 to shut down. 10 v fb2 output voltage feedback pin for regulator 2. see v fb1 section. 11 power ground connect to the (?) terminal of cout, and (?) terminal of c in . must be soldered to electrical ground on pcb.
rev.01 7 EP3003 operation the EP3003 uses current mode architecture with freq uency set at 1.5mhz and can be synchronized to an external oscillator. both channels share the same clock and run in-phase. to suit a variety of applications, the selectable mode pin allows t he user to trade-off noise for efficiency. output voltage is set by an external divider return ed to the vfb pins. an error amplifier compares the divided output voltage with a reference voltage of 0.6v and adjusts the peak inductor current accordingly. over voltage and under voltage comparators will pu ll the por output low if the output voltage is not within 8.5%. the por output will go high after 270k clock cycles of achieving regulation. during normal operation, the top power switch (p-c hannel mosfet) is turned on at the beginning of a clock cycle when the vfb voltage is below the reference voltage. the current into the inductor and the load increases until the current limit is reached. the switch turns off and energy stored in the inductor flows through the bottom switch (n-channel mosfet) into the load until the next clock cycle. the peak inductor current is controlled by the interna lly compensated ith voltage, which is the output of the error amplifier. this amplifier compares the vf b pin to the 0.6v reference. when the load current increases, the v fb voltage decreases slightly below the refe rence. this decrease causes the error amplifier to increase the ith voltag e until the average inductor current matches the new load current. the main control loop is shut down by pulling the run pin to ground. low current control two modes are available to control the operati on of the EP3003 at low currents. both modes automatically switch from continuous operation to the selected mode when the load current is low. to optimize efficiency, the burst mode operation can be selected. when the load is relatively light, the EP3003 automatically switches into burst mode operation in which the pmos switch operates intermittently based on load demand with a fixed peak inductor current. by running cycles periodically, the switching losses which are dominated by the gate charge losses of the power mosfets are minimized. the main control loop is interrupted w hen the output voltage reac hes the desired regulated value. a hysteretic voltage com parator trips when ith is below 0.35v, shutting off the switch and reducing the power. the out put capacitor and the inductor supply t he power to the load until ith exceeds 0.65v, turning on the switch and the main control loop which starts another cycle. for lower ripple noise at low currents, the puls e skipping mode can be used. in this mode, the EP3003 continues to switch at a constant frequency down to very low currents, where it will begin skipping pulses.
rev.01 8 EP3003 dropout operation the EP3003 allows the main switch to remain on for more than one switching cycle and increases the duty cycle until it reaches 100%. the output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. at low input supply voltage, the r ds(on) of the p channel mosfet increases, and the efficienc y of the converter decreases. caut ion must be exercised to ensure the heat dissipated not to exceed the ma ximum junction temperature of the ic. note 3. the duty cycle d of a step-down converter is defined as: d = t on x f osc x 100% v out /v in x 100% where t on is the main switch on time, and f osc is the oscillator frequency (1.5mhz). maximum load current the EP3003 will operate with input supply voltage as low as 2.5v, however, the maximum load current decreases at lower input due to large ir drop on t he main switch and synchronous rectifier. the slope compensation signal reduces the peak inductor cu rrent as a function of t he 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 a general application circuit for EP3003 is shown in figure 1, which is the baseline for some calculation mentioned below. all external component selection for EP3003 application design will be illustrated as the following. setting the output voltage the external resistor sets the output vo ltage according to the following equation: ? ? ? ? ? ? + = 1 2 1 6 . 0 r r v v out r1 = 150k ? ; r2 = 300k ? for v out = 1.8v; r3 = 100k ? ; r4 = 330k ? for v out = 2.5v.
rev.01 9 EP3003 inductor selection for most designs, the EP3003 operates with induct ors of 1h to 4.7h. low inductance values are physically smaller but require faster switching, which results in some efficiency loss. large value inductors lower ripple current and small value inductors result in high ripple currents. the inductor value can be derived from the following equation: () osc l in out in out f i v v v v l ? = where l i is inductor ripple current. choose inductor ripple current approximately 35% of the maximum load current 600ma, or 2 10ma. for output voltages above 2.0v, wh en light-load efficiency is important, the minimum recommended inductor is 2.2h. for optimum vo ltage-positioning load transients, choose an inductor with dc series resistance in the 50m ? to 150m ? range. for higher efficiency at heavy loads (above 200ma), or minimal load regulation (but some transient overs hoot), the resistance should be kept below 100m ? . the dc current rating of the inductor s hould be at least equal to the maximum load current plus half the ripple current to prevent core saturation (600ma+105ma). t able 1 lists some typical surface mount inductors that meet target applications for the EP3003. part # l (h) max dcr (m.) rated d.c. current (a) size wxlxh (mm) sumida cr43 1.4 2.2 3.3 4.7 56.2 71.2 86.2 108.7 2.52 1.75 1.44 1.15 4.5x4.0x3.5 sumida cdrh4d18 1.5 2.2 3.3 4.7 75 110 162 1.32 1.04 0.84 4.7x4.7x2.0 toko d312c 1.5 2.2 3.3 4.7 120 140 180 240 1.29 1.14 0.98 0.79 3.6x3.6x1.2
rev.01 10 EP3003 input capacitor selection the input capacitor reduces the sur ge current drawn from the input and switching noise from the device. the input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input. a low esr input capacitor sized for maximum rms current must be used. ceramic capac itors with x5r or x7r dielectrics are highly recommended because of their low esr and small te mperature coefficients. a 10f ceramic capacitor for most applications is sufficient. output capacitor selection the output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. the output capacitor must have low impedance at the switch ing frequency. ceramic capacitors with x5r or x7r dielectrics are recommended due to their low esr and minimization of large temperature and voltage coe fficients. the output ripple out v is determined by: () ? ? ? ? ? ? ? ? + ? 3 8 1 c f esr l f v v v v v osc osc in out in out out
rev.01 11 EP3003 package description dfn:
rev.01 12 EP3003 msop:

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