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esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 1/17 1.3mhz 2a, synchronous step-down regulator general description EML3418 is designed with high efficiency step down dc/dc converter for portable devices applications. it features with extreme low quiescent current with no load which is the best fit for extending battery life during the standby mode. the device operates from 2.5v to 5.5v input voltage and up to 2.0a output current capability. high 1.3mhz internal frequency makes small surface mount inductors and capacitors possible and reduces overall pcb board space. further, build-in synchronous switch makes external schottky diode is no longer needed and efficiency is improved. EML3418 is designed base on pulse width modulation (pwm) for low output voltage ripple and fixed frequency noise, low dropout mode provides 100% duty cycle operation. low reference voltage is designed for achieving regulated output down to 0.6v. the device is available in an adjustable version for tdfn-8 and sop-8fd package. features ? achieve 95% efficiency ? input voltage : 2.5v to 5.5v ? output current up to 2a ? reference voltage 0.6v ? quiescent current 240 a with no switching ? internal switching frequency 1.3mhz ? no schottky diode needed ? low dropout operation: 100% duty cycle ? shutdown current < 1 a ? excellent line and load transient response ? over-current and over-temperature protection applications ? blue-tooth devices ? cellular and smart phones ? personal multi-media player (pmp) ? wireless networking ? digital still cameras ? portable applications typical application (adjustable) fig. 1 fig. 2
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 2/17 connection diagram order information tdfn-8 package EML3418-00ff08nrr 00 adj operation ff08 tdfn-8 package nrr rohs & halogen free rating: -40 to 85c package in tape & reel sop-8fd package EML3418-00se08grr/nrr 00 adj operation se08 sop-8fd package grr rohs (pb free) rating: -40 to 85c package in tape & reel nrr rohs & halogen free (by request) rating: -40 to 85c package in tape & reel order, mark & packing information package vout product id marking packing tdfn-8 adj EML3418-00ff08nrr 5kpcs tape & reel sop-8fd adj EML3418-00se08grr 3kpcs tape & reel
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 3/17 package configuration sop-8 adjustable pin functions pin # pin name function v fb (adjustable) feedback pin. receives the feedback voltage from an external resistive divider across the output. 1 v out (fixed voltage) output voltage pin. an internal re sistive divider divides the output voltage down for comparison to the internal refe rence voltage. 2 vss_cln analog ground pin. 3 vss_pwr power ground pin. 4 sw switch pin. must be connected to inductor. this pin connects to the drains of the internal main and synchronous power mosfet switches. 5, 6 v in_pwr power input pin. must be closel y decoupled to gnd pin with a 4.7 f or greater ceramic capacitor. 7 v in_cln analog input pin. must be closely decoupled to gnd pin with a 4.7 f or greater ceramic capacitor. 8 en enable pin. minimum 1.2v to enable the device. maximum 0.4v to shut down the device. do not leave this pin floating and enable the chip after vin is in the input voltage range. exposed pad connect to ground.
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 4/17 absolute maximum ratings devices are subjected to failure if they stay above absolute maximum ratings. input voltage ------------------------ ? 0.3v to 6v en, v fb voltages -------------------- ? 0.3v to v in sw voltage --------------- ? 0.3v to (v in + 0.3v) pmos switch source current (dc) ----- 2.5a nmos switch sink current (dc) --------- 2.5a peak switch sink and source current - 3.5a operating temperature range ---------------- -------------------------------------------- ?40c to 85c junction temperature (notes 1, 3) --- 125c storage temperature range ? 65c to 150c lead temperature (soldering, 5 sec) -- 260c esd susceptibility hbm---------------------------2kv mm -------------------------------------------------- 200v thermal data tdfn thermal resistance parameter value ja junction-ambient 55 o c/w jc junction-case 10 o c/w electrical characteristics the denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25c. v in = 5v unless otherwise specified. symbol parameter conditions min typ max units i vfb feedback current 100 na t a = 25c 0.588 0.6 0.612 v fb regulated feedback voltage ?40c t a 85c 0.585 0.6 0.615 v v out % output voltage accuracy -3 3 % v fb reference voltage line regulation v in = 2.5v to 5.5v 0.4 %/v v ovl = v ovl ? v fb , EML3418 20 50 80 mv v ovl output over-voltage lockout v ovl = v ovl ? v out , EML3418-fixed 2.5 7.8 13 % v out output voltage line regulation v in = 2.5v to 5.5v 0.2 0.4 %/v i pk peak inductor current v in = 3v, v fb = 0.5v or v out = 90%, duty cycle < 35% 2.4 a v loadreg output voltage load regulation i out =10ma to 2a 0.2 %/a quiescent current (note 2) v fb = 0.5v or v out = 90% 240 340 a i s shutdown v en = 0v, v in = 4.2v 0.1 1 a f osc oscillator frequency v fb = 0.6v or v out = 100% 1.04 1.30 1.56 mhz r pfet r ds(on) of pmos i sw = 750ma 0.18 r nfet r ds(on) of nmos i sw = ?750ma 0.16 i lsw sw leakage v en = 0v, v sw = 0v or 5v, v in = 5v 1 a enable threshold 1.2 v v en shutdown threshold 0.4 v i en en leakage current 1 a
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 5/17 note 1: t j is a function of the ambient temperature t a and power dissipation p d ( t j = t a + (p d )(55c/w) ) note 2: dynamic quiescent current is higher due to the gate charge be ing delivered at the switching frequency. note 3: this ic is build-in over-tem perature protection to avoid damage from overload conditions.
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 6/17 typical performance characteristics efficiency vs output current efficiency vs output current reference voltage vs temperature efficiency vs output current efficiency vs output current output voltage vs load current
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 7/17 pmos r ds(on) vs temperature pmos r ds(on) vs supply voltage dynamic supply current vs temperature nmos r ds(on) vs temperature nmos r ds(on) vs supply voltage dynamic supply current vs supply voltage
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 8/17 switching frequency vs temperature start-up from shutdown load step switching frequency vs supply voltage start-up from shutdown load step i load 500ma/div v out 100mv/div ac coupled i l 500ma/div v in =3.3v, v out =1.5v, i load =500ma to 1a i l 1a/div v in =5v v out =1.2v i load =10ma (120 r) v out 100mv/div ac coupled v in =5v, v out =2.5v, i load =500ma to 1a en 2v/div v out 1v/div v out 1v/div i l 1a/div v in =5v v out =1.2v i load =1.5a (0.8 r) i load 500ma/div i l 500ma/div en 2v/div v in =5.0v, v out =2.5v, i load =500ma to 1a
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 9/17 functional block diagram
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 10/17 applications the typical application circuit of adjustable version is shown in fig.1. fixed voltage version is shown below: inductor selection basically, inductor ri pple current and core saturation current are tw o factors considered to decide the inductor value. ? ? ? ? ? ? ? ? ? ? = in v out v out v l i 1 1 l f eq. 1 the eq. 1 shows the inductor ripple current is a function of frequency, inductance, vin and vout. it is recommended to set ripple current to 40% of max. load current. a low esr inductor is preferred. c in and c out selection a low esr input capacitor can prevent large voltage transients at v in . the rms current of input capacitor is required larger than i rms calculated by: () in out in out v v v v omax i rms i ? ? eq. 2 esr is an important parameter to select c out . the output ripple v out is determined by: ? ? ? ? ? ? ? ? ? ? + ? out c f 8 1 l i out v esr eq. 3 higher values, lower cost ceramic capacitors are now available in smaller sizes. these ceramic capacitors have high ripple currents, high voltage ratings and low esr that make them ideal for switching regulator applications. optimize very low ou tput ripple and small circuit size is doable from cout selection since cout does not affect the internal control loop stability. it is recommended to use the x5r or x7r which have the best temperature and voltage characteristics of all the ceramics for a given value and size. output voltage (EML3418 adjustable) in the adjustable version, the output voltage can be determined by: ? ? ? ? ? ? ? ? + = 1 r 2 r 1 v out v 6 . 0 eq. 4 short circuit behavior EML3418 has over-current and over-temperature protection. over-current protection cycle by cycle limits p-driver fet current to prevent induct or current from losing control. over-temperature protection function turns off driver fets when junction temperature is high and recovers to normal operation after it is cool enough. when EML3418 is used to transfer vin=5v to vout=1.2v, shorting vout to ground makes over-current and over- temperature protection active. the waveform is shown as the following diagram. short circuit response thermal considerations although thermal shutdown is build-in in EML3418 that protect the device from thermal damage, the total power dissipation that EML3418 can sustain should be base on the package thermal capability. the formula to ensure the safe operation is shown in note 1. to avoid the EML3418 from exceeding the maximum junction temperature, the user will need to do some thermal analysis. guidelines for pcb layout to ensure proper operation of the EML3418, please note the following pcb layout guidelines: 1. the gnd trace, the sw trace and the v in trace should be kept sh ort, direct and wide. 2. v fb pin must be connected directly to the v out 1v/div sw 5v/div i l 2a/div i in 1a/div
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 11/17 feedback resistors. resistive divider r 1 /r 2 must be connected and parallel to the output capacitor c out . 3. the input capacitor c in must be connected to pin v in as closely as possible. 4. keep sw node away from the sensitive v fb node since this node is with high frequency and voltage swing. 5. keep the (?) plates of c in and c out as close as possible. 6. connect all analog grounds to a common node and connect the common node to power ground through an independent path. self-enable application a self-enable function could be used when EML3418 is connected as the following diagram: the resistor ratio r3:r4=1:1.5 is recommended. output voltage ripple when v in closes to v out EML3418 goes into ldo mode when input voltage closes to output voltage. the transition from pwm mode to ldo mode is smooth. bottom diagram shows the relationship of output voltage ripple versus input voltage when output voltage is 3.3v and EML3418 provides 200ma load current. v out ripple when v in closes to v out recommended components supplier inductance ( u h) i sat (a) dcr max (m ) dimensions (mm) part number coilcraft 1.5 14 13 12.3 x 12.3 x 6 mss1260-152nlb supplier capacitance ( u f) package part number yageo 4.7 0805 cc0805kkx5r6bb475 taiyo yuden 22 1812 emk432bj226km-t
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 12/17 application (continued) typical schematic for pcb layout
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 13/17
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 14/17 package information tdfn-8 common dimensions millimeter dimensions inch symbol min. nom. max. min. nom. max. a 0.70 0.75 0.80 0.028 0.030 0.031 a3 0.203 bsc 0.008 bsc b 0.25 0.30 0.35 0.010 0.012 0.014 d 3.00 bsc 0.118bsc d2 1.60 - 2.50 0.063 - 0.098 e 3.00 bsc 0.118bsc e2 1.35 - 1.75 0.053 - 0.069 e 0.650 bsc 0.026 bsc l 0.30 0.40 0.50 0.012 0.016 0.020
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 15/17 sop-8fd
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 16/17 revision history revision date description 2.0 2009.06.05 emp transferred from version 1.0 2.1 2010.06.02 to revise circuitry 2.2 2010.10.07 tdfn package dimension update 2.3 2011.01.28 revise electrical characteristics(ven)
esmt/emp EML3418 elite semiconductor memory technology inc./ elite micropower inc. publication date: jan. 2011 revision: 2.3 17/17 important notice all rights reserved. no part of this docume nt may be reproduced or duplicated in any form or by any means without the prior permission of esmt. the contents contained in this document are believed to be accurate at the time of publication. esmt assu mes no responsibility for any error in this document, and reserves the right to change the products or specification in this document without notice. the information contained herein is presented only as a guide or examples for the application of our products. no responsibility is assumed by esmt for any infringement of patents, copyrights, or other intellectual property rights of third parties which may result from its use. no license, either express , implied or otherwise, is granted under any patents, copyrights or other intellectual property rights of esmt or others. any semiconductor devices may have inherently a certain rate of failure. to minimize risks associ ated with customer's application, adequate design and operating safe guards against injury, damage, or loss from such failure, should be provided by the customer when making application designs. esmt's products are not authorized for use in critical applications such as, but not limited to, life support devices or system, where failure or abnormal operation may directly aff ect human lives or cause physical injury or property damage. if products described here are to be used for such kinds of application, purchase r must do its own quality assurance testing appropriate to such applications.

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