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esmt/emp preliminary emd2055 elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 1/13 pwm step-up dc/dc converter for panel backlight (11 wleds driver) general description the emd2055 is a highly efficient, step-up dc/dc converter for driving white leds. the device can drive up to 11 serially connected white leds from a single li-ion battery, or to drive multiple serial and parallel combinations with a dc power supply from 2.5v to 5.5v. the emd2055 uses current mode and pulse-width modulated (pwm) operation. its high switching operation frequency of 1.0mhz allows the system to use small inductor, input and output capacitors. an internal compensation circuit can reduce the external component count. to safeguard the system, the emd2055 includes various protection circuits such as under-voltage lockout, current limit, over voltage and thermal shutdown. emd2055 are available in the tiny packages of sot-23-6l and tdfn-8l (2x2mm). applications mobile phone digital still cameras portable applications mp3 players gps receivers features up to 11 wleds supports low quiescent current: 120 a over voltage protection: 36.5v inherently matched led current shutdown current < 1a reference voltage 0.24v pwm dimming control (100hz~100khz) internal soft start and compensation 1.5a internal power mosfet switch low profile sot-23-6 and tdfn-8l packages typical application (9s3p) fig. 1
esmt/emp preliminary emd2055 elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 2/13 connection diagram order information EMD2055-00VC06NRR 00 output voltage vc06 sot-23-6l package nrr rohs & halogen free package rating: -40 to 85c package in tape & reel emd2055-00fk08nrr 00 output voltage fk08 tdfn-8l package nrr rohs & halogen free package rating: -40 to 85c package in tape & reel order, marking & packing information package vout product id marking packing sot-23-6l adjustable EMD2055-00VC06NRR tape & reel 3kpcs tdfn-8l (2x2mm) adjustable emd2055-00fk08nrr pin1 dot 2055 tracking code 1 2 3 4 8 7 6 5 tape & reel 3kpcs
esmt/emp preliminary emd2055 elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 3/13 function block fig. 2 pin functions pin name sot-23-6l pin # tdfn-8l pin # function lx 1 8 switch pin. connect inductor/diode here. gnd 2 1, 5, 9 ground pin. fb 3 6 feedback pin. reference voltage is 0.24v, connect cathode of lowest led and resistor here. en 4 4 chip enable pin and pwm dimming control pin. connect to 1.2v or higher to enable device, 0.4v or less to disable device. out 5 3 over voltage protection pin. in 6 2 input voltage pin. nc n/a 7 not connected.
esmt/emp preliminary emd2055 elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 4/13 absolute maximum ratings devices are subjected to failure if they stay above absolute maximum ratings input voltage C 0.3v to 6v en, vfb voltages C 0.3v to vin lx ,out voltage C 0.3v to 37v esd susceptibility hbm 2kv mm 200v operating temperature range C40c to 85c storage temperature C65c to 150c junction temperature 150c lead temperature (soldering, 10 sec) 260c thermal data package thermal resistance parameter value ja (note 2) junction-ambient 250c/w sot-23-5 jc (note 3) junction-case 81 o c/w ja (note 2) junction-ambient 165 o c/w tdfn-8 (2x2 mm) jc (note 3) junction-case 24 o c/w note 1: t j is a function of the ambient temperature t a and power dissipation p d (t j = t a + (p d ) * (165c/w)). note 2: ja is measured in the natural convection at t a =25 on a highly effective thermal conductivity test bo ard (2 layers , 2s0p ) according to the jedec 5 1-7 thermal measurement standard. note 3: jc represents the heat resistance between the chip an d the package top case. electrical characteristics (v cc = 3.7v, t a = 25c, unless otherwise specified.) parameter test condition min typ max unit under voltage lock out 1.8 2.4 v supply current continuously switching 1 ma quiescent current no switching, vfb = 1v 120 a shutdown current ven < 0.4v 1 ua operation frequency 0.8 1.0 1.2 mhz maximum duty cycle 93 95 % feedback voltage 0.228 0.240 0.252 v thermal shutdown protection 165 thermal shutdown hysteresis 20 ron isw = 200ma 0.5 0.8 ohm current limit 1.5 a shutdown voltage low 0.4 v enable voltage high 1.2 v en leakage current 1.3 a maximum output voltage 36 v ovp 41 v ovp hysteresis 0.2 1 3 v
esmt/emp elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 5/13 typical performance characteristics vin=3.7v, unless otherwise specified efficiency vs. input voltage (v out =34v) efficiency vs. output current (v out =34v) efficiency vs. input voltage (v out =34v) 0 10 20 30 40 50 60 70 80 90 100 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) efficiency (%) iload=20ma iload=40ma iload=60ma efficiency vs. output current (v out =34v) 0 10 20 30 40 50 60 70 80 90 100 1 10 100 output current (ma) efficiency (%) vin=3.7v vin=5v efficiency vs. output current (v out =24v) efficiency vs. output current (v out =12v) efficiency vs. output current (v out =24v) 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current (ma) efficiency (%) vin=3.7v vin=5v efficiency vs. output current (v out =12v) 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current (ma) efficiency (%) vin=3.7v vin=5v power on from en power off from en
esmt/emp elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 6/13 typical performance characteristics vin=3.7v, unless otherwise specified fosc vs. temperature v fb vs. temperature frequency vs. temperature 860 880 900 920 940 960 980 1000 -40 -20 0 20 40 60 80 100 120 140 temperature ( ) frequency (khz) vin=3.7v, iled=20ma v fb vs. temperature 236.0 236.2 236.4 236.6 236.8 237.0 237.2 237.4 237.6 237.8 238.0 -40 -20 0 20 40 60 80 100 120 140 temperature( ) v fb (mv) vin=3.7v ovp waveform led current vs. duty (v in =3.7v, i led =20ma) led current vs. duty 0 5 10 15 20 0 10 20 30 40 50 60 70 80 90 100 duty (%) led current (ma) f=500hz f=2khz f=20khz
esmt/emp elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 7/13 application information detailed description the emd2055 is a constant frequency, current-mode b oost dc-dc converter which can drive up to wleds 11s1p ~ 9s3p, depending on the input voltage range. the device can provide the well matched output current through each wled serial chain to obtain un iform illumination. the fast operation frequency al lows smaller inductor and input/output capacitors to be used. during normal operation, the internal oscillator se nds a pulse signal to set latch and turn on interna l mosfet each duty circle. a current sense voltage sums mosf et current and slope signal connected to the negati ve terminal of the pwm comparator. when this signal vo ltage exceeds output voltage of the error amplifier , the pwm comparator sends a signal to reset the latch an d turn off internal mosfet. the output voltage of t he error amplifier is magnified from the difference between reference voltage and feedback voltage. if the refe rence voltage is higher than feedback voltage, more curre nt is delivered to the output; otherwise, less curr ent is delivered. uvlo the emd2055 provides under-voltage-lock-out (uvlo) protection. when vin is lowered below uvlo threshol d, the uvlo circuit will send a signal to turn off the internal power mosfet, which will stop supplying o utput current. the 100mv hysteresis circuit in the uvlo c ircuit can prevent supply transients from causing a false restart. once the vin exceeds uvlo threshold again, the device will unlock the latch and turn on the i nternal power mosfet to continue the normal operation. enable / disable the emd2055 enters shutdown mode when en pin voltag e is less than 0.4v. during shutdown mode, all inte rnal circuits of the emd2055 are turned off and the quie scent current is reduced to less than 1ua. when the en pin voltage is higher than 1.2v, the device will start operation. the en pin can also be used for dimming control by using a pwm modulated signal. the frequency of this pwm signal can range from 100hz to 100khz. the average led driving current is directly proportional to the duty cycle of the pwm duty cycle, i.e., 0% duty cycle co rresponding to zero wleds current and 100% duty cyc le corresponding to full wleds current. ovp when any of the serially connected wleds chain is o pen, the boost control loop behaves as an open loop operation, which may cause damage on the lx pin due to excessive voltage. in order to prevent this dam age from happening, the emd2055 provides an over-voltag e-protection (ovp) circuit, with the protection threshold set at 41v. when lx pin exceeds 41v, the internal operation will be shut off.
esmt/emp elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 8/13 otp the internal thermal sensor will turn off the inter nal power mosfet when the junction temperature exce eds 165 . this over-temperature-protection (ovt) circuit ha s a built-in 20 hysteresis. led current setting referring to a typical application shown in figure 1 the brightness of the wled is controlled by adjus ting the operating current. the emd2055 regulates its opera ting current by adjusting the sense resistor (r1), which is given by: led current = 0.240v / r1 cin and cout selection it is recommended to use the x5r or x7r which have best temperature and voltage characteristics of all the ceramics for a give value and size. a minimum input capacitance of 4.7f is required for the emd2055, the capacitor value may be increased without limit. the typical output capacitor value is 1f, higher capa citance can be used to reduce voltage ripple. inductor selection the inductor values range from 4.7h to 22h. the t ypical inductor value is 10h. the low dcr inductor is preferred. in addition, the limit saturation curren t of inductor must exceed current limit of the emd2 055. diode selection referring to figure 1 of the typical application, t he emd2055 is high switching control devise which d emands a high speed rectification diode for optimum efficien cy. the schottky diode is preferred, for high effic iency, schottky diode provide fast recovery time and low f orward voltage that reduce power loss. the recover breakdown voltage of schottky diode must exceed out put voltage.
esmt/emp elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 9/13 application circuit application circuit for 10s1p fig. 3 application circuit for 9s3p fig. 4
esmt/emp elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 10/13 package outline drawing sot-23-6 min. max. a 0.90 1.45 a1 0.00 0.15 b 0.30 0.50 c 0.08 0.25 d 2.70 3.10 e 1.40 1.80 e1 2.60 3.00 e l 0.30 0.60 0.95 bsc symbol dimension in mm
esmt/emp elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 11/13 package outline drawing tdfn-8l (2x2 mm) exposed pad min max a 0.70 0.80 min max a1 0.00 0.05 d2 1.10 1.25 a3 0.18 0.25 e2 0.55 0.70 b 0.18 0.30 d 1.95 2.05 e 1.95 2.05 e l 0.20 0.45 dimension in mm symbol dimension in mm 0.50 bsc
esmt/emp elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 12/13 revision history revision date description 0.01 1/4/2013 draft version. 0.02 1/7/2013 draft version, reduced cin & cout capa citor requirement. 0.03 1/16/2013 updated measurement data into this d atasheet.
esmt/emp elite semiconductor memory technology inc./elite mi cropower inc. publication date : jan. 2013 revision : 0.03 13/13 important notice all rights reserved. no part of this document may be reproduced or dupli cated in any form or by any means without the prior permission of esmt. the contents contained in this document are believe d to be accurate at the time of publication. esmt assumes no responsibi lity for any error in this document, and reserves the right to change the produ cts 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 responsibil ity i s assumed by esmt for any infringement of patents, copyrights, or other i ntellectual 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 cer tain rate of failure. to minimize risks associated with customer's applic ation, adequate design and operating safeguards against injury, damage, or loss from such failure, should be provided by the customer when making appl ication designs. esmt's products are not authorized for use in criti cal applications such as, but not limited to, life support devices or system, where failure or abnormal operation may directly affect human lives or cause physical injury or property damage. if products described here are to be used for such kinds of application, purchaser must do its own quality a ssurance testing appropriate to such applications.

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