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march 2009 1 mic4826 mic4826 micrel mic4826 low input voltage, 160v pp output voltage, el driver general description micrels mic4826 is a high output voltage, dc to ac converter, designed for driving el (electroluminescent) lamps. the device operates from an input voltage range of 1.8v to 5.5v, making it suitable for 1-cell li ion and 2- or 3-cell alkaline/ nicad/nimh battery applications. the mic4826 converts a low voltage dc input to a 160v pp ac output signal that drives the el lamp. the mic4826 is comprised of two stages: a boost stage, and an h-bridge, lamp driver, stage. the boost stage steps the input voltage up to +80v. the h-bridge stage then alternately switches the +80v output to each terminal of the el lamp, thus creating a 160v pp ac signal to drive the el lamp and generate light. the mic4826 features separate oscillators for the boost- and h-bridge stages. external resistors independently set the operating frequency of each stage. this fexibility allows the el lamp circuit to be optimized for maximum effciency and brightness. the mic4826 uses a single inductor and a minimum number of external components, making it ideal for portable, space- sensitive applications. the mic4826 is available in an 8-pin msop package with an ambient temperature range of C40c to +85c. typical application features ? 1.8v to 5.5v dc input voltage ? 160v pp regulated ac output waveform ? independently adjustable el lamp frequency ? independently adjustable boost converter frequency ? 0.1a shutdown current applications ? lcd panel backlight ? cellular phones ? pdas ? pagers ? calculators ? remote controls ? portable phones ordering information part number standard pb-free temp. range package mic4826bmm mic4826ymm C40c to +85c msop-8 micrel, inc. ? 1849 fortune drive ? san jose, ca 95131 ? usa ? tel + 1 (408) 944-0800 ? fax + 1 (408) 944-0970 ? http://www.micrel.com high voltage el driver 442k 2m v in c out 0.01f/100v d1 ba v19ws l1 220h 2in 2 el lamp 15 6 8 7 2 3 4 sw cs va vb vdd rsw rel gnd mic4826 c in 10f time (2ms/div) v b (50v/div) v a (50v/div) v a e v b (50v/div) v in = 3.0v l = 220h? c out = 0.01f lamp = 2i n 2 ? r sw = 332k ? r el = 3.32m
mic4826 micrel mic4826 2 march 2009 pin confguration 1 vdd rsw rel gnd 8v a vb cs sw 7 6 5 2 3 4 8-pin msop package (mm) pin description pin number pin name pin function 1 vdd supply (input): 1.8v to 5.5v for internal circuitry. 2 rsw switch resistor (external component): set switch frequency of the internal power mosfet by connecting an external resistor to vdd. connecting the external resistor to gnd disables the switch oscillator and shutdown the device. 3 rel el resistor (external component): set el frequency of the internal h-bridge driver by connecting an external resistor to vdd. connecting the external resistor to gnd disables the el oscillator. 4 gnd ground return. 5 sw switch node (input): internal high-voltage power mosfet drain. 6 cs regulated boost output (external component): connect to the output ca - pacitor of the boost regulator and connect to the cathode of the diode. 7 vb el output: connect to one end of the el lamp. polarity is not important. 8 va el output: connect to the other end of the el lamp. polarity is not important.
march 2009 3 mic4826 mic4826 micrel electrical characteristics v in = v dd = 3.0v, r sw = 560k ? , r el = 1.0m ? . t a = 25c unless otherwise specifed. bold values indicate - 40c t a +85c symbol parameter condition min typ max units r ds(on) on-resistance of switching transistor i sw = 100 ma, v cs = 75v 3.8 7.0 ? v cs output voltage regulation v dd = 1.8v to 5.5v 75 80 85 v 73 87 v v a C v b output peak-to-peak voltage v dd = 1.8v to 5.5v 150 160 170 v 146 174 v v en-l input low voltage (turn off) v dd = 1.8v to 5.5v 0.5 v v en-h input high voltage (turn on) v dd = 1.8v to 5.5v v dd C0.5 v i sd shutdown current, note 4 r sw = low; r el = low; 0.01 0.1 a v dd = 5.5v 0.5 a i vdd input supply current r sw = high; r el = high; 21 75 a v cs = 75v; v a , v b open i cs boosted supply current r sw = high; r el = high; 200 400 a v cs = 75v; v a , v b open i in input current including inductor v in = v dd = 1.8v 28 ma current (see test circuit) f el v a Cv b output drive frequency 285 360 435 hz f sw switching transistor frequency 53 66 79 khz d switching transistor duty cycle 90 % note 1. exceeding the absolute maximum rating may damage the device. note 2. the device is not guaranteed to function outside its operating rating. note 3. devices are esd sensitive. handling precautions recommended. note 4. shutdown current is defned as the sum of current going into pin 1, 5, and 6 when the device is disabled. test circuit 442k 2m c out 0.01f/100v d1 ba v19ws l1 220h 15 6 8 7 2 3 4 sw cs va vb vdd rsw rel gnd mic4826 c in 10f v in 10nf 100? absolute maximum rating (note 1) supply voltage (v dd ) ....................................... C0.5v to +6v output voltage (v cs ) ................................... C0.5v to +100v frequency control voltage (v rsw , v rel ) ... C0.5v to (v dd + 0.3v) power dissipation @ t a = 85c .............................. 200mw storage temperature (t s ) ........................ C65c to +150c esd rating .............................................................. note 3 operating ratings (note 2) supply voltage (v dd ) ........................................ 1.8v to 5.5v lamp drive frequency (f el ) ....................... 60hz to 1000hz switching transistor frequency (f sw ) ........ 8khz to 200khz ambient temperature (t a ) .......................... C40c to +85c package thermal resistance 8-pin msop ( ja ) .............................................. 206c/w
mic4826 micrel mic4826 4 march 2009 typical characteristics 0 5 10 15 20 25 30 35 40 45 50 0 1 2 3 4 5 6 input current (ma) input voltage (v) total input curren t vs. input volt a g e r sw = 332k r el = 3.32 m r sw = 442k r el = 2m r sw = 562k, r el = 1m lamp = 2in 2 l = 22 0h d = bav19ws c out = 0.1 f 0 5 10 15 20 25 30 35 40 45 50 -40 -20 02 04 06 08 0 100 input current (ma) temperature (c) total input curren t vs. temperatur e r sw = 332k r el = 3.32m r sw = 442k r el = 2m r sw = 562k r el = 1m v in = 3.0 v lamp = 2in 2 l = 22 0h d = bav19ws c out = 0.1 f 0 20 40 60 80 100 120 140 160 180 200 1 2 3 4 5 6 v a ?v b (v pp ) input voltage (v) output voltag e vs. input volt a g e r sw = 332k r el = 3.32m r sw = 442k r el = 2m r sw = 562k r el = 1m lamp = 2in 2 l = 22 0h d = bav19ws c out = 0.1 f 0 20 40 60 80 100 120 140 160 180 200 -40 -20 02 04 06 08 0 100 output voltage (v pp ) temperature (c) output voltag e vs. temperatur e v in = 3.0 v lamp = 2in 2 l = 22 0h c out = 0.1 f d = bav19ws r sw = 332k r el = 3.32m r sw = 442k r el = 2m r sw = 562k r el = 1m 0 10 20 30 40 50 60 70 80 90 100 -40 -20 02 04 06 08 0 100 v cs (v avg ) temperature (c) cs voltag e vs. temperatur e v in = 3.0 v lamp = 2in 2 l = 22 0h c out = 0.1 f d = bav19ws r sw = 332k r el = 3.32m r sw = 442k r el = 2m r sw = 562k r el = 1m 0 1 2 3 4 5 6 7 1 2 3 4 5 6 switch resistance (?) input voltage (v) switch resistance vs. input volt a g e 10 100 1000 10000 0.1 1 1 0 el frequency (hz) el resistor (m?) el frequenc y vs. el resistor 1 10 100 1000 100 1000 10000 switching frequency (khz) switch resistor (k?) switching frequenc y vs. switch resistor 0 20 40 60 80 100 120 -40 -20 02 04 06 08 0 100 frequency (khz) temperature (c) switching frequenc y vs. temperatur e r sw = 332k v in = 3.0v r sw = 442k r sw = 562k 0 20 40 60 80 100 120 1 2 3 4 5 6 switching frequency (hz) input voltage (v) switching frequenc y vs. input volt a g e r sw = 562k r sw = 442k r sw = 332k 0 10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 6 v cs (v) input voltage (v) output voltage regulatio n vs. input voltag e r sw = 332k r el = 3.32 m r sw = 442k r el = 2m r sw = 562k r el = 1m lamp = 2in 2 l = 22 0h c out = 0.0 1f 0 50 100 150 200 250 300 350 400 1 2 3 4 5 6 el frequency (hz) input voltage (v) el frequenc y vs. input volt a g e r el = 1m r el = 2m r el = 3.32m
march 2009 5 mic4826 mic4826 micrel 0 50 100 150 200 250 300 350 400 -40 -20 02 04 06 08 0 100 frequency (khz) temperature (c) el frequenc y vs. temperatur e r sw =1m v in = 3.0v r sw = 2m r sw = 3.32m 0 20 40 60 80 100 120 140 160 180 0 1234567 output voltage (v pp ) lamp size (sq. in.) output voltag e vs. lamp siz e r sw = 332k r el = 3.32m v in = 3.0v l = 220h c out = 0.1f d = bav19ws 0 2 4 6 8 10 12 14 16 18 20 0 1234567 input current (ma) lamp size (sq. in.) total input curren t vs. lamp siz e r sw = 332k r el = 3.32m v in = 3.0v l = 220h d = bav19ws c out = 0.1f
mic4826 micrel mic4826 6 march 2009 functional diagram q 1 q 2 q 3 q 4 el oscillator gnd 4 vb el lamp 7 va 8 cs 6 sw c out d1 l1 220h 5 1 rw s r sw c in 2 rel r el 3 switch oscillator v dd v ref v in figure 1. mic4826 block diagram functional description see application information for component selection and pre-designed circuits. overview the mic4826 is a high voltage el driver with an ac output voltage of 160v peak-to-peak capable of driving el lamps up to 6 in 2 . input supply current for the mic4826 is typically 21a with a typical shutdown current of 10na. the high voltage el driver has two internal oscillators to control the switching mosfet and the h-bridge driver. both of the internal oscil - lators frequencies can be individually programmed through the external resistors to maximize the effciency and the brightness of the lamps. regulation referring to figure 1, initially power is applied to v dd . the internal feedback voltage is less than the reference voltage causing the internal comparator to go low which enables the switching mosfets oscillator. when the switching mosfet turns on, current fows through the inductor and into the switch. the switching mosfet will typically turn on for 90% of the switching frequency. during the on-time, energy is stored in the inductor. when the switching mosfet turns off, current fowing into the inductor forces the voltage across the induc - tor to reverse polarity. the voltage across the inductor rises until the external diode conducts and clamps the voltage at v out +v d1 . the energy in the inductor is then discharged into the c out capacitor. the internal comparator continues to turn the switching mosfet on and off until the internal feedback voltage is above the reference voltage. once the internal feedback voltage is above the reference voltage, the internal comparator turns off the switching mosfets oscillator. when the el oscillator is enabled, v a and v b switch in op - posite states to achieve a 160v peak-to-peak ac output signal. the external resistor that connects to the rel pin determines the el frequency. time (2ms/div) v b (50v/div) v a (50v/div) v a ? v b (50v/div) v in = 3.0v l = 220h c out = 0.01f lamp = 2in 2 r sw = 332k r el = 3.32m figure 2. 108hz typical output waveform switching frequency the switching frequency of the converter is controlled via an external resistor between rsw pin and vdd pin of the device. the switching frequency increases as the resistor value decreases. for resistor value selections, see typical characteristics: switching frequency vs. switch resistor or use the equation below. the switching frequency range is 8khz to 200khz, with an accuracy of 20%. f khz rm sw sw () () = ? 36
march 2009 7 mic4826 mic4826 micrel el frequency the el lamp frequency is controlled via an external resistor connected between rel pin and vdd pin of the device. as the lamp frequency increases, the resistor value decreases. for resistor value selections, see the typical character - istics: el frequency vs. el resistor or use the equation below. the el frequency range is 60hz to 1000hz, with an accuracy of 20%. fh z rm el el () () = ? 360 time (2ms/div) v b (50v/div) v a (50v/div) v a ? v b (50v/div) v in = 3.0v l = 220h c out = 0.01f lamp = 2in 2 r sw = 562k r el = 1m figure 3. 180hz output waveform in general, as the el lamp frequency increases, the amount of current drawn from the battery will increase. the color of the el lamp and the intensity are dependent upon its frequency. time (2ms/div) v in = 3.0v l = 220h? c out = 0.01f? lamp = 2i n 2 ? r sw = 562k ? r el = 1m v b (50v/div) v a (50v/div) v a e v b (50v/div) figure 4. 360hz output waveform enable function the enable function of the mic4826 is implemented by switch - ing the r sw and r el resistor between ground and v dd . when r sw and r el are connected to ground, the switch and the el oscillators are disabled; therefore the el driver becomes disabled. when these resistors connect to v dd , both oscilla -
mic4826 micrel mic4826 8 march 2009 r1 322k r2 3.32m li-ion battery v in 3.0v to 4.2v c1 0.22f/10v murata grm39x7r 224k10 c out 0.01f/100v grm40x7r103k d1 vi shay t elefunken ba v19ws l1 220h murata lqh4c221k04 3in 2 lamp 15 6 7 8 2 3 4 sw cs vb va vdd rsw rel gnd mic4826 c2 10f/6.3v murata grm42-6x5r106k6. 3 tors will function and the el driver is enabled. application information inductor in general, smaller value inductors, which can handle more current, are more suitable to drive larger size lamps. as the inductor value decreases, the switching frequency (controlled by r sw ) should be increased to avoid saturation or the input voltage should be increased. typically, inductor values ranging from 220h to 560h can be used. murata offers the lqh3c series up to 560h and lqh4c series up to 470h, with low dc resistance. a 220h murata (lqh4c221k04) inductor is recommended for driving a lamp size of 3 square inches. it has a maximum dc resistance of 4.0?. diode the diode must have a high reverse voltage (100v) since the output voltage at the cs pin can reach up to 100v. a fast switching diode with lower forward voltage and higher reverse voltage (100v), such as bav19ws, can be used to enhance effciency. output capacitor low esr capacitors should be used at the regulated boost output (cs pin) of the mic4826 to minimize the switching output ripple voltage. selection of the capacitor value will depend upon the peak inductor current, inductor size, and the load. murata offers the grm40 series with up to 0.015f at 100v, with a x7r temperature coeffcient in 0805 surface-mount package. typically, values ranging from 0.01f to 0.1f at 100v can be used for the regulated boost output capacitor. pre-designed application circuits v in i in v a Cv b f el lamp size 3.3v 20ma 160v pp 100hz 3in 2 time (2ms/div) v b (50v/div) v a (50v/div) v a e v b (50v/div) v in = 3.0v l = 220h? c out = 0.01f lamp = 2i n 2 ? r sw = 332k ? r el = 3.32m )ljxuh7\slfdo+](/'ulyhuirulq 2 lamp
march 2009 9 mic4826 mic4826 micrel v in i in v a Cv b f el lamp size 3.3v 14ma 160v pp 100hz 2in 2 time (2ms/div) v b (50v/div) v a (50v/div) v a e v b (50v/div) v in = 3.0v l = 220h? c out = 0.01f lamp = 2i n 2 ? r sw = 332k ? r el = 3.32m figure 6. typical el driver for 2in 2 lamp with c s = 0.1f r1 332k r2 3.32m v in 2.5v to 5.5v c out 0.1f/100v grm42-2x7r104k100 d1 diodes ba v20ws l1 220h murata lqh4c221k04 el lamp lsi? x533-13 15 6 7 8 2 3 4 sw cs vb va vdd rsw rel gnd mic4826 c2 10f/6.3v murata grm42-6x5r106k6.3
mic4826 micrel mic4826 10 march 2009 v in i in v a Cv b f el lamp size 3.3v 13.2ma 160v pp 100hz 2in 2 ? time (2ms/div) v b? (50v/div) v a? (50v/div) v a ? v b? (50v/div) figure 7. typcial el driver for 2in 2 lamp with 560h inductor r1 332k r2 3.32m v in 3.3v to 5.5v c out 0.01f/100v grm40x7r103k100 d1 diodes ba v20ws l1 560h murata lq32cn561k21 el lamp lsi x533-13 15 6 7 8 2 3 4 sw cs vb va vdd rsw rel gnd mic4826 c2 10f/6.3v murata grm42-6x5r106k6.3
march 2009 11 mic4826 mic4826 micrel ? time (2ms/div) v b? (50v/div) v a? (50v/div) v a ? v b? (50v/div) figure 8. typical split power supplies applications v in i in v dd i dd v a Cv b f el lamp size 1.5v 22ma 3.0v 36a 160v pp 100hz 1.6in 2 r1 442k r2 3.32m v in 1.5v c out 0.01f/100v grm40x7r103k100 d1 diodes ba v20ws l1 220h murata lqh4c221k04 el lamp 15 6 7 8 2 3 4 sw cs vb va vdd rsw rel gnd mic4826 c2 10f/6.3v murata grm42-6x5r106k6.3 c1 0.01f/50v murata grm40-x7r103k50 v dd 1.8v to 5.5v
mic4826 micrel mic4826 12 march 2009 package information 8-lead msop (mm) micrel inc. 2180 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fa x + 1 (408) 474-1000 w e b http://www.micrel.com the information furnished by micrel in this data sheet is believed to be accurate and reliable. however, no responsibility is assumed by micrel for its use. micrel reserves the right to change circuitry and specifcations at any time without notifcation to the customer . micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a signifcant injury to the user . a purchasers use or sale of micrel products for use in life support appliances, devices or systems is a purchasers own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2001 micrel incorporated

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