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1 standby current 5 1000 supply current i 21 28 enable current o n 15 50 off 20 output voltage vout 160 188 220 lamp frequency lf 190 260 330 inductor frequency hf 14 18 24 general description: the durel? d372a is designed to drive el lamps with a regulated high-voltage signal. this driver ic uses a proprietary circuit design for programmable wave-shaping for low-noise performance in applications that are sensitive to audible and electrical noise, such as cellular phones and handsets. data sheet d372a electroluminescent lamp driver ic msop-10 ? regulated high ac voltage output ? cellular phones and handsets ? adjustable output frequency ? data organizers/pdas ? flexible wave-shaping capability ? lcd backlighting ? small package size ? external clock compatible features applications na e = gnd ma e = 3.3v a e = 3.3v na e = gnd vpp hz khz parameter symbol minimum typical maximum unit conditions (using standard test circuit at ta=25 c unless otherwise specified.) lamp driver specifications: standard test circuit load a v+ clf chf e gnd rd el2 el1 cs l+ d372a 2.2 mh dcr = 2 ? 47 nf 820 ? 68 pf 2.0 nf .1 f +3.3 v 1 2 3 4 5 10 9 8 7 6 +3.3 v off on d 372a
2 supply voltage operating range v+ 2.0 6.5 v e = v+ withstand range -0.5 9.0 e = gnd enable voltage e -0.5 (v+) +0.5 v lamp output vout 220 vpp e = v+ operating temperature t a -40 85 c storage temperature t s -65 150 c load a* physical data: pin # name function absolute maximum ratings: note: the above are stress ratings only. functional operation of the device at these ratings or any other above those indicated in the specifications is not implied. exposure to absolute maximum rating conditions for extended periods of time may affect reliability. parameter symbol minimum m aximum unit comments 1 v+ dc power supply input 2 clf low frequency oscillator capacitor/lf clock input 3 chf high frequency oscillator capacitor/hf clock input 4e system enable: hi = on 5 gnd system ground connection 6 l+ charge pumping inductor input 7 cs high voltage storage capacitor 8 el1 ac output to lamp 9 el2 ac output to lamp 10 rd wave shaping resistor * load a approximates a 3in 2 el lamp. 1 2 3 4 5 10 9 8 7 6 sample output waveform 100 ? 10 nf
3 typical performance characteristics using standard test circuit output frequency vs. dc supply voltage 0 50 100 150 200 250 300 350 400 1234567 dc input voltage lf (hz) 0 50 100 150 200 250 300 350 400 -40-20 0 20406080 temperature ( o c) lf (hz) output frequency vs. ambient temperature 0 50 100 150 200 250 300 1234567 dc input voltage output voltage (vpp) output frequency vs. dc supply voltage 0 50 100 150 200 250 300 -40-20 0 20406080 temperature ( o c) ouput voltage (vpp) output frequency vs. ambient temperature 0 5 10 15 20 25 1234567 dc input voltage avg supply current (ma) output frequency vs. dc supply voltage 0 5 10 15 20 25 -40 -20 0 20 40 60 80 temperature ( o c) avg supply current (ma) output frequency vs. ambient temperature
4 theory of operation electroluminescent (el) lamps are essentially capacitors with one transparent electrode and a special phosphor material in the dielectric. when a strong ac voltage is applied across the el lamp electrodes, the phosphor glows. the required ac voltage is typically not present in most systems and must be generated from a low voltage dc source. the d372 chip inverter drives the el lamp by using a switching bjt to repeatedly charge an external inductor and discharge it to the high voltage capacitor cs. the discharging causes the voltage at cs to continually increase. when the voltage at cs reaches a nominal value, the switching bjt is turned off. the internal circuitry uses the h-bridge technology, using both electrodes to drive the el lamp. one of the outputs, el1 or el2, is used to discharge cs into the el lamp during the first half of the low frequency (lf) cycle. by alternating the state of the h-bridge, the other output is used to charge the el lamp during the second half of the lf cycle. the alternating states make it possible to achieve 200v peak-to-peak across the el lamp. the el driving system is divided into several parts: on-chip logic control, on-chip high voltage output circuitry, on-chip discharge logic circuitry, and off-chip components. the on-chip logic controls the lamp operating frequency (lf) and the inductor switching frequency (hf). these signals are used to drive the high voltage output circuitry (h-bridge) by delivering the power from the inductor to the lamp. the integrated discharge logic circuitry uses a patented wave shaping technique for reducing audible noise from an el lamp. changing the rd value changes the slope of the linear discharge as well as the shape of the waveform. the off-chip component selection provides a degree of flexibility to accommodate various lamp sizes, system voltages, and brightness levels. typical d372 el driving configurations for driving el lamps in various applications are shown on the following page. the expected system outputs for the various circuit configurations are also shown with each respective figure. these examples are only guides for configuring the driver. durel provides a d372 designers kit, which includes a printed circuit evaluation board intended to aid you in developing an el lamp driver configuration using the d372 that meets your requirements. a section on designing with the d372 is included in this datasheet to serve as a guide to help you select the appropriate external components to complete your d372 el driver system. block diagram of the driver circuitry el lamp ev+ l+ gnd el1 high frequency oscillator chf low frequency oscillator clf r d v bat l o g i c l o g i c divide by 2 el2 c s
5 typical d372a el driver configurations 3.0v handset lcd typical output brightness = 6.0 fl (20.6 cd/m 2 ) lamp frequency = 285 hz supply current = 12 ma vout = 208 vpp load = 1 in 2 (645 mm 2 ) durel ? 3 green el 5.0 v lcd backlight typical output luminance = 6.0 fl (24.3 cd/m 2 ) lamp frequency = 300 hz supply current = 22 ma vout = 206 vpp load = 4 in 2 (2580 mm 2 )durel ? 3 green el 3.3 v handset lcd and keypad typical output luminance = 5.5 fl (18.8 cd/m 2 ) lamp frequency = 290 hz supply current = 17 ma vout = 200 vpp load = 1.5 in 2 (950 mm 2 )durel ? 3 green el v+ clf chf e gnd rd el2 el1 cs l+ d372a 1.5 in 2 el lamp murata lqh3ks 2.2 mh 47 nf 1.0 k ? 68 pf 2.0 nf 0.1 f +3.3 v 1 2 3 4 5 10 9 8 7 6 +3.3 v 0 v off on 3.3 v v+ clf chf e gnd rd el2 el1 cs l+ d372a 4.0 in 2 el lamp sumida cls62 1.5 mh 47 nf 220 ? 68 pf 2.0 nf 0.1 f +5.0 v 1 2 3 4 5 10 9 8 7 6 +5.0 v 0 v off on 5.0 v v+ clf chf e gnd rd el2 el1 cs l+ d372a 1.0 in 2 el lamp bujeon bds-3516s 1.5 mh 47 nf 1.0 k ? 68 pf 2.0 nf 0.1 f +3.0 v 1 2 3 4 5 10 9 8 7 6 +3.0 v 0 v off on 3.0 v
6 designing with d372 i. lamp frequency capacitor (clf) selection selecting the appropriate value of capacitor (clf) for the low frequency oscillator will set the output frequency of the d372 inverter. figure 1 graphically represents the effect of the clf capacitor value on the oscillator frequency at v+ = 3.0v. the lamp frequency may also be controlled with an external clock signal. the resulting lamp frequency will be half of the clock signal frequency. the differential output voltage will increase in magnitude during the high portion of the clock signal and decrease during the low portion of the clock signal. lamp frequencies of 200-500hz are typically used. the selection of the clf value can also affect the output brightness and current consumption of the driver. the el lamp frequency (lf) depends on lamp size, drive conditions, and mainly on the clf value selected. figures 2 and 3 show typical brightness and current draw of a d372 circuit at different frequencies. the data was taken with an average 1.0mh inductor and 68 pf chf capacitor. figure 1: typical lamp frequency vs. clf capacitor figure 2: typical luminance and current vs. lamp frequency conditions: v+ = 3.0 v, 1.5 in 2 el lamp figure 3: typical luminance and current vs. lamp frequency conditions: v+ = 5.0 v, 4.0 in 2 el lamp 100 200 300 400 500 600 12345 clf (nf) lamp frequency (hz) 0 1 2 3 4 5 6 7 8 9 0 100 200 300 400 500 600 frequency (hz) 10 15 20 25 30 35 40 45 luminance current luminance (fl) current (ma) 0 1 2 3 4 5 6 7 8 9 0 100 200 300 400 500 600 frequency (hz) 10 15 20 25 30 35 40 45 luminance current luminance (fl) current (ma)
7 selecting the appropriate value of capacitor (chf) for the high frequency oscillator will set the inductor switching frequency of the d372 inverter. figure 4 graphically represents the effect of the chf capacitor value on the oscillator frequency at v+ = 3.0v. figure 4: typical inductor frequency vs. chf capacitor the inductor switching frequency may also be controlled with an external clock signal. the inductor will charge during the low portion of the clock signal and discharge into the el lamp during the high portion of the clock signal. ii. inductor switching frequency (chf) selection iii. inductor (l) selection the inductor value and inductor switching frequency have the greatest impact on the output brightness and current consumption of the driver. figures 5 and 6 show typical brightness and current draw of a d372 circuit with several different inductor and chf values. the clf value was modified in each case such that the output voltage was approximately 200vpp. the data was taken with average inductors. please note that the dc resistance (dcr) and current rating of inductors with the same inductance value may vary with manufacturer and inductor type. thus, inductors made by a different manufacturer may yield different outputs, but the trend of the different curves should be similar. figure 5: luminance and current vs. inductor and chf value conditions: v+ = 3.0 v, 1.5 in 2 el lamp figure 6: luminance and current vs. inductor and chf value conditions: v+ = 5.0 v, 4in 2 el lamp 10 15 20 25 50 75 100 125 150 175 200 chf (pf) inductor frequency (khz) 0 1 2 3 4 5 6 7 8 9 0.0 1.0 2.0 3.0 4.0 5.0 6.0 clf (nf) 10 15 20 25 30 35 40 45 50 68 pf luminance 100 pf luminanc e 68 pf current 100 pf current luminance (fl) current (ma) 0 1 2 3 4 5 6 7 8 9 0.0 1.0 2.0 3.0 4.0 5.0 6.0 clf (nf) 10 15 20 25 30 35 40 45 50 68 pf luminance 100 pf luminance 68 pf current 100 pf current luminance (fl) current (ma)
iv. wave-shape (rd) selection the r d resistor determines the slope of the charge and discharge portions of the output waveform. the optimal value of this resistor depends on the lamp size and drive conditions. typical values range from 0 - 2.0k . recommended starting values for various lamp sizes are shown in the table below. the optimal waveform is trapezoidal which will result in the best combination of high brightness and low audible noise performance. using a larger value of rd than recommended will result in a triangular waveform and correspond to reducing the audible noise of the el lamp and increase lamp life. however, the luminance of the el lamp will decrease. using a smaller value of rd than recom- mended will result in a square waveform and correspond to higher initial luminance from the el lamp, but will not take advantage of the noise reduction capability of the d372. typical waveforms corresponding to the selected r d values for a 2in 2 lamp and a 4in 2 lamp are shown below. rd = 820 optimal waveform for 2 in 2 rd lamp size 1.2k <1.0 in 2 820 1.0-2.0 in 2 470 2.0-4.0 in 2 220 >4.0 in 2 lamp size 2 in 2 rd = 1.2k reduced noise with lower luminance rd = 470 optimal waveform for 4 in 2 lamp size 4 in 2 rd = 0 higher luminance with more noise 8
v. storage capacitor (cs) selection the cs capacitor is used to store the energy transferred from the inductor. capacitors with larger values have a larger time constant and will store the energy for longer periods of time. the recommended cs values range from 10nf to 47nf and are to be rated to at least 100v. larger el lamps typically require larger values of cs. in general, increasing the value of cs will increase the rms voltage and increase the brightness of an el lamp. typical waveforms for varying cs values for a 2.0 in 2 lamp are shown below. cs = 10nf cs = 22nf cs = 47nf 9
d372 design ideas i. lamp frequency control with an external clock signal an external clock signal may be used to control the el lamp frequency (lf) by applying the clock signal to the clf pin. the oscillator frequency can be varied to synchronize the inverter with other elements in the application. an internal divider network in the ic divides the clock signal by two. the recommended clocking frequencies range from 500hz to 1khz and result in an el lamp frequency range of 250hz to 500hz respectively. the amplitude of the clock signal typically ranges from 1.0v to v+. ii. controlling el brightness through clock pulse width modulation an external clock signal may be used to control the inductor oscillating frequency (hf). pulse width modulation of the external clock signal may be used to regulate the brightness of an el lamp. in this circuit, when the positive duty cycle of the external clock is at 20%, the lamp is at full brightness. incremental dimming occurs as the positive duty cycle is increased to as high as 85%. this scheme may also be used inversely to regulate lamp brightness over the life of the battery or to compensate for lamp aging. (note: operation at duty cycles higher than 85% and lower than 20% is not recommended.) the recommended clocking frequency ranges from 10khz to 24khz, and the amplitude of the clock signal typically ranges from 1.0v to v+. 10 v+ clf chf e gnd rd el2 el1 cs l+ d372a 1 2 3 4 5 10 9 8 7 6 chf 0.1 f vbat off on el lamp l cs rd vbat 1v 0v lf clk 50%dc v+ clf chf e gnd rd el2 el1 cs l+ d372a 1 2 3 4 5 10 9 8 7 6 clf 0.1 f vbat off on el lamp l cs rd vbat hf clk 20%-85% +dc 1v 0v
iii. split voltage supply a split supply voltage may also be used to drive the d372. to operate the on-chip logic, a regulated voltage supply (v+) ranging from 2.0v to 6.5v is applied. to supply the d372 with the necessary power to drive an el lamp, another supply voltage (vbat) is applied to the inductor. the voltage range of vbat is determined by the following conditions: driver application, lamp size, inductor selection, and voltage and current limitations. two different examples of the split supply are shown below. the first example shows a regulated 3.0v applied to the v+ pin, and a vbat voltage that may range from 2.7v to 4.5v. the enable voltage is in the range of 2.0v to 3.0v. this is a typical setup used in cell phone applications. the second example shows that v+ may range from 2.0v to 6.5v, and the vbat voltage may be as high as 12.0v. the enable voltage is in the range of 2.0v to v+. this is useful in many high voltage applications. 11 v+ clf chf e gnd rd el2 el1 cs l+ d372a 1 2 3 4 5 10 9 8 7 6 chf 0.1 f v+ regulated 3.0 v 0 v off 2.0v - 3.0v on el lamp l cs rd vbat 2.7 v - 4.5 v clf v+ clf chf e gnd rd el2 el1 cs l+ d372a 1 2 3 4 5 10 9 8 7 6 chf 0.1 f v+ 2.0 v - 6.5 v 0v off 2.0v - v+ on el lamp l cs rd vbat 12.0 v clf
the d372a ic is available in standard msop-10 plastic package per tape and reel. a durel d372 designers kit (1ddd372aa-k01) provides a vehicle for evaluating and identifying the optimum component values for any particular application using d372. durel engineers also provide full support to customers including specialized circuit optimiza- tion and application retrofits. durel corporation 2225 w. chandler blvd. chandler, az 85224-6155 tel: (480) 917-6000 fax: (480) 917-6049 website: http://www.durel.com ? 2000, 2001 durel corporation printed in u.s.a. lit-i9032 rev. a04 the durel name and logo are registered trademarks of durel corporation. this information is not intended to and does not create any warranties, express or implied, including any warranty of merchanta bility or fitness for a particular purpose. the relative merits of materials for a specific application should be determined by your evaluation. this driver is covered by the following u.s. patents: #5,313,141, #5,789,870; #6,297,597 b1. corresponding foreign patents are issued and pending. iso 9001 certified ordering information f h i a b g c d e a 0.92 0.036 1.00 0.039 1.08 0.043 b 0.05 0.002 0.10 0.004 0.15 0.006 c 0.15 0.006 0.23 0.009 0.31 0.012 d 0.40 0.016 0.55 0.022 0.70 0.028 e 0.13 0.005 0.18 0.007 0.23 0.009 f 2.90 0.114 3.00 0.118 3.10 0.122 g 0.35 0.014 0.50 0.020 0.65 0.026 h 4.75 0.187 4.90 0.193 5.05 0.199 i 2.90 0.114 3.00 0.118 3.10 0.122 mm. in. mm. in. mm. in. msop-10 min. typical max. msops are marked with part number (372a) and 3-digit wafer lot code. bottom of marking is on the pin 1 side. msops in tape and reel: 1DDD372AA-M04 recommended pad layout embossed tape on 360 mm diameter reel per eia-481-2. 2500 units per reel. quantity marked on reel label. tape orientation e c a b d f mm. in. mm. in. mm. in. min. typical max. msop-10 pad layout a 0.5 0.0197 b 2.0 0.0788 c 3.3 0.130 3.45 0.136 d 0.89 0.035 0.97 0.038 1.05 0.041 e 5.26 0.207 5.41 0.213 f 0.3 0.012 12

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