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data sheet rev. 1.2 / august 2011 zled 7320 high current 40v led driver with internal switch
zled7320 high current 40v led driver with internal switch ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. the information furnished in this publication is su bject to changes without notice. brief description the zled7x20 continuous-mode inductive step- down converter family is part of our line of led- control ics. it is designed for applications requir ing high brightness and high current. it can efficientl y drive a single led or multiple series-connected leds from a voltage input higher than the led for- ward voltage: vin = 6 to 40 vdc. it provides an adjustable output current 1.2a, which is set via an external resistor and controlled by the zled7x20s integrated high-side output current-sensing circuit and high speed internal 40v power switch. an external control signal, which can be a dc voltage, pwm, or microcontroller-generated waveform, on the adj pin can also be used to linearly adjust a continuous output current or to control a gated out - put current. the output can be turned off by applying a voltage lower than 0.2v to the adj pin, which puts the zled7x20 in a low-current standby state. the zled7x20 enables diverse industrial and consumer lighting applications requiring high driving currents, wide operating voltage range, high efficiency, and variable brightness control. i t offers over-temperature and led open-circuit pro- tection. the zled7x20 can also minimize bill-of- material costs because very few external com- ponents are required for most applications. only a resistor, a diode, an inductor, and three capacitor s are needed for a typical basic application. zled7x20 typical application circuit features up to 1.0a output current internal 40v power switch wide dc input voltage range 6 to 40 vdc output current accuracy: 3% (typical) dimming ratio: 1200:1 led open-circuit protection thermal shutdown protection benefits high efficiency: up to 98% single pin on/off and brightness control using dc voltage or pwm very few external components needed for operation footprint compatible to our zled7000 depending on the application. available support evaluation kit physical characteristics operating temperature: -40c to 105c switching frequency: up to 1mhz zled7x20 family selection matrix product max. current output package zled7020 1.2a sot89-5 zled7320 1.0a dfn-5 zled7520 0.75a dfn-5 zled7720 0.35a dfn-5 for additional information on our zled driver family, visit www.zmdi.com/products/led-drivers/
zled7320 high current 40v led driver with internal switch ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. the information furnished in this publication is su bject to changes without notice. typical applications illuminated led signs and other displays interior/exterior led lighting led street and traffic lighting (low voltage) mr16 led spot lights architecture/building led lighting retrofit led lighting fixtures led backlighting general purpose industrial and consumer led applica tions zled7x20 block diagram ordering information product sales code description package zled7020-zi1r zled7020 C high current (1200ma) 40v led driver wit h internal switch sot89-5 (tape & reel) zled7320-zi1r zled7320 C high current (1000ma) 40v led driver wit h internal switch dfn-5 (tape & reel) zled7520-zi1r zled7520 C high current (750ma) 40v led driver with internal switch dfn-5 (tape & reel) ZLED7720-ZI1R zled7720 C high current (350ma) 40v led driver with internal switch dfn-5 (tape & reel) zled7020kit-d1 zled7020-d1 demo board, 1 zled-pcb8 and 5 zled7020 ics kit zled-pcb8 test pcb with one 5w white high brightness (hb) led , cascadable to one multiple led string printed circuit board (pcb) sales and further information www.zmdi.com led_drivers@zmdi.com zentrum mikroelektronik dresden ag (zmd ag) grenzstrasse 28 01109 dresden germany zmd america, inc. 8413 excelsior drive suite 200 madison, wi 53717 usa zentrum mikroelektronik dresden ag, japan office 2nd floor, shinbashi tokyu bldg. 4-21-3, shinbashi, minato-ku tokyo, 105-0004 japan zmd far east, ltd. 3f, no. 51, sec. 2, keelung road 11052 taipei taiwan phone +49 (0)351.8822.7.533 fax +49 (0)351.8822.8.7533 phone +1 (608) 829-1987 fax +1 (631) 549-2882 phone +81.3.6895.7410 fax +81.3.6895.7301 phone +886.2.2377.8189 fax +886.2.2377.8199 disclaimer : this information applies to a product under devel opment. its characteristics and specifications are subject to change without notice. zentrum mikroelek tronik dresden ag (zmd ag) assumes no obligation regarding future manufacture unless otherwise agree d to in writing. the information furnished hereby i s believed to be true and accurate. however, under no circumstances shall zmd ag be liable to any custo mer, licensee, or any other third party for any special, indirect, in cidental, or consequential damages of any kind or n ature whatsoever arising out of or in any way relat ed to the furnishing, performance, or use of this t echnical data. zmd ag hereby expressly disclaims any liability of zmd ag to any customer, licensee or any other third party, and any such customer, licensee and any other thir d party hereby waives any liability of zmd ag for a ny damages in connection with or arising out of the furnishing, p erformance or use of this technical data, whether b ased on contract, warranty, tort (including neglige nce), strict liability, or otherwise .
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 4 of 27 contents 1 ic characteristics ................................ ................................................... ................................................... .................... 6 1.1 absolute maximum ratings ........................... ................................................... ................................................... .. 6 1.2 operating conditions .............................. ................................................... ................................................... ......... 6 1.3 electrical parameters ............................... ................................................... ................................................... ........ 7 1.4 typical operation graphs .......................... ................................................... ................................................... ...... 8 2 circuit description ............................... ................................................... ................................................... .................. 13 2.1 zled7x20 overview .................................. ................................................... ................................................... .... 13 2.2 control of output current via external sense resisto r rs .............................................. .................................... 13 2.3 control of output current via an external dc control voltage on the adj pin.............................. ...................... 13 2.4 control of output current via a pwm signal on the adj pin ............................................... ................................ 14 2.5 control of output current via a microcontroller sig nal on the adj pin .................................. .............................. 14 2.6 shutdown mode ...................................... ................................................... ................................................... ....... 14 2.7 zled7x20 protection features ........................ ................................................... ................................................. 1 4 2.7.1 thermal shut-down protection ........................ ................................................... .......................................... 14 2.7.2 led open load protection ............................ ................................................... ............................................ 14 3 application circuit design.......................... ................................................... ................................................... ............ 15 3.1 applications ....................................... ................................................... ................................................... ............. 15 3.2 thermal considerations for application design ...... ................................................... .......................................... 17 3.2.1 temperature effects of load, layout, and component se lection ........................................... ...................... 17 3.2.2 temperature effects of low supply voltage v in .................................................. ......................................... 17 3.3 external component selection ...................... ................................................... ................................................... . 17 3.3.1 sense resistor rs .................................. ................................................... ................................................... 17 3.3.2 inductor l1 ....................................... ................................................... ................................................... ....... 18 3.3.3 bypass capacitor c1 ................................ ................................................... ................................................. 1 9 3.3.4 de-bouncing capacitor c2........................... ................................................... .............................................. 21 3.3.5 capacitor c3 for reducing output ripple ........... ................................................... ....................................... 21 3.3.6 diode d1 .......................................... ................................................... ................................................... ....... 21 3.4 application circuit layout requirements ............ ................................................... .............................................. 21 4 esd protection ....................................... ................................................... ................................................... ............... 22 5 pin configuration and package ....................... ................................................... ................................................... ...... 23 5.1 sot89-5 package pin-out and dimensions for the zled7020 .................................................. ......................... 23 5.2 dfn-5 package pin-out and dimensions for the zled7320, zled7520 and zled7720 .............................. ..... 25 6 ordering information .............................. ................................................... ................................................... ............... 27 7 document revision history ......................... ................................................... ................................................... .......... 27
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 5 of 27 list of figures figure 1.1 zled7x20 supply operating current vs. input supply volt age (v in = 6 to 40 v) ...................................... ..... 8 figure 1.2 zled7x20 supply quiescent shutdown current vs. input s upply voltage (v in = 6 to 40 v) .......................... 8 figure 1.3 efficiency (%) vs. input supply voltage (v in = 6 to 40 v) per number of leds (rs=0.10 , l1=47 h).......... 9 figure 1.4 efficiency vs. input supply voltage (v in = 6 to 40 v) per number of leds (rs=0.15 , l1=47 h) ................ 9 figure 1.5 efficiency vs. input supply voltage (v in = 6 to 40 v) ? per number of leds (rs=0.30 , l1=47 h) ............. 10 figure 1.6 output current variation vs. input supply voltage (v in = 6 to 40 v) per number of leds (rs=0.15 , l1=47 h) ................................................ ................................................... ............................... 10 figure 1.7 sense voltage vs. operating temperature (rs=0.10 , l1=47 h, v in = 40 v) ........................................... . 11 figure 1.8 dimming rate with 100hz square wave control signal (p wm) at adj pin (current rise time=7.85 s) ..... 11 figure 1.9 led open-circuit protection (rs=0.30 , l1=47 h, v in = 24 v) ........................................... ....................... 12 figure 3.1 basic zled7x20 application circuit with output current determined only by rs ............................ ............ 15 figure 3.2 basic zled7x20 application circuit with output current controlled by external dc voltage .................. .... 16 figure 3.3 basic zled7x20 application circuit with output current set by external square wave voltage (pwm) .... 16 figure 3.4 basic zled7x20 application circuit with output current controlled by external microcontroller signal ...... 17 figure 5.1 zled7020 pin configuration C sot89-5 package .......... ................................................... .......................... 23 figure 5.2 sot89-5 package dimensions for the zled7020 .......... ................................................... .......................... 24 figure 5.3 zled7320, zled7520 & zled7720 pin configuration dfn-5 package ........................................... ..... 25 figure 5.4 dfn-5 (dfn4*4-05l) package dimensions for the zled732 0, zled7520 & zled7720 ........................... 26 list of tables table 3.1 recommended values for sense resistor rs (adj pin floa ting at nominal voltage v ref =1.2v) .................. 18 table 5.1 zled7020 pin descriptionssot89-5 package ............. ................................................... ......................... 23 table 5.2 zled7320, zled7520 & zled7720 pin descriptions dfn-5 package ............................................ ...... 25
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 6 of 27 1 ic characteristics note: exceeding the maximum ratings given in this s ection could cause operation failure and/or cause p ermanent damage to the zled7x20. exposure to these condition s for extended periods may affect device reliabilit y. 1.1 absolute maximum ratings no. parameter symbol conditions min typ max unit 1.1.1 input voltage (also see specification 1.2.2) v in -0.3 50 v 1.1.2 i sense pin voltage v isense v in 5v v in -5v v in +0.3v v v in <5v -0.3v v in +0.3v v 1.1.3 lx pin output voltage v lx -0.3 50 v 1.1.4 adj pin input voltage v adj -0.3 6 v 1.1.5 lx pin switch output current i lx 1.5 a 1.1.6 power dissipation p tot 0.5 w 1.1.7 esd performance human body model 3.5 kv 1.1.8 junction temperature t j 150 c 1.1.9 junction to ambient thermal resistance r ja 100 k/w 1.1.10 storage temperature t s -55 150 c 1.2 operating conditions no. parameter symbol conditions min typ max unit 1.2.1 operating temperature t amb -40 105 c 1.2.2 input voltage (also see specification 1.1.1) v in 6 40 v
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 7 of 27 1.3 electrical parameters test conditions for the following specifications ar e t amb = 25c typical and v in = 12v unless otherwise noted. production testing of the chip is performed at 25c unless otherwise stated. functional operation of t he chip and specified parameters at other temperatures are guar anteed by design, characterization, and process con trol. no. parameter symbol conditions min typ max unit 1.3.1 quiescent supply current i inqoff output offadj pin grounded 90 120 160 a i inqon output switchingadj pin floating 450 600 a 1.3.2 mean current sense threshold voltage v sense 97 100 103 mv 1.3.3 sense threshold hysteresis v sensehys 15 % 1.3.4 i sense pin input current i sense v sense = v in -0.1v 8 a 1.3.5 internal reference voltage measured at adj pin v ref adj pin floating 1.2 v 1.3.6 resistance between v ref and adj pin r adj 500 k 1.3.7 external dc brightness control voltage on adj pin v adj 0.3 1.2 v 1.3.8 dc on-off control voltage on adj pin for switching zled7x20 from active state to quiescent state v adjoff v adj falling 0.15 0.2 0.25 v 1.3.9 dc off-on control voltage on adj pin for switching zled7x20 from quiescent state to active state v adjon v adj rising 0.2 0.25 0.3 v 1.3.10 lx switch continuous current i lxmean_0 zled7020 1.2 a i lxmean_3 zled7320 1.0 a i lxmean_5 zled7520 0.75 a i lxmean_7 zled7720 0.35 a 1.3.11 lx switch leakage current i lx(leak) 1 a 1.3.12 lx switch on resistance r lx 0.27 0.4 1.3.13 minimum switch on time t onmin lx switch on 200 ns 1.3.14 minimum switch off time t offmin lx switch off 200 ns 1.3.15 dimming rate d dim 1 led, f =100hz, vin=15v, l1 = 27 h 1200:1 1.3.16 recommended operating frequency maximum f lxmax 1 mhz 1.3.17 recommended output switch duty cycle range at f lxmax d lx 0.3 0.9
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 8 of 27 0 100 200 300 400 500 600 5 10 15 20 25 30 35 40 vin(v) icc(ua) 0 50 100 150 200 250 5 10 15 20 25 30 35 40 vin(v) icc(ua) no. parameter symbol conditions min typ max unit 1.3.18 propagation delay of internal comparator t pd 50 ns 1.3.19 thermal shutdown temperature t sd 150 c 1.3.20 thermal shutdown hysteresis t sd-hys 20 k 1.4 typical operation graphs the curves are valid for the typical application ci rcuit and t amb = 25c unless otherwise noted. figure 1.1 zled7x20 supply operating current vs. inp ut supply voltage (v in = 6 to 40 v) figure 1.2 zled7x20 supply quiescent shutdown current vs. input supply voltage (v in = 6 to 40 v)
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 9 of 27 rs=0.15 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 5 10 15 20 25 30 35 40 vin(v) effiency(%) 1led 3led 7led 10led rs=0.10 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 5 10 15 20 25 30 35 40 vin(v) effiency(%) 1led 3led 7led 10led figure 1.3 efficiency (%) vs. input supply voltage (v in = 6 to 40 v) ? per number of leds (rs=0.10 , l1=47 h) figure 1.4 efficiency vs. input supply voltage (v in = 6 to 40 v) ? per number of leds (rs=0.15 , l1=47 h) ? minimum v in depends on number of leds. ? minimum v in depends on number of leds.
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 10 of 27 rs=0.30 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 5 10 15 20 25 30 35 40 vin(v) effiency(%) 1led 3led 7led 10led rs=0.15 0.6 0.61 0.62 0.63 0.64 0.65 0.66 0.67 0.68 0.69 0.7 5 10 15 20 25 30 35 40 vin(v) iout(a) 1led 3led 7led 10led figure 1.5 efficiency vs. input supply voltage (v in = 6 to 40 v) ? per number of leds (rs=0.30 , l1=47 h) figure 1.6 output current variation vs. input supply voltage (v in = 6 to 40 v) per number of leds (rs=0.15 , l1=47 h) minimum v in depends on number of leds.
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 11 of 27 97.8 98.0 98.2 98.4 98.6 98.8 99.0 99.2 99.4 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 vsense(mv) v sense (mv) temperature ( c) trigger c1 hfr stop -50mv edge positive timebase -3.00 ms 1.00ms/div 500ks 50 ms/s figure 1.7 sense voltage vs. operating temperature (r s=0.10 , l1=47 h, v in = 40 v) figure 1.8 dimming rate with 100hz square wave cont rol signal (pwm) at adj pin (current rise time=7.85 s)
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 12 of 27 trigger c1 dc stop 15.0v edge negative timebase -5.2 s roll 5.00s/div 500ks 10 ks/s figure 1.9 led open-circuit protection (rs=0.30 , l1=47 h, v in = 24 v)
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 13 of 27 rs v1.0 i outnom = s adj outdc r v 083.0 i * = 2 circuit description 2.1 zled7x20 overview the zled7x20 is a continuous-mode inductive step-do wn converter led driver for driving single or multi ple series-connected leds from a voltage input higher t han the led voltage (vin = 6 to 40 vdc; see section 3.2.2 for important details). the zled7x20 provides an adjust able output current (1.2a maximum for zled7020; 1.0 a maximum for zled7320; 0.75a maximum for zled7520; 0 .35a maximum for zled7720), which is nominally set via an external sense resistor rs and controlled by the zled7x20s integrated high-si de output current-sensing circuit and output switch. an external control sign al (e.g., dc voltage, pwm waveform, or microprocess or signal) on the adj pin can be used to linearly adjust the o utput for continuous, variable, or gated-output cur rent. see page 3 for a block diagram of the zled7x20. the output can be turned off by applying a voltage 0.2v (typical) to the adj pin, which puts the zled7 x20 in a low-current standby state. see section 2.6 for a de scription of this shutdown mode. only a resistor, a diode, an inductor, and three ca pacitors are needed for a typical basic application . refer to the application circuits in section 3 for the location of the components referenced in the following secti ons. 2.2 control of output current via external sense re sistor rs external sense resistor rs, which is connected betw een the v in and i sense pins as shown in figure 3.1, sets i outnom , the nominal average output current. equation (1) can be used to calculate the nominal output current , which is the lx switch output current i lx if the adj pin is floating (v adj = v ref =1.2v). see section 3.3.1 for recommended values for rs in a typical basic applic ation and section 3.4 for layout guidelines for rs. note that the peak i outnom including ripple (see section 3.3.5) must not exce ed the maximum current specifications (1.3.10). (1) 2.3 control of output current via an external dc co ntrol voltage on the adj pin an external dc voltage (v adj ) input on the adj pin can control brightness by se tting the output current to a value below the nominal average current i outnom determined by r s . with this method, the output current can be adjus ted from 25% to 100% of i outnom . the dc voltage source must be capable of driving the adj pins input impedance r adj (500k approximately 25%; internal pull-up resistor to v ref ). see figure 3.2 for a typical application circuit . the nominal average output current i outdc resulting from an external dc control voltage v adj can be calculated via equation (2) where 0.3v v adj 1.2v: (2) brightness is 100% if v adj = v ref, the internal reference voltage, which can be measur ed on the adj pin when it is floating (1.2v, typical). if v adj 1.2v, current is automatically clamped at 100% brig htness. note: absolute maximum v adj = 6v.
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 14 of 27 2.4 control of output current via a pwm signal on t he adj pin an external pulse width modulation (pwm) control si gnal input on the adj pin can be used for brightnes s or gated on/off control of the output current by driving the output current to a value below the nominal averag e current determined by r s . see figure 3.3 for a typical application circuit. the pwm or gated on/off control signal can be within the range of 0 to 5 v. the logic high level must be higher than 1.2v and the logic low level mu st be below 0.2v. it must be capable of driving the adj pins i nput impedance r adj (approximately 500k ; internal pull-up resistor to v ref ). 2.5 control of output current via a microcontroller signal on the adj pin an external control signal from the open drain outp ut of a microcontroller can provide on/off or pwm b rightness control by driving the adj pin. see figure 3.4 for a typical application circuit. diode d2 and resisto r r1 shown in figure 3.4 suppress any negative high-amplitude spi kes on the adj input due to the drain-source capaci tance of the fet in the microcontrollers output. negative s pikes on the adj input could cause output current e rrors or unintended zled7x20 operation. the signal input to the adj pin must be capable of driving the adj pin s input impedance r adj (approximately 500k ; internal pull-up resistor to vref). 2.6 shutdown mode if the adj pin voltage v adj is v adjoff (0.2v 0.05v), the supply current and output on t he lx pin are quiescent at a low standby level (i inqoff = 120 a nominal). raising the adj pin voltage so that v adj v adjion (0.25v 0.05v) will switch the output back to full operational mod e. 2.7 zled7x20 protection features 2.7.1 thermal shut-down protection the zled7x20 automatically protects itself from dam age due to over-temperature conditions. if the zled 7x20s temperature exceeds the thermal shutdown threshold (t sd = 150c, typical), the zled7x20 will shutdown. to avoid erratic zled7x20 operation, a 20k hysteresis (t sd-hys ) is applied that prevents it from returning to ope ration until its temperature falls below the hysteresis th reshold (t sd - t sd-hys ). also refer to section 3.2 for additional thermal considerations. 2.7.2 led open load protection as a step-down converter, the zled7x20 has inherent open-load circuit protection. since the l1 inducto r is connected in series with the led string, the curren t flow is interrupted if the load is open and the l x output of the zled7x20 will not be damaged. this provides an adva ntage over other products such as boost converters, for which the internal switch can be damaged by back em f forcing the drain above its breakdown voltage.
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 15 of 27 vin i sense lx gnd zled7x20 d1 led string vs = 6 to 40 vdc c3 rs l1 c1 c2 0.1f adj 3 application circuit design 3.1 applications the zled7x20 is designed for applications requiring features such as high-speed switching, variable br ightness control, operation with voltages up to 40v, high ef ficiency, or protection from over-temperature, or o pen led circuit conditions. typical applications include mr16/mr11 led spot lig hts, led street lights, parabolic aluminized reflec tor (par) led lights, and other general purpose industrial an d consumer led applications. figure 3.1, figure 3.2, figure 3.3, and figure 3.4 demonstrate basic application circuits for the four options for controlling output current described in section 2. figure 3.1 basic zled7x20 application circuit with o utput current determined only by rs
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 16 of 27 vin i sense lx gnd zled7x20 d1 vs = 6 to 40 vdc c3 rs l1 c1 c2 0.1f adj + _ dc (0.3v to 1.2v) led string figure 3.2 basic zled7x20 application circuit with o utput current controlled by external dc voltage figure 3.3 basic zled7x20 application circuit with o utput current set by external square wave voltage (pwm)
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 17 of 27 figure 3.4 basic zled7x20 application circuit with o utput current controlled by external microcontroller signal 3.2 thermal considerations for application design 3.2.1 temperature effects of load, layout, and comp onent selection do not exceed the package power dissipation limits by driving high load currents or by operating the c hip at high ambient temperatures. power dissipation also increa ses if the efficiency of the circuit is low as coul d result from selecting the wrong coil or from excessive parasiti c output capacitance on the switch output. see the layout guidelines in section 3.4. 3.2.2 temperature effects of low supply voltage v in until the supply input voltage on the v in pin has risen above the internally-set startup thre shold, the zled7x20s internal regulator disables the drive to the intern al power mosfet output switch. above this threshold , the mosfet on-resistance is low enough for the chip to start to operate; however, if the supply voltage re mains below the specified minimum (6v), the duty cycle of the output switch will be high and the zled7x20 po wer dissipation will be at a maximum. avoid operating t he zled7x20 under such conditions to reduce the ris k of damage due to exceeding the maximum die temperature . when driving multiple leds, their combined forwar d voltage drop is typically high enough to prevent th e chip from switching when v in is below 6v, so there is less risk of thermal damage. 3.3 external component selection note: also see section 3.4 for layout guidelines fo r the following external components. 3.3.1 sense resistor rs table 3.1 gives values for rs under normal operatin g conditions in the typical application shown in fi gure 3.1. these values assume that the adj pin is floating an d at the nominal voltage of v ref =1.2v. note: under the conditions given in table 3.1, in o rder to maintain the switch current below the maxim um value specified in section 1, 0.082 is the minimum value for rs for the zled7020, 0.1 for the zled7320, 0.13 for the zled7520 and 0.27 for the zled7720. it is possible to use different values of rs if the adj pin is driven from an external voltage.
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 18 of 27 ) (* * lx l s avg led in on r r r i v v i l t + + - - d = ) (* * l s avg d led off r r i v v i l t + + + d = to ensure stable output current, use a 1% accuracy resistor with adequate power tolerance and a good temperature characteristic for rs. table 3.1 recommended values for sense resistor rs (adj pin floating at nominal voltage v ref =1.2v) nominal average output current (ma) value for r s ( ) 1200 (maximum for zled7020) 0.082 1000 (maximum for zled7320) 0.1 750 (maximum for zled7520) 0.13 667 0.15 350 (maximum for zled7720) 0.27 333 0.3 3.3.2 inductor l1 the recommended range for the l1 inductor is 33 h to 220 h. select the inductor value for l1 as needed to ensure that switch on/off times are optimized acros s the load current and supply voltage ranges. if th e application requires a high supply voltage and low output curre nt, inductance values at the high end of this range are recom- mended to minimize errors due to switching delays, which can reduce efficiency and increase ripple on the output. also see section 3.4 for layout considerations for l1. equations (3) and (4) can be used to calculate t on and t off . on time for lx switch (t onmin >200ns): (3) off time for lx switch (t offmin >200ns): (4) where: symbol description l l1 coil inductance in h ? i l1 coil peak-peak ripple current in a (internally s et to 0.3 * i avg ) v in supply voltage in v v led total forward voltage in v for led string i avg nominal average led current in a rs external current sense resistor in r l l1 coil resistance in r lx lx switch resistance in v d d1 diode forward voltage at the required load curr ent in v
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 19 of 27 khz 8. 121 s 56.5 s 64.2 1 t t 1 f off on lx = m + m = + = 3.0 s 56.5 s 64.2 s 64.2 t t t v 12 v4.3 v v d off on on in led lx ? m + m m = + ? = = ( ) s 56.5 26.0 30.0*a 333.0 v 36.0 v4.3 a 333.0*3.0*h 220 t off m = w +w + + m = ( ) s 64.2 27.0 26.0 3.0*a 333.0 v4.3 v 12 a 333.0*3.0*h 220 t on m = w +w +w - - m = the inductance value has an equivalent effect on t on and t off and therefore affects the switching frequency. for the same reason, the inductance has no influence on the duty cycle, for which the relationship of the summed led forward voltages n * v f to the input voltage v in is a reasonable approximation. because the input v oltage is a factor in the on time, variations in the input volt age affect the switching frequency and duty cycle. to achieve optimum performance, duty cycles close t o 0.5 at the nominal average supply voltage are pre ferable for improving the temperature stability of the outp ut current. equations (5), (6), (7), and (8) provide an example of calculating t on , t off , operating frequency f lx , and duty cycle d lx when using a 220 h inductor for l1 and v in =12v, rs = 0.30 , r l =0.26 , v led =3.4v, i avg =333ma, v d =0.36v, and r lx =0.27 . example: (5) (6) (7) (8) for the l1 inductor, use a coil with a continuous c urrent rating higher than the required mean output current and a saturation current that exceeds the peak output cur rent by 30% to 50% for robustness against transient con- ditions; e.g., during start-up. 3.3.3 bypass capacitor c1 the bypass capacitor c1 has two functions: maintain ing operating voltage and bypassing the current rip ple of the switching converter. in general low esr capacitors must be used. if the circuit is supplied by rectified line voltag e, c1 must provide enough charge to maintain the zl ed7x20s minimum operating voltage as well as the forward vo ltage of the led string to keep the application wor king even if the rectified supply voltage periodically drops below these values. a rough estimate for the minimu m capacity needed can be calculated with equation (9).
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 20 of 27 lx max lx f max d avg min f* v d*i v t* i 1c d = d = f 135 v2.3*3 2 *v 24 ms 10*a 33.0 1c min m = - = ripple on avg min v t* i 1c = (9) where: symbol description i avg average nominal led string current assuming that the contribution of the ic supply current is negligible. t d discharge time at given ac frequency. will be a maxi mum of 10ms (? period duration) at 50hz. ? v max peak rectified supply voltage minus led string forwar d voltage or minimum zled7x20 supply voltage, whichever is greater. example: for an application with 3 leds with 3.2v f orward voltage each driven at 0.33a and supplied wi th rectified 24vac, a minimum bypass capacitor c1 of 2 20 f or 330 f might be adequate. compared to the calculation, a safety margin of about 50% must be a dded to consider temperature effects and aging. (10) a second function of c1 is to bypass the current ri pple of the switching converter and thus prevent it from disturbing a stable ic supply or backlash on the po wer supply circuit. for this reason, even in dc-sup plied applications, the use of an adequate c1 might be us eful. the defining parameters are now as shown in equation (11): (11) where: symbol description i avg average nominal led string current. t on on time of the internal mosfet output switch. note: t on must be longer than t onmin =200ns. v ripple permissible voltage ripple on the supply voltage.
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 21 of 27 nf 367 1.0*v 24 s 67.2*a 33.0 1c min = m = example: for an application of 3 leds driven at 0.3 3a and supplied with 24vdc, a maximum ripple of 10% is allowed. the zled7x20 is operated at 150khz with a duty cycle of 0.4 leading to an on time of 2.67 s. as calculated in equation 12, a capacitor c1 of 470nf may be adequate, again including a safety margin of about 50%. (12) to achieve maximum stability over temperature and v oltage, an x7r, x5r, or better dielectric is recomm ended while y5v must be avoided. 3.3.4 de-bouncing capacitor c2 external capacitor c2 minimizes ground bounce durin g switching of the internal mosfet output switch. g round bounce is typically caused by parasitic inductance and resistance due to the distance between the grou nds for the power supply and the zled7x20 gnd pin. use a 0.1 f, x7r ceramic capacitor to ground for c2. 3.3.5 capacitor c3 for reducing output ripple if required, the c3 can be used to reduce peak-to-p eak ripple current in the led string. low esr capac itors should be used because the efficiency of c3 largely depends on its esr and the dynamic resistance of t he leds. for an increased number of leds, using the same cap acitor will be more effective. lower ripple can be achieved with higher capacitor values, but this will increas e start-up delay by reducing the slope of the led v oltage as well as cause increased current during converter start-u p. the capacitor will not affect operating frequenc y or effici- ency. for a simulation or bench optimization, c3 va lues of a few f are an applicable starting point for the given configuration. ripple current reduction is approxim ately proportional to the value of c3. 3.3.6 diode d1 the flyback diode d1 must have a continuous current rating greater than the maximum output load curren t and a peak current rating higher than the peak l1 coil cu rrent. important: use a low-capacitance, fast schot tky diode that has low reverse leakage at the maximum operati ng temperature and maximum operating voltage for th e application to avoid excess power dissipation and o ptimize performance and efficiency. for silicon dio des, there is a concern that the higher forward voltage and incre ased overshoot from reverse recovery time could inc rease the peak lx pin voltage (v lx ). the total voltage v lx (including ripple voltage) must not be >50v. 3.4 application circuit layout requirements the following guidelines are strongly recommended w hen laying out application circuits: important: locate the l1 inductor and the c1 input decoupling capacitor as close as possible to the zled7x20 to minimize parasitic inductance and resis tance, which can compromise efficiency. use low resistance connections from l1 to the lx and v in pins. all circuit board traces to the lx pin must be as s hort as possible because it is a high-speed switchi ng node. if the adj pin floats, all circuit board traces to the adj pin must be as short as possible to reduce noise pickup.
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 22 of 27 do not lay out high-voltage traces near the adj pin because if the board is contaminated, leakage curr ent can affect the adj pin voltage and cause unintended output current. to further reduce this risk, use a ground ring around the adj pin. (also see section 2 .7 regarding the zled7x20s protection circuitry fo r preventing excessive output current.) to minimize ground bounce, locate the 0.1 f external capacitor c2 as close as possible to the v in pin and solder the zled7x20s gnd pin directly to the groun d plane. (also, see section 3.3.4 regarding ground bounce.) because rs is typically a low value resistor, it is important to consider the resistance of the traces in series with r s as part of the total current sense resistance. use traces that are as short and wide as possible to minimize this effect. the zled7x20s thermal pad must be grounded. 4 esd protection all pins have an esd protection of 3 3500v according to the human body model (hbm). th e esd test follows the human body model with 1.5 k /100 pf based on mil 883-h, method 3015.8.
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 23 of 27 lx v in gnd thermal pad adj i sense 5 pin configuration and package 5.1 sot89-5 package pin-out and dimensions for the zled7020 figure 5.1 zled7020 pin configuration C sot89-5 packag e table 5.1 zled7020 pin descriptionssot89-5 package pin no. description (also see section 3.3 for layout guidelines) lx 1 drain of internal power switch gnd 2 ground adj 3 on/off and brightness control input i sense 4 current adjustment input. resistor r s from i sense to v in determines the nominal average output current. i outnom =0.1v/r s thermal pad connect to gnd. v in 5 input voltage (6v to 40v).
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 24 of 27 b b1 e1 e d d 1 l e 1 e figure 5.2 sot89-5 package dimensions for the zled7020 symbol dimension (mm) min max a 1.400 1.600 b 0.320 0.520 b1 0.360 0.560 c 0.350 0.440 d 4.400 4.600 d1 1.400 1.800 e 2.300 2.600 e1 3.940 4.250 e 1.500 typical e1 2.900 3.100 l 0.900 1.100
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 25 of 27 lx gnd adj v in i sense 12 3 4 5 12 3 4 5 top bottom 5.2 dfn-5 package pin-out and dimensions for the zl ed7320, zled7520 and zled7720 figure 5.3 zled7320, zled7520 & zled7720 pin configura tion dfn-5 package table 5.2 zled7320, zled7520 & zled7720 pin descriptio ns dfn-5 package pin no. description (also see section 3.3 for layout guidelines) lx 1 drain of internal power switch gnd 2 ground adj 3 on/off and brightness control input i sense 4 current adjustment input. resistor r s from i sense to v in determines the nominal average output current. i outnom =0.1v/r s thermal pad connect to gnd. v in 5 input voltage (6v to 40v).
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 26 of 27 figure 5.4 dfn-5 (dfn4*4-05l) package dimensions for the zled7320, zled7520 & zled7720 b a c n m d j i g h k1 e k f symbol dimension (mm) min max a 3.95 4.05 b 3.95 4.05 c 0.70 0.80 d 0.37 0.47 e 0.75 0.95 f 2.17 2.42 g 1.50 h 0.41 0.51 i 0.55 j 1.70 k 1.75 k1 1.40 1.55 m 0.000 0.050 n 0.200
zled7320 high current 40v led driver with internal switch data sheet august 12, 2011 ? 2011 zentrum mikroelektronik dresden ag rev. 1.2 all rights reserved. the material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. t he information furnished in this publication is subject to changes without notice. 27 of 27 6 ordering information ordering information product sales code description package zled7020-zi1r zled7020 C high current (1200ma) 40v led driver wit h internal switch sot89-5 (tape & reel) zled7320-zi1r zled7320 C high current (1000ma) 40v led driver wit h internal switch dfn-5 (tape & reel) zled7520-zi1r zled7520 C high current (750ma) 40v led driver with internal switch dfn-5 (tape & reel) ZLED7720-ZI1R zled7720 C high current (350ma) 40v led driver with internal switch dfn-5 (tape & reel) zled7020kit-d1 zled7020-d1 demo board, 1 zled-pcb8 and 5 zled7020 ics kit zled-pcb8 test pcb with one 5w white high brightness (hb) led , cascadable to one multiple led string printed circuit board (pcb) zled-pcb2 10 unpopulated test pcbs for modular led string wit h footprints of 9 common hb led types printed circuit board (pcb) 7 document revision history revision date description 1.0 june 27, 2011 first issue. 1.1 august 9, 2011 second issue. updated demo kit desc ription. 1.2 august 12, 2011 third issue. updated to include zled7520 & zled7720. updated demo kit description sales and further information www.zmdi.com led_drivers@zmdi.com zentrum mikroelektronik dresden ag (zmd ag) grenzstrasse 28 01109 dresden germany zmd america, inc. 8413 excelsior drive suite 200 madison, wi 53717 usa zentrum mikroelektronik dresden ag, japan office 2nd floor, shinbashi tokyu bldg. 4-21-3, shinbashi, minato-ku tokyo, 105-0004 japan zmd far east, ltd. 3f, no. 51, sec. 2, keelung road 11052 taipei taiwan phone +49 (0)351.8822.7.533 fax +49 (0)351.8822.8.7533 phone +1 (608) 829-1987 fax +1 (631) 549-2882 phone +81.3.6895.7410 fax +81.3.6895.7301 phone +886.2.2377.8189 fax +886.2.2377.8199 disclaimer : this information applies to a product under devel opment. its characteristics and specifications are subject to change without notice. zentrum mikroelek tronik dresden ag (zmd ag) assumes no obligation regarding future manufacture unless otherwise agree d to in writing. the information furnished hereby i s believed to be true and accurate. however, under no circumstances shall zmd ag be liable to any custo mer, licensee, or any other third party for any special, indirect, in cidental, or consequential damages of any kind or n ature whatsoever arising out of or in any way relat ed to the furnishing, performance, or use of this t echnical data. zmd ag hereby expressly disclaims any liability of zmd ag to any customer, licensee or any other third party, and any such customer, licensee and any other thir d party hereby waives any liability of zmd ag for a ny damages in connection with or arising out of the furnishing, p erformance or use of this technical data, whether b ased on contract, warranty, tort (including neglige nce), strict liability, or otherwise .
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