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data sheet rev. 1.0 0 / december 2011 zled7015 1.0mhz boost converter with internal 35v switch
z led7015 1.0mhz boost converter with internal 35v switch ? 2011 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. the material c o ntained herein may not be reproduced, adapted, merged, t ranslated, stored, or used without the prior written consent of the copyright owner. the information furnished in this publication is subject to changes without notice. brief description the zled7 015 , one of our zled f amily of led control ics, is a constant current boost converter w ith an inter nal high - power 35 v switch. it is opti - mal for driving multiple white le ds connected in series so that the led current is uniform for better brightness and color control . it can also drive devices that require a constant voltage and is c apable of operating efficiently with voltage s upplies ranging from 6 vdc to 3 0 vdc . it is ideal for diverse lighting appli cations requiring low sup - ply voltages such as selv applications . typically, s maller, less expensive external components can be used since the zled7015 switches at 1 .0mhz (typical) . the zled7015 output current is adjustable via an external current sense resistor r s connected from the fb pin to ground. the zled7015 improves efficiency and minimizes power losses in the current setting resistor r s by use of an internal 0.3v feedback ref erence vol - tage . dimming can be controlled using a pulse - width modulation (pwm) waveform or a dc voltage applied to the fb pin. the zled7015 provides a soft - start function to prevent excessive in - rush current on start - up and ensure s a controlled rise o f the output voltage . over - voltage protection is adjustable via external resistors r 1 and r 2 . zled7015 typical application circuit features ? integrated 3 5 v power switch ? w ide input range : 6 vdc to 3 0 vdc ? over - temperature protection ? over - voltage (open led st ring) protection adjusted via external resistor divider ? under - voltage lockout ensures reliable circuit operation ? control of output current during start - up via internal soft - start ? switching f requen cy: 1 . 0 mh z ? single pin on/off or brightness control via pw m, microcontroller, or dc voltage control signal input ? msop - 10 package benefits ? high efficiency: up to 95 % efficiency ? few small, low - profile components needed for operation ? small form - factor package available support ? evaluation kit physical characteristi cs ? operating temperature: - 40 c to 85 c ? rohs - compliant e n l x z l e d 7 0 1 5 l e d s t r i n g v i n = 6 t o 3 0 v d c c o u t r 1 l 1 c i n d 1 f b p g n d a g n d o v p r 2 r s v p v d d c 1 c v d d c v p c 2 r v d d r e n c o v p v o u t
z led7015 1.0mhz boost converter with internal 35v switch ? 201 1 zentrum mik roelektronik dresden ag rev. 1.00 all rights reserved. the materi al c o ntained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. typical applications ? low - voltage retro - fit lighting ? architectural/building lighting ? mr16 lights ? replacement tubes ? selv lighting ? led backlighting ? signage and outdoor lighting ? general purpose low - voltage industrial and consumer applications zled7015 block diagram ordering information product s ales code description package zled7015 - zi1r zled7015 C 1 .0 mhz boost converter with internal 35v switch msop - 10 (tape & reel) zled7015kit - e 1 zled7015 - e 1 evaluation board, 1 zled - pcb10 , and 5 zled7015 ics kit sales and further information www.zmdi.com led_drivers@zmdi.com zentrum mikroelektronik dresden ag grenzstrasse 28 01109 dresden germany zmd america, inc. 275 south 5th avenue pocatello, id 83201 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 zentrum mikroelektronik dresden ag, korean office posco centre building west tower, 11th floor 892 daechi, 4 - dong, kangnam - gu seoul, 135 - 777 korea phone +49.351.8822.7.533 fax +49.351.8822.8.7533 phone +1.208.478.7200 fax +1.208.478.7200 phone +81.3.6895.7410 fax +81.3.6895.7301 phone +886.2.2377.8189 fax +886.2.2377.8199 phone +82.2.559.0660 fax +82.2.559.0700 disclaimer : this information applies to a product under development. its characteristics and specifications are subject to change without notice. zentrum mikroelektronik dresden ag (zmd ag) assumes no obligation regarding future manufacture unless otherwise agreed to in writing. the information furnished hereby is believed to be true and accurate. however, under no circumstances shall zmd ag be liable to any customer, licensee, or any other third party for any special, indirect, incide ntal, or consequential damages of any kind or nature whatsoever arising out of or in any way related to the furnishing, performanc e, or use of this technical 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 third party hereby waives any liability of zmd ag for any da mages in connection with or arising out of the furnishing, performance or use of this technical data, whether based on contract, warranty, tort (including negligence), strict liability , or otherwise. b a n d g a p s h u t d o w n n l e d l 1 3 , 5 4 r s c v p v i n c v d d r e n 6 t o 3 0 v d c 6 7 r v d d e n f b v d d o v p a g n d z l e d 7 0 1 5 b i a s & r e f e r e n c e 9 l d o v p c i n 2 c 1 d 1 o s c i l l a t o r c o u t c 2 l x c o v p r s s r q + C c u r r e n t l i m i t o v e r - v o l t a g e p r o t e c t i o n r a m p g e n s l o p e c o m p e n s a t i o n c u r r e n t s e n s e v r e f t h e r m a l p r o t e c t i o n r 2 r 1 1 p g n d 1 0
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 4 of 22 contents 1 ic characteristics ................................ ................................ ................................ ................................ .......................... 6 1.1 absolute maximum ratings ................................ ................................ ................................ ................................ ... 6 1.2 operating conditions ................................ ................................ ................................ ................................ ............. 6 1.3 electrical parameters ................................ ................................ ................................ ................................ ............. 7 1.4 typical operating characteristics ................................ ................................ ................................ .......................... 8 1.5 characteristic waveforms ................................ ................................ ................................ ................................ .... 10 2 circuit description ................................ ................................ ................................ ................................ ....................... 12 2.1 en pin, vp pin, and soft - st art function ................................ ................................ ................................ .............. 12 2.2 output current control ................................ ................................ ................................ ................................ ......... 12 2.2.1 output current and r s ................................ ................................ ................................ ................................ .. 12 2.2.2 dimming via external dc voltage control ................................ ................................ ................................ .... 13 2.2.3 dimming via pwm control ................................ ................................ ................................ ............................ 14 2.2.4 microcontroller led control ................................ ................................ ................................ .......................... 15 2.2.5 constant voltage application ................................ ................................ ................................ ........................ 15 3 application circuit design ................................ ................................ ................................ ................................ ........... 17 3.1 external component C r s ................................ ................................ ................................ ................................ .... 17 3.2 external component C inductor l 1 ................................ ................................ ................................ ....................... 17 3.3 external components C input decoupling capacitors c 1 and c in ................................ ................................ ........ 17 3.4 external component C output capacitors c 2 and c out ................................ ................................ ........................ 17 3.5 external component C diode d 1 ................................ ................................ ................................ .......................... 17 3.6 additional external components ................................ ................................ ................................ .......................... 17 4 operating conditi ons ................................ ................................ ................................ ................................ ................... 18 4.1 under - voltage lockout ................................ ................................ ................................ ................................ ........ 18 4.2 over - voltage threshold and open - circuit protection ................................ ................................ .......................... 18 4.3 over - temperature protection ................................ ................................ ................................ .............................. 18 5 esd/latch - up - protec tion ................................ ................................ ................................ ................................ ............ 19 6 pin configuration and package ................................ ................................ ................................ ................................ ... 19 7 layout requirements ................................ ................................ ................................ ................................ .................. 21 7.1 general considerations and ground traces ................................ ................................ ................................ ....... 21 7.2 layout considerations for c 1 , c in , c 2 and c out ................................ ................................ ................................ ... 21 7.3 layout considerations for the en pin ................................ ................................ ................................ .................. 21 7.4 layout considerations for the lx pin, l 1 external coil, and d 1 diode ................................ ................................ . 21 7.5 layout considerations for the external current sense resistor (r s ) ................................ ................................ .. 21 7.6 layout considerations for c vp and c vdd ................................ ................................ ................................ .............. 21 7.7 layout considerations for the thermal pad ................................ ................................ ................................ ......... 21 8 glossary of terms ................................ ................................ ................................ ................................ ....................... 22 9 ordering information ................................ ................................ ................................ ................................ ................... 22 10 document revision history ................................ ................................ ................................ ................................ ......... 22
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 5 of 22 list of figures figure 1.1 i out vs. v in with r s = 0.42 ................................ ................................ ................................ ............................ 8 figure 1.2 i out vs. v in with r s = 0.88 ................................ ................................ ................................ ............................ 8 figure 1.3 i o ut vs. v out with r s = 0.42 ................................ ................................ ................................ ......................... 8 figure 1.4 i out vs. v out with r s = 0.88 ................................ ................................ ................................ ......................... 8 figure 1.5 efficiency vs. v in with r s = 0.42 ................................ ................................ ................................ .................. 8 figure 1 .6 efficiency vs. v in with r s = 0.88 ................................ ................................ ................................ .................. 8 figure 1.7 efficiency vs. v out with r s = 0.42 ................................ ................................ ................................ ................ 9 figure 1.8 efficiency vs. v out with r s = 0.88 ................................ ................................ ................................ ................ 9 figure 1.9 v fb reverence voltage vs. v in ................................ ................................ ................................ ....................... 9 figure 1.10 i out vs. pwm duty cycle ................................ ................................ ................................ ................................ 9 figure 1.11 v out , v in , and i l1 during soft start ................................ ................................ ................................ ................ 10 figure 1.12 v out , v lx , and i out during typical operation ................................ ................................ ................................ 10 figure 1.13 v out , v lx , and i l1 when over - voltag e protection (ovp) threshold is exceeded ................................ ......... 11 figure 2.1 typical application circuit ................................ ................................ ................................ ............................ 13 figure 2.2 example circuit for controlling output current via an external dc control voltage ................................ .... 13 figure 2.3 example circuit for controlling output current via a pwm control signal ................................ ................... 14 figure 2.4 example circuit for constant voltage source applications ................................ ................................ .......... 16 figure 6.1 zled7015 pin configurati on msop - 10 package ................................ ................................ ...................... 19 figure 6.2 msop - 10 package dimensions for the zled7015 ................................ ................................ ...................... 20 list of tables table 1.1 absolute maximum ratings ................................ ................................ ................................ ............................ 6 table 1.2 operating conditions ................................ ................................ ................................ ................................ ...... 6 table 1.3 electrical parameters ................................ ................................ ................................ ................................ ..... 7 table 6.1 pin description msop - 10 ................................ ................................ ................................ ............................. 19
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 6 of 22 1 ic characteristics note: exceeding the maximum ratings given in this section could cause operation failure and/or cause permanent damage to the zled7015. exposure to these conditions for extended periods may affect device reliability. 1.1 absolute maximum ratings table 1 . 1 absolute maximum ratings n o . parameter symbol conditions min typ max unit 1.1.1 supply voltage on v dd pin (also see specification 1.2.2 ) v dd - 0.3 40.0 v 1.1.2 lx pin output voltage v lx - 0.3 4 0 .0 v 1.1.3 all other pins - 0.3 6 .0 v 1.1.4 esd performance human body model high voltage pins: 1, 4, 5, 9 , and 10 2.5 kv low voltage pins: 2, 3, 6, 7 , and 8 4 kv 1.1.5 junction temperature t j max - 40 1 50 c 1.1.6 storage temperature t st - 6 5 150 c 1.1.7 lead soldering temperature 10 seconds maximum 260 c 1.1.8 junction - to - ambient thermal resistance r ja 60 c/w 1.2 operating conditions table 1 . 2 operating conditions no. parameter symbol conditions min typ max unit 1.2.1 operating temperature t op - 40 + 8 5 c 1.2.2 supply voltage on v dd pin (also see absolute maxi - mum specification 1.1.1 ) v dd 6 3 0 v
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 7 of 22 1.3 electrical pa rameters test conditions for the following specifications are t amb = 25 c ( typical ) and v dd = 12v , unless otherwise noted . production testing of the zled7015 is performed at 25c unless otherwise stated. functional operation of the zled7015 and specified parameters at other temperatures are guaranteed by design, characterization, and process control. table 1 . 3 electrical parameters n o . parameter symbol conditions min typ max unit 1.3.1 supply current i dd continuous switching 2 ma quiescent: no switching 1.1 ma 1.3.2 shutdown current i sd shutdown: no switching; v en =0v 15 a 1.3.3 lx switching frequency f ocs 1 mhz 1.3.4 maximum duty cycle d lx 90 % 1.3.5 en pin on threshold voltage v en on rising v en 1.4 v 1.3.6 en pin off threshold voltage v en off falling v en 0.4 v 1.3.7 internal f eedback r eference voltage v fb 0.285 0.3 0.315 v 1.3.8 integrated switch on resistance r ds on 0.8 1.2 1.3.9 integrated switch current limit i swlimit duty cycle = 90% 1.8 2.1 2.4 a 1.3.10 integrated switch leakage current i swleak v lx = 40v 1 a 1.3.11 internal regulator v p 6v z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 8 of 22 1.4 typical operating c haracteristics th e curves are valid f or the typical application circuit and t amb = 25c unless otherwise note d . figure 1 . 1 i out vs. v in with r s = 0.42 figure 1 . 2 i out vs. v in with r s = 0.88 figure 1 . 3 i out vs. v out with r s = 0.42 figure 1 . 4 i out vs. v out with r s = 0.88 figure 1 . 5 efficiency vs. v in with r s = 0.42 figure 1 . 6 efficiency vs. v in with r s = 0.88 670 680 690 700 710 720 730 18 20 22 24 26 28 v in (v) i out (ma) v out =30v, r s =0.42 ? ,l 1 =10 ? h 330 335 340 345 350 355 360 10 15 20 25 30 i out (ma) v in (v) v out =3 0v, r s =0.88 ? ,l 1 =10 ? h 670 680 690 700 710 720 730 25 26 27 28 29 30 v in =24v, r s =0.42 ? ,l 1 =10 ? h v out (v) i out (ma) 330 335 340 345 350 355 360 12 15 18 21 24 27 30 v in =12v, r s =0.88 ? ,l 1 =10 ? h v out (v) i out (ma) 50 60 70 80 90 100 18 20 22 24 26 28 v out =30v, r s =0.42 ? ,l 1 =10 ? h v in (v) efficiency (%) 50 60 70 80 90 100 10 15 20 25 30 v out =30v, r s =0.88 ? ,l 1 =10 ? h v in (v) efficiency (%)
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 9 of 22 figure 1 . 7 efficiency vs. v out with r s = 0.42 figure 1 . 8 efficiency vs. v out with r s = 0.88 figure 1 . 9 v fb reverence voltage vs. v in figure 1 . 10 i out vs. pwm duty cycle (for details of pwm dimming, see section 2.2.3 .) 50 60 70 80 90 100 25 26 27 28 29 30 v in =24v, r s =0.42 ? ,l=10 ? h v ou t (v) efficiency (%) 50 60 70 80 90 100 12 15 18 21 24 27 30 v in =12v, r s =0.88 ? ,l=10 ? h v out (v) efficiency (%) 250 260 270 280 290 300 310 320 6 10 14 18 22 26 30 v in (v) reference voltage (mv) 0 50 100 150 200 250 30 0 350 400 0 20 40 60 80 100 120 500hz 10khz i out (ma) pwm duty cycle (%)
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 10 of 22 v out 10v/div v in 10v/div i l1 inductor current 1a/div v in = 12vdc, r s = 0.88 , l 1 = 10 h, v out = 28v v out 2 0v/div v lx 2 0v/div i out 20m a/div 2 s/div v in = 12vdc, r s = 0.88 , l 1 = 10 h, v out = 28v 1.5 characteristic waveforms figure 1 . 11 v out , v in , and i l1 during soft start figure 1 . 12 v out , v lx , and i out during typical operation
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 11 of 22 v out 2 0v/div v lx 2 0v/div i l1 500m a/div v in = 12vdc, r s = 0.88 , l 1 = 10 h, v out = 28v, v ovp = 33v figure 1 . 13 v out , v lx , and i l1 when ove r - voltage protection (ovp) threshold is exceeded
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 12 of 22 2 circuit description the zled7015 is a constant - current boost converter that can also function as a constant voltage driver for led applications. the boost converter topology features an internal 3 5 v powe r switch and feedback circuit to control the output to the led string. optimal performance is achieved by operating in continuous conduction mode within the applications load current range; i.e., the current through inductor l1 is always above 0 a . the out put current is set by an external resistor and the device supports dc linear or pwm dimming. additional d evice features include selectable o pen - load / over - voltage protection , over - temperature protection , under - voltage lockout , and an automatic soft - start fu nction to minimize the inrush current during startup . 2.1 en pin , vp pin, and soft - start function the en pin can be used to enable or disable the zled7015 . when the voltage on the en pin rises above the on threshold voltage v enon specified in table 1 . 3 , the zled7015 begins its soft - start . when the voltage at en falls below the off threshold voltage v enoff , the zled7015 shuts down. there is a hysteresis between v enon and v enoff to prevent intermittent operation. the z led7015s internal soft - start function ensures a smooth device start - up by prevent ing excessive in - rush current and providing a controlled rise in the output current. when the soft - start function is initiated, the internal circuitry clamps the internal s witch current threshold to zero during a 1millisecond delay . the soft - start function then gradually increases the internal switch current threshold over a 4 - 5 msec period . see figure 1 . 11 for an illustration of typ ical waveforms during start - up. important: the en pin requires termination. if the en pin is not used to control operation, connect it to the positive power supply through a 100k resistor. do not allow the en pin to float. the vp pin is connected to the zled7015s internal power regulator and requires a n external bypass capa - citor, c vp , to ensure correct device operation. 2.2 output current control t he led current is determined by th e voltage across the external sense resistor r s , which is fed back to the input fb. i nternally, t his is compared with the internal feedback reference voltage, v fb (see typic al application shown on page 2) , and the duty cycle of the internal power switch is adjusted to reduce or increase the output current i out . selection of r s is discussed in section 2.2.1 , and other external components are discussed in section 3 . dimm ing can be controlled by super im posing a dc or filtered pulse - width modulated (pwm) signal on the feedback voltage from r s . r efer to sections 2.2.2 and 2.2.3 , respectively , for more details . 2.2.1 output current and r s the zled7015 continually adjust s the output current, i out , in order to maintain the voltage level at the fb pin equ al to the internal feedback reference voltage, v fb . equation (1) shows th e basic relationship between i out , v fb , and r s for the basic application shown in figure 2 . 1 . (1) where i out = average output current through the led(s) in amperes v fb = internal feedback reference voltage (see table 1 . 3 , parameter 1.3.7 ) s s fb out r v r v i 3 . 0 ? ?
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 13 of 22 figure 2 . 1 typical application circuit 2.2.2 dimming via external dc voltage control the led output curre nt can b e set below the nominal average value defined on section 2.2.1 by using an external dc voltage control signal superimposed on the fb pin as shown in the example circuit in figure 2 . 2 . as the dc control signal , v dc , increases, the current through r 3 increases with a subsequent increase in the voltage at the fb pin . this caus e s the zled7015 to compensate by reducing the output current through the led string. consequently, the outpu t current is inversely proportional to the dc control voltage. note: it is important to ensure that the led output voltage v out remains higher than the input voltage v in in dimming applications. figure 2 . 2 e xample circuit for controlling output current via an external dc control voltage e n l x z l e d 7 0 1 5 l e d s t r i n g v i n = 6 t o 3 0 v d c c o u t r 1 l 1 c i n d 1 f b p g n d a g n d o v p r 2 r s v p v d d c 1 c v d d c v p c 2 r v d d r e n c o v p r 4 r 3 d c c o n t r o l s i g n a l v d c = 0 t o 5 v v o u t e n l x z l e d 7 0 1 5 l e d s t r i n g v i n = 6 t o 3 0 v d c c o u t r 1 l 1 c i n d 1 f b p g n d a g n d o v p r 2 r s v p v d d c 1 c v d d c v p c 2 r v d d r e n c o v p v o u t
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 14 of 22 the output current controlled by the dc voltage on fb can be calculated using equation (2) : (2) where i out = o utput current thro ugh the led(s) with a dc control voltage v fb = internal f eedback r eference v oltage ( table 1 . 3 , parameter 1.3.7 ) v dc = external dc control voltage 2.2.3 dimming via pwm control an extern al pu lse - width modulat ed (pwm) signal input can be used to control the led output current by driving the output current to a value below the nominal average value defined i n section 2.2.1 . a microcontroller can be used to generate t he pwm signal. see figure 2 . 3 for an example circuit . the pwm signal is superimposed on the feedback voltage from r s at the fb pin via the input filter r 5 /c 3 and r 4 , which produces a dc voltage with a ripple . this method of controlling dimming is similar to the external dc voltage control described in section 2.2.2 . the duty cycle of the pwm signal regulates the filtered dc voltage level , which inversely controls the led output current level. when the duty cycle is at 100%, the output current is at the minimum. with a 0% duty cycle, the output current is at the maximum. recommendation: with a pwm signal of 0 to 5v, use an r 3 value of 10k and a pwm frequency of >2khz to mi nimize the filtered pwm voltage ripple. note: it is important to ensure that the led output voltage v out remains higher than the input voltage v in in dimming applications. figure 2 . 3 example circuit for contr olling output current via a pwm control signal ? ? s fb dc fb out r r v v r v i ? ? ? ? ? ? ? ? ? ? ? ? 4 3 e n l x a g n d z l e d 7 0 1 5 l e d s t r i n g v i n = 6 t o 3 0 v d c c o u t r 1 l 1 c i n d 1 f b p g n d o v p r 2 r s v p v d d c 1 c v d d c v p c 2 r v d d r e n c o v p r 4 r 3 r 5 c 3 m i c r o c o n t r o l l e r p m w s i g n a l 5 v 0 v
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 15 of 2 2 the output current controlled by the pwm voltage on fb can be calculated using equation (3) : (3) where i out = output current through the led(s) with a pwm control voltage v fb = internal feedback reference v oltage ( see table 1 . 3 , parameter 1.3.7 ) v pwm = external pwm control voltage d pwm = duty cycle of the pwm control signal 2.2.4 microcontroller led control a micro controller can control the led output current by providing a pwm control signal to the fb pin as described in section 2.2.3 . depending on the application, the microcontroller can also be used to control the shut down circuitry via the en pin (see section 2.1 ) providing a fast and smooth transition to shutdown. 2.2.5 constant voltage application in addition to functioning as a constant - current boost converter for driving an l ed string , the zled7015 can be configured as a constant - voltage boost converter for other applications . figure 2 . 4 demonstrates a typical circuit for this application. the output voltage contr olled by the values of r 3 and r s can be calculated using equation (4) : (4) where v out = output voltage to the load v fb = internal f eedback r eference v ol tage ( table 1 . 3 , parameter 1.3.7 ) s s r r r v v fb out ) ( 3 ? ? ? ? ? s r r r v d v r v i fb pwm pwm fb out ? ? ? ? ? ? ? ? ? ? ? ? ? ? 5 3 4
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 16 of 22 figure 2 . 4 example circuit for constant voltage source applications e n l x z l e d 7 0 1 5 v i n = 6 t o 3 0 v d c c o u t r 1 l 1 c i n d 1 f b p g n d a g n d o v p r 2 r s v p v d d c 1 c v d d c v p c 2 r v d d r e n r 3 c o v p l o a d
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 17 of 22 3 application circuit design the following sections cover selection of the external components shown in the typic al application on page 2 . 3.1 external component C r s recommendation: use precision resistors ( 1% or better tolerance) for the r s resistor to ensure accurate control of the led current. see section 2.2.1 for the equation for selecting the value of r s , which sets the nominal current output. 3.2 external component C inductor l 1 designing the circuit so that the current through inductor l 1 is always above 0v (i.e., continuous mode) typically give s the best performance due to improved load regulation and reduced output ripple. select an inducto r that has a saturation current and a current rating greater than the mean input current. the inductor value selection requires trade - offs between unwanted r ipple current and parasitic effects. a larger value inductor reduces inductor ripple current, resulting in less output ripple voltage; however, higher values also increase parasitic resistance , which can degrade performance. for most applications, a 10 h i nductor with a saturation current > 2 .5 a is adequate. see section 7.4 for layout restrictions. 3.3 external component s C in put decoupling capacitor s c 1 and c in the input capacitors c 1 and c in minimize the input volta ge noise and ripple. recommendation: use a 22 f or larger low - esr electrolytic capacitor for c in in parallel with a 1 f ceramic capacitor rated at greater than the input voltage plus a safety margin for c 1 . 3.4 external component C output capacitor s c 2 and c ou t the output capacitors c 2 and c out minimize the output voltage ripple. recommendation: use a 22 f or larger low - esr electrolytic capacitor for c out in parallel with a 1 f ceramic capacitor rated at greater than the output voltage plus a safety margin for c 2 . 3.5 external component C diode d 1 for the diode d 1 , select a high - speed, low - capacitance schottky diode with low reverse leakage at the maximum operating voltage and temperature to ensure maximum efficiency and performance. important: choose diodes with a continuous current rating higher than the maximum output load current and a peak current rating above the peak coil current. when operating above 85c, the reverse leakage of the diode must be addressed because it can cause excessive power dissipation in t he diode, especially when the output voltage is relatively high. its reverse breakdown voltage must be greater than the over - voltage protection level v ovp (see section 4.2 ). note: silicon diodes have higher forw ard voltage and higher voltage overshoot before they start conducting, which can increase the peak voltage on the lx output. ensure that the total voltage appearing on the lx pin, including supply ripple, is within the specified range (see table 1 . 1 ). 3.6 additional external components for the vdd input, connect resistor r vdd to the positive power supply and connect ceramic capacitor c vdd to ground. recommendation s : use 1f for c vdd ; use 300 for r vdd with input voltages 8v, use 50 for r vdd with input voltages < 8v. for the vp pin, connect a 10 f ceramic bypass capacitor to ground (c vp ) . if the en pin is not used, connect a 100k resistor to the positive power supply (r en ) . do not allow th e en pin to float.
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 18 of 22 4 operating conditions 4.1 under - voltage lockout the u nder - v oltage l ockout (uvlo) monitors the zled7015s internal regulator output voltage, vp , to ensure correct operation of the internal circuitry. when the vp voltage is lower than the uvlo threshold v uvlo , the zled7015 disables the internal power switch. if the vp voltage reaches a level higher than the uvlo threshold plus uvlo hysteresis (v uvlo +v uvlo_hys ) the uvlo turn s off and the internal power switch is re - enabled. see parameters 1.3.14 and 1.3.15 in section 1.3 for the uvlo threshold and hysteresis. 4.2 over - voltage threshold and open - circuit protection if th e led string becomes open or the fb pin is shorted to ground, the zled7015 would normally continually boost the output voltage to potentially damaging levels. to prevent this , the zled7015 includes an integrated over - voltage protection (ovp) mechanism. if the output voltage reaches the zled7015s ovp threshold v ovp , the protection circuitry is triggered and the device automatically turns off the internal switch , stopping the boost function and protecting the device. once the output voltage falls below the o vp threshold minus ovp threshold hysteresis (v ovp_th - v ov p _th_hys ) , the device will enter soft - start mode. the ovp threshold v ovp for the zled7015 is selectable via the r1 and r2 resistor values determined by equation (5) : (5) where v ovp = over - v oltage p rotection t hreshold v ovp_ th = internal o ver - v oltage t hreshold reference voltage ( see table 1 . 3 , parameter 1.3.16 ) important: care must be taken to select proper r 1 and r 2 values to ensure proper functioning of the zled7015. see specification 1. 3.16 in table 1 . 3 for the over - voltage protection threshold voltage . set v ovp 3v higher than the normal operation output voltage. important: when setting v ovp , care must be taken to ensure v out can not exceed 35v. minimize noise coupling on the ovp pin, which could interfere with proper protection, by connecting a 10nf cera mic capacitor to gnd from ovp (c ovp ) . 4.3 over - temperature protection the zled7015 features on - chip over - temperature protection. if its internal temperature exceeds the o ver - t emperature p rotection (otp) threshold, t otp , due to high power dissipation and improp er heat sinking, the internal power switch is disabled. once the internal temperature has fallen belo w the otp threshold minus the otp threshold hysteresis (t otp - t otp _ hys ), the zled7015 enters the soft - start mode (see section 2.1 ) . refer to table 1 . 1 for the maximum package power dissipation specifications for the zled70 15 s msop - 10 package . 2 2 _ ) ( 1 r r r v v th ovp ovp ? ? ?
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 19 of 22 5 esd/latch - up - protection all high voltage pins ( 1, 4, 5, 9 , and 10 ) have an esd protection of > 2500 v according to the h uman b ody m odel (hbm). the esd test follows the human body model based on mil 883 - h, method 3015.8 all low voltage pins (2, 3, 6, 7 , and 8) have an esd protection of > 4000v according to the human body model (hbm). the esd test fo llows the human body model based on mil 883 - h, method 3015.8 all pins pass t he l atch - u p test based on the jedec standard no . 78b, december 2008 . 6 p in configuration and package the zled7015 package is an msop - 10, which has a thermal resistance (junction to ambient) of r ja = 60 c/w. figure 6 . 1 zled7015 pin configuration msop - 10 package table 6 . 1 pin d escription msop - 10 pin name no. description pgnd 1 power ground vp 2 internal 5v linear regulator output. vp is the power supply for the internal s witch gate driver and the internal control circuitry. use a 10 f ceramic bypass capacitor between v p and ground . a gnd 3 analog (signal) ground. en 4 enable c ontrol i nput. important: do not allow this pin to float. a gnd 5 analog (signal) ground. ovp 6 over - voltage p rotection control input. fb 7 feedback voltage input. the n ominal average output current is set by the value of r s connected from fb to g nd C see section 2.2.1 for details . important: do not allow the fb pin to float. n.c. 8 no connection v dd 9 supply voltage (6v to 3 0v) see section 7 for layout cons iderations. lx 10 d rain of the internal switch . connect the power inductor between lx and the power supply . connect the output rectifier d 1 between lx and the output circuit . see section 1.1 for output range spe cifications. thermal pad connect to ground. p g n d v p a g n d a g n d e n l x v d d n c f b o v p
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 20 of 22 figure 6 . 2 msop - 10 package dimensions for the zled7015 symbol dimension (mm, except ) symbol dimension (mm) min max min max a 0.82 1.10 d 2.90 3.10 a 1 0.02 0.15 d1 1.70 1.90 a2 0.75 0.95 e 0.50 bsc b 0.18 0.28 e 2.90 3.10 c 0.09 0.23 e1 4.75 5.05 e2 1.45 1.65 0 6 l 0.40 0.80 e e 1 e e 2 d d 1 c l b a 2 a a 1 t h e r m a l p a d ( b o t t o m )
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 21 of 22 7 layout requirements follow these layout guidelines t o avoid circuit instability and emi vulnerability, especially with high current or high sw itching frequency applications . important: route traces connecting the feedback network to the fb and ovp pin away from the l 1 inductor, the d 1 schottky diode, and the lx pin. these traces should be as short as possible. shield the fb pin and feedback network with a ground plane or trace to prevent noise coupling. 7.1 general considerations and ground traces make the ground traces as wide and short as possible. to prevent a signal ground shift, keep traces for the signal ground (pin 5) separate from traces for the power ground (pin 1). connect the signal and power ground traces together at either the large ground plane or the negative terminal of c in . connect the grounds for other components to the signal ground. use wide traces for connection of the high current loop. 7.2 layout considerations for c 1 , c in , c 2 and c out place c 1 , c 2 and c out as close as possible to the zled7015 to minimize ripple. the c in input decoupling capacitor must be placed as close as possible to the vdd pin to mini mize power supply noise, which can reduce efficiency. 7.3 layout considerations for the en pin important: do not allow the en pin to float. it must be terminated if it is not used. 7.4 layout considerations for the lx pin , l 1 external coil, and d 1 diode minimize the length of circuit board tr a ces connected to the lx pin because it is a fast switching output . place l 1 and d 1 as close as possible to the lx pin using traces that are as short and wide as possible. avoid routing other traces crossing or in parallel wit h this node to minimize the noise coupling into this circuit. 7.5 layout considerations for the external current sense resistor (r s ) any trace resistance in series with r s must be taken into consideration when selecting its value. for the most accurate led cu rrent control, use a trace that is as wide and short as possible for the r s connection to ground. connect it to the signal ground (pin 5), not the power ground (pin 1). 7.6 layout considerations for c vp and c vdd for good filtering, connect c vp as close as poss ible to the vp pin and place c vdd as close as possible to the vdd pin . 7.7 layout considerations for the thermal pad to optimize heat dissipation, solder the thermal pad on the back of the msop - 10 package to the large ground plan.
z led7015 1.0mhz boost converter with internal 35v switch data sheet december 20 , 20 11 ? 201 1 zentrum mikroelektronik dresden ag rev. 1.00 all rights reserved. th e 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 publicatio n is subject to changes without notice. 22 of 22 8 glossary of terms term defini tion ldo low dropout regulator otp over - temperature protection ovp over - voltage protection uvl under - voltage lockout 9 ordering information product sales code description package zled7015 - zi1r zled7015 C 1mhz boost converter with internal 35v switch m sop - 10 (tape & reel) zled7015kit - e 1 zled7015 - e 1 evaluation board, 1 zled - pcb10 , and 5 zled7015 ics kit 10 document revision history revision date description 1.0 0 december 20 , 201 1 first issue . sales and further information www.zmdi.com led_drivers@zmdi.com zentrum mikroelektronik dresden ag grenzstrasse 28 01109 dresden germany zmd america, inc. 275 south 5th avenue pocatello, id 83201 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 zentrum mikroelektronik dresden ag, korean office posco centre building west towe r, 11th floor 892 daechi, 4 - dong, kangnam - gu seoul, 135 - 777 korea phone +49.351.8822.7.533 fax +49.351.8822.8.7533 phone +1.208.478.7200 fax +1.208.478.7200 phone +81.3.6895.7410 fax +81.3.6895.7301 phone +886.2.2377.8189 fax +886.2.2377.8199 phone +82.2.559.0660 fax +82.2.559.0700 disclaimer : this information applies to a product under development. its characteristics and specifications are subject to change without notice. zentrum mikroelektronik dresden ag (zmd ag) assumes no obligation reg arding future manufacture unless otherwise agreed to in writing. the information furnished hereby is believed to be true and accurate. however, under no circumstances shall zmd ag be liable to any customer, licensee, or any other third party for any specia l, indirect, incidental, or consequential damages of any kind or nature whatsoever arising out of or in any way related to the furnishing, performance, or use of this technical data. zmd ag hereby expressly d isclaims any liability of zmd ag to any customer , licensee or any other third party, and any such customer, licensee and any other third party hereby waives any liability of zmd ag for any da mages in connection with or arising out of the furnishing, performance or use of this technical data, whether bas ed on contract, warranty, tort (including negligence), strict liability, or otherwise.
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