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data sheet rev. 1.1 / august 2010 zled7010 40v led driver with temperature compensation
zled7010 40v led driver with temperature compensation ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 subject to changes without notice. brief description the zled7010, one of our zled family of led control ics, is an inductive step-down converter that is optimal for driving a single led or multiple leds (connected in series) from a voltage source greater than the voltage rating of the led. the zled 7010 operates in continu- ous mode. capable of operating efficiently with voltage supplies ranging from 6 vdc to 40 vdc, it is ideal for low-voltage lighting applications. the zled7010 mini- mizes current consumption by remaining in a low-current standby mode (output is o ff) until a voltage of 0.3v is applied to the adj i pin. in operating mode, the zled7010 can source leds with an output current of 750ma ( 30 watts of output power * ) that is externally adjustable. the zled7010?s integr ated output switch and high-side current sensing circuit use an external resistor to adjust the average out- put current. led control is achieved via an external con- trol signal at the zled7010?s adj i pin, implemented as a pulse-width modulation (pwm) waveform for a gated output current or a dc voltage for continuous current. the zled7010 provides a temperature compen- sation function for maintaining stable and reliable led operation. led ove r-temperature conditions are detected via a negative temperature coefficient (ntc) thermistor mounted close to the leds. if an over-temperature condition occurs, the ntc value reaches the value of a threshold resistor and the ic reduces led current automatically. after the circuit recovers to a safe temperature, current returns to the set value. adj o outputs and adj i inputs of consecutive ics can be interconnected as a driver chain deploying the temperature compensation information of the predecessor. this reduces the part count because only the first stage of the series requires an ntc. r ntc v in r th adj i adj o gnd i sense lx zled7010 v s n led l1 r3 ntc c1 1 f c2 100nf r2 50k ? r s d1 47 h 6 to 40 vdc 12 8 5 7 6 3 4 * see section 2.3 for details features ? capable of 95% efficiency* ? operates in continuous mode with a wide input range from 6 vdc to 40 vdc ? integrated 40v power switch ? one-pin on/off or bright ness control via dc voltage or pwm control signal ? switching frequency: 1mhz ? dimming rate: 1200:1 (typical) ? output current accuracy: 5% (typical) ? built-in temperature compensation and open-circuit protection for leds ? thermal shutdown protection for the zled7010 ? very few external components needed for operation ? broad range of applications: outputs up to 750ma ? sop-8 package application examples ? illuminated led signs and other displays ? led traffic and street lighting (low-voltage) ? architectural led lighting, including low-voltage applications for buildings ? halogen replacement leds (low-voltage) ? led flood-lighting ? led backlighting ? general purpose exterior and interior led lighting, including applications requiring low-voltage ? general purpose low-voltage industrial applications zled7010 application circuit
zled7010 40v led driver with temperature compensation ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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. sop-8 package dimensions and pin assignments dimension (mm) dimension (mm, except ) symbol min max symbol min max a 1.350 1.750 e 3.800 4.000 a1 0.100 0.250 e1 5.800 6.240 a2 1.450 typical e 1.270 typical b 0.350 0.490 l 0.400 1.270 c 0.178 0.250 0 8 d 4.800 5.000 ordering information product sales code description package ZLED7010-ZI1R zled7010 ? 40v led driver with temperature compensation sop8 (tape & reel) zled7010kit-d1 zled7010 demo board with led on cool body 12vac/vdc kit zled-pcb1 test pcb with one 3w white hb-led, cascadable to 1 multiple led string printed circuit board zled-pcb2 10 unpopulated test pcbs for modular led string with footprints of 9 common hb-led types printed circuit board 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 development. its char acteristics 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 he reby 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, incident al, 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 dis claims 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 dama ges in connection with or arising out of the furnishing, perfor- mance or use of this technical data, whether based on contract, warranty, tort (including negligence), strict liability, or oth erwise.
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 4 of 23 contents 1 ic characte ristics ............................................................................................................. ............................................. 6 1.1. absolute maxi mum rati ngs ................................................................................................................................... 6 1.2. operating c onditio ns ........................................................................................................... .................................. 6 1.3. electrical parameters.......................................................................................................... ................................... 6 1.4. characteristic o perating curves ................................................................................................ ............................ 8 2 circuit de scripti on ....................................................................................................................................................... 10 2.1. voltage supply................................................................................................................. .................................... 10 2.2. zled7010 sta ndby mo de.......................................................................................................... .......................... 10 2.3. output current cont rol......................................................................................................... ................................ 10 2.3.1. output current and r s ............................................................................................................................... ... 10 2.3.2. pwm cont rol .................................................................................................................... ............................ 11 2.3.3. external dc voltage cont rol of out put cu rrent .................................................................................. .......... 11 2.3.4. microcontroller led cont rol.................................................................................................... ...................... 12 3 application cir cuit de sign ........................................................................................................................................... 13 3.1. external component ? induc tor l1 ............................................................................................... ....................... 13 3.2. external component ? capaci tor c1 .............................................................................................. ..................... 14 3.3. external compone nt ? dio de d1 .................................................................................................. ....................... 14 3.4. output ripple .................................................................................................................. ..................................... 15 4 operating c onditio ns................................................................................................................................................... 16 4.1. thermal c onditi ons............................................................................................................. ................................. 16 4.2. thermal shut-dow n protection ................................................................................................... ......................... 16 4.3. open-circuit protec tion........................................................................................................ ................................ 16 4.4. external temperature compen sation of ou tput cu rrent............................................................................ .......... 16 5 chaining multiple zled70 10 ics ................................................................................................. ............................... 19 6 esd/latch-up- protec tion ........................................................................................................ .................................... 20 7 pin configurati on and pa ckage .................................................................................................. ................................. 20 8 layout requ irements .................................................................................................................................................. 22 8.1. layout considerations for adj i (pin 6) ................................................................................................................ 22 8.2. layout consid erations for lx (pin 8) ........................................................................................... ........................ 22 8.3. layout considerations for v in (pin 1) and the external decoupling capac itor (c 1)............................................. 22 8.4. layout consid erations for gnd (pin 7).......................................................................................... ...................... 22 8.5. layout considerations for adj o (pin 5) ............................................................................................................... 22 8.6. layout considerations for r th and r ntc (pins 3 and 4) ....................................................................................... 22 8.7. layout consider ations for high voltage traces.................................................................................. ................. 22 8.8. layout considerat ions for the exte rnal co il ( l1) ............................................................................... .................. 22 8.9. layout considerations for the external current sense resistor (r s ) .................................................................. 22 9 ordering in formati on ................................................................................................................................................... 23 10 document revi sion hist ory ...................................................................................................... ................................... 23
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 5 of 23 list of figures figure 1.1 characteristic operating curves 1 ................................................................................................................. 8 figure 1.2 characteristic operating curves 1 ................................................................................................................. 9 figure 2.1 directly driving adj i input with a pwm control signal ................................................................................. 11 figure 2.2 external dc control voltage at adj i pin ...................................................................................................... 11 figure 2.3 driving adj i input from a microcontroller ..................................................................................................... 12 figure 3.1 output ripple reduction .............................................................................................................................. 1 5 figure 4.1 temperature compensation ......................................................................................................................... 16 figure 4.2 temperature compensation graphs ............................................................................................................ 18 figure 5.1 zled7010 chain connections ..................................................................................................................... 19 figure 5.2 zled7010 system application .................................................................................................................... 19 figure 7.1 pin configuration zled7010 ........................................................................................................................ 20 figure 7.2 sop-8 package drawing .............................................................................................................................. 2 1 list of tables table 4.1 pin description sop-8 ............................................................................................................................... ... 20 table 7.2 ........................................................................................................................ 21 package dimensions sop-8
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 6 of 23 1 ic characteristics 1.1. absolute maximum ratings no. parameter symbol conditions min typ max unit 1.1.1 input voltage v in -0.3 50 v v in >5v v in - 5 v in + 0.3 v 1.1.2 i sense voltage v isense v in <5v 0 v in + 0.3 v 1.1.3 lx output voltage v lx -0.3 50 v 1.1.4 control pin input voltage v adj , v adjo , r th , r ntc -0.3 6 v 1.1.5 switch output current i lx 900 ma 1.1.6 power dissipation p tot sop-8 1.2 w 1.1.7 storage temperature t st -55 150 c 1.1.8 junction temperature t j max 150 c 1.2. operating conditions no. parameter symbol conditions min typ max unit 1.2.1 operating temperature t op -40 +85 c 1.2.2 input voltage v in 6 40 v 1.3. electrical parameters production testing is at 25c. at othe r temperatures within the specified operating range, functional operation of the chip and specified parameters are guaranteed by characterization, design, and process control. test conditions are t amb = 25c; v in = 12v except as noted. no. parameter symbol conditions min typ max unit 1.3.1 quiescent supply current with output off i inqoff adj i pin grounded 40 60 80 a 1.3.2 quiescent supply current with output switching i inqon adj i pin floating 450 600 a 1.3.3 mean current sense threshold voltage v sense measured on i sense pin with respect to v in ; adj i pin floating 91 95 101 mv 1.3.4 sense threshold hysteresis v sensehys 15 % 1.3.5 i sense pin input current i sense v sense = 0.1v 8 10 a 1.3.6 internal reference voltage v ref measured on adj i pin with pin floating 1.2 v 1.3.7 external control voltage range on adj i pin for dc brightness control v adji 0.3 1.2 v
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 7 of 23 no. parameter symbol conditions min typ max unit 1.3.8 dc voltage on adj i pin to switch chip from active (on) state to quiescent (off) state v adjioff v adji falling 0.15 0.2 0.25 v 1.3.9 dc voltage on adj i pin to switch chip from quiescent (off) state to active (on) state v adjion v adji rising 0.2 0.25 0.3 v 1.3.10 r th and r ntc pin offset voltage v os 10 mv 1.3.11 continuous lx switch current i lxmean 0.65 0.75 a 1.3.12 lx switch leakage current i lx(leak) 1 a 1.3.13 adj o terminal voltage v adjo no temperature compen- sation, adj i pin floating i adjo =30 a 1.20 v 1.3.14 lx switch on resistance r lx 0.9 1.5 ? 1.3.15 continuous lx switch current i lxmean 0.65 a 1.3.16 resistance between adj i pin and v ref r adji 500 k ? 1.3.17 brightness control range at low frequency pwm signal d pwm(lf) pwm frequency =100hz pwm amplitude=5v, v in =15v, l=27 h, driving 1 led 1200:1 1.3.18 brightness control range at high frequency pwm signal d pwm(hf) pwm frequency =10khz pwm amplitude=5v, v in =15v, l=27 h, driving 1 led 13:1 1.3.19 operat ing frequency f lx adj i pin floating l=100 h (0.82 ? ) i out =350ma @ v led =3.4v, driving 1 led 154 khz 1.3.20 minimum switch on time t onmin lx switch on 200 ns 1.3.21 minimum switch off time t offmin lx switch off 200 ns 1.3.22 recommended maximum operating frequency f lxmax 1 mhz 1.3.23 recommended duty cycle range of output switch at f lxmax d lx 0.2 0.8 1.3.24 internal comparator propagation delay t pd 50 ns 1.3.25 thermal shutdown temperature t sd 140 c 1.2.26 thermal shutdown hysteresis tsd-hys 20 c
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 8 of 23 1.4. characteristic operating curves the curves are valid for the typical application circuit and t amb = 25c unless otherwise noted. figure 1.1 characteristic operating curves 1
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 9 of 23 figure 1.2 characteristic operating curves 1
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 10 of 23 2 cir cuit description the zled7010 is an inductive step-down converter for driving leds. it operates in continuous mode, enabling proper led current control. the zled7010 supports lin ear or pwm control of the led current. it provides temperature compensation to maintain stable and re liable operation of the leds. only a few external components are needed for typical applications. 2.1. voltage supply the zled7010 has an internal regulator that disables the lx output until the voltage supply rises above a start-up threshold voltage set internally as needed to ensure that the power mosfet on-resistance is low enough for proper operation. when the supply voltage ex ceeds the threshold, the zled7010 begins normal operation. important: the zled7010 must be operated within the operating voltage range specified in section 1.2 to avoid co nditions that could result in thermal damage to the zled7010. operating with the supply voltage below the minimum can result in a high switch duty cycle and excessive zled7010 power dissipation, risking over-temperature conditions (also see section 4.1 regarding thermal restrictions) which could result in activation of the zled7010?s thermal shut-down circuitry (see section 4.2 ). with multiple leds , the forward drop is typically adequate to prevent the chip from swit ching below the minimum voltage supply specification (6v), so there is less risk of thermal shut-down. 2.2. zled7010 standby mode whenever the adj i pin voltage falls below 0.2v, the zled7010 turns the output off and the supply current drops to approximately 60 a. this standby mode minimizes current consumption. 2.3. output current control the led control current output on t he lx pin is determined by the val ue of external components and the control voltage input at the adj i pin. selection of the external component r s is discussed below, and other external components are discussed in section 3 . the subsequent sections descri b e the two options for control voltage input at the adj i pin: a pulse width modulation (pwm) c ontrol signal or a dc control voltage. the adj i pin has an input impedance ? of 500k ? 25%. 2.3.1. output current and r s the current sense threshold voltage and the valu e of the external current sense resistor (r s ) between v in and i sense set the output current through the leds (i out ). equation (1) shows this basic relationship. unless the adj pi n is driven from an external voltage (see section 2.3.3 ), the minimum value for r s is 0.13 ? to prevent exceeding the maximum switch current (see section 1.3 ). s out r mv95 i ? (1) where i out = nominal average output current through the led(s) r s 0.13? ? at room temperature.
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 11 of 23 2.3.2. pwm control the output current on lx can b e set to a value below the nominal average value determined by resistor r s by using an external pwm signal as the control signal applied to the adj i pin. this control signal must be capable of driving the zled7010?s internal 500k ? pull-up resistor. see figure 2.1 for an illustration. the minimum si gnal voltage range is 0v to 1.8v; the maximum voltage range is 0v to 5v. see section 1.3 for the s pecifications for the signal?s duty cycle d pwm . any negative spikes on the control signal could interfere with current control or proper operation of the zled7010. figure 2.1 directly driving adj i input with a pwm control signal s adj dc_out r v079.0 i ? ? zled gnd adj o 7010 adj i 1.8v to 5v 0v pwm 2.3.3. external dc voltage control of output current the output current on lx can b e set to a value below the nominal average value determined by resistor r s by using an external dc voltage v adj (0.3 v v adj 1.2v) to drive the voltage at the adj i pin. this allows adjusting the output current from 25% to 100% of i outnom . see figure 2.2 for an illustration. the output current can be cal culated using equation (2) . if v adj matches or exceeds v ref (1.2v), the brightness setting is clamped at its maximum (100%). figure 2.2 external dc control voltage at adj i pin adj i adj o gnd zled7010 dc (2) where i out_dc = nominal average output current through the led(s) with a dc control voltage v adj = external dc control voltage: 0.3v v adj 1.2v r s 0.13?
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 12 of 23 2.3.4. microcontroller led control the o pen-drain output of a microcontro ller can control current to the leds by outputting a pwm control signal to the adj i input. see figure 2.3 for an example circuit. figure 2.3 driving adj i input from a microcontroller 10k mc adj i adj o gnd zled7010
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 13 of 23 3 application circuit design 3.1. external component ? inductor l1 select the inductor value for l1 as needed to ensure t hat switch on/off times are optimized across the load current and supply voltage ranges. select a coil that has a continuous current rating above the required average output current to the leds and a satu ration current exceeding the peak output current. recommendation: use inductors in the range of 15 h to 220 h with saturation current greater than 1a for 700ma output current or saturation current greater than 500ma for 350ma output current. for higher supply voltages with low output current, select higher values of inductance, which result in a smaller change in output current across the supply voltage ran ge (refer to the graphs in section 1.4 ). see section 8.8 for layout rest rictions. equations (3) and (4) illustrate calculating the timing for lx switchi ng for the example application circuit shown on page 2. as given in section 1.3 , the minimum period for t on is 200ns; the minimum period for t off is also 200ns . lx switch off time ( t off in s) ?? ????? ? ? ? where l coil inductance in h ? coil peak-peak ripple current in a * v led total led forward voltage in v v d diode forward voltage at the required load current in v i avg required average led current in a r s external current sense resistance in ? r l coil resistance in ? v in supply voltage in v r lx switch resistance in ? ?? ???? ? ? ? (3) lx switch on time ( t on in s) (4) * with the zled7010, the current ripple ? i is internally set to an appropriate value of 0.3 * i avg . the inductance value has an equivalent effect on ton and toff and therefore affects the switching frequency. for the same reason the inductance has no influence on the duty cycle for which the relation of the summed led forward voltages n ? v f to the input voltage v in is a reasonable approximation. because the input voltage is a factor in the on time, variations in the input voltage affect the switchi ng frequency and duty cycle.
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 14 of 23 the following calculation example yields an operati ng frequency of 122khz and a duty cycle of 0.33: input data: v in =12v, l=220 h, r l =0.48 ? , v led =3.4v, i avg =333ma and v d =0.36v ?? s47.5 3.048.0a333.0v36.0v4.3 a333.03.0h220 t off ? ?? ? ? ???? ?? ? (5) and ?? s73.2 9.048.03.0a333.0v4.3v12 a333.03.0h220 t on ? ??? ? ? ????? ? ? ? (6) 3.2. external component ? capacitor c1 to improve system efficiency, use a low-equivalent-ser ies-resistance (esr) capacitor for input decoupling because this capacitor must pass the input current ac component. the capacitor value is defined by the target maximum ripple of the supply voltage; the value is given by equation (7) . max onf min v ti c ? ? ? (7) where i f value of output current v max maximum ripple of power supply t on maximum on time of mosfet in the case of an ac supply with a rectifier, the c apacitor value must be chosen high enough to make sure that the dc voltage does not drop below the maximum forward voltage of the led string plus some margin for the voltage drops across the coil resistance, shunt resist or, and on resistance of the switching transistor. recommendation: use capacitor s with x5r, x7r, or better dielectric for maximum stability over temperature and voltage. do not use y5v capacitors for decoupling in this application. for higher capacitance values, aluminum electrolytic caps with high switching capab ility should be used. in this case improved performance can be reached by an additional x7r/x5r bypass capacitor of at least 100nf. 3.3. external component ? diode d1 for the rectifier d1, select a high-speed low-capaci tance 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 ra ting 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 exce ssive power dissipation in the zled7010. note: silicon diodes have a greater forward voltage and overshoot caused by reverse recovery time, 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 section 1.3 ).
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 15 of 23 3.4. o utput ripple shunt a capacitor c led across the led(s) as shown in figure 3.1 to minimize the peak-to-peak ripple current in the led if necessary. figure 3.1 output ripple reduction low-esr capacitors should be used because the efficiency of c led largely depends on its esr and the dynamic resistance of the led(s). for an increased number of leds, using the same capacitor will be more effective. lower ripple can be achiev ed with higher capacitor values, but it will increase start-up delay by reducing the slope of the led voltage. the capacitor will not affect operating frequency or efficiency. for a simulation or bench optimization, c led values of a few f are an applicable start point for the given configuration.
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 16 of 23 4 oper ating conditions 4.1. thermal conditions refer to section 1.1 for maximum package power dissipation specifications for the zled7010?s sop-8 packa ge. exceeding these specifications due to operating the chip at high ambient temperatures (see section 1.2 for maximum operating temperature range) or driv i ng over the maximum load current (see section 1.3 ) can damag e the zled7010. the zled7010 can be used for led current applications up to750ma when properly mounted to a high wattage land pattern. conditions such as operating below the minimum supply voltage or inefficiency of the circuit due to improper coil select ion or excessive parasitic capacitance on the output can cause excessive chip power dissipation. 4.2. t hermal shut-down protection the zled7010 includes an on-board temperature sensing circ uit that stops the output if the junction exceeds approximately 160c. 4.3. o pen-circuit protection the zled7010 is inherently protected if there is an open-circuit in the connec tion to the leds because in this case, the coil is isolated from the lx pin. this prev ents any back emf from damaging the internal switch due to forcing the drain above its breakdown voltage. 4.4. e xternal temperature compensation of output current the zled7010?s temperature compensation feature is us eful in applications that require a temperature compensated led control current to ensure stability and re liability over temperature, such as high luminance leds. when output current compensation is needed, use an external temperature sensing network, typically with negative temperature coefficient (ntc) thermistors/diodes, located close to the led(s) and connected to the r ntc and r th inputs. with this circuit configuration, t he internal circuitry of the zled7010 reduces the output current if the temperature sensin g input indicates a rising temperature. figure 4.1 temperature compensation r ntc r th adj i adj o gnd zled7010 r2 r3 ntc r4 as shown in figure 4.1 , the temperature compensation curve is determined by r2, r3 (ntc) and r4. when the led te mperature increases, the resistance of r3 de creases. as r3 reaches the point that r3 plus r4 equal r2, the temperature compensation function starts to work by reducing i out .
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 17 of 23 the i out current with temperature compensation can be calculated with the following equations: for 0.3v v adji 1.2v: ? ? ? ? ? ? ? ? ? ? 2r 4r3r r vv079.0 i s adji dc_out (8) for v adji > 1.2v: ? ? ? ? ? ? ? ?? 2r 4r3r r v095.0 i s dc_out (9) r3 and r4 determine the slope of temperature compensation. if r4 is just 0 ? , the slope is solely driven by the ntc component?s characteristic -constant. larger values of r4 will decrease the slope. when dimensioning r2, consider that larger values will make the r th pin more noise sensitive and lower values will increase power consumption therefore values from 1k to 100k are recommended. for a selected temperature compensation threshold, larger r3 and r4 require larger r2 to match and vice versa. also see section 5 regarding driver chains and temperature compensation. figure 4.2 shows some examples of current -temp erature curves resulting from different dimensioning of the three resistors.
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 18 of 23 figure 4.2 temperature compensation graphs
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 19 of 23 5 chaining multiple zled7010 ics figure 5.1 shows a typical circuit for chaining multiple zled7010s using the adj i and adj o pins and a temperature sensing network of r2, r4, and r3, which is an ntc component. note that only one temperature sensing network is needed. when r3+r4 > r2, v adjo = v adji. when r3+r4 < r2, the adj o pin outputs the adj i input voltage with temperature compensation information. figure 5.1 zled7010 chain connections r ntc r th adj i adj o gnd zled7010 r2 r3 ntc 100pf 100pf 100pf 100pf r ntc r th adj i adj o gnd zled7010 r4 in figure 5.2 , note that each zled7010 can drive up to thr ee slave ics in the next stage. using more than three stages to maintain current coherence is not recommended. up to thirteen zled7010 can be connected in one system. figure 5.2 zled7010 system application
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 20 of 23 6 esd/latch-up-protection all pins have an esd protection of > 2000v according the human body model (hbm) except for pin 8, which has a protection level of > 1000v. the esd te st follows the human body model with 1.5 k ? /100 pf based on mil 883-g, method 3015.7. latch-up protection of > 100ma has been proven based on jedec no. 78a feb. 2006, temperature class 1. 7 pin c onfiguration and package figure 7.1 pin configuration zled7010 lx gnd adj i adj o r ntc r th i sense v in table 4.1 pin description sop-8 pin name no. description vin 1 supply voltage (6v to 40v)?see section 8 for layout considerations. isense 2 nominal average output current is set by the value of a resistor rs connected from isense to vin. see section 2.3.1 for details. rth 3 threshold input from external temperature sens ing network. sets the starting temperature of temperature compensation via an external resistor. see section 4.4 for details. rntc 4 ntc input from external temperature sensing network. see section 4.4 for details. adjo 5 output for control signal for led driver chain applications adji 6 output current control pin?see section 2.3 for details gnd 7 ground (0v)?see section 8.4 for layout considerations lx 8 power switch drain
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 21 of 23 figure 7.2 sop-8 package drawing table 7.2 package dimensions sop-8 dimension (mm) dimension (mm, except ) symbol min max symbol min max a 1.350 1.750 e 3.800 4.000 a1 0.100 0.250 e1 5.800 6.240 a2 1.450 typical e 1.270 typical b 0.350 0.490 l 0.400 1.270 c 0.178 0.250 0 8 d 4.800 5.000 the sop-8 package has a thermal resistance (junction to ambient) of r ja = 128 k/w.
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 22 of 23 8 layo ut requirements 8.1. l ayout considerations for adj i (pin 6) for applications in which the adj i pin is unconnected, minimize the lengt h of circuit board traces connected to adj i to reduce noise coupling through this high impedance input. 8.2. l ayout considerations for lx (pin 8) minimize the length of circuit board traces connected to the lx pin because it is a fast switching output. 8.3. l ayout considerations for v in (pin 1) and the external decoupling capacitor (c1) the c1 input decoupling capacitor must be placed as clos e as possible to the vin pin to minimize power supply noise, which can reduce efficiency. see section 3.2 regarding capacitor selection. 8.4. l ayout considerations for gnd (pin 7) the zled7010 gnd (ground) pin must be soldered directly to the circuit board?s ground plane to minimize ground bounce due to fast switching of the lx pin. 8.5. layout considerations for adj o (pin 5) when the application requires a driver chain of multip le zled7010s, noise might be coupled in if there are longer pcb traces from the driving adj o pin to next stage adj i pin. in this case, a 200pf (maximum) capacitor must be connected between the line and ground to filter out the noise. the best practice is to connect one capacitor each close to the adj o output pin and the next stage adj i input pins. the total capacitance in addition to the paras itic capacitance from the adj o pin to ground must not exceed 200pf. see figure 5.1 . 8.6. layout considerations for r th and r ntc (pins 3 and 4) the pcb trace from r2 to the r th pin should be as short as possible to minimize noise coupling. because the ntc thermistor r3 is mounted close to the leds and remote from the zled7010, the pcb trace from r3 to r ntc pin is longer and more susceptible to noise. a 100nf capacitor from the r ntc pin to ground and close to the r ntc pin is recommended to filter the noise and provide protection against high voltage transients. 8.7. layout considerations for high voltage traces avoid laying out any high voltage traces near the adj pin to minimize the risk of leakage in cases of board contamination, which could raise t he adj pin voltage resulting in unintentional output current. leakage current can be minimized by laying out a ground ring around the adj pin. 8.8. layout considerations for the external coil (l1) the l1 coil must be placed as close as possible to the chip to minimize parasitic resistance and inductance, which can reduce efficiency. the connection between the coil and the lx pin must be low resistance. 8.9. 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 the value for r s .
zled7010 40v led driver with temperature compensation data sheet august 12, 2010 ? 2010 zentrum mikroelektronik dresden ag ? rev. 1.1 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 preliminary and subject to changes without notice. 23 of 23 9 ordering information product sales code description package ZLED7010-ZI1R zled7010 ? 40v led driver with temperature compensation sop8 (tape & reel) zled7010kit-d1 zled7010 demo board with led on cool body 12vac/vdc kit zled-pcb1 test pcb with one 3w white hb-led, cascadable to one multiple led string printed circuit board zled-pcb2 10 unpopulated test pcbs for modular led string with footprints of 9 common hb-led types printed circuit board 10 document revision history revision date description 1.0 june 10, 2010 production release version 1.1 august 12, 2010 revision to equation (5) for toff. update for contact information. 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 development. its char acteristics 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, incident al, 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 dis claims 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 dama ges in connection with or arising out of the furnishing, perfor- mance or use of this technical data, whether based on contract, warranty, tort (including negligence), strict liability, or oth erwise.
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