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high current 40v led driver with internal switch zled7x20 datasheet ? 2016 integrated device technology, inc. 1 april 20, 2016 vin i sense lx gnd zled7x20 d1 led string vs = 6 to 40 vdc (c3) rs l1 (c1) c2 0.1f adj 33h to 220h brief description the zled 7x20 continuous - mode inductive step - down converter family is part of our line of led - control ics. it is designed for applications requiring high brightness and high current. it can efficiently drive a single led or multiple serie s - connected leds from a voltage input higher than the led for - ward voltage : vin = 6 to 40 vdc. i t provides an adjust able output current 1.2a , which is set via an external resistor and controlled by the zled 7x20 ?s integrated high - side output current - sensing circuit and high speed internal 40v power switch . an externa l control signal , which can be a dc voltage, pwm , or micro controller - gener ated waveform , on the adj pin can also be used to linearly adjust a continuous output current or to control a gated out - put current. the output can be turned off by applying a voltage lower than 0.2v to th e adj pin, which puts the zled 7x20 in a low - curren t standby state. the zled 7x20 enables diverse industrial and consumer lighting applica tions requiring high driving currents , wide operating voltage range , high efficiency, and variable bright ness control. it offers over - temperature and led open - circuit pro - tection. the zled 7x20 can also minimize bill - of - material costs because very few external com - ponents are required for most applications . only a resistor, a diode, an inductor, and t hree capacitor s are needed for a typical basic application. features ? up t o 1.2a output current ? internal 40v power switch ? wide dc input voltage range 6 to 40 vdc ? output current accuracy: 3% (typical) ? dimming ratio: 1200:1 ? led open - circuit protection ? thermal shutdown protection benefits ? high efficiency: up to 98% ? single pin on/ off and brightness control using dc voltage or pwm ? very few external components needed for operation ? footprint compatible with our zled7000 depending on the application. available support ? evaluation kit physical characteristics ? operating junction tempera ture: - 40c to 1 2 5 c ? switching frequency: up to 1mhz zled7x20 family selection matrix product max. current output package zled7020 1.2a sot89 -5 zled7320 1.0a dfn -5 ZLED7520 0.75a dfn -5 zled7720 0.35a dfn -5 zled7x20 typical application circuit
high current 40v led driver with internal switch zled7x20 datasheet ? 2016 integrated device technology, inc. 2 april 20, 2016 zled 7x20 block diagram trim 1 v s 6 to 40 vdc 3 adj lx gnd 2 4 zled7x20 vdda vddd n led l1 d1 (c3) (c1) c2 0.1f rs v in 5 vcc i sense i sense uv por v ref v in 500k shutdown sd sd dr i sense and driver lx por i sense power supply, oscillator, and under- voltage detection (uv) power mos 33h to 220h typical applications ? illuminated led signs and other displays ? interior/exterior led lighting ? led street and traffic lighting (low voltage) ? mr16 led spot lights ? architecture/building led lighting ? retrofit led lighting fixtures ? led backlighting ? general purpose industrial and consumer led applications ordering information product code description package zled7020 zi1r zled7020 ? high current (1200ma) 40v led driver with internal switch s ot89 - 5 (tape & r eel) zled7320 zi1r zled7320 ? high current (1000ma) 40v led driver with internal switch dfn - 5 (tape & reel) ZLED7520 zi1r ZLED7520 ? high current (750ma) 40v led driver with internal switch dfn - 5 (tape & reel) zled7720 zi1r zled7720 ? high current ( 350m a ) 40v led driver with internal switch dfn - 5 (tape & reel) zled7020kit - d1 zled7020 - d1 demo board, 1 zled - pcb8 and 5 zled7020 ics kit zled - pcb8 test pcb with a 5w white h igh b rightness (hb) led, cascadable to a multiple led string printed circuit board (p cb) corporate headquarters 6024 silver creek valley road san jose, ca 95138 www.idt.com sales 1- 800- 345- 7015 or 408 - 284- 8200 fax: 408 - 284- 2775 www.idt.com/go/sales tech support www.idt.com/go/support disclaimer integrated device technology, inc. (idt) reserves the right to modify the products and/or specifications described herein at any time, without notice, at idt' s sole discretion. performance specifications and operating parameters of the described products are determined in an independent state and are not guarante ed to perform the same way when installed in customer products. the information contained herein is provided without representation or warranty of any kind, whether express or implied, including, but not limited to, the suita bility of idt's products for any particular purpose, an implied warranty of merchantability, or non - infringement of the intellectua l property rights of others. this document is presented only as a guide and does not convey any license under intellectual pr operty rights of idt or any third parties. idt's products are not intended for use in applications involving extreme environmental conditions or in life support systems or similar devices where the failure or malfunction of an idt product can be reasonably expected to significantly affect the health or safety of users. anyone using an idt product in such a manner does so at their own risk, absent an express, written agreement by idt. integrated device technology, idt and the idt logo are trademarks or registered trademarks of idt and its subsidiaries in the united states and other countries. other trademarks used herein are the prope rty of idt or their respective third party owners. for datasheet type definitions and a glossary of common terms, visit www.idt.com/go/glossary . all contents of this document are copyright of integrated devic e technology, inc. all rights reserved.
zled7x20 datasheet ? 2016 integrated device technology, inc. 3 april 20, 2016 contents 1 ic characteristics .......................................................................................................................................................... 5 1.1 absolute maximum ratings ................................................................................................................................... 5 1.2 operating conditions ............................................................................................................................................. 5 1.3 electrical parameters ............................................................................................................................................. 6 1.4 typical operation graphs ...................................................................................................................................... 7 2 circuit description ....................................................................................................................................................... 12 2.1 zled7x20 overview ............................................................................................................................................ 12 2.2 control of output current via external sense resistor rs .................................................................................. 12 2.3 control of output current via an external dc control voltage on the adj pin ................................................... 12 2.4 additional requirements if the v in input voltage has a high slew rate .............................................................. 13 2.5 control of output current via a pwm signal on the adj pin ............................................................................... 13 2.6 control of output current via a microcontroller signal on the adj pin ................................................................ 13 2.7 shutdown mode ................................................................................................................................................... 13 2.8 zled7x20 protec tion features ............................................................................................................................ 14 2.8.1 thermal shut - down protection ..................................................................................................................... 14 2.8.2 led open load protection ........................................................................................................................... 14 3 application circuit design ........................................................................................................................................... 15 3.1 applications ......................................................................................................................................................... 15 3.2 thermal considerations for application design ................................................................................................... 17 3.2.1 temperature effects of load, layout, and component selection ................................................................ 17 3.2.2 temperature effects of low supply voltage v in ........................................................................................... 17 3.3 external component selection ............................................................................................................................ 17 3.3.1 sense resistor rs ........................................................................................................................................ 17 3. 3.2 inductor l1 .................................................................................................................................................... 18 3.3.3 bypass capacitor c1 .................................................................................................................................... 19 3.3.4 de - bouncing capacitor c2 ........................................................................................................................... 20 3.3.5 capacitor c3 for reducing output ripple ..................................................................................................... 21 3.3.6 diode d1 ....................................................................................................................................................... 21 3.4 application circuit layout requirements ............................................................................................................. 21 4 esd protection ............................................................................................................................................................ 22 5 pin configuration and package ................................................................................................................................... 22 5.1 s ot89 - 5 package pin- out and dimensions for the zled7020 ........................................................................... 22 5.2 dfn - 5 package pin- out and dimensions for the zled7320, ZLED7520 and zled7720 ................................... 24 6 ordering information ................................................................................................................................................... 26 7 related documents ..................................................................................................................................................... 26 8 glossary ...................................................................................................................................................................... 26 9 document revision history ......................................................................................................................................... 27
zled7x20 datasheet ? 2016 integrated device technology, inc. 4 april 20, 2016 list of figures figure 1.1 zled7x20 supply operating current vs. input supply voltage (v in = 6 to 40 v) ................................................... 7 figure 1.2 zled7x20 supply quiescent shutdown current vs. input supply voltage (v in = 6 to 40 v) .................................. 7 figure 1.3 efficiency (%) vs. input supply vo ltage (v in = 6 to 40 v) per number of leds (rs=0.10 , l1=47 h) .................. 8 figure 1.4 efficiency vs. input supply voltage (v in = 6 to 40 v) per number of leds (rs=0.15 , l1=47 h) ........................ 8 figure 1 .5 efficiency vs. input supply voltage (v in = 6 to 40 v) ? per number of leds (rs=0.30 , l1=47 h) ....................... 9 figure 1.6 output current variation vs. input supply voltage (v in = 6 to 40 v) per number of leds (rs = 0.15 , l1 = 47 h) ............................................................................................................................................................................... 9 figure 1.7 sense voltage vs. operating temperature (rs=0.10 , l1=47 h, v in = 40 v) .................................................... 10 figure 1.8 dimming rate with 100hz square wave control signal (pwm) at adj pin (current rise time=7.85 s) ............. 10 figure 1.9 led open - circuit protection (rs=0.30 , l1=47 h, v in = 24 v) .......................................................................... 11 figure 3.1 basic zled7x20 application circuit with output current determined only by rs ................................................ 15 figure 3.2 basic zled7x20 application circuit with output current controlled by external dc voltage .............................. 15 figure 3.3 basic zled7x20 application circuit with output current set by external square wave voltage (pwm) ............ 16 figure 3.4 basic zled7x20 application circuit with output current controlled by external microcontroller signal .............. 16 figure 5.1 zled7020 pin configuration ? sot89 -5 package ............................................................................................... 22 figure 5.2 sot89 - 5 package dimensions for the zled7020 ............................................................................................... 23 figure 5.3 zled7320, ZLED7520 & zled7720 pin configuration ? dfn - 5 package ......................................................... 24 figure 5.4 dfn - 5 (dfn4*4 - 05l) package dimensions for the zled7320, ZLED7520 & zled7720 ................................... 25 list of tables table 3.1 recommended values for sense resistor rs (adj pin floating at nominal voltage v ref =1.2v) .......................... 17 table 5.1 zled7020 pin descriptions ? sot89 - 5 package ................................................................................................. 22 table 5.2 zled7320, ZLED7520 & zled7720 pin descriptions ? dfn - 5 package .......................................................... 24
zled7x20 datasheet ? 2016 integrated device technology, inc. 5 april 20, 2016 1 ic characteristics note: exceeding the maximum ratings given in this section could cause operat ion failure and /or caus e permanent damage to the zled 7x20 . exposure to these conditions for extended periods may affect device reliability. 1.1 absolute maximum ratings n o . parameter symbol conditions min typ max unit 1.1.1 input voltage (also see specification 1.2.2 ) v in - 0.3 50 v 1.1.2 i sense pin voltage v isense v in 5v v in -5v v in +0.3v v v in <5v - 0.3v v in +0.3v v 1.1.3 lx pin output voltage v lx - 0.3 50 v 1.1.4 adj pin input voltage v adj - 0.3 6 v 1.1.5 lx pin switch output c urrent i lx 1.5 a 1.1.6 power d issipation p tot 0.5 w 1.1.7 esd p erformance human body model 3 .5 kv 1.1.8 junction temperature t j 150 c 1.1.9 junction to ambient thermal resistance r ja sot89 - 5 package 100 k/w dfn5 package 130 k/w 1.1.10 storage temperatur e t s -55 150 c 1.2 operating conditions no. parameter symbol conditions min typ max unit 1.2.1 operating j unction temperature t j -40 1 2 5 c 1.2.2 input voltage (also see specification 1.1.1 ) v in 6 40 v
zled7x20 datasheet ? 2016 integrated device technology, inc. 6 april 20, 2016 1.3 electric al parameters t est c onditions for the following specifications are t amb = 25c typical and v in = 12 v unless otherwise noted . production testing of the chip is performed at 25c unless otherwise stated . functional operation of the chip and specified paramet ers at other temperatures are guaranteed by design, characterization, and process control . no. parameter symbol conditions min typ max unit 1.3.1 quiescent supply current i inqoff output off ? adj pin grounded 90 120 160 a i inqon output switching ? adj pin floa ting 450 600 a 1.3.2 mean current sense threshold vol t age v sense 97 100 103 mv 1.3.3 sense threshold hysteresis v sensehys 15 % 1.3.4 i sense pin input current i sense v sense = v in - 0.1v 8 a 1.3.5 internal reference voltage measured at adj pin v ref adj pin floating 1.2 v 1.3.6 resistance between v ref and adj pin r adj 500 k 1.3.7 external dc brightness control voltage on adj pin v adj 0.3 1.2 v 1.3.8 dc on - off control voltage on adj pin for switching zled 7x20 from active state to quiescent state v adjoff v adj falling 0.1 5 0.2 0.25 v 1.3.9 dc off - on control voltage on adj pin for switching zled 7x20 from quiescent state to active state v adjon v adj rising 0.2 0.25 0.3 v 1.3.10 lx switch continuous current i lxmean_0 zled7020 1.2 a i lxmean_3 zled7320 1.0 a i lxmean_5 ZLED7520 0.75 a i lxmean_7 zled7720 0.35 a 1.3.11 lx switch leakage current i lx(leak) 1 a 1.3.12 lx switch on resistance r lx 0.27 0.4 1.3.13 minimum switch on time t onmin lx switch on 200 ns 1.3.14 minimum switch off time t offmin lx switch off 200 ns 1.3.15 dimming rate d dim 1 led, f =100hz, vin=15v, l1 = 27 h 1200:1
zled7x20 datasheet ? 2016 integrated device technology, inc. 7 april 20, 2016 no. parameter symbol conditions min typ max unit 1.3.16 recommended operating frequenc y maximum f lxmax 1 mhz 1.3.17 recommended output switch duty cycle range at f lxmax d lx 0.3 0.9 1.3.18 propagation delay of internal comparator t pd 50 ns 1.3.19 thermal shutdown temperature t sd 150 c 1.3.20 thermal shutdown hysteresis t sd - hys 20 k 1.4 typical ope ration graphs the curves are valid for the typical application circuit and t amb = 25c unless otherwise noted. figure 1 . 1 zled 7x20 supply operating current vs. input supply voltage (v in = 6 to 40 v) 0 100 200 300 400 500 600 5 10 15 20 25 30 35 40 vin(v) icc(ua) figu re 1 . 2 zled 7x20 supply quiescent shutdown current vs. input supply voltage (v in = 6 to 40 v) 0 50 100 150 200 250 5 10 15 20 25 30 35 40 vin(v) icc(ua)
zled7x20 datasheet ? 2016 integrated device technology, inc. 8 april 20, 2016 figure 1 . 3 efficiency (%) vs. input supply voltage (v in = 6 to 4 0 v) ? per number of leds (rs=0.10 , l1=47 h) rs=0.10 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 5 10 15 20 25 30 35 40 vin(v) effiency(%) 1led 3led 7led 10led figure 1 . 4 efficiency vs. input supply voltage (v in = 6 to 40 v) ? per number of leds (rs=0.15 , l1=47 h) rs=0.15 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 5 10 15 20 25 30 35 40 vin(v) effiency(%) 1led 3led 7led 10led ? minimum v in depends on number of leds. ? minimum v in depends on number of leds.
zled7x20 datasheet ? 2016 integrated device technology, inc. 9 april 20, 2016 figure 1 . 5 efficiency vs. input sup ply voltage (v in = 6 to 40 v) ? per number of leds (rs=0.30 , l1=47 h) rs=0.30 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 5 10 15 20 25 30 35 40 vin(v) effiency(%) 1led 3led 7led 10led figure 1 . 6 output current variation vs. input supply voltage (v in = 6 to 40 v) per numb er of leds (rs = 0.15 , l1 = 47 h) rs=0.15 0.6 0.61 0.62 0.63 0.64 0.65 0.66 0.67 0.68 0.69 0.7 5 10 15 20 25 30 35 40 vin(v) iout(a) 1led 3led 7led 10led minimum v in depends on number of leds.
zled7x20 datasheet ? 2016 integrated device technology, inc. 10 april 20, 2016 figure 1 . 7 sense voltage vs. operating temperature (rs=0.10 , l1=47 h , v in = 40 v ) figure 1 . 8 dimming rate with 100hz square wave control signal (pwm) at adj pin (cur rent rise time=7.85 s) t rigger c1 hfr stop - 50mv edge positive timeb ase - 3.00 ms 1.00ms/div 500ks 50 ms/s 97.8 98.0 98.2 98.4 98.6 98.8 99.0 99.2 99.4 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 v sense (mv) temperature ( c)
zled7x20 datasheet ? 2016 integrated device technology, inc. 11 april 20, 2016 figure 1 . 9 led open - circuit protection (rs=0.30 , l1=47 h, v in = 24 v) t rigger c1 dc stop 15.0v edge negative timeb ase - 5.2 s roll 5.00s /div 500ks 10 ks /s
zled7x20 datasheet ? 2016 integrated device technology, inc. 12 april 20, 2016 rs v 1 . 0 i outnom = s adj outdc r v 083 . 0 i ? = 2 circuit description 2.1 zled 7x20 overview the zled 7x20 is a continuous - mode inductive step - down converter led driver for driving single or multiple series - connected leds from a voltage input higher than the led voltage (vin = 6 to 40 vdc ; see section 3.2.2 for important details ). the zled 7x20 provides an adjustable output current (1.2a maximum for zled7020; 1.0a maximum for zled7320 ; 0.75a maximum for ZLED7520; 0.35a maximum for zled7720 ), which is nominally set via an external sense resistor rs and controlled by the zled 7x20 ?s integrated high - side output current - sensing circuit and output switch. an external control signal ( e.g., dc voltage , pwm waveform , or microprocessor signal ) on the ad j pin can be used to linearly adjust the output for continuous , variable, or gated - output current. s ee page 2 for a block diagram of the zled 7x20 . the output can be turned off by applying a voltage 0.2v (typical) to the adj pin, which puts the zled 7x20 in a low - current standby state. see section 2.7 for a description of this shutdown mode. only a resistor, a diode, an inductor, and three capacitors are ne eded for a typical basic application. refer to the application circuit s in section 3 for the location of the components referenced in the following sections. 2.2 control of output current via external sense resistor rs external sense resistor rs , which is connected between the v in and i sense pin s as shown in figure 3 . 1 , sets i outnom , the nominal average output current. equation (1) can be used to calculate the nominal output current , which is the lx switch output current i lx if the adj pin is floating (v adj = v ref =1.2v ) . see section 3.3.1 for recommended values for rs in a typical basic application and section 3.4 for layout guidelines for rs . note that the peak i outnom including ripple (see section 3.3.5 ) must not exceed the maximum current specific ations ( 1.3.10 ). (1) 2.3 control of output current via an external dc control voltage on the adj pin a n external dc voltage (v adj ) input on the adj pin can control brightness by setting the output current to a value b elow the nominal average current i outnom determined by r s . with this method, the output current can be adjust ed from 25% to 100% of i outnom . the dc voltage source must be capable of driving the adj pin?s input impedance r adj ( 50 0k approximately 25%; internal pull - up resistor to v ref ). see figure 3 . 2 for a typical application circuit. the nominal average output current i outdc resulting from an external dc control voltage v adj can be cal culated via equation (2) where 0.3v v adj 1.2v : (2)
zled7x20 datasheet ? 2016 integrated device technology, inc. 13 april 20, 2016 b rightness is 100% if v adj = v ref, the internal reference voltage, which can be measured on the adj pin when it is floating (1.2v, typical). if v adj 1.2v , the current is automatically clamped at 100% brightness. note: absolute maximum v adj = 6v. 2.4 additional requirements if the v in input voltage has a high slew rate the analog dimming input adj can be used for implementing a soft - start function of the leds by con necting a capacitor to ground. the soft - start time constant is determined by the product of the internal pull - up resistor (500k ? typical) and the external capacitor. important: if the supply voltage v in might have a high slew rate (> 1v/s) when powered on , a resistor that is 1k ? must be placed in series with the capacitor to guarantee correct power - on timing for the zled7x20 and proper loading of the current sense trimming data into the appropriate register. this resistor is not necessary if the capacito r is 470pf. if the adj pin is controlled from an external voltage source or pwm signal, a series resistor is strongly recommended for noise immunity reasons and to avoid bulk current injection. 2.5 control of output current via a pwm signal on the adj pin an external pulse width modulation (pwm) control signal input on the adj pin can be used for brightness or gated on/off control of the output current by driving the output current to a value below the nominal average current determined by r s . see figure 3 . 3 for a typical application circuit. the pwm or gated on/off control signal can be within the range of 0 to 5 v . t he logic hig h level must be higher than 1.2 v and the logic low level must be below 0.2v . i t must be ca pable of driving the adj pin?s input impedance r adj ( approximately 500k; internal pull - up resistor to v ref ) . 2.6 control of output current via a microcontroller signal on the adj pin an external control signal from the open drain output of a microcontroller can provide on/off or pwm brightness control by driving the adj pin. see figure 3 . 4 for a typical application circuit. diode d2 and resistor r 1 shown in figure 3 . 4 suppress any negative high - amplitude spikes on the adj input due to the drain - source capacitance of the fet in the microcontroller?s output. negative spikes on the adj input could cause output current errors or unintended zled 7x20 operation. the signal input to th e adj pin must be capable of driving the adj pin?s input impedance r adj ( approximately 500k; internal pull - up resistor to vref) . 2.7 shutdown mode if the adj pin voltage v adj is v adjoff ( 0.2v 0.05v ) , the supply current and output on the lx pin are quiesc ent at a low standby level (i inqoff = 120a nominal ) . raising the adj pin voltage so that v adj v adjion (0.25v 0.05v) will switch the output back to full operational mode.
zled7x20 datasheet ? 2016 integrated device technology, inc. 14 april 20, 2016 2.8 zled 7x20 protection features 2.8.1 thermal shut - down protection t he zled 7x20 automatica lly protect s itself from damage due to over - temperature conditions . if the zled 7x20 ?s temperature exceeds the thermal shutdown threshold (t sd = 150 c, typical), the zled 7x20 will shut down . to avoid erratic zled 7x20 operation, a 20 k hysteresis (t sd- hys ) is applied that prevents it from returning to operation until its temperature falls below the hysteresis threshold (t sd - t sd- hys ). also refer to section 3.2 for additional thermal considerations. 2.8.2 led open load p rotection as a step - down converter , t he zled 7x20 has inherent open - load circuit protection . since the l1 inductor is connected in series with the led string , the current flow is interrupted if the load is open and the lx output of the zled 7x20 will not be damaged. this provides an advantage over other products such as boost converters, for which the internal switch can be damaged by back emf forcing the drain above its breakdown voltage.
zled7x20 datasheet ? 2016 integrated device technology, inc. 15 april 20, 2016 3 application circuit design 3.1 applications the zled 7x20 is designed for applications requiring features such as high - speed switching, variable brightness control, operation with voltages up to 40v, high efficiency, or protection from over - temperature, or open led circuit conditions. typical applications include mr16/mr11 led spotlights , l ed street lights , parabolic aluminized reflector (par) led lights, and other g eneral purpose industrial and consumer led applications. figure 3 . 1 , figure 3 . 2 , figure 3 . 3 , and figure 3 . 4 demonstrate basic application circuits for the four options for controlling output current described in section 2 . figure 3 . 1 basic zled 7x20 application circuit with output current determined o nly by rs vin i sense lx gnd zled7x20 d1 led string vs = 6 to 40 vdc c3 rs l1 c1 c2 0.1f adj figure 3 . 2 basic zled 7x2 0 application circuit with output current controlled by external dc voltage v in i sense lx gnd zled 7 x 20 d 1 vs = 6 to 40 vdc c 3 rs l 1 c 1 c 2 0 . 1 f adj + _ dc ( 0 . 3 v to 1 . 2 v ) led string
zled7x20 datasheet ? 2016 integrated device technology, inc. 16 april 20, 2016 figure 3 . 3 basic zled 7x20 application circuit with output current set by external square wave voltage (pwm) v in i sense lx gnd zled 7 x 20 d 1 vs = 6 to 40 vdc c 3 rs l 1 c 1 c 2 0 . 1 f adj pwm ( 0 v to ~ 5 v ) led string figure 3 . 4 basic zled 7x20 application circuit with output current controlled by external microcontroller signal v in i sense lx gnd zled 7 x 20 d 1 vs = 6 to 40 vdc c 3 rs l 1 c 1 c 2 0 . 1 f adj led string r 1 10 k d 2 micro - processor gnd
zled7x20 datasheet ? 2016 integrated device technology, inc. 17 april 20, 2016 3.2 thermal considerations fo r application design 3.2.1 temperature effects of load, layout , and component selection do not exceed the package power dissipation limits by driving high load current s or by operating the chip at high ambient temperatures. power dissipation also increases if th e efficiency of the circuit is low as could result from selecting the wrong coil or from excessive parasitic output capacitance on the switch output. see the layout guidelines in section 3.4 . 3.2.2 temperature effects of low supply voltage v in until the supply input voltage on the v in pin has risen above the internally - set startup threshold, the zled 7x20 ?s internal regulator disables the drive to the internal power mosfet output switch. above this threshold, the mosfe t on - resistance is low enough for the chip to start to operate ; h owever, if the supply voltage remains below the specified minimum (6v) , the duty cycle of the output switch will be high and the zled 7x20 power dissipation will be at a maximum. a void operati ng the zled 7x20 under such conditions to reduce the risk of damage due to exceeding the maximum die temperature. w hen driving multiple leds, the ir combined forward voltage drop is typically high enough to prevent the chip from switching when v in is below 6 v , so there is less risk of thermal damage. 3.3 external component selection note: also see section 3.4 for layout guidelines for the following external components. 3.3.1 sense resistor rs table 3 . 1 gives values for rs under normal operating conditions in the typical application shown in figure 3 . 1 . these values assume that the adj pin is floating and at the nominal voltage of v ref =1.2v. n ote : under the conditions given in table 3 . 1 , in order t o maintain the switch current below the maximum value specified in section 1 , 0.082 is the minimum value for rs for the zled7020 , 0.1 for the zled7320 , 0.13 for the zled75 20 and 0.27 for the zled77 20. it is possible to use different values of r s if the adj pin is d riven from an external voltage. to ensure stable output current, use a 1% accuracy resistor with adequate power tolerance and a good temperature characteristic for rs . table 3 . 1 recommended values for sense resistor rs (adj pin floating at nominal voltage v ref =1.2v) nominal average output current (ma) value for r s () 1200 (maximum for zled7020) 0.082 1000 (maximum for zled7320) 0.1 750 (maximum for ZLED7520) 0.13 667 0.15 350 (maximum for zled7720) 0.27 333 0.3
zled7x20 datasheet ? 2016 integrated device technology, inc. 18 april 20, 2016 ) r r r ( * i v v i * l t lx l s avg led in on + + ? ? ? = ) r r ( * i v v i * l t l s avg d led off + + + ? = 3.3.2 inductor l1 the r ecommended range for the l1 inductor is 33 h to 220h . select the inductor valu e for l1 as needed to ensure that switch on/off times are optimized across the load current and supply voltage ranges. if the application requires a high supply voltage and low output current , inductance values at the high end of this range are recom - mende d to minimize errors due to switching delays, which can reduce efficiency and increase ripple on the output . also see section 3.4 for layout considerations for l1. equations (3) and (4) can be used to calculate t on and t off . on time for lx switch ( t onmin >200ns): (3) off time for lx switch ( t offmin >200ns) : (4) where: symbol description l l1 coil inductance in h i l1 coil peak - peak ripple current in a (internally set to 0.3 ? i avg ) v in supply voltage in v v led total forward voltage in v for led string i avg nominal average led current in a rs external current sense resistor in r l l1 coil resistance in r lx lx switch r esistance in v d d1 diode forward voltage at the required load current in v the inductance value has an equivalent effect on t on and t off and therefore affects the switching frequency. for the same reason , the inductance has no influence on the duty cyc le , for which the relation ship 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 switching frequency and duty c ycle. to achieve optimum performance, duty cycle s close to 0.5 at the nominal average supply voltage are preferable for improving the temperature stability of the output current.
zled7x20 datasheet ? 2016 integrated device technology, inc. 19 april 20, 2016 khz 8 . 121 s 56 . 5 s 64 . 2 1 t t 1 f off on lx = + = + = 3 . 0 s 56 . 5 s 64 . 2 s 64 . 2 t t t v 12 v 4 . 3 v v d off on on in led lx + = + = = ( ) s 56 . 5 26 . 0 30 . 0 * a 333 . 0 v 36 . 0 v 4 . 3 a 333 . 0 * 3 . 0 * h 220 t off = ? + ? + + = ( ) s 64 . 2 27 . 0 26 . 0 3 . 0 * a 333 . 0 v 4 . 3 v 12 a 333 . 0 * 3 . 0 * h 220 t on = ? + ? + ? ? ? = lx max lx f max d avg min f * v d * i v t * i 1 c ? = ? = equations (5) , (6) , (7) , and (8) provide an example of calculating t on , t off , operating frequency f lx , and duty cycle d lx when using a 220 h inductor for l1 and v in =12v , rs = 0 . 30 , r l =0.26, v led =3.4v, i avg =333ma , v d =0.36v , and r lx =0.27 . example: (5) (6) (7) (8) for the l1 inductor, u se a coil with a continuous current rating higher than the required mean output current and a saturation current that exceeds th e peak output current by 30% to 50% for robustness against transient con - ditions ; e.g ., during start - up. 3.3.3 bypass capacitor c 1 the bypass capacitor c1 has two functions: maintaining operating voltage and bypassing the current ripple of the switching convert er. in general low esr capacitors must be used. if the circuit is supplied by rectified line voltage, c1 must provide enough charge to maintain the zled 7x20 ?s minimum operating voltage as well as the forward voltage of the led string to keep the applicatio n working even if the rectified supply voltage periodically drops below these values. a rough estimate for the minimum capacity needed can be calculated with equation (9) . (9) where: symbol description i avg avera ge nominal led string current assuming that the contribution of the ic supply cu rrent is negligible . t d discharge time at given ac frequency. will be a maximum of 10ms (? period duration) at 50hz. v max peak rectified supply voltage minus led string forward voltage or minimum zled 7x20 supply voltage, wh ichever is greater .
zled7x20 datasheet ? 2016 integrated device technology, inc. 20 april 20, 2016 f 135 v 2 . 3 * 3 2 * v 24 ms 10 * a 33 . 0 1 c min = ? = ripple on avg min v t * i 1 c = nf 367 1 . 0 * v 24 s 67 . 2 * a 33 . 0 1 c min = = example: for an application with 3 leds with 3.2v forward voltage each driven at 0.33a and supplied with rectified 24vac , a min imum bypass capacitor c1 of 220f or 330f m ight be adequate. compared to the calculation , a safety margin of about 50% must be added to consider temperature effects and aging . (10) a second function of c1 is to bypass the current ripple of the switching con verter and thus prevent it from disturbing a stable ic supply or backlash on the power supply circuit. for this reason , even in dc- supplied applications , the use of an adequate c1 m ight be useful. the defining parameters are now as shown in equation (11) : (11) where: symbol description i avg avera ge nominal led string current. t on o n time of the interna l mosfet output switch. note: t on must be longer than t onmin =200ns . v ripple permissible voltage ripple on the s upply voltage. example: for an application of 3 leds driven at 0.33a and supplied with 24vdc , a maximum ripple of 10% is allowed. the zled 7x20 is operated at 150khz with a duty cycle of 0.4 leading to an on time of 2.67 s . as calculated in equation 12 , a capacitor c1 of 470nf may be adequate, again including a safety margin of about 50% . (12) to achieve maximum stability over temperature and voltage, an x7r, x5r, or better dielectric is recommended while y5v must be avoided. 3.3.4 de - bouncing capacitor c2 exte rnal capacitor c2 minimizes ground bounce during switching of the internal mosfet output switch. ground bounce is typically caused by parasitic inductance and resistance due to the distance between the grounds for the power supply and the zled 7x20 gnd pin. use a 0.1 f , x7r ceramic capacitor to ground for c2.
zled7x20 datasheet ? 2016 integrated device technology, inc. 21 april 20, 2016 3.3.5 capacitor c3 for reducing output ripple if required, the c3 can be used to reduce p eak - to - peak ripple current in the led string. low esr capacitors should be used because the efficiency of c3 largely de pends on its esr and the dynamic resistance of the leds. for an increased number of leds, using the same capacitor will be more effective. lower ripple can be achieved with higher capacitor values, but this will increase start - up delay by reducing the slop e of the led voltage as well as cause increased current during converter start - up . the capacitor will not affect operating frequency or effici - ency. for a simulation or bench optimization, c3 values of a few f are an applicable starting point for the given configuration. ripple current reduction is approximately proportional to the value of c3. 3.3.6 diode d1 t he flyback diode d 1 must have a continuo us current rating greater than the maximum output load current and a peak current rating higher than the peak l1 coil current. important: u se a low - capacitance, fast schottky diode that has low reverse leakage at the maximum operating temperature and maxim um operating voltage for the application to avoid excess power dissipation and optimize performance and efficiency. for silicon diodes, there is a concern that the higher forward voltage and increased overshoot from reverse recovery time could increase the peak lx pin voltage (v lx ). the total voltage v lx (includ ing ripple voltage) must not be >50v. 3.4 application circuit layout requirements the following guidelines are strongly recommended when laying out application circuits: ? important: locate t he l 1 inductor and the c1 input decoupling capacitor as close as possible to the zled 7x20 to minimize parasitic inductance and resistance, which can compromise efficiency . use low resistance connections from l 1 to the lx and v in pins. ? all circuit board traces to the lx pin must be as short as possible because it is a high - speed switching node. ? if the adj pin floats, all circuit board traces to the adj pin must be as short as possible to reduce noise pickup. ? d o not lay out high - voltage traces near the adj pin because if the board is contaminated, leakage current can affect the adj pin voltage and cause unintended output current. to further reduce this risk, use a ground ring around the adj pin. (also see section 2.8 regarding t he zled 7x20 ?s protection circuitry for preventing excessive output current.) ? to minimize ground bounce, locate the 0.1 f external capacitor c2 as close as possible to the v in pin and solder the zled 7x20 ?s gnd pin directly to the ground plane. (also, see se ction 3.3.4 regarding ground bounce.) ? because rs is typically a low value resistor, it is important to consider the resistance of the traces in series with r s as part of the total current sense resistance. use t races that are as short and wide as possible to minimize this effect. ? the zled 7x20 ?s thermal pad must be grounded.
zled7x20 datasheet ? 2016 integrated device technology, inc. 22 april 20, 2016 4 esd protection all pins have an esd protection of 3 500 v according to the h uman b ody m odel (hbm) . the esd test follows the h uman body model with 1.5 k/100 pf based on mil 883 - h, method 3015.8 . 5 pin configuration and package 5.1 sot89 - 5 package pin - out and dimensions for the zled7020 figure 5 . 1 zled7 0 20 pin configuration ? sot89 - 5 package table 5 . 1 zled7 0 20 pin desc riptions ? so t89 - 5 package pin no. description (also see section 3.3 for layout guidelines) lx 1 drain of internal po wer switch gnd 2 ground adj 3 on/off and brightness control input i sense 4 current adjustment input. resistor r s from i sense to v in determines the nominal average output current. i outnom =0.1 v/r s thermal pad connect to gnd. v in 5 input voltage (6v to 40v). 1 2 3 5 4 lx v in gnd thermal pad adj i sense
zled7x20 datasheet ? 2016 integrated device technology, inc. 23 april 20, 2016 figure 5 . 2 sot89 - 5 package dimensions for the zled7020 symbol dimension (mm) min max a 1.400 1.600 b 0.320 0.520 b1 0.360 0.560 c 0.350 0.440 d 4.400 4.600 d1 1 .400 1.800 e 2.300 2.600 e1 3.940 4.250 e 1.500 typ ical e1 2.900 3.100 l 0.900 1.100 b b 1 e 1 e d d 1 l e 1 e c a
zled7x20 datasheet ? 2016 integrated device technology, inc. 24 april 20, 2016 5.2 dfn - 5 package pin - out and dimensions for the zled7320 , ZLED7520 and zled7720 figure 5 . 3 zled7 3 20 , ZLED7520 & zled7720 pin configuration ? dfn - 5 package lx gnd adj v in i sense 1 2 3 4 5 1 2 3 4 5 top bottom table 5 . 2 zled7 3 20 , ZLED7520 & zled7720 pin descriptions ? dfn - 5 package pin no. description (also see section 3.3 for layo ut guidelines) lx 1 drain of internal power switch gnd 2 ground adj 3 on/off and brightness control input i sense 4 current adjustment input. resistor r s from i sense to v in determines the nominal average output current. i outnom =0.1v/r s thermal pad co nnect to gnd. v in 5 input voltage (6v to 40v).
zled7x20 datasheet ? 2016 integrated device technology, inc. 25 april 20, 2016 figure 5 . 4 dfn - 5 (dfn4*4 - 05l) package dimensions for the zled7320 , ZLED7520 & zled7720 b a c n m d j i g h k 1 e k f symbol dimension (mm) min max a 3.95 4.05 b 3.95 4.05 c 0.70 0 .80 d 0.37 0.47 e 0.75 0.95 f 2.17 2.42 g 1.50 h 0.41 0.51 i 0.55 j 1.70 k 1.75 k1 1.40 1.55 m 0.000 0.050 n 0.200
zled7x20 datasheet ? 2016 integrated device technology, inc. 26 april 20, 2016 6 ordering information ordering information product sales code description package zled7020 zi1r zled7020 ? high current (1200ma) 40v led driver with internal switch sot89 - 5 (tape & reel) zled7320 zi1r zled7320 ? high current (1000ma) 40v led driver with internal switch dfn - 5 (tape & reel) ZLED7520 zi1r ZLED7520 ? high current (750ma) 40v led driver with internal switch dfn - 5 (tap e & reel) zled7720 zi1r zled7720 ? high current (350ma) 40v led driver with internal switch dfn - 5 (tape & reel) zled7020kit - d1 zled7020 - d1 demo board, 1 zled - pcb8 and 5 zled7020 ics kit zled - pcb8 test pcb with one 5w white high brightness (hb) led, casc adable to one multiple led string printed circuit board (pcb) zled - pcb2 10 unpopulated test pcbs for modular led string with footprints of 9 common hb led types printed circuit board (pcb) 7 related documents document zled7x20 feature sheet zled7020 application note ? pcb layout visit the zled7x20 product page s at h ttp://www.idt.com/ or contact your nearest sales office for the latest version of these documents. 8 glossary term description esd electrostatic discharge emf electromagnetic force esr equivalent series resistance pwm pulse width modulation
zled7x20 datasheet ? 2016 integrated device technology, inc. 27 april 20, 2016 9 document revision history revision date description 1.0 0 june 27, 2011 first issue. 1.1 0 august 9, 2011 update to demo kit description. 1. 2 0 august 12, 2011 update to inclu de ZLED7520 & zled7720. update for demo kit description 1. 3 0 february 6 , 2012 update to inc lude operating junction temperature. 1.40 june 1 1 , 2014 update to add new section 2. 4 regarding requirements if v in has a high slew rate. updates for cover and page header imagery. updates for idt contact information. addition of ?related documents? and ?glossary? sections. a pril 20 , 2016 changed to idt branding. corporate headquarters 6024 silver creek valley road san jose, ca 95138 www.idt.com sales 1- 800- 345- 7015 or 408 - 284- 8200 fax: 408 - 284- 2775 www.idt.c om/go/sales tech support www.idt.com/go/support disclaimer integrated device technology, inc. (idt) reserves the right to modify the products and/or specifications described herein at any time, without n otice, at idt's sole discretion. performance specifications and operating parameters of the described products are determined in an independent state and are not guarante ed to perform the same way when installed in customer products. the information contai ned herein is provided without representation or warranty of any kind, whether express or implied, including, but not limited to, the suitability of idt's products for any particular purpose, an implied warranty of merchantability, or non - infringement of t he intellectual property rights of others. this document is presented only as a guide and does not convey any license under i ntellectual property rights of idt or any third parties. idt's products are not intended for use in applications involving extreme environmental conditions or in life support systems or similar devices where the failure or malfunction of an idt product can be reasonably expected to significantly affect the health or safety of users. anyone using an idt product in such a manner does s o at their own risk, absent an express, written agreement by idt. integrated device technology, idt and the idt logo are trademarks or registered trademarks of idt and its subsidiaries in the united states and other countries. other trademarks used herein are the property of idt or their respective third party owners. for datasheet type definitions and a glossary of common terms, visit www.idt.com/go/glossary . all contents of this document are copyright of in tegrated device technology, inc. all rights reserved.

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