zxld383 zxld383 document number: ds32189 rev. 3 - 2 1 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated single or multi cell led driver solution summary the zxld383 is a single or multi cell led driver designed for ap plications requiring step-up volt age conversion from a very low input voltage. the ic generates consta nt current pulses that are ideal for drivin g single or multiple leds over a wide range of operating voltages. it includes an on/off enable input t hat can be driven directly fr om a photocell array or an open collector/drain logic output. the enable input features an ultr a-low voltage drop diode to ground, eliminating the need for a photocell array isolation diode in garden light applications. the zxld383 uses a pfm control technique to drive an internal switching transistor which exhibits a low saturation resistance. this ensures high efficiency, even for input voltages as low as 1.0v. the ic can start up under full load and operates down to an input voltage of below 0.9v. the zxld383 is offered in the space saving tsot23-5 package or in die form, offering an excellent cost vs. performance solution for single cell led driving applications. features ? 85% efficiency ? user adjustable output current ? single cell operation ? low saturation voltage ? tsot23-3 package ? available also in die form ? simple application circuit application ? garden lights ? door/pathway illumination ? led flashlight and torches ? led backlights ? white led driver ? gated boost supply generator pin assignments tsot23-3 (top view) typical application circuit ena 1 2 3 5 4 gnd nc v cc v out
zxld383 zxld383 document number: ds32189 rev. 3 - 2 2 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated block diagram fig 1. zxld383 block diagram pin description pin no. name description 1 ena enable / photodiode array battery charge input 2 gnd ground 3 nc not connected (internally open circuit) 4 v out switch output external inductor/led 5 v cc supply voltage, generally alkaline, nimh or nicd single cell zxld383 gnd vout vcc l1 nimh 1.2v led coff con pulse control rsense dch ena diode array
zxld383 zxld383 document number: ds32189 rev. 3 - 2 3 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated absolute maximum ratings parameter rating unit supply voltage (v cc ) -0.6 to 6 v output voltage (v out ) -0.6 to 20 v enable voltage (v ena ) -1 to 3.5 v supply current 20 ma output switch current 800 ma power dissipation (tsot23-3) 450 mw power dissipation die 1 w operating temperature range -20 to 85 c storage temperature range -55 to 150 c electrical characteristics measured at t amb = 25c, l = 6.8h, i ena = 0 and v cc = 1.5v unless otherwise specified. parameter conditions limits units min typ. max supply voltage operating range l = 10 h 0.9 3.3 v minimum supply start-up voltage l = 10 h 0.8 0.9 v supply current quiescent 2 4 8 ma supply current shutdown v ena = v cc ? 0.8v 17 30 a supply current under-voltage v cc = 0.6v 20 a switch current at turn-off 250 320 400 ma switch satura tion voltage i out = 200ma 100 300 mv switch leakage current v out = 20v, v ena = 0v 10 a mean led current v led = 3.5v 40 50 65 ma efficiency v led = 3.5v 85 % operating frequency v led = 3.5v 330 khz discharge pulse width 0.7 1.5 2.5 s enable input threshold v cc - 0.8 v cc - 0.6 v cc - 0.2 v enable input current v ena = 0.2v 0 -11 -20 a enable input voltage i ena = -20ma 0 -90 -250 mv
zxld383 zxld383 document number: ds32189 rev. 3 - 2 4 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated device description the zxld383 is a simple pfm, dc-dc controller combined with a high performance internal switching transistor, enabling the production of a high efficiency boost converter for use in si ngle cell applications. it includes a dual function enable inp ut which serves both as an operation inhibit control and an ultr a-low voltage drop isolation diode for battery charging purposes in garden light applications. a block diagram is shown for the zxld383 in figure 1. with power applied and the enable pin held at v cc , an oscillator within the pulse control block forces the internal switching transistor to switch on to start an energy charge cy cle. the low saturation voltage switch pulls the v out pin close to ground which forces the supply voltage across the external inductor l1. this causes a current to build up, storing energy in the inductor. during this phase, switch current and supply volt age are monitored and used by the pulse control circuit to determine the optimum drive condit ions and on-time. at the end of the energy char ge cycle, the internal switch is turned off rapidly, interrupting the current flow through l1 which causes the voltage on v out to rise dramatically. when the voltage on v out reaches the load led?s forward (on) volt age, the inductor current is transferred from the internal switch to the led, starting the energy discharge cycle. with the voltage across the inductor reversed, the current flowing through it (and the led) now falls. when the inductor current reaches zero, the voltage on the v out pin falls back towards v cc . this action is sensed by the pulse control circuit and is combined with the out put of an off-period timer to initiate the next energy charge cycle. except for low level losses, all the energy stored in the inductor during a charge cycle is channeled to the load led during the following discharge cycle. the current fed into the load led has a sa wtooth waveform, the average (dc) value of which is kept constant by the pulse control circuit for varying supply voltage and temperature. it is possible to change the output current given by the zxld383 by changing the value of inductor l1. the larger the inductance of l1, the lower the output current. a table/graph showing the relationship between inductance and out put current is given later in this dat asheet. since the output current of the zxld383 is a sawtooth waveform, its peak value is substantially larger than the dc/average valu e. the table also provides this data. the internal switching transistor has a minimum collector-emitter breakdown voltage of 20v and this sets the maximum load voltage allowable. the minimum value is set by a feature of the pulse control circuit t hat requires the load voltage to be at least 0.5v greater than v cc . (the device will function with load voltages smaller than this but output current regulation will be impaired.) higher than nominal load voltages will lower the average (dc) output current generated for a given inductor value. the enable pin inhibits the operation of the output switch if held at a potential of vcc-0.8v or lower. it also includes a diod e to ground which allows the input to be wired directly to a photocell array that will then both enable operation of the converter when in darkness and charge the ic?s power source in daylight conditions. the diode function is performed by an active circuit that gives an ultra low forward voltage drop (typic ally less than 0.1v at 20ma). th is allows the use of a lower output voltage photocell array (lower co st) without degrading performance.
zxld383 zxld383 document number: ds32189 rev. 3 - 2 5 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated typical characteristics 0 10 20 30 40 50 60 70 80 90 0.8 1 1.2 1.4 1.6 1.8 2 i (ma) out v (v) i vs. v cc out(average) cc 4.7h 6.8h 10h 22h 47h 0 10 20 30 40 50 60 70 80 90 100 0.8 1 1.2 1.4 1.6 1.8 2 efficiency (%) v (v) efficiency vs. v for l = 2.2h to 47h cc c c 4.7h 6.8h 10h 22h 47h 0 50 100 150 200 250 0.8 1 1.2 1.4 1.6 1.8 2 i (ma) in v (v) i vs. v cc in c c 4.7h 6.8h 10h 22h 47h 0 50 100 150 200 250 300 350 400 450 500 0.8 1 1.2 1.4 1.6 1.8 2 i (ma) in v (v) peak i vs. v cc in c c 4.7h 6.8h 10h 22h 47h notes: v led = 3.5v for all graphs
zxld383 zxld383 document number: ds32189 rev. 3 - 2 6 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated typical characteristics (cont.) ? 0 50 100 150 200 250 300 350 400 450 01020304050 v (ma) ena iv (ma) v vs. i for v = 0.8, 1.2, 1.4v ena (ena) ena in 0.8v 1.0v 1.2v 1.4v channel-1 (upper): i @ 100ma/cm channel-2 (lower): v @ 1v/cm timebase: 500ns/cm operating waveform for l = 6.8h, v = 1.5v led out cc notes: v led = 3.5v for all graphs
zxld383 zxld383 document number: ds32189 rev. 3 - 2 7 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated application examples apart from the garden light application circuit shown on the front page of this datasheet, the zxld383 may be used in many other ways. the following circuits and notes show some other possibilities and give typical performance details. standard operating mode the following circuit demonstrates how few components are required to produce a light source using the zxld383. operating from a single cell, this simple circuit is suited for use in car key fobs, novelty products etc. where small size and low cost are critical aspects. by directly wiring the ena pin to v cc , the part is permanently enabled once a power supply is provided. the zxld383 is highly tolerant of supply ripple so no decoupling of v cc should be needed in a compactly constructed circuit. also, the part?s capability of operating with a v cc below 0.9v means that this simple circuit will make the best use of available battery capacity. the attached table shows the average led currents that can be obtained using a ra nge of inductor values. also shown are the peak currents required to achieve the given currents. notes: v led = 3.5v low ripple led current mode it is possible that the peak led current required to achieve a gi ven average current is either too high for the led of choice or it leads to some loss of efficiency (due to led resistance losses). in these cases, just two extra low cost components can be added to provide a low ripple current supply for the led. the schottky diode d1 and capacitor c1 rectifies and smoothes the output of the zxld383 giving a low ripple current supply to the load led. of course, this circuit could also be used to power loads other than leds. notes: v led = 3.5v, d1 = zhcs1000, c1 = 1f (low esr) li led (peak) i led (avg) (uh) (m a) (m a) 47 45 8.5 22 100 17.3 10 210 34 6.8 330 50 4.7 415 63 zxld383 3 2 1 4 ena gnd vout 5 vcc l1 1.5v led nc li led (uh) (m a) 47 7.5 22 15.5 10 31 6.8 46 4.7 58 d1 led c1 zxld383 3 2 1 4 ena gnd vout 5 vcc l1 1.5v nc
zxld383 zxld383 document number: ds32189 rev. 3 - 2 8 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated buck-boost mode simple boost converters can run into problems when the input supply voltage is similar to or exceeds the intended load voltage as there is usually a direct curre nt path from the power source through to the load via the boost inductor. this path does not require switching action and so is uncontrolled. when using the zxld383, this problem can be avoided by wiring the cathode of the load led to vcc rat her than ground. without switching action , the led is reverse-biased and so no current can flow. when switching, the an ode of the led is driven to vcc + vf(led) . the higher than normal output voltage reduces the available output current as described earlier and this is shown in the typical data provided. notes: v led = 3.5v low ripple buck-boost mode the output of the buck-boost converter ca n be rectified and smoothed as with the standard circuit to give a low ripple output to improve led efficiency or to give a dc output for other loads. note: v led =3.5v, d1=zhcs1000, c1 = 1uf (low esr) li led (uh) (m a) 47 5 22 9.7 10 21.7 6.8 34 4.7 43 d1 led c1 zxld383 3 2 1 4 ena gnd vout 5 vcc l1 nc 3v l i led ( u h ) (m a) 4 7 5.5 2 2 10.3 1 0 23.2 6 . 8 36.7 4 . 7 46.2 zxld383 3 2 1 4 ena gnd vout 5 vcc l1 led nc 3v
zxld383 zxld383 document number: ds32189 rev. 3 - 2 9 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated ordering information part number package part mark tape width (mm) quantity (per reel) zxld383et5ta tsot23-5 383 8 3000 package outline dimensions dim. millimeters inches dim. millimeters inches min. max. min. max. min. max. min. max. a - 1.00 - 0.0393 e1 1.60 bsc 0.062 bsc a1 0.01 0.10 0.0003 0.0039 e 0.95 bsc 0.037 bsc a2 0.84 0.90 0.0330 0.0354 1.90 bsc 0.074 bsc b 0.30 0.45 0.0118 0.017 7 l 0.10 0.60 0.0039 0.0236 c 0.12 0.20 0.0047 0. 0078 l2 0.25 bsc 0.010 bsc d 2.90 bsc 0.114 bsc q 4 12 4 12 e 2.80 bsc 0.110 bsc
zxld383 zxld383 document number: ds32189 rev. 3 - 2 10 of 10 www.diodes.com may 2010 ? diodes incorporated a product line o f diodes incorporated important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries rese rve the right to make modifications, enhanc ements, improvements, corrections or ot her changes without further notice to this document and any product described herein. diodes incorporated does not assume any liability arising out of the application or use of this document or any product described her ein; neither does diodes incorporated convey any license under its patent or trademark rights, nor the rights of others. any customer or us er of this document or products described herein in such applica tions shall assume all risks of such use and will agree to hold diodes in corporated and all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability what soever in respect of any prod ucts purchased through unauthoriz ed sales channel. should customers purchase or use diodes in corporated products for any unintended or unauthorized application, customers shall i ndemnify and hold diodes incorporated and its representatives harmless a gainst all claims, damages, expens es, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. products described herein may be covered by one or more united states, international or foreign patents pending. product names and markings noted herein may also be covered by one or mo re united states, international or foreign trademarks. life support diodes incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the chief executive officer of diodes incorporated. as used herein: a. life support devices or syst ems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when prop erly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. b. a critical component is any component in a life support dev ice or system whose failure to perform can be reasonably expect ed to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of diodes incorporated products in such safety-cri tical, life support devices or systems, notwithstanding any devic es- or systems- related information or support that may be provided by diodes inco rporated. further, customers must fully indemnify diodes inc orporated and its representatives against any damages aris ing out of the use of diodes incorporated products in such safety-critical, life su pport devices or systems. copyright ? 2010, diodes incorporated www.diodes.com
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