1 dc1706af demo manual dc1706a description LT3796 100v led controller with current monitor dc1706a is a 100v led controller with an input current monitor. it is a single switch boost led driver with led + to gnd short circuit protection. it accepts an input volt- age from 8v to 100v (7.5v uvlo and 8.7v turn-on), and drives up to 85v of leds at 400ma (when pvin is less than v led ). dc1706a features both pwm and analog dimming of the led string. it has a vmode flag that indicates when the led string has been removed and it has a fault flag that indicates that the output has been shorted to gnd. in both cases, the ic remains in control and well protected. dc1706a features high efficiency at 300khz switching frequency. at high led string voltages up to 85v and 400ma of led current, the single switch controller has 93% efficiency. there are input current (csout) and out- put current (ismon) monitor pins that deliver a voltage proportional to the current for quick diagnostics. small ceramic input and output capacitors are used to save space and cost. the open led overvoltage protection uses the ics constant voltage regulation loop to regulate the output to approximately 92.5v if the led string is opened although it may reach 96.5v peak during transient from running leds to open. for low input voltage operation, the ctrl pin voltage is reduced as the input voltage drops below 9v, reducing led brightness and restraining the peak switch currents in order to limit inductor and switch size. uvlo turns the leds off when vin drops below 7.5v. l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. dc1706a pwm dimming is simple. the topside pwm dimming mosfet (m2) turns the led string on and off with an input to the pwm dimming terminal. for the high- est pwm dimming ratio, it is recommended to use 100hz as a pwm dimming frequency. information regarding pwm dimming ratios and performance can be found in the LT3796 data sheet in the applications section. analog dimming is also simple to use with a single voltage source on the ctrl terminal. modifications can be made to dc1706a in order to convert the board to higher or lower power or from an led driver to a constant voltage regulator or battery charger. it can easily be changed from a boost topology to a sepic, buck mode, or buck-boost mode led driver. please consult the factory or refer to the LT3796 data sheet for details. the LT3796 data sheet gives a complete description of the part, operation and applications information. the data sheet must be read in conjunction with this demo manual for dc1706a. the LT3796 is assembled in a 28- lead plastic tssop fe package with a thermally enhanced ground pad. proper board layout is essential for maximum thermal performance. see the data sheet section layout considerations. design files for this circuit board are available at http://www.linear.com/demo
2 dc1706af demo manual dc1706a quick start procedure dc1706a is easy to set up to evaluate the performance of the LT3796. follow the procedure below: note: pwm must be pulled high to run. if pwm is not used, connect pwm to a 3.3v or 5v source or to vref on the pcb using 0 resistor r24. 1. connect a string of leds that will run with forward volt- age less than 85v, but greater than pvin, to the led + and gnd terminals on the pcb as shown in figure 1. 2. connect the en/uvlo terminal to gnd. 3. with power off, connect the input power supply to the pvin and gnd terminals. make sure that the pvin dc input voltage will not exceed 100v (or v led ). 4. connect the pwm terminal. if pwm is not used, connect pwm to a 3.3v or 5v source or to vref on the pcb us- ing 0 resistor r24. pwm must be pulled high to run. 5. turn the input power supply on and make sure the voltage is between 8v and v led . 6. release the en/uvlo-to-gnd connection. 7. observe the led string running at the programmed led current. 8. observe the csout and ismon input and output cur- rent monitor voltages. 9. for pwm dimming, connect a pwm (100hz or higher is recommended) signal to the pwm terminal. for analog dimming, connect a dc voltage between 0v and 2v to the ctrl terminal. 10. observe the reduction of brightness in the led string when pwm or analog dimming. performance summary (t a = 25c) parameter conditions units input voltage pvin range operating 7.5v to v led switching frequency r18 = 26.1k 300khz i led rs2 = 0.62, 9v < pvin < v led 400ma low pvin i led (ctrl foldback) rs2 = 0.62, pvin = 8v 350ma v led range r5 = 1m, r9 = 13.7k pvin < v led < 85v open led voltage r5 = 1m, r9 = 13.7k 92.5v typical efficiency pvin = 14v, v led = 85v, i led = 400ma 93% under voltage lockout (falling turn-off) r1 = 499k and r8 = 100k 7.5v under voltage lockout (rising turn-on) r1 = 499k and r8 = 100k 8.7v v intvcc operating 7.7v peak switch current limit rs3 = 0.015 6.6a suggested maximum pwm dimming ratio f pwm = 100hz, pvin=12v, v led = 85v, i led = 400ma 100:1
3 dc1706af demo manual dc1706a figure 1. test procedure setup drawing for dc1706a quick start procedure
4 dc1706af demo manual dc1706a figure 2. dc1706a efficiency with 85v leds at 400ma figure 3. dc1706a 100hz 100:1 to 1000:1 pwm dimming waveforms at 12v pvin and 85v v led pvin input voltage (v) 0 80 efficiency (%) 86 84 82 88 92 90 96 94 98 100 10 20 30 40 dc1706a f02 50 60 70 80 90 85v led 400ma quick start procedure 500:1 250:1 125:1 100:1 dc1706a f03 85v led pvin = 12v 1000:1 i led 100ma/div f pwm = 100hz
5 dc1706af demo manual dc1706a figure 4. dc1706a ctrl led current foldback at low pvin with uvlo falling and rising quick start procedure pvin (v) 7 0 iled (a) 0.15 0.10 0.05 0.20 0.30 0.25 0.35 0.40 0.45 7.5 8 8.5 9 dc1706a f04 9.5 10 10.5 11 11.5 12 under voltage lockout (falling) turn-on (rising)
6 dc1706af demo manual dc1706a parts list item qty reference part description manufacturer/part number required circuit components 1 2 c1, c2 cap , x7s 4.7f 100v 10% 1210 tdk c3225x7s2a475k 2 5 c3, c4, c5, c6, c12 cap , x7r 2.2f 100v 10% 1210 murata grm32er72a225ka35l 3 1 c8 cap , x5r 4.7f 10v 10% 0603 avx 0603zd475kat2a 4 1 c9 cap , x7r 0.01f 25v 10% 0603 avx 06033c103kat2a 5 1 c11 cap , x7r 0.1f 25v 10% 0603 avx 06033c104kat2a 6 1 d1 schottky diode 100v 5a powerdi5 diodes inc pds5100h 7 1 l1 inductor, 22h hc9-series cooper bussmann hc9-220-r 8 1 m1 mosfet n-chan, 100v/15a lfpak renesas rjk1051dpb-00-j5 #pbf 9 1 m2 mosfet p-chan, 100v powerpak 1212-8 siliconix si7113dn-t1-e3 #pbf 10 1 rs2 res, lrc 0.620 0.5w 1% 2010 irc lr2010lf-01-r620-f 11 1 rs3 res, 0.015 0.5w 1% 2010 vishay wsl2010r0150fea 12 1 r5 res, chip 1m 0.06w 1% 0402 vishay crcw04021m00fked 13 1 r9 res, chip 13.7k 0.06w 1% 0402 vishay crcw040213k7fked 14 1 r16 res, chip 4.7k 0.06w 5% 0402 vishay crcw04024k70jned 15 1 r18 res, chip 26.1k 0.06w 1% 0402 vishay crcw040226k1fked 16 1 u1 100v led controller ic tssop28-fe/eb linear technology LT3796 optional electrical components 1 0 c13, c14, c15 cap , 1210 optional 2 1 c16 cap , x7r 0.01f 25v 10% 0603 avx 06033c103kat2a 3 1 c17 cap , x7r 0.1f 25v 10% 0603 avx 06033c104kat2a 4 1 d2 schottky rect, 150v/1a sma fairchild semi es1c 5 0 d3 diode, sod-123 optional 6 0 m3 mosfet sot23 optional 7 1 q1 trans, pnp sot23 zetex/diodes inc fmmt589 8 1 rs1 res, 0.025 0.5w 1% 2010 vishay wsl2010r0250fea 9 1 r1 res, chip 499k 0.06w 1% 0402 vishay crcw0402499kfked 10 3 r2, r4, r17 res/jumper, chip 0 1/16w 1a 0402 vishay crcw04020000z0ed 11 1 r3 res, chip 2k 0.06w 1% 0402 vishay crcw04022k00fked 12 1 r6 res/jumper, chip 0 1/4w 1a 1206 vishay crcw12060000zoea 13 1 r7 res, chip 1m 0.06w 1% 0402 vishay crcw04021m00fked 14 1 r8 res, chip 100k 0.06w 1% 0402 vishay crcw0402100kfked 15 1 r10 res, chip 137k 0.06w 1% 0402 vishay crcw0402137kfked 16 0 r11, r12, r15, r19 to r22, r25, r27, r28, r31, r33 res 0402 optional 17 2 r13, r14 res, chip 100k 0.06w 5% 0402 vishay crcw0402100kjned 18 0 r24, r30, r32 res, 0603 optional 19 1 r26 res/jumper, chip 0 1/16w 1a 0603 vishay crcw06030000z0ea 20 1 r29 res, chip 82.5k 0.06w 1% 0402 vishay crcw040282k5fked 21 0 r34 res, 1206 optional optional hardware 1 18 e1 to e18 turret, testpoint mill max 2501-2-00-80-00-00-07-0
7 dc1706af demo manual dc1706a information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. schematic diagram
8 dc1706af demo manual dc1706a linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2012 lt 0512 ? printed in usa demonstration board important notice linear technology corporation (ltc) provides the enclosed product(s) under the following as is conditions: this demonstration board (demo board) kit being sold or provided by linear technology is intended for use for engineering development or evaluation purposes only and is not provided by ltc for commercial use. as such, the demo board herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. as a prototype, this product does not fall within the scope of the europ ean union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or ot her regulations. if this evaluation kit does not meet the specifications recited in the demo board manual the kit may be returned within 30 days from the date of delivery for a full refund. the foregoing warranty is the exclusive warranty made by the seller to buyer and is in lieu of all other warranties, expressed, implied, or statutory, including any warranty of merchantability or fitness for any particular purpose. except to the extent of this indemnity, neither party shall be liable to the other for any indirect, special, incidental, or consequential damages. the user assumes all responsibility and liability for proper and safe handling of the goods. further, the user releases ltc fro m all claims arising from the handling or use of the goods. due to the open construction of the product, it is the users responsibility to take any and all appropriate precautions with regard to electrostatic discharge. also be aware that the products herein may not be regulatory co mpliant or agency certified (fcc, ul, ce, etc.). no license is granted under any patent right or other intellectual property whatsoever. ltc assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind . ltc currently services a variety of customers for products around the world, and therefore this transaction is not exclusive . please read the demo board manual prior to handling the product . persons handling this product must have electronics training and observe good laboratory practice standards. common sense is encouraged . this notice contains important safety information about temperatures and voltages. for further safety concerns, please contact a ltc applica- tion engineer. mailing address: linear technology 1630 mccarthy blvd. milpitas, ca 95035 copyright ? 2004, linear technology corporation
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