? semiconductor components industries, llc, 2012 january, 2012 ? rev. 1 1 publication order number: NCL30160/d NCL30160 1.0a constant-current buck regulator for driving high power leds the NCL30160 is an nfet hysteretic step ? down, constant ? current driver for high power leds. ideal for automotive, industrial and general lighting applications utilizing minimal external components. the NCL30160 operates with an input voltage range from 6.3 v to 40 v. the hysteretic control gives good power supply rejection and fast re sponse during load transients and pwm dimming to led arrays of varying number and type. a dedicated pwm input (dim /en) enables wide range of pulsed dimming and a high switching frequency up to 1.4 mhz allows the use of smaller external components minimizing space and cost. protection features include resistor ? programmed constant led current, shorted led protection, under ? voltage and thermal shutdown. the NCL30160 is available in a soic ? 8 package. features ? integrated 1.0a mosfet ? vin range 6.3 v to 40 v ? short led shutdown protection ? up to 1.4 mhz switching frequency ? no control loop compensation required ? adjustable led current ? single pin brightness and enable/disable control using pwm ? supports all ? ceramic output capacitors and capacitor ? less outputs ? thermal shutdown protection ? capable of 100% duty cycle operation ? this is a pb ? free device typical application ? led driver ? constant current source ? automotive lighting ? general illumination ? industrial lighting http://onsemi.com device package shipping ? ordering information NCL30160dr2g soic ? 8 (pb ? free) 2500 / tape & reel ?for information on tape and reel specifications, including part orientation and tape sizes, please refer to our t ape and reel packaging specifications brochure, brd8011/d. soic ? 8 nb case 751 marking diagram 30160 alywx 1 8 a = assembly location l = wafer lot y = year w = work week = pb ? free package 1 8 pin connections cs cs gnd vcc lx vin rot dim /enable
NCL30160 http://onsemi.com 2 figure 1. typical application circuit d1 NCL30160 r ot c in vin vin vcc cs lx l1 c vcc r sense gnd rot dim /enable led led pin function description pin pin name description application information 1, 2 cs current sense feedback pin set the current through the led array by connecting a resistor from this pin to ground. 3 gnd ground pin ground. reference point for all voltages 4 vcc output of internal 5 v linear regulator the vcc pin supplies the power to the internal circuitry. the vcc is the output of a linear regulator which is powered from vin. a 2 uf ceramic capacitor is recommended for bypassing and should be placed as close as possible to the vcc and agnd pins. do not connect to an external load. 5 r ot off ? time setting resistor resistor rot from this pin to vcc sets the off ? time range for the hysteretic controller. 6 dim /en pwm dimming control & enable connect a logic ? level pwm signal to this pin to enable/disable the power mosfet and led array 7 vin input voltage pin nominal operating input range is 6.3 v to 40 v. input supply pin to the internal circuitry and the positive input to the current sense comparators. due high frequency noise, a 10 f ceramic capacitor is recommended to be placed as close as possible to vin and power ground. 8 lx drain of internal power mosfet the lx pin connects to the inductor and provides the switching current necessary to operate in hysteretic mode.
NCL30160 http://onsemi.com 3 maximum ratings rating symbol min max unit vin to gnd vin ? 0.3 40 v mosfet drain voltage to gnd lx ? 40 v vcc to gnd vcc ? 6 v dim /en to gnd dim ? 0.3 6 v cs to gnd cs ? 0.3 6 v rot to gnd rot ? 0.3 6 v absolute maximum junction temperature t j (max) 150 c operating junction temperature range t j ? 40 125 c maximum led drive current ilim 1.5 a storage temperature range t stg ? 55 to +125 c thermal characteristics soic ? 8 plastic package maximum power dissipation @ t a = 25 c (note 1) thermal resistance junction ? to ? air (note 2) pd r ja 1.11 111.7 w c/w lead temperature soldering (10 sec): re ? flow (smd styles only) pb ? free (note 3) t l 260 peak c moisture sensitivity level (note 4) msl 1 ? stresses exceeding maximum ratings may damage the device. maximum ratings are stress ratings only. functional operation above t he recommended operating conditions is not implied. extended exposure to stresses above the recommended operating conditions may af fect device reliability. 1. the maximum package power dissipation limit must not be exceeded. p d t j(max) t a r ja 2. when mounted on a multi ? layer board with 35 mm 2 copper area, using 1 oz cu. 3. 60 ? 180 seconds minimum above 237 c. 4. moisture sensitivity level (msl): 1 per ipc/jedec standard: j ? std ? 020a.
NCL30160 http://onsemi.com 4 electrical characteristics (unless otherwise noted: v in = 12 v, t a = 25 c, unless otherwise specified.) symbol characteristics min typ max unit system parameters v in input supply voltage range normal operation 8.0 40 v functional (note 5) 6.3 i q_in quiescent current into v in 1.5 ma v cc internal regulator output (note 6) 5.0 v v uv+ under ? voltage lock ? out threshold (v in rising) 5.5 6.0 6.5 v v uv ? under ? voltage lock ? out threshold (v in falling) 5.2 5.6 6.3 v current limit and regulation v cs_ul cs regulation upper limit (cs increasing, fet turns ? off) 25 c 213 220 226 mv ? 40 to 125 c 209 231 v cs_ll cs regulation lower limit (cs decreasing, fet turns ? on) 25 c 174 180 186 mv ? 40 to 125 c 171 189 v ocp over current protect limit (reference to cs pin) 500 mv f sw switching frequency range (note 7) 1400 khz dim input v pwmh/l pwm (dim/en) high level input voltage 1.4 v v pwml pwm (dim/en) low level input voltage 0.4 v i dim ? pu dim/en pull ? up current 50 a f pwm pwm (dim/en) dimming frequency range 0.1 20 khz dmax maximum duty cycle (note 7) 100 % power mosfet v brdss drain ? to ? source breakdown voltage 40 v i dss drain ? to ? source leakage current (v gs = 0 v, v ds = 40 v) 10 a r ds(on) on resistance (id = 500 ma) 55 m v sd source ? drain body diode (forward on ? voltage) 0.8 1.1 v t pd_off propagation delay v cs_ul ? lx_high 35 ns thermal shutdown t sd thermal shutdown 165 c t hyst thermal hysteresis 40 c off timer t off ? min minimum off ? time 137 ns 5. the functional range of v in is the voltage range over which the device will function. output current and internal parameters may deviate from normal values for v in and v cc voltages between 6.3 v and 8 v, depending on load conditions 6. v cc should not be driven from a voltage higher than v in or in the absence of a voltage at v in . 7. guaranteed by design.
NCL30160 http://onsemi.com 5 figure 2. simplified block diagram s r q q timer (t off ) & thermal shutdown 5 v regulator (6.3 v to 40 v max ) peak current comparator valley current comparator 220 mv 180 mv gate driver lx cs vin vcc rot 500 mv short circuit protection comparator dim / enable v cc gnd enable pull ? up resistor typical application circuits and waveforms (t j = 25 c, unless otherwise specified) figure 3. typical application circuit to drive one led (buck) pwm d1 NCL30160 r ot cin vin vin vcc cs lx led l1 c vcc r sense gnd rot dim /enable
NCL30160 http://onsemi.com 6 figure 4. typical operation waveforms (v cc = 12 v, v led = 6.5 v, r sense = 0.68 , l = 100 h) theory of operation this switching power supply is comprised of an inverted buck regulator controlled by a current mode, hysteretic control circuit. the buck regulator operates exactly like a conventional buck regulator except the power device placement has been inverted to allow for a low side power fet. referring to figure 1, when the fet is conducting, current flows from the input,through the inductor, the led and the fet to ground. when the fet shuts off, current continues to flow through the inductor and led, but is diverted through the diode (d1). this operation keeps the current in the led continuous with a continuous current ramp. the control circuit controls the current hysteretically. figure 2 illustrates the operation of this circuit. the cs comparator thresholds are set to provide a 10% current ripple. the peak current comparator threshold of 220 mv sets i peak at 10% above the average current while the valley current comparator threshold of 180 mv sets i valley at 10% below the average current. when the fet is conducting, the current in the inductor ramps up. this current is sensed by an external sense resistor that is connected from cs to ground. when the cs pin reaches 220 mv, the peak current comparator turns off the power fet. a conventional hysteretic controller would monitor the load current and turn the switch back on when the cs pin reaches 180 mv. but in this topology, the current information is not available to the control circuit when the fet is off. to set the proper fet off time, the cs voltage is sensed when the fet is turned back on and a correction signal is sent to the off time circuit to adjust the off time as necessary. figure 5. typical current waveforms the current waveshape is triangular, and the peak and valley currents are controlled. the average value for a triangular waveshape is halfway between the peak and valley, so even with changes in duty cycle due to input voltage variations or load changes, the average current will remain constant. in the event there is a short ? circuit across the leds, a large amount of current could potentially flow through the circuit during startup. to protect against this, the NCL30160 comes with a short circuit protection feature. if the voltage on the cs pin is detected to be greater than 500 mv (equating to 2.5 times the intended average output current), the ncl31060 will turn off the fet, and prevent the fet from turning on again until power is recycled to NCL30160.
NCL30160 http://onsemi.com 7 figure 6. short-circuit protection when v in rises above the uvlo threshold voltage, switching operation of the fet will begin. however, until the v in voltage reaches 8 v, the vcc regulator may not provide the expected gate drive voltage to the fet. this could result in the r ds(on) of the fet being higher than expected or there not being enough gate drive capability to operate at the maximum rated switching frequency. for optimal performance, it is recommended to operate the part at a v in voltage of 8 v or greater. setting the output current the average output current is determined as being the middle of the peak and valley of the output current, set by the cs comparator thresholds. the nominal average output current will be the current value equivalent to 200 mv at the cs pin. the proper r sense value for a desired average output current can be calculated by: r sense 200 mv i led pwm dimming for a given r sense value, the average output current, and therefore the brightness of the led, can be set to a lower value through the dim/en pin. when the dim/en pin is brought low, the internal fet will turn off and switching will remain off until the dim/en pin is brought back into its high state. figure 7. dimming waveforms by applying a pulsed signal to dim/en, the average output current can be adjusted to the duty ratio of the pulsed signal. it is recommended to keep the frequency of the dim/en signal above 100 hz to avoid any visible flickering of the led. figure 8. dimming performance inductor selection the inductor that is used directly affects the switching frequency the driver operates at. the value of the inductor sets the slope at which the output current rises and falls during the switching operation. the slope of the current, in turn, determines how long it takes the current to go from the valley point of the current ripple to the peak when the fet is on and the current and rising, and how long it takes the current to go from the peak point of the current to the valley when the fet is off and the current is falling. these times can be approximated from the following equations: l i vin v led i out fet r ds (on) dcr l r sense t on
NCL30160 http://onsemi.com 8 t off l i v led v diode i out dcr l where dcr l is the dc resistance of the inductor, v led is the forward voltages of the leds, fet rds(on) is the on-resistance of the power mosfet, and v diode is the forward voltage of the catch diode. the switching frequency can then be approximated from the following: f sw 1 t on t off higher values of inductance lead to slower rates of rise and fall of the output current. this allows for smaller discrepancies between the expected and actual output current ripple due to propagation delays between sensing at the cs pin and the turning on and off of the power mosfet. however, the inductor value should be chosen such that the peak output current value does not exceed the rated saturation current of the inductor. catch diode selection the catch diode needs to be selected such that average current through the diode does not exceed the rated average forward current of the diode. the average current through the diode can be calculated as: i avg_diode i out t off t on t off it is also important to select a diode that is capable of withstanding the peak reverse voltage it will see in the application. it is recommended to select a diode with a rated reverse voltage greater than vin. it is also recommended to use a low-capacitance schottky diode for better efficiency performance. selecting the off-time setting resistor the off-time setting resistor (r ot ) programs the NCL30160 with the initial time duration that the mosfet is turned off when the switching operation begins. during subsequent switching cycles, the voltage at the cs pin is sensed every time the mosfet is turned on, and the off-time will be adjusted depending on how much of a discrepancy exists between the sensed value and the cs lower limit threshold value. the r ot value can be calculated using the following equation: r ot t off 10 11 where t off is the expected off time during normal switching operation, calculated in the inductor selection section above. input capacitor a decoupling capacitor from vin to ground should be used to provide the current needed when the power mosfet turns on. a 4.7 f ceramic capacitor is recommended.
NCL30160 http://onsemi.com 9 figure 9. efficiency, 350 ma, v f_led = 3.5 v figure 10. efficiency, 700 ma, v f_led = 3.5 v figure 11. efficiency, 1 a, v f_led = 3.5 v figure 12. iqin vs. vin figure 13. led current vs. dimming duty ratio 100 95 90 85 80 75 70 65 60 0 5 10 15 20 25 30 35 40 vin (v) efficiency (%) 100 95 90 85 80 75 70 65 60 0 5 10 15 20 25 30 35 40 vin (v) efficiency (%) 100 95 90 85 80 75 70 65 60 0 5 10 15 20 25 30 35 40 vin (v) efficiency (%) 1.70 1.65 1.60 1.55 1.50 1.45 1.40 1.35 1.30 5 10 15202530 3540 vin (v) iqin (ma) dimming duty ratio (%) led current (ma) 0 20406080100 700 600 500 400 300 200 100 100 hz 10 khz ? 40 ? 20 0 20 40 60 80 100 120 240 220 200 180 160 140 120 100 100 switching frequency (khz) figure 14. switching frequency vs. temperature (12 v v in , 3 leds, 0.7 a, 0.47 h) temperature ( c)
NCL30160 http://onsemi.com 10 package dimensions soic ? 8 nb case 751 ? 07 issue ak seating plane 1 4 5 8 n j x 45 k notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: millimeter. 3. dimension a and b do not include mold protrusion. 4. maximum mold protrusion 0.15 (0.006) per side. 5. dimension d does not include dambar protrusion. allowable dambar protrusion shall be 0.127 (0.005) total in excess of the d dimension at maximum material condition. 6. 751 ? 01 thru 751 ? 06 are obsolete. new standard is 751 ? 07. a b s d h c 0.10 (0.004) dim a min max min max inches 4.80 5.00 0.189 0.197 millimeters b 3.80 4.00 0.150 0.157 c 1.35 1.75 0.053 0.069 d 0.33 0.51 0.013 0.020 g 1.27 bsc 0.050 bsc h 0.10 0.25 0.004 0.010 j 0.19 0.25 0.007 0.010 k 0.40 1.27 0.016 0.050 m 0 8 0 8 n 0.25 0.50 0.010 0.020 s 5.80 6.20 0.228 0.244 ? x ? ? y ? g m y m 0.25 (0.010) ? z ? y m 0.25 (0.010) z s x s m 1.52 0.060 7.0 0.275 0.6 0.024 1.270 0.050 4.0 0.155 mm inches scale 6:1 *for additional information on our pb ? free strategy and soldering details, please download the on semiconductor soldering and mounting techniques reference manual, solderrm/d. soldering footprint* on semiconductor and are registered trademarks of semiconductor components industries, llc (scillc). scillc reserves the right to mak e changes without further notice to any products herein. scillc makes no warranty, representation or guarantee regarding the suitability of its products for an y particular purpose, nor does scillc assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including wi thout limitation special, consequential or incidental damages. ?typical? parameters which may be provided in scillc data sheets and/or specifications can and do vary in different application s and actual performance may vary over time. all operating parameters, including ?typicals? must be validated for each customer application by customer?s technical experts. scillc does not convey any license under its patent rights nor the rights of others. scillc products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the scillc product could create a sit uation where personal injury or death may occur. should buyer purchase or use scillc products for any such unintended or unauthorized application, buyer shall indemnify and hold scillc and its of ficers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, direct ly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that scillc was negligent regarding the design or manufacture of the part. scillc is an equal opportunity/affirmative action employer. this literature is subject to all applicable copyright laws and is not for resale in any manner. NCL30160/d publication ordering information n. american technical support : 800 ? 282 ? 9855 toll free usa/canada europe, middle east and africa technical support: phone: 421 33 790 2910 japan customer focus center phone: 81 ? 3 ? 5817 ? 1050 literature fulfillment : literature distribution center for on semiconductor p.o. box 5163, denver, colorado 80217 usa phone : 303 ? 675 ? 2175 or 800 ? 344 ? 3860 toll free usa/canada fax : 303 ? 675 ? 2176 or 800 ? 344 ? 3867 toll free usa/canada email : orderlit@onsemi.com on semiconductor website : www.onsemi.com order literature : http://www.onsemi.com/orderlit for additional information, please contact your local sales representative
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