? semiconductor components industries, llc, 2013 may, 2013 ? rev. 0 1 publication order number: NCL30161/d NCL30161 constant-current buck regulator for driving high power leds the NCL30161 is a hysteretic step ? down, constant ? current driver for high power leds. ideal for industrial and general lighting applications utilizing minimal external components. the NCL30161 operates with an input voltage range from 6.3 v to 40 v. the hysteretic control gives good power supply rejection and fast response during load transients and pwm dimming to led arrays of varying number and type. a dedicated pwm input (dim /en) enables a wide range of pulsed dimming, and a high switching frequency 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 NCL30161 is available in a dfn10 3 mm x 3 mm package. features ? vin range 6.3 v to 40 v ? short led shutdown protection: (NCL30161 latching) ? 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 ? general illumination ? industrial lighting d1 NCL30161 vin vin vcc cs gate gnd rot led led r sense l1 c in r ot c vcc dim /enable figure 1. typical application circuit http://onsemi.com device package shipping ? ordering information NCL30161mntxg dfn10 (pb ? free) 3000 / 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. dfn10 case 485c marking diagram pin connections cs nc gnd vcc gate vin rot dim /en 30161 = specific device code a = assembly location l = wafer lot y = year w = work week = pb ? free package 30161 alyw (*note: microdot may be in either location) nc nc 1 2 3 4 5 10 9 8 7 6 (top view)
NCL30161 http://onsemi.com 2 pin function description pin pin name description application information 1 cs current sense feedback pin set the current through the led array by connecting a resistor from this pin to ground. 2, 4, 7 nc no connect 3 gnd ground pin ground. reference point for all voltages 5 vcc output of internal 5 v linear regulator the vcc pin supplies the power to the internal circuitry. the vcc is the out- put of a linear regulator which is powered from vin. a 2 f ceramic capacitor is recommended for bypassing and should be placed as close as possible to the vcc and gnd pins. do not connect to an external load. 6 r ot initial off ? time setting resistor resistor rot from this pin to vcc sets the initial off ? time range for the hys- teretic controller. 8 dim /en pwm dimming control and enable connect a logic ? level pwm signal to this pin to enable/disable the power mosfet and led array 9 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 to high frequency noise, a 10 f ceramic capacitor is recommended to be placed as close as possible to vin and power ground. 10 gate driver output connect to the gate of the external mosfet. 11 flag thermal flag. there is no electrical connection to the ic. connect to ground plane.
NCL30161 http://onsemi.com 3 maximum ratings rating symbol min max unit vin to gnd vin ? 0.3 40 v driver output voltage to gnd gate ? 6.5 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 tj ? 40 125 c storage temperature range t stg ? 55 to +125 c thermal characteristics dfn10 3x3 plastic package maximum power dissipation @ t a = 25 c (note 1) pd 1.46 w thermal resistance junction ? to ? ambient (note 2) r ja 86 c/w lead temperature soldering (10 sec): reflow (smd styles only) pb ? free (note 3) tl 260 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.
NCL30161 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 vhys cs hysteresis 35 ? 45 mv v ocp over current protect limit (reference to cs pin) 475 500 525 mv f sw switching frequency range (note 7) 2400 khz c in_cs cs pin input capacitance (note 7) 4.0 5.0 6.0 pf t blanking cs blanking timer (note 7) 60 73 90 ns 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 35 50 65 a f pwm pwm (dim/en) dimming frequency range 0.1 20 khz d max maximum duty cycle (note 7) 100 % mosfet driver r gate_source sourcing current 4.5 9.0 13.5 r gate_sink sinking current 0.2 0.4 0.6 thermal shutdown t sd thermal shutdown (note 7) 160 165 180 c t hyst thermal hysteresis (note 7) 30 40 60 c off timer t off ? min minimum off ? time 110 137 165 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.
NCL30161 http://onsemi.com 5 figure 2. simplified block diagram s rq 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 gate cs vin vcc rot 500 mv short circuit protection comparator dim / enable v cc gnd enable pull ? up resistor v cc d1 NCL30161 vin vin vcc cs gate gnd rot led led r sense l1 c in r ot c vcc dim /enable figure 3. typical application circuit to drive multiple leds (buck)
NCL30161 http://onsemi.com 6 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 of f, 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 the sense resistor that is connected from cs to ground. when the voltage on 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. when the fet is tur ned on, there can be a lot of ringing on the cs pin that would make the voltage on the cs pin be an unreliable measure of the current through the fet. an 85 ns blanking timer is started when the gate voltage starts to go high, to allow this ringing to settle down. at the end of this blanking timer, cs voltage is sensed to determine the valley current. figure 4. typical current waveforms the current wave shape is triangular, and the peak and valley currents are controlled. the average value for a triangular wave shape 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. over current protection feature 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 NCL30161 comes with a short circuit protection feature. if the voltage on the cs pin is detected to be greater than the over current protection limit, the NCL30161 will turn off the fet, and prevent the fet from turning on again until power is recycled to the NCL30161. undervoltage lockout when vin rises above the uvlo threshold voltage, switching operation of the fet will begin. however, until the vin 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 vin 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. 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.
NCL30161 http://onsemi.com 7 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 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 ripp le 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 the 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 NCL30161 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. selecting an appropriate r ot value allows the system to quickly achieve the intended current regulation. the r ot value can be calculated using the following equation: r ot t off 10 11 where t off is the expecte d off time during normal switching operation, calculated in the inductor selection section above. every time the dim/en pin is brought from a low state to a high state, the initial off ? time program is reset. the first off ? time of the mosfet after the dim/en is brought high will be set by the rot value. the off ? time will then be adjusted in subsequent switching cycles. input capacitor a decoupling capacitor from vin to ground should be used to provide the current needed when the power mosfet turns on. a 10 f ceramic capacitor is recommended.
NCL30161 http://onsemi.com 8 package dimensions dfn10, 3x3, 0.5p case 485c issue c 10x seating plane l d e 0.15 c a a1 e d2 e2 b 15 10 6 notes: 1. dimensioning and tolerancing per asme y14.5m, 1994. 2. controlling dimension: millimeters. 3. dimension b applies to plated terminal and is measured between 0.25 and 0.30 mm from terminal. 4. coplanarity applies to the exposed pad as well as the terminals. 5. terminal b may have mold compound material along side edge. mold flashing may not exceed 30 microns onto bottom surface of terminal b. 6. details a and b show optional views for end of terminal lead at edge of package. 7. for device opn containing w option, detail b alternate construction is not applicable. ??? ??? ??? b a 0.15 c top view side view bottom view pin 1 reference 0.10 c 0.08 c (a3) c 10x 10x 0.10 c 0.05 c a b note 3 k 10x dim min max millimeters a 0.80 1.00 a1 0.00 0.05 a3 0.20 ref b 0.18 0.30 d 3.00 bsc d2 2.40 2.60 e 3.00 bsc e2 1.70 1.90 e 0.50 bsc l 0.35 0.45 l1 0.00 0.03 detail a k 0.19 typ 2x 2x l1 detail a bottom view (optional) *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* 2.1746 2.6016 1.8508 0.5000 pitch 0.5651 10x 3.3048 0.3008 10x dimensions: millimeters on semiconductor and are registered trademarks of semiconductor co mponents industries, llc (scillc). scillc owns the rights to a numb er of patents, trademarks, copyrights, trade secrets, and other intellectual property. a list ing of scillc?s product/patent coverage may be accessed at ww w.onsemi.com/site/pdf/patent ? marking.pdf. scillc reserves the right to make changes without further notice to any products herein. scillc makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does scillc assume any liability arising out of the application or use of any product or circuit, and s pecifically disclaims any and all liability, including without 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 applications and actual performance may vary over time. all operating parame ters, 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 right s of others. scillc products are not designed, intended, or a uthorized 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 whic h the failure of the scillc product could create a situation where personal injury or death may occur. should buyer purchase or us e scillc products for any such unintended or unauthorized appli cation, buyer shall indemnify and hold scillc and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unin tended or unauthorized use, even if such claim alleges that scil lc 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 copyrig ht laws and is not for resale in any manner. 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 NCL30161/d 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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