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. http://onsemi.com DFN10 CASE 485C MARKING DIAGRAM 30161 ALYWG G 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 30161 = Specific Device Code A = Assembly Location L = Wafer Lot Y = Year W = Work Week G = Pb−Free Package (*Note: Microdot may be in either location) PIN CONNECTIONS CS 1 10 GATE NC 2 9 VIN 8 DIM/EN GND 3 NC 4 CIN 6 ROT VCC 5 D1 VIN 7 NC (Top View) L1 LED LED VIN ORDERING INFORMATION Device GATE NCL30161MNTXG DIM/Enable CS ROT ROT VCC NCL30161 RSENSE Package Shipping† DFN10 (Pb−Free) 3000 / Tape & Reel †For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. GND CVCC Figure 1. Typical Application Circuit © Semiconductor Components Industries, LLC, 2013 May, 2013 − Rev. 0 1 Publication Order Number: NCL30161/D NCL30161 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 5 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 mF 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 ROT Initial Off−Time Setting Resistor Resistor ROT from this pin to VCC sets the initial off−time range for the hysteretic controller. 8 DIM/EN PWM Dimming Control and ENABLE 9 VIN Input Voltage Pin 10 GATE Driver Output 11 FLAG Ground. Reference point for all voltages Connect a logic−level PWM signal to this pin to enable/disable the power MOSFET and LED array 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 mF ceramic capacitor is recommended to be placed as close as possible to VIN and power ground. Connect to the gate of the external MOSFET. Thermal flag. There is no electrical connection to the IC. Connect to ground plane. http://onsemi.com 2 NCL30161 MAXIMUM RATINGS Rating Symbol Min Max Unit 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 −0.3 VIN to GND ROT to GND 6 TJ(MAX) Operating Junction Temperature Range TJ Storage Temperature Range Tstg −55 to +125 °C Thermal Characteristics DFN10 3x3 Plastic Package Maximum Power Dissipation @ TA = 25°C (Note 1) PD 1.46 W Thermal Resistance Junction−to−Ambient (Note 2) RqJA 86 °C/W TL 260 °C MSL 1 − Lead Temperature Soldering (10 sec): Reflow (SMD styles only) Pb−Free (Note 3) Moisture Sensitivity Level (Note 4) 150 V Absolute Maximum junction temperature −40 °C 125 °C Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. 1. The maximum package power dissipation limit must not be exceeded. PD + T J(max) * T A R qJA 2. When mounted on a multi−layer board with 35 mm2 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. http://onsemi.com 3 NCL30161 ELECTRICAL CHARACTERISTICS (Unless otherwise noted: VIN = 12 V, TA = 25°C, unless otherwise specified.) Symbol Characteristics Min Typ Max Unit 40 V SYSTEM PARAMETERS VIN Input Supply Voltage Range Normal Operation 8.0 Functional (Note 5) 6.3 IQ_IN Quiescent Current into VIN 1.5 mA VCC Internal Regulator Output (Note 6) 5.0 V VUV+ Under−Voltage Lock−out Threshold (VIN Rising) 5.5 6.0 6.5 V VUV− Under−Voltage Lock−out Threshold (VIN Falling) 5.2 5.6 6.3 V 220 226 mV CURRENT LIMIT AND REGULATION VCS_UL CS Regulation Upper Limit (CS Increasing, FET Turns−OFF) 25°C 213 −40 to 125°C 209 VCS_LL CS Regulation Lower Limit (CS Decreasing, FET Turns−ON) 25°C 174 −40 to 125°C 171 VHYS CS Hysteresis 35 − 45 mV VOCP Over Current Protect Limit (Reference to CS Pin) 475 500 525 mV FSW Switching Frequency Range (Note 7) 2400 kHz Cin_CS 231 180 186 mV 189 CS Pin Input Capacitance (Note 7) 4.0 5.0 6.0 pF CS Blanking Timer (Note 7) 60 73 90 ns VPWMH/L PWM (DIM/EN) high level input voltage 1.4 VPWML PWM (DIM/EN) low level input voltage IDIM−PU DIM/EN Pull−up Current 35 fpwm PWM (DIM/EN) dimming frequency range 0.1 dmax Maximum Duty Cycle (Note 7) tBLANKING DIM INPUT V 50 0.4 V 65 mA 20 kHz 100 % MOSFET DRIVER RGATE_Source RGATE_Sink Sourcing Current 4.5 9.0 13.5 W Sinking Current 0.2 0.4 0.6 W THERMAL SHUTDOWN TSD Thermal Shutdown (Note 7) 160 165 180 °C THyst Thermal Hysteresis (Note 7) 30 40 60 °C Minimum Off−time 110 137 165 ns OFF TIMER tOFF−MIN 5. The functional range of VIN is the voltage range over which the device will function. Output current and internal parameters may deviate from normal values for VIN and VCC voltages between 6.3 V and 8 V, depending on load conditions 6. VCC should not be driven from a voltage higher than VIN or in the absence of a voltage at VIN. 7. Guaranteed by design. http://onsemi.com 4 NCL30161 VIN DIM / Enable VCC 5 V Regulator (6.3 V to 40 Vmax) VCC Enable Pull−Up Resistor VCC Gate Driver S Q R Q GATE Peak Current Comparator 220 mV CS Timer (toff) ROT Valley Current Comparator & Thermal Shutdown 180 mV Short Circuit Protection Comparator 500 mV GND Figure 2. Simplified Block Diagram D1 VIN CIN L1 LED LED VIN GATE DIM/Enable CS ROT ROT VCC NCL30161 RSENSE GND CVCC Figure 3. Typical Application Circuit To Drive Multiple LEDs (Buck) http://onsemi.com 5 NCL30161 Theory of Operation 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. 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 Ipeak at 10% above the average current while the valley current comparator threshold of 180 mV sets Ivalley 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 turned 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. 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 RDS(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 RSENSE value for a desired average output current can be calculated by: R SENSE + 200 mV I LED PWM Dimming For a given RSENSE 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. Figure 4. Typical Current Waveforms The current wave shape is triangular, and the peak and valley currents are controlled. The average value for a http://onsemi.com 6 NCL30161 Inductor Selection forward current of the diode. The average current through the diode can be calculated as: 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: 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. t ON Selecting The Off−Time Setting Resistor + VIN * V LED * I OUT t OFF + ǒ L DI FET R L The off−time setting resistor (ROT) 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 ROT value allows the system to quickly achieve the intended current regulation. The ROT value can be calculated using the following equation: Ǔ (on) ) DCR L ) R SENSE DS DI V LED ) V diode ) I OUT DCR L Where DCRL is the dc resistance of the inductor, VLED is the forward voltages of the LEDs, FETRDS(ON) is the on−resistance of the power MOSFET, and Vdiode is the forward voltage of the catch diode. The switching frequency can then be approximated from the following: f SW + R OT + t OFF 1 t ON ) t OFF 10 11 W Where tOFF is the expected 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. 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. 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 mF ceramic capacitor is recommended. Catch Diode Selection The catch diode needs to be selected such that the average current through the diode does not exceed the rated average http://onsemi.com 7 NCL30161 PACKAGE DIMENSIONS DFN10, 3x3, 0.5P CASE 485C ISSUE C D PIN 1 REFERENCE 2X 2X L1 ÇÇÇ ÇÇÇ ÇÇÇ 0.15 C EDGE OF PACKAGE A B E DETAIL A Bottom View (Optional) EXPOSED Cu TOP VIEW MOLD CMPD 0.15 C (A3) DETAIL B 0.10 C A1 A 10X A1 D2 10X 1 DIM A A1 A3 b D D2 E E2 e K L L1 C DETAIL A e L A3 DETAIL B Side View (Optional) SEATING PLANE 0.08 C SIDE VIEW ÉÉÉ ÉÉÉ 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. SOLDERING FOOTPRINT* 5 MILLIMETERS MIN MAX 0.80 1.00 0.00 0.05 0.20 REF 0.18 0.30 3.00 BSC 2.40 2.60 3.00 BSC 1.70 1.90 0.50 BSC 0.19 TYP 0.35 0.45 0.00 0.03 2.6016 10X E2 K 10 10X 0.10 C A B 0.05 C 6 1.8508 2.1746 b 3.3048 BOTTOM VIEW NOTE 3 10X 0.5651 10X 0.5000 PITCH 0.3008 DIMENSIONS: MILLIMETERS *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. 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