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 response 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. http://onsemi.com 8 1 SOIC−8 NB CASE 751 MARKING DIAGRAM 8 30160 ALYWX G 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 1 A L Y W G = Assembly Location = Wafer Lot = Year = Work Week = Pb−Free Package PIN CONNECTIONS CS LX CS VIN GND DIM/ENABLE VCC ROT Typical Application • • • • • LED Driver Constant Current Source Automotive Lighting General Illumination Industrial Lighting ORDERING INFORMATION Device NCL30160DR2G Package Shipping† SOIC−8 2500 / Tape & Reel (Pb−Free) †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. © Semiconductor Components Industries, LLC, 2012 January, 2012 − Rev. 1 1 Publication Order Number: NCL30160/D NCL30160 D1 VIN CIN L1 … LED LED VIN LX DIM/Enable ROT ROT CS NCL30160 VCC CVCC RSENSE GND Figure 1. Typical Application Circuit 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 4 VCC Output of Internal 5 V linear regulator 5 ROT 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 8 LX Drain of Internal Power MOSFET Ground. Reference point for all voltages 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. 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 mF ceramic capacitor is recommended to be placed as close as possible to VIN and power ground. The LX pin connects to the inductor and provides the switching current necessary to operate in hysteretic mode. http://onsemi.com 2 NCL30160 MAXIMUM RATINGS Symbol Min Max Unit VIN to GND Rating 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 −0.3 ROT to GND Absolute Maximum Junction Temperature TJ(MAX) Operating Junction Temperature Range TJ 6 150 −40 V °C 125 °C Maximum LED Drive Current ILIM 1.5 A Storage Temperature Range Tstg −55 to +125 °C PD RqJA 1.11 111.7 W °C/W TL 260 peak °C MSL 1 − Thermal Characteristics SOIC−8 Plastic Package Maximum Power Dissipation @ TA = 25°C (Note 1) Thermal Resistance Junction−to−Air (Note 2) Lead Temperature Soldering (10 sec): Re−flow (SMD styles only) Pb−Free (Note 3) Moisture Sensitivity Level (Note 4) 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 + TJ(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 NCL30160 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 25°C 213 220 226 mV −40 to 125°C 209 CURRENT LIMIT AND REGULATION VCS_UL CS Regulation Upper Limit (CS Increasing, FET Turns−OFF) VCS_LL CS Regulation Lower Limit (CS Decreasing, FET Turns−ON) 25°C 174 −40 to 125°C 171 VOCP Over Current Protect Limit (Reference to CS Pin) FSW Switching Frequency Range (Note 7) 231 180 186 mV 189 500 mV 1400 kHz DIM INPUT VPWMH/L PWM (DIM/EN) high level input voltage VPWML PWM (DIM/EN) low level input voltage IDIM−PU DIM/EN Pull−up Current fpwm PWM (DIM/EN) dimming frequency range dmax Maximum Duty Cycle (Note 7) 1.4 V 0.4 50 0.1 V mA 20 100 kHz % POWER MOSFET VBRDSS Drain−to−Source Breakdown Voltage IDSS Drain−to−Source Leakage Current (VGS = 0 V, VDS = 40 V) 10 mA RDS(on) On Resistance (Id = 500 mA) 55 mW VSD Source−Drain Body Diode (Forward On−Voltage) 0.8 1.1 V tPD_Off Propagation Delay VCS_UL − LX_High 35 ns TSD Thermal Shutdown 165 °C THyst Thermal Hysteresis 40 °C Minimum Off−time 137 ns 40 V THERMAL SHUTDOWN 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 NCL30160 DIM / Enable VIN VCC 5 V Regulator (6.3 V to 40 Vmax) VCC LX Enable Pull−Up Resistor Gate Driver S Q R Q Peak Current Comparator 220 mV CS Valley Current Timer (toff) & Thermal Shutdown ROT Comparator 180 mV Short Circuit Protection Comparator 500 mV GND Figure 2. Simplified Block Diagram TYPICAL APPLICATION CIRCUITS AND WAVEFORMS (TJ = 25°C, Unless Otherwise Specified) D1 VIN CIN L1 LED LX VIN DIM/Enable ROT PWM ROT CS NCL30160 VCC CVCC RSENSE GND Figure 3. Typical Application Circuit To Drive One LED (Buck) http://onsemi.com 5 NCL30160 Figure 4. Typical Operation Waveforms (VCC = 12 V, VLED = 6.5 V, RSENSE = 0.68 W, L = 100 mH) THEORY OF OPERATION 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. 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 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 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. http://onsemi.com 6 NCL30160 Figure 7. Dimming Waveforms Figure 6. Short-Circuit Protection 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. 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 Figure 8. Dimming Performance 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. 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: t ON + VIN * V LED * I OUT http://onsemi.com 7 ǒ L FET R DI DS Ǔ (on) ) DCRL ) RSENSE NCL30160 t OFF + L DI V LED ) V diode ) I OUT 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. DCRL 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 + Selecting The Off-Time Setting Resistor The off-time setting resistor (ROT) 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 ROT value can be calculated using the following equation: 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. R OT + t OFF Where tOFF is the expected off time during normal switching operation, calculated in the Inductor Selection section above. 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 10 11 W 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 mF ceramic capacitor is recommended. t OFF t ON ) t OFF http://onsemi.com 8 NCL30160 95 95 90 90 EFFICIENCY (%) 100 EFFICIENCY (%) 100 85 80 75 70 65 60 85 80 75 70 65 0 5 10 15 20 25 30 35 60 40 15 20 25 30 35 Figure 10. Efficiency, 700 mA, Vf_LED = 3.5 V 1.65 90 1.60 85 1.55 IQIN (mA) 95 EFFICIENCY (%) 10 Figure 9. Efficiency, 350 mA, Vf_LED = 3.5 V 1.70 80 75 1.45 1.40 65 1.35 5 10 15 20 VIN (V) 25 30 35 1.30 40 40 1.50 70 0 5 VIN (V) 100 60 0 VIN (V) 5 10 15 Figure 11. Efficiency, 1 A, Vf_LED = 3.5 V 20 25 VIN (V) 30 35 40 100 120 Figure 12. IQIN vs. VIN SWITCHING FREQUENCY (kHz) 700 LED CURRENT (mA) 600 500 100 Hz 400 10 kHz 300 200 100 0 20 40 60 DIMMING DUTY RATIO (%) 80 240 220 200 180 160 140 120 100 −40 100 −20 0 20 40 60 TEMPERATURE (°C) 80 Figure 14. Switching Frequency vs. Temperature (12 V VIN, 3 LEDs, 0.7 A, 0.47 mH) Figure 13. LED Current vs. Dimming Duty Ratio http://onsemi.com 9 NCL30160 PACKAGE DIMENSIONS SOIC−8 NB CASE 751−07 ISSUE AK −X− 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 8 5 S B 0.25 (0.010) M Y M 1 4 −Y− K G C N DIM A B C D G H J K M N S X 45 _ SEATING PLANE −Z− 0.10 (0.004) H D 0.25 (0.010) M Z Y S X M J S MILLIMETERS MIN MAX 4.80 5.00 3.80 4.00 1.35 1.75 0.33 0.51 1.27 BSC 0.10 0.25 0.19 0.25 0.40 1.27 0_ 8_ 0.25 0.50 5.80 6.20 INCHES MIN MAX 0.189 0.197 0.150 0.157 0.053 0.069 0.013 0.020 0.050 BSC 0.004 0.010 0.007 0.010 0.016 0.050 0 _ 8 _ 0.010 0.020 0.228 0.244 SOLDERING FOOTPRINT* 1.52 0.060 7.0 0.275 4.0 0.155 0.6 0.024 1.270 0.050 SCALE 6:1 mm Ǔ ǒinches *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 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 specifically 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 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. 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