April 30, 2009 LM3429 N-Channel Controller for Constant Current LED Drivers General Description Features The LM3429 is a versatile high voltage LED driver controller. With the capability to be configured in a Buck, Boost, BuckBoost (Flyback), or SEPIC topology, and an input and output operating voltage rating of 75V, the LM3429 is ideal for illuminating LEDs in a very diverse, large family of applications. Adjustable high-side current sense with a typical sense voltage of 100 mV allows for tight regulation of the LED current with the highest efficiency possible. Output LED current regulation is based on peak current-mode control with predictive Off-Time Control. This method of control eases the design of loop compensation while providing inherent input voltage feed-forward compensation. The LM3429 includes a high-voltage startup regulator that operates over a wide input range of 4.5V to 75V. The internal PWM controller is designed for adjustable switching frequencies of up to 2.0MHz, thus enabling compact solutions. Additional features include: precision reference, logic compatible DIM input suitable for fast PWM dimming, cycle-by-cycle current limit, and thermal shutdown. The LM3429 comes in a low profile, thermally efficient TSSOP EP 14-lead package. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ VIN range from 4.5V to 75V 2% Internal reference voltage (1.235V) Current sense voltage adjustable from 20 mV High-side current sensing 2Ω MOSFET gate driver Dimming MOSFET gate driver Input under-voltage protection Over-voltage protection Low shutdown current, IQ < 1µA Fast (50kHz) PWM dimming Cycle-by-cycle current limit Programmable switching frequency TSSOP EP 14-lead package Applications ■ ■ ■ ■ ■ ■ LED Drivers Constant-Current Buck-Boost Regulator Constant-Current Boost Regulator Constant-Current Flyback Regulator Constant-Current SEPIC Regulator Thermo-Electric Cooler (Peltier) Driver Typical Application Circuit 30094431 Boost LED Driver © 2009 National Semiconductor Corporation 300944 www.national.com LM3429 N-Channel Controller for Constant Current LED Drivers PRELIMINARY LM3429 Connection Diagram Top View 30094404 14-Lead TSSOP EP NS Package Number MXA14A Ordering Information Order Number Spec. Package Type NSC Package Drawing Supplied As LM3429MH NOPB TSSOP-14 EP MXA14A 92 Units, Rail LM3429MHX NOPB TSSOP-14 EP MXA14A 2500 Units, Tape and Reel Pin Descriptions LM3429 Name Function 1 VIN Power supply input (4.5V-75V). Bypass with 100nF capacitor to AGND as close to the device as possible in the circuit board layout. 2 COMP Compensation: PWM controller error amplifier compensation pin. This pin connects through a series resistorcapacitor network to AGND. 3 CSH Current Sense High: Output of the high side sense amplifier and input to the main regulation loop error amplifier. 4 RCT Resistor Capacitor Timing: External RC network sets the predictive “off-time” and thus the switching frequency. The RC network should be placed as close to the device as possible in the circuit board layout. 5 AGND Analog Ground: The proper place to connect the compensation and timing capacitor returns. This pin should be connected via the circuit board to the PGND pin through the EP copper circuit board pad. 6 OVP Over-Voltage Protection sense input: 1.24V threshold with hysteresis that is user programmable by the selection of the OVP Over-Voltage Lock-Out (OVLO) resistor divider network. If not used connect pin to GND. 7 nDIM Not DIM input: Dual function pin. Primarily used as the Pulse Width Modulation (PWM) input. When driven with a resistor divider from VIN, this pin also functions as a user programmable VIN Under-Voltage Lock-Out (UVLO) with 1.24V threshold and programmable hysteresis by the UVLO resistor divider network. The PWM and UVLO functions can be performed simultaneously. 8 NC 9 PGND Power Ground: GATE and DDRV gate drive ground current return pin. This pin should be connected via the circuit board to the AGND pin through the EP copper circuit board pad. 10 GATE Main switching MOSFET gate drive output. 11 VCC Internal Regulator Bypass: 6.9V low dropout linear regulator output. Bypass with a 2.2 µF–3.3 µF, ceramic type capacitor to PGND. 12 IS Main Switch Current Sense input: This pin is used for current mode control and cycle-by-cycle current limit. This pin can be tied to the drain of the main N-channel MOSFET switch for RDS(ON) sensing or tied to a sense resistor installed in the source of the same device. HSP High Side Sense Positive: LED current sense positive input. An external resistor sets a reference current flowing into this pin from the programmed high-side sense voltage. Although the current into this pin can be set to values ranging from 10 µA through 1 mA, a value of 100 µA is recommended. This pin is a virtual ground whose potential is set by the voltage on the HSN pin. 13 www.national.com No connection. Leave this pin open. 2 Name Function 14 HSN High Side Sense Negative: This pin sets the reference voltage for the HSP input. An external resistor of the same value as that used on the HSP pin should be connected from this pin to the negative side of the current sense resistor. EP (15) EP EP: Star ground, connecting AGND and PGND. For thermal considerations please refer to (Note 4) of the Electrical Characteristics table. 3 www.national.com LM3429 LM3429 LM3429 Absolute Maximum Ratings (Notes 1, 2) PGND If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Maximum Junction Temperature (Internally Limited) Storage Temperature Range Maximum Lead Temperature (Soldering) (Note 5) Continuous Power Dissipation (Note 4) ESD Susceptibility (Note 6) Human Body Model VIN, nDIM -0.3V to 76.0V -1mA continuous -0.3V to 76.0V -100 µA continuous -0.3V to 76.0V -1 mA to +5 mA continuous -0.3V to 76.0V -2V for 100 ns -1 mA continuous -0.3V to 8.0V -0.3V to 6.0V -200 µA to +200 µA Continuous -0.3V to VCC -2.5V for 100 ns VCC+2.5V for 100 ns -1 mA to +1 mA continuous OVP, HSP, HSN RCT IS VCC COMP, CSH GATE -0.3V to 0.3V -2.5V to 2.5V for 100 ns 165°C Operating Conditions Operating Junction Temperature Range (Note 7) Input Voltage VIN −65°C to +150°C 300°C Internally Limited 2 kV (Notes 1, 2) −40°C to +150°C 4.5V to 75V Electrical Characteristics (Note 2) Specifications in standard type face are for TJ = 25°C and those with boldface type apply over the full Operating Temperature Range ( TJ = −40°C to +125°C). Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = +25°C, and are provided for reference purposes only. Unless otherwise stated the following condition applies: VIN = +14V. Symbol Parameter Conditions Min (Note 7) Typ (Note 8) Max (Note 7) Units STARTUP REGULATOR VCCREG VCC Regulation ICC = 0 mA ICCLIM VCC Current Limit VCC = 0V IQ Quiescent Current Static 1.5 3 VCCUV VCC UVLO Threshold VCC Increasing 4.17 4.50 VCCHYS VCC UVLO Hysteresis 6.30 6.90 20 25 7.35 V mA VCC SUPPLY VCC Decreasing 3.70 4.08 V 0.1 OV THRESHOLDS OVPCB OVP OVLO Threshold OVP Increasing OVPHYS OVP Hysteresis Source Current OVP Active (high) 1.185 1.240 1.285 V 10 20 30 µA 1.210 1.235 1.260 V -0.6 0 0.6 10 26 40 ERROR AMPLIFIER VREF CSH Reference Voltage With Respect to AGND Error Amplifier Input Bias Current COMP Sink / Source Current Transconductance Linear Input Range (Note 9) Transconductance Bandwidth -6dB Unloaded Response (Note 9) 0.5 µA 100 µA/V ±125 mV 1.0 MHz OFF TIMER Minimum Off-time RRCT RCT Reset Pull-down Resistance VRCT VIN/25 Reference Voltage www.national.com RCT = 1V through 1 kΩ VIN = 14V 540 4 35 75 ns 36 120 Ω 565 585 mV f Parameter Continuous Conduction Switching Frequency Conditions Min (Note 7) Typ (Note 8) Max (Note 7) 2.2 nF > CT > 470 pF 25/(CTRT) Units Hz PWM COMPARATOR COMP to PWM Offset 700 800 900 mV 215 245 275 mV 35 75 250 450 CURRENT LIMIT (IS) ILIM Current Limit Threshold ILIM Delay to Output Leading Edge Blanking Time 75 ns HIGH SIDE TRANSCONDUCTANCE AMPLIFIER Input Bias Current 10 µA Transconductance 20 119 Input Offset Current -1.5 0 1.5 µA Input Offset Voltage -7 0 7 mV 250 500 Transconductance Bandwidth ICSH = 100 µA (Note 9) mA/V kHz GATE DRIVER (GATE) RSRC(GATE) GATE Sourcing Resistance GATE = High 2.0 6.0 RSNK(GATE) GATE Sinking Resistance GATE = Low 1.3 4.5 Ω DIM DRIVER (nDIM) nDIMVTH nDIM / UVLO Threshold 1.180 1.240 1.280 V nDIMHYS nDIM Hysteresis Current 10 20 30 µA THERMAL SHUTDOWN TSD Thermal Shutdown Threshold 165 THYS Thermal Shutdown Hysteresis 25 °C THERMAL RESISTANCE θJA Junction to Ambient (Note 4) 14L TSSOP EP 38 °C/W θJC Junction to Exposed Pad (EP) 14L TSSOP EP 2.8 °C/W Note 1: Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended to be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: All voltages are with respect to the potential at the AGND pin, unless otherwise specified. Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=165°C (typical) and disengages at TJ=140°C (typical). Note 4: Junction-to-ambient thermal resistance is highly board-layout dependent. The numbers listed in the table are given for a reference layout wherein the 14L TSSOP package has its EP pad populated with 6 vias. In applications where high maximum power dissipation exists, namely driving a large MOSFET at high switching frequency from a high input voltage, special care must be paid to thermal dissipation issues during board design. In high-power dissipation applications, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125°C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the package in the application (θJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (θJA × PD-MAX). In most applications there is little need for the full power dissipation capability of this advanced package. Under these circumstances, no vias would be required and the thermal resistances would be TBD °C/W for the 14L TSSOP. It is possible to conservatively interpolate between the full via count thermal resistance and the no via count thermal resistance with a straight line to get a thermal resistance for any number of vias in between these two limits. Note 5: Refer to National’s packaging website for more detailed information and mounting techniques. http://www.national.com/packaging/ Note 6: Human Body Model, applicable std. JESD22-A114-C. Note 7: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Note 8: Typical numbers are at 25°C and represent the most likely norm. Note 9: These electrical parameters are guaranteed by design, and are not verified by test. 5 www.national.com LM3429 Symbol LM3429 Physical Dimensions inches (millimeters) unless otherwise noted TSSOP-14 Pin EP Package (MXA) For Ordering, Refer to Ordering Information Table NS Package Number MXA14A www.national.com 6 LM3429 Notes 7 www.national.com LM3429 N-Channel Controller for Constant Current LED Drivers Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage Reference www.national.com/vref Design Made Easy www.national.com/easy PowerWise® Solutions www.national.com/powerwise Solutions www.national.com/solutions Serial Digital Interface (SDI) www.national.com/sdi Mil/Aero www.national.com/milaero Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic Wireless (PLL/VCO) www.national.com/wireless Analog University® www.national.com/AU THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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