LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 LM3404/04HV 1.0A Constant Current Buck Regulator for Driving High Power LEDs Check for Samples: LM3404, LM3404HV FEATURES * * 1 * * * * * * * 2 * Integrated 1.0A MOSFET VIN Range 6V to 42V (LM3404) VIN Range 6V to 75V (LM3404HV) 1.2A Output Current Over Temperature Cycle-by-Cycle Current Limit No Control Loop Compensation Required Separate PWM Dimming and Low Power Shutdown Supports all-ceramic output capacitors and capacitor-less outputs Thermal shutdown protection SO-8 Package, PSOP-8 Package APPLICATIONS * * * * * LED Driver Constant Current Source Automotive Lighting General Illumination Industrial Lighting DESCRIPTION The LM3404/04HV are monolithic switching regulators designed to deliver constant currents to high power LEDs. Ideal for automotive, industrial, and general lighting applications, they contain a high-side N-channel MOSFET switch with a current limit of 1.5A (typical) for step-down (Buck) regulators. Hysteretic controlled on-time and an external resistor allow the converter output voltage to adjust as needed to deliver a constant current to series and series-parallel connected LED arrays of varying number and type. LED dimming via pulse width modulation (PWM), broken/open LED protection, low-power shutdown and thermal shutdown complete the feature set. Typical Application CB VIN BOOT VIN L1 SW RON CIN D1 RON IF LM3404/04HV CS RSNS DIM GND VCC CF Connection Diagram 1 8 SW VIN 2 7 BOOT VCC DIM RON 3 6 4 5 GND CS Figure 1. 8-Lead Plastic SO-8 Package 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2006-2010, Texas Instruments Incorporated LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com 1 2 3 4 VIN SW BOOT DIM GND DAP VCC RON CS 8 7 6 5 Figure 2. 8-Lead Plastic PSOP-8 Package Pin Functions Pin Descriptions Pin(s) Name Description 1 SW Switch pin Application Information 2 BOOT MOSFET drive bootstrap pin 3 DIM Input for PWM dimming 4 GND Ground pin 5 CS Current sense feedback pin 6 RON On-time control pin A resistor connected from this pin to VIN sets the regulator controlled ontime. 7 VCC Output of the internal 7V linear regulator Bypass this pin to ground with a minimum 0.1 F ceramic capacitor with X5R or X7R dielectric. 8 VIN Input voltage pin Nominal operating input range for this pin is 6V to 42V (LM3404) or 6V to 75V (LM3404HV). DAP GND Thermal Pad Connect this pin to the output inductor and Schottky diode. Connect a 10 nF ceramic capacitor from this pin to SW. Connect a logic-level PWM signal to this pin to enable/disable the power MOSFET and reduce the average light output of the LED array. Connect this pin to system ground. Set the current through the LED array by connecting a resistor from this pin to ground. Connect to ground. Place 4-6 vias from DAP to bottom layer ground plane. These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings(LM3404) (1) VIN to GND -0.3V to 45V BOOT to GND -0.3V to 59V SW to GND -1.5V to 45V BOOT to VCC -0.3V to 45V BOOT to SW -0.3V to 14V VCC to GND -0.3V to 14V DIM to GND -0.3V to 7V CS to GND -0.3V to 7V RON to GND -0.3V to 7V Junction Temperature 150C Storage Temp. Range -65C to 125C ESD Rating (2) 2kV Soldering Information Lead Temperature (Soldering, 10sec) 260C Infrared/Convection Reflow (15sec) 235C (1) (2) 2 Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see Electrical Characteristics. The human body model is a 100 pF capacitor discharged through a 1.5 k resistor into each pin. Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 Operating Ratings (LM3404) (1) VIN 6V to 42V -40C to +125C Junction Temperature Range Thermal Resistance JA (SO-8 Package) 155C/W Thermal Resistance JA (PSOP-8 Package) (2) 50C/W (1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see Electrical Characteristics. JA of 50C/W with DAP soldered to a minimum of 2 square inches of 1oz. copper on the top or bottom PCB layer. (2) Absolute Maximum Ratings(LM3404HV) (1) VIN to GND -0.3V to 76V BOOT to GND -0.3V to 90V SW to GND -1.5V to 76V BOOT to VCC -0.3V to 76V BOOT to SW -0.3V to 14V VCC to GND -0.3V to 14V DIM to GND -0.3V to 7V CS to GND -0.3V to 7V RON to GND -0.3V to 7V Junction Temperature 150C Storage Temp. Range -65C to 125C ESD Rating (2) 2kV Soldering Information Lead Temperature (Soldering, 10sec) 260C Infrared/Convection Reflow (15sec) 235C (1) (2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see Electrical Characteristics. The human body model is a 100 pF capacitor discharged through a 1.5 k resistor into each pin. Operating Ratings (LM3404HV) (1) VIN 6V to 75V -40C to +125C Junction Temperature Range Thermal Resistance JA (SO-8 Package) 155C/W Thermal Resistance JA (PSOP-8 Package) (2) 50C/W (1) (2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see Electrical Characteristics. JA of 50C/W with DAP soldered to a minimum of 2 square inches of 1oz. copper on the top or bottom PCB layer. Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 3 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com Electrical Characteristics LM3404 VIN = 24V unless otherwise indicated. Typicals and limits appearing in plain type apply for TA = TJ = +25C. (1) Limits appearing in boldface type apply over full Operating Temperature Range. Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis. Symbol Parameter Conditions Min Typ Max Units SYSTEM PARAMETERS (1) tON-1 On-time 1 VIN = 10V, RON = 200 k 2.1 2.75 3.4 s tON-2 On-time 2 VIN = 40V, RON = 200 k 515 675 835 ns Min Typ Max Units Typical specifications represent the most likely parametric norm at 25C operation. Electrical Characteristics LM3404HV Symbol Parameter Conditions SYSTEM PARAMETERS 4 tON-1 On-time 1 VIN = 10V, RON = 200 k 2.1 2.75 3.4 s tON-2 On-time 2 VIN = 70V, RON = 200 k 325 415 505 ns Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 Electrical Characteristics LM3404/LM3404HV (1) Symbol Parameter Conditions Min Typ Max Units 194 200 206 mV REGULATION AND OVER-VOLTAGE COMPARATORS VREF-REG CS Regulation Threshold CS Decreasing, SW turns on VREF-0V CS Over-voltage Threshold CS Increasing, SW turns off 300 mV ICS CS Bias Current CS = 0V 0.1 A VSD-TH Shutdown Threshold RON / SD Increasing VSD-HYS Shutdown Hysteresis RON / SD Decreasing 40 mV Minimum Off-time CS = 0V 270 ns SHUTDOWN 0.3 0.7 1.05 V OFF TIMER tOFF-MIN INTERNAL REGULATOR VCC-REG VCC Regulated Output VIN-DO VIN - VCC ICC = 5 mA, 6.0V < VIN < 8.0V 300 mV VCC-BP-TH VCC Bypass Threshold VIN Increasing 8.8 V VCC-BP-HYS VCC Bypass Hysteresis VIN Decreasing 230 mV VCC-Z-6 VCC Output Impedance (0 mA < ICC < 5 mA) VIN = 6V 55 VIN = 8V 50 VIN = 24V 0.4 VCC-Z-8 6.4 VCC-Z-24 7 7.4 V VCC-LIM VCC Current Limit (Note 3) VIN = 24V, VCC = 0V 16 mA VCC-UV-TH VCC Under-voltage Lock-out Threshold VCC Increasing 5.3 V VCC-UV-HYS VCC Under-voltage Lock-out Hysteresis VCC Decreasing 150 mV VCC-UV-DLY VCC Under-voltage Lock-out Filter 100 mV Overdrive Delay 3 s IIN-OP IIN Operating Current Non-switching, CS = 0.5V 625 900 A IIN-SD IIN Shutdown Current RON / SD = 0V 95 180 A 1.5 1.8 A CURRENT LIMIT ILIM Current Limit Threshold 1.2 DIM COMPARATOR VIH Logic High DIM Increasing VIL Logic Low DIM Decreasing IDIM-PU DIM Pull-up Current DIM = 1.5V 2.2 V 0.8 80 V A MOSFET AND DRIVER RDS-ON Buck Switch On Resistance ISW = 200mA, BST-SW = 6.3V VDR-UVLO BST Under-voltage Lock-out Threshold BST-SW Increasing VDR-HYS BST Under-voltage Lock-out Hysteresis BST-SW Decreasing 1.7 0.37 0.75 3 4 V 400 mV THERMAL SHUTDOWN TSD Thermal Shutdown Threshold 165 C TSD-HYS Thermal Shutdown Hysteresis 25 C 155 C/W THERMAL RESISTANCE JA Junction to Ambient SOIC-8 Package PSOP-8 Package (1) (2) (2) 50 VCC provides self bias for the internal gate drive and control circuits. Device thermal limitations limit external loading. JA of 50C/W with DAP soldered to a minimum of 2 square inches of 1oz. copper on the top or bottom PCB layer. Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 5 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com Typical Performance Characteristics 6 VREF vs Temperature (VIN = 24V) VREF vs VIN, LM3404 (TA = 25C) VREF vs VIN, LM3404HV (TA = 25C) Current Limit vs Temperature (VIN = 24V) Current Limit vs VIN, LM3404 (TA = 25C) Current Limit vs VIN, LM3404HV (TA = 25C) Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 Typical Performance Characteristics (continued) RON TON vs VIN, = 100 k (TA = 25C) TON vs VIN, (TA = 25C) TON vs VIN, (TA = 25C) TON vs RON, LM3404 (TA = 25C) TON vs RON, LM3404HV (TA = 25C) VCC vs VIN (TA = 25C) Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 7 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com Typical Performance Characteristics (continued) 8 VO-MAX vs fSW, LM3404 (TA = 25C) VO-MIN vs fSW, LM3404 (TA = 25C) VO-MAX vs fSW, LM3404HV (TA = 25C) VO-MIN vs fSW, LM3404HV (TA = 25C) Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 Block Diagram 7V BIAS REGULATOR VIN VIN SENSE VCC UVLO BYPASS SWITCH 0.7V VCC THERMAL SHUTDOWN + 300 ns MIN OFF TIMER Complete ON TIMER RON RON Complete 5V BOOT Start Start GATE DRIVE SD UVLO 75 PA DIM 1.5V 0.2V + - VIN LEVEL SHIFT + - LOGIC CS SW 0.3V + - CURRENT LIMIT OFF TIMER GND + - 1.5A Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV BUCK SWITCH CURRENT SENSE Submit Documentation Feedback 9 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com Application Information THEORY OF OPERATION The LM3404 and LM3404HV are buck regulators with a wide input voltage range, low voltage reference, and a fast output enable/disable function. These features combine to make them ideal for use as a constant current source for LEDs with forward currents as high as 1.2A. The controlled on-time (COT) architecture is a combination of hysteretic mode control and a one-shot on-timer that varies inversely with input voltage. Hysteretic operation eliminates the need for small-signal control loop compensation. When the converter runs in continuous conduction mode (CCM) the controlled on-time maintains a constant switching frequency over the range of input voltage. Fast transient response, PWM dimming, a low power shutdown mode, and simple output overvoltage protection round out the functions of the LM3404/04HV. CONTROLLED ON-TIME OVERVIEW Figure 3 shows the feedback system used to control the current through an array of LEDs. A voltage signal, VSNS, is created as the LED current flows through the current setting resistor, RSNS, to ground. VSNS is fed back to the CS pin, where it is compared against a 200 mV reference, VREF. The on-comparator turns on the power MOSFET when VSNS falls below VREF. The power MOSFET conducts for a controlled on-time, tON, set by an external resistor, RON, and by the input voltage, VIN. On-time is governed by the following equation: tON = 1.34 x 10-10 x RON VIN (1) At the conclusion of tON the power MOSFET turns off for a minimum off-time, tOFF-MIN, of 300 ns. Once tOFF-MIN is complete the CS comparator compares VSNS and VREF again, waiting to begin the next cycle. VO LED 1 VF IF LM3404/04HV LED n CS Comparator One-shot + VSNS CS VREF + - IF RSNS Figure 3. Comparator and One-Shot The LM3404/04HV regulators should be operated in continuous conduction mode (CCM), where inductor current stays positive throughout the switching cycle. During steady-state CCM operation, the converter maintains a constant switching frequency that can be selected using the following equation: fSW = VO 1.34 x 10-10 x RON VO = n x VF + 200 mV (2) (3) VF = forward voltage of each LED, n = number of LEDs in series AVERAGE LED CURRENT ACCURACY The COT architecture regulates the valley of VSNS, the AC portion of VSNS. To determine the average LED current (which is also the average inductor current) the valley inductor current is calculated using the following expression: IL-MIN = 10 0.2 VO x tSNS L RSNS Submit Documentation Feedback (4) Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 In this equation tSNS represents the propagation delay of the CS comparator, and is approximately 220 ns. The average inductor/LED current is equal to IL-MIN plus one-half of the inductor current ripple, iL: IF = IL = IL-MIN + iL / 2 (5) Detailed information for the calculation of iL is given in the Design Considerations section. MAXIMUM OUTPUT VOLTAGE The 300 ns minimum off-time limits the maximum duty cycle of the converter, DMAX, and in turn the maximum output voltage, VO(MAX), determined by the following equations: DMAX = tON tON + tOFF-MIN VO(max) = DMAX x VIN (6) The maximum number of LEDs, nMAX, that can be placed in a single series string is governed by VO(MAX) and the maximum forward voltage of the LEDs used, VF(MAX), using the expression: nMAX = VO(max) - 200 mV VF(MAX) (7) At low switching frequency the maximum duty cycle and output voltage are higher, allowing the LM3404/04HV to regulate output voltages that are nearly equal to input voltage. The following equation relates switching frequency to maximum output voltage, and is also shown graphically in the Typical Performance Characteristics section: VO(MAX) = VIN x TSW - 300 ns TSW TSW = 1/fSW (8) MINIMUM OUTPUT VOLTAGE The minimum recommended on-time for the LM3404/04HV is 300 ns. This lower limit for tON determines the minimum duty cycle and output voltage that can be regulated based on input voltage and switching frequency. The relationship is determined by the following equation, shown on the same graphs as maximum output voltage in the Typical Performance Characteristics section: VO(MIN) = VIN x 300 ns TSW (9) HIGH VOLTAGE BIAS REGULATOR The LM3404/04HV contains an internal linear regulator with a 7V output, connected between the VIN and the VCC pins. The VCC pin should be bypassed to the GND pin with a 0.1 F ceramic capacitor connected as close as possible to the pins of the IC. VCC tracks VIN until VIN reaches 8.8V (typical) and then regulates at 7V as VIN increases. Operation begins when VCC crosses 5.25V. INTERNAL MOSFET AND DRIVER The LM3404/04HV features an internal power MOSFET as well as a floating driver connected from the SW pin to the BOOT pin. Both rise time and fall time are 20 ns each (typical) and the approximate gate charge is 6 nC. The high-side rail for the driver circuitry uses a bootstrap circuit consisting of an internal high-voltage diode and an external 10 nF capacitor, CB. VCC charges CB through the internal diode while the power MOSFET is off. When the MOSFET turns on, the internal diode reverse biases. This creates a floating supply equal to the VCC voltage minus the diode drop to drive the MOSFET when its source voltage is equal to VIN. Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 11 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com FAST SHUTDOWN FOR PWM DIMMING The DIM pin of the LM3404/04HV is a TTL compatible input for low frequency PWM dimming of the LED. A logic low (below 0.8V) at DIM will disable the internal MOSFET and shut off the current flow to the LED array. While the DIM pin is in a logic low state the support circuitry (driver, bandgap, VCC) remains active in order to minimize the time needed to turn the LED array back on when the DIM pin sees a logic high (above 2.2V). A 75 A (typical) pull-up current ensures that the LM3404/04HV is on when DIM pin is open circuited, eliminating the need for a pull-up resistor. Dimming frequency, fDIM, and duty cycle, DDIM, are limited by the LED current rise time and fall time and the delay from activation of the DIM pin to the response of the internal power MOSFET. In general, fDIM should be at least one order of magnitude lower than the steady state switching frequency in order to prevent aliasing. PEAK CURRENT LIMIT The current limit comparator of the LM3404/04HV will engage whenever the power MOSFET current (equal to the inductor current while the MOSFET is on) exceeds 1.5A (typical). The power MOSFET is disabled for a cooldown time that is approximately 75x the steady-state on-time. At the conclusion of this cool-down time the system re-starts. If the current limit condition persists the cycle of cool-down time and restarting will continue, creating a low-power hiccup mode, minimizing thermal stress on the LM3404/04HV and the external circuit components. OVER-VOLTAGE/OVER-CURRENT COMPARATOR The CS pin includes an output over-voltage/over-current comparator that will disable the power MOSFET whenever VSNS exceeds 300 mV. This threshold provides a hard limit for the output current. Output current overshoot is limited to 300 mV / RSNS by this comparator during transients. The OVP/OCP comparator can also be used to prevent the output voltage from rising to VO(MAX) in the event of an output open-circuit. This is the most common failure mode for LEDs, due to breaking of the bond wires. In a current regulator an output open circuit causes VSNS to fall to zero, commanding maximum duty cycle. Figure 4 shows a method using a zener diode, Z1, and zener limiting resistor, RZ, to limit output voltage to the reverse breakdown voltage of Z1 plus 200 mV. The zener diode reverse breakdown voltage, VZ, must be greater than the maximum combined VF of all LEDs in the array. The maximum recommended value for RZ is 1 k. As discussed in the Maximum Output Voltage section, there is a limit to how high VO can rise during an output open-circuit that is always less than VIN. If no output capacitor is used, the output stage of the LM3404/04HV is capable of withstanding VO(MAX) indefinitely, however the voltage at the output end of the inductor will oscillate and can go above VIN or below 0V. A small (typically 10 nF) capacitor across the LED array dampens this oscillation. For circuits that use an output capacitor, the system can still withstand VO(MAX) indefinitely as long as CO is rated to handle VIN. The high current paths are blocked in output open-circuit and the risk of thermal stress is minimal, hence the user may opt to allow the output voltage to rise in the case of an open-circuit LED failure. CB VIN CIN VIN BOOT L1 SW RON D1 Z1 RON LM3404/04HV RZ CS RSNS DIM GND VCC CF Figure 4. Output Open Circuit Protection 12 Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 LOW POWER SHUTDOWN The LM3404/04HV can be placed into a low power state (IIN-SD = 90 A) by grounding the RON pin with a signallevel MOSFET as shown in Figure 5. Low power MOSFETs like the 2N7000, 2N3904, or equivalent are recommended devices for putting the LM3404/04HV into low power shutdown. Logic gates can also be used to shut down the LM3404/04HV as long as the logic low voltage is below the over temperature minimum threshold of 0.3V. Noise filter circuitry on the RON pin can cause a few pulses with longer on-times than normal after RON is grounded or released. In these cases the OVP/OCP comparator will ensure that the peak inductor or LED current does not exceed 300 mV / RSNS. CB L1 VIN VIN BOOT SW RON CIN D1 RON IF LM3404/04HV ON/OFF CS Q1 2N7000 or equivalent RSNS DIM GND VCC CF Figure 5. Low Power Shutdown THERMAL SHUTDOWN Internal thermal shutdown circuitry is provided to protect the IC in the event that the maximum junction temperature is exceeded. The threshold for thermal shutdown is 165C with a 25C hysteresis (both values typical). During thermal shutdown the MOSFET and driver are disabled. Design Considerations SWITCHING FREQUENCY Switching frequency is selected based on the trade-offs between efficiency (better at low frequency), solution size/cost (smaller at high frequency), and the range of output voltage that can be regulated (wider at lower frequency.) Many applications place limits on switching frequency due to EMI sensitivity. The on-time of the LM3404/04HV can be programmed for switching frequencies ranging from the 10's of kHz to over 1 MHz. The maximum switching frequency is limited only by the minimum on-time and minimum off-time requirements. LED RIPPLE CURRENT Selection of the ripple current, iF, through the LED array is analogous to the selection of output ripple voltage in a standard voltage regulator. Where the output ripple in a voltage regulator is commonly 1% to 5% of the DC output voltage, LED manufacturers generally recommend values for iF ranging from 5% to 20% of IF. Higher LED ripple current allows the use of smaller inductors, smaller output capacitors, or no output capacitors at all. The advantages of higher ripple current are reduction in the solution size and cost. Lower ripple current requires more output inductance, higher switching frequency, or additional output capacitance. The advantages of lower ripple current are a reduction in heating in the LED itself and greater tolerance in the average LED current before the current limit of the LED or the driving circuitry is reached. BUCK CONVERTERS WITHOUT OUTPUT CAPACITORS The buck converter is unique among non-isolated topologies because of the direct connection of the inductor to the load during the entire switching cycle. By definition an inductor will control the rate of change of current that flows through it, and this control over current ripple forms the basis for component selection in both voltage regulators and current regulators. A current regulator such as the LED driver for which the LM3404/04HV was designed focuses on the control of the current through the load, not the voltage across it. A constant current Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 13 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com regulator is free of load current transients, and has no need of output capacitance to supply the load and maintain output voltage. Referring to the Typical Application circuit on the front page of this datasheet, the inductor and LED can form a single series chain, sharing the same current. When no output capacitor is used, the same equations that govern inductor ripple current, iL, also apply to the LED ripple current, iF. For a controlled on-time converter such as LM3404/04HV the ripple current is described by the following expression: 'iL = 'iF = VIN - VO L tON (10) A minimum ripple voltage of 25 mV is recommended at the CS pin to provide good signal to noise ratio (SNR). The CS pin ripple voltage, vSNS, is described by the following: vSNS = iF x RSNS (11) BUCK CONVERTERS WITH OUTPUT CAPACITORS A capacitor placed in parallel with the LED or array of LEDs can be used to reduce the LED current ripple while keeping the same average current through both the inductor and the LED array. This technique is demonstrated in Design Examples 1 and 2. With this topology the output inductance can be lowered, making the magnetics smaller and less expensive. Alternatively, the circuit could be run at lower frequency but keep the same inductor value, improving the efficiency and expanding the range of output voltage that can be regulated. Both the peak current limit and the OVP/OCP comparator still monitor peak inductor current, placing a limit on how large iL can be even if iF is made very small. A parallel output capacitor is also useful in applications where the inductor or input voltage tolerance is poor. Adding a capacitor that reduces iF to well below the target provides headroom for changes in inductance or VIN that might otherwise push the peak LED ripple current too high. Figure 6 shows the equivalent impedances presented to the inductor current ripple when an output capacitor, CO, and its equivalent series resistance (ESR) are placed in parallel with the LED array. The entire inductor ripple current flows through RSNS to provide the required 25 mV of ripple voltage for proper operation of the CS comparator. 'iL CO rD 'iC 'iF ESR 'iL RSNS Figure 6. LED and CO Ripple Current To calculate the respective ripple currents the LED array is represented as a dynamic resistance, rD. LED dynamic resistance is not always specified on the manufacturer's datasheet, but it can be calculated as the inverse slope of the LED's VF vs. IF curve. Note that dividing VF by IF will give an incorrect value that is 5x to 10x too high. Total dynamic resistance for a string of n LEDs connected in series can be calculated as the rD of one device multiplied by n. Inductor ripple current is still calculated with the expression from Buck Regulators without Output Capacitors. The following equations can then be used to estimate iF when using a parallel capacitor: 'iF = 'iL 1+ rD ZC ZC = ESR + 1 2S x fSW x CO (12) The calculation for ZC assumes that the shape of the inductor ripple current is approximately sinusoidal. 14 Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 Small values of CO that do not significantly reduce iF can also be used to control EMI generated by the switching action of the LM3404/04HV. EMI reduction becomes more important as the length of the connections between the LED and the rest of the circuit increase. INPUT CAPACITORS Input capacitors at the VIN pin of the LM3404/04HV are selected using requirements for minimum capacitance and rms ripple current. The input capacitors supply pulses of current approximately equal to IF while the power MOSFET is on, and are charged up by the input voltage while the power MOSFET is off. Switching converters such as the LM3404/04HV have a negative input impedance due to the decrease in input current as input voltage increases. This inverse proportionality of input current to input voltage can cause oscillations (sometimes called `power supply interaction') if the magnitude of the negative input impedance is greater the the input filter impedance. Minimum capacitance can be selected by comparing the input impedance to the converter's negative resistance; however this requires accurate calculation of the input voltage source inductance and resistance, quantities which can be difficult to determine. An alternative method to select the minimum input capacitance, CIN(MIN), is to select the maximum input voltage ripple which can be tolerated. This value, vIN(MAX), is equal to the change in voltage across CIN during the converter on-time, when CIN supplies the load current. CIN(MIN) can be selected with the following: CIN (MIN) = IF x tON 'VIN (MAX) (13) A good starting point for selection of CIN is to use an input voltage ripple of 5% to 10% of VIN. A minimum input capacitance of 2x the CIN(MIN) value is recommended for all LM3404/04HV circuits. To determine the rms current rating, the following formula can be used: IIN(rms) = IF x D(1 - D) (14) Ceramic capacitors are the best choice for the input to the LM3404/04HV due to their high ripple current rating, low ESR, low cost, and small size compared to other types. When selecting a ceramic capacitor, special attention must be paid to the operating conditions of the application. Ceramic capacitors can lose one-half or more of their capacitance at their rated DC voltage bias and also lose capacitance with extremes in temperature. A DC voltage rating equal to twice the expected maximum input voltage is recommended. In addition, the minimum quality dielectric which is suitable for switching power supply inputs is X5R, while X7R or better is preferred. RECIRCULATING DIODE The LM3404/04HV is a non-synchronous buck regulator that requires a recirculating diode D1 (see the Typical Application circuit) to carrying the inductor current during the MOSFET off-time. The most efficient choice for D1 is a Schottky diode due to low forward drop and near-zero reverse recovery time. D1 must be rated to handle the maximum input voltage plus any switching node ringing when the MOSFET is on. In practice all switching converters have some ringing at the switching node due to the diode parasitic capacitance and the lead inductance. D1 must also be rated to handle the average current, ID, calculated as: ID = (1 - D) x IF (15) This calculation should be done at the maximum expected input voltage. The overall converter efficiency becomes more dependent on the selection of D1 at low duty cycles, where the recirculating diode carries the load current for an increasing percentage of the time. This power dissipation can be calculating by checking the typical diode forward voltage, VD, from the I-V curve on the product datasheet and then multiplying it by ID. Diode datasheets will also provide a typical junction-to-ambient thermal resistance, JA, which can be used to estimate the operating die temperature of the device. Multiplying the power dissipation (PD = ID x VD) by JA gives the temperature rise. The diode case size can then be selected to maintain the Schottky diode temperature below the operational maximum. Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 15 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com LED CURRENT DURING DIM MODE The LM3402 contains high speed MOSFET gate drive circuitry that switches the main internal power MOSFET between "on" and "off" states. This circuitry uses current derived from the VCC regulator to charge the MOSFET during turn-on, then dumps current from the MOSFET gate to the source (the SW pin) during turn-off. As shown in the block diagram, the MOSFET drive circuitry contains a gate drive under-voltage lockout (UVLO) circuit that ensures the MOSFET remains off when there is inadequate VCC voltage for proper operation of the driver. This watchdog circuitry is always running including during DIM and shutdown modes, and supplies a small amount of current from VCC to SW. Because the SW pin is connected directly to the LEDs through the buck inductor, this current returns to ground through the LEDs. The amount of current sourced is a function of the SW voltage, as shown in Figure 7. 25 SW CURRENT (PA) 20 15 10 5 0 0 1 2 3 4 5 6 SW VOLTAGE (V) Figure 7. LED Current From SW Pin Though most power LEDs are designed to run at several hundred milliamps, some can be seen to glow with a faint light at extremely low current levels, as low as a couple microamps in some instances. In lab testing, the forward voltage was found to be approximately 2V for LEDs that exhibited visible light at these low current levels. For LEDs that did not show light emission at very low current levels, the forward voltage was found to be around 900mV. It is important to remember that the forward voltage is also temperature dependent, decreasing at higher temperatures. Consequently, with a maximum Vcc voltage of 7.4V, current will be observed in the LEDs if the total stack voltage is less than about 6V at a forward current of several microamps. No current is observed if the stack voltage is above 6V, as shown in Figure 7. The need for absolute darkness during DIM mode is also application dependent. It will not affect regular PWM dimming operation. The fix for this issue is extremely simple. Place a resistor from the SW pin to ground according to the chart below. 16 Number of LEDs Resistor Value (k) 1 20 2 50 3 90 4 150 5 200 >5 300 Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 The luminaire designer should ensure that the suggested resistor is effective in eliminating the off-state light output. A combination of calculations based on LED manufacturer data and lab measurements over temperature will ensure the best design. Transient Protection Considerations Considerations need to be made when external sources, loads or connections are made to the switching converter circuit due to the possibility of Electrostatic Discharge (ESD) or Electric Over Stress (EOS) events occurring and damaging the integrated circuit (IC) device. All IC device pins contain zener based clamping structures that are meant to clamp ESD. ESD events are very low energy events, typically less than 5J (microjoules). Any event that transfers more energy than this may damage the ESD structure. Damage is typically represented as a short from the pin to ground as the extreme localized heat of the ESD / EOS event causes the aluminum metal on the chip to melt, causing the short. This situation is common to all integrated circuits and not just unique to the LM340X device. CS PIN PROTECTION When hot swapping in a load (e.g. test points, load boards, LED stack), any residual charge on the load will be immediately transferred through the output capacitor to the CS pin, which is then damaged as shown in Figure 8 below. The EOS event due to the residual charge from the load is represented as VTRANSIENT. From measurements, we know that the 8V ESD structure on the CS pin can typically withstand 25mA of direct current (DC). Adding a 1k resistor in series with the CS pin, shown in Figure 9, results in the majority of the transient energy to pass through the discrete sense resistor rather than the device. The series resistor limits the peak current that can flow during a transient event, thus protecting the CS pin. With the 1k resistor shown, a 33V, 49A transient on the LED return connector terminal could be absorbed as calculated by: V = 25mA * 1k + 8V = 33V (16) I = 33V / 0.67 = 49A (17) This is an extremely high energy event, so the protection measures previously described should be adequate to solve this issue. LM3404 SW Module Connector Module Connector VTRANSIENT CS 8V ~ 0.675 GND Figure 8. CS Pin, Transient Path Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 17 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com LM3404 SW Module Connector Module Connector VTRANSIENT CS 1 k5 8V ~ 0.675 GND Figure 9. CS Pin, Transient Path with Protection Adding a resistor in series with the CS pin causes the observed output LED current to shift very slightly. The reason for this is twofold: (1) the CS pin has about 20pF of inherent capacitance inside it which causes a slight delay (20ns for a 1k series resistor), and (2) the comparator that is watching the voltage at the CS pin uses a pnp bipolar transistor at its input. The base current of this pnp transistor is approximately 100nA which will cause a 0.1mV change in the 200mV threshold. These are both very minor changes and are well understood. The shift in current can either be neglected or taken into consideration by changing the current sense resistance slightly. CS PIN PROTECTION WITH OVP When designing output overvoltage protection into the switching converter circuit using a zener diode, transient protection on the CS pin requires additional consideration. As shown in Figure 10, adding a zener diode from the output to the CS pin (with the series resistor) for output overvoltage protection will now again allow the transient energy to be passed Adding an additional series resistor to the CS pin as shown in Figure 11 will result in the majority of the transient energy to pass through the sense resistor thereby protecting the LM340X device. LM3404 SW Module Connector Module Connector VTRANSIENT CS 1 k5 8V ~ 0.675 GND Figure 10. CS Pin with OVP, Transient Path 18 Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 LM3404 SW Module Connector Module Connector VTRANSIENT CS 1 k5 5005 8V ~ 0.675 GND Figure 11. CS Pin with OVP, Transient Path with Protection VIN PIN PROTECTION The VIN pin also has an ESD structure from the pin to GND with a breakdown voltage of approximately 80V. Any transient that exceeds this voltage may damage the device. Although transient absorption is usually present at the front end of a switching converter circuit, damage to the VIN pin can still occur. When VIN is hot swapped in, the current that rushes in to charge CIN up to the VIN value also charges (energizes) the circuit board trace inductance as shown in Figure 12. The excited trace inductance then resonates with the input capacitance (similar to an under-damped LC tank circuit) and causes voltages at the VIN pin to rise well in excess of both VIN and the voltage at the module input connector as clamped by the input TVS. If the resonating voltage at the VIN pin exceeds the 80V breakdown voltage of the ESD structure, the ESD structure will activate and then "snap-back" to a lower voltage due to its inherent design. If this lower snap-back voltage is less than the applied nominal VIN voltage, then significant current will flow through the ESD structure resulting in the IC being damaged. An additional TVS or small zener diode should be placed as close as possible to the VIN pins of each IC on the board, in parallel with the input capacitor as shown in Figure 13. A minor amount of series resistance in the input line would also help, but would lower overall conversion efficiency. For this reason, NTC resistors are often used as inrush limiters instead. Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 19 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com LM3404 Board Trace Inductance VIN Module Connector 80V VIN TVS CIN GND Module Connector Figure 12. VIN Pin with Typical Input Protection LM3404 Board Trace Inductance VIN Module Connector 80V VIN TVS CIN TVS or smaller zener diode GND Module Connector Figure 13. VIN Pin with Additional Input Protection GENERAL COMMENTS REGARDING OTHER PINS Any pin that goes "off-board" through a connector should have series resistance of at least 1k to 10k in series with it to protect it from ESD or other transients. These series resistors limit the peak current that can flow (or cause a voltage drop) during a transient event, thus protecting the pin and the device. Pins that are not used should not be left floating. They should instead be tied to GND or to an appropriate voltage through resistance. Design Example 1: LM3404 The first example circuit will guide the user through component selection for an architectural accent lighting application. A regulated DC voltage input of 24V 10% will power a 5.4W "warm white" LED module that consists of four LEDs in a 2 x 2 series-parallel configuration. The module will be treated as a two-terminal element and driven with a forward current of 700 mA 5%. The typical forward voltage of the LED module in thermal steady state is 6.9V, hence the average output voltage will be 7.1V. The objective of this application is to place the 20 Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 complete current regulator and LED module in a compact space formerly occupied by a halogen light source. (The LED will be on a separate metal-core PCB and heatsink.) Switching frequency will be 400 kHz to keep switching loss low, as the confined space with no air-flow requires a maximum temperature rise of 50C in each circuit component. A small solution size is also important, as the regulator must fit on a circular PCB with a 1.5" diameter. A complete bill of materials can be found in Table 1 at the end of this datasheet. CB VIN = 24V VIN CIN BOOT IF = 700 mA L1 SW RON D1 RON LED1 CO LM3404 CS RSNS DIM GND VCC CF Figure 14. Schematic for Design Example 1 RON and tON A moderate switching frequency is needed in this application to balance the requirements of magnetics size and efficiency. RON is selected from the equation for switching frequency as follows: RON = VO 1.34 x 10-10 x fSW (18) (19) RON = 7.1 / (1.34 x 10-10 x 4 x 105) = 132.5 k The closest 1% tolerance resistor is 133 k. The switching frequency and on-time of the circuit can then be found using the equations relating RON and tON to fSW: fSW = 7.1 / (1.33 x 105 x 1.34 x 10-10) = 398 kHz (20) tON = (1.34 x 10-10 x 1.33 x 105) / 24 = 743 ns (21) OUTPUT INDUCTOR Since an output capacitor will be used to filter some of the AC ripple current, the inductor ripple current can be set higher than the LED ripple current. A value of 40%P-P is typical in many buck converters: iL = 0.4 x 0.7 = 0.28A (22) With the target ripple current determined the inductance can be chosen: LMIN = VIN - VO 'iL x tON (23) LMIN = [(24 - 7.1) x 7.43 x 10-7] / (0.28) = 44.8 H Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV (24) Submit Documentation Feedback 21 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com The closest standard inductor value is 47 H. The average current rating should be greater than 700 mA to prevent overheating in the inductor. Separation between the LM3404 drivers and the LED arrays means that heat from the inductor will not threaten the lifetime of the LEDs, but an overheated inductor could still cause the LM3404 to enter thermal shutdown. The inductance of the standard part chosen is 20%. With this tolerance the typical, minimum, and maximum inductor current ripples can be calculated: iL(TYP) = [(24 - 7.1) x 7.43 x 10-7] / 47 x 10-6 = 266 mAP-P (25) iL(MIN) = [(24 - 7.1) x 7.43 x 10-7] / 56 x 10-6 = 223 mAP-P (26) iL(MAX) = [(24 - 7.1) x 7.43 x 10-7] / 38 x 10-6 = 330 mAP-P (27) The peak LED/inductor current is then estimated: IL(PEAK) = IL + 0.5 x iL(MAX) (28) IL(PEAK) = 0.7 + 0.5 x 0.330 = 866 mA (29) In the case of a short circuit across the LED array, the LM3404 will continue to deliver rated current through the short but will reduce the output voltage to equal the CS pin voltage of 200 mV. The inductor ripple current and peak current in this condition would be equal to: iL(LED-SHORT) = [(24 - 0.2) x 7.43 x 10-7] / 38 x 10-6 = 465 mAP-P IL(PEAK) = 0.7 + 0.5 x 0.465 = 933 mA (30) In the case of a short at the switch node, the output, or from the CS pin to ground the short circuit current limit will engage at a typical peak current of 1.5A. In order to prevent inductor saturation during these fault conditions the inductor's peak current rating must be above 1.5A. A 47 H off-the shelf inductor rated to 1.4A (peak) and 1.5A (average) with a DCR of 0.1 will be used. USING AN OUTPUT CAPACITOR This application does not require high frequency PWM dimming, allowing the use of an output capacitor to reduce the size and cost of the output inductor. To select the proper output capacitor the equation from Buck Regulators with Output Capacitors is re-arranged to yield the following: ZC = 'iF 'iL - 'iF x rD (31) The target tolerance for LED ripple current is 100 mAP-P, and a typical value for rD of 1.8 at 700 mA can be read from the LED datasheet. The required capacitor impedance to reduce the worst-case inductor ripple current of 333 mAP-P is therefore: ZC = [0.1 / (0.333 - 0.1] x 1.8 = 0.77 (32) A ceramic capacitor will be used and the required capacitance is selected based on the impedance at 400 kHz: CO = 1/(2 x x 0.77 x 4 x 105) = 0.51 F 22 Submit Documentation Feedback (33) Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 This calculation assumes that impedance due to the equivalent series resistance (ESR) and equivalent series inductance (ESL) of CO is negligible. The closest 10% tolerance capacitor value is 1.0 F. The capacitor used should be rated to 25V or more and have an X7R dielectric. Several manufacturers produce ceramic capacitors with these specifications in the 0805 case size. A typical value for ESR of 3 m can be read from the curve of impedance vs. frequency in the product datasheet. RSNS A preliminary value for RSNS was determined in selecting iL. This value should be re-evaluated based on the calculations for iF: 0.2 x L RSNS = IF x L + VO x tSNS - VIN - VO x tON 2 (34) (35) tSNS = 220 ns, RSNS = 0.33 Sub-1 resistors are available in both 1% and 5% tolerance. A 1%, 0.33 device is the closest value, and a 0.33W, 1206 size device will handle the power dissipation of 162 mW. With the resistance selected, the average value of LED current is re-calculated to ensure that current is within the 5% tolerance requirement. From the expression for average LED current: IF = 0.2 / 0.33 - (7.1 x 2.2 x 10-7) / 47 x 10-6 + 0.266 / 2 = 706 mA, 1% above 700 mA (36) (37) INPUT CAPACITOR Following the calculations from the Input Capacitor section, vIN(MAX) will be 24V x 2%P-P = 480 mV. The minimum required capacitance is: CIN(MIN) = (0.7 x 7.4 x 10-7) / 0.48 = 1.1 F (38) To provide additional safety margin the a higher value of 3.3 F ceramic capacitor rated to 50V with X7R dielectric in an 1210 case size will be used. From the Design Considerations section, input rms current is: IIN-RMS = 0.7 x Sqrt(0.28 x 0.72) = 314 mA (39) Ripple current ratings for 1210 size ceramic capacitors are typically higher than 2A, more than enough for this design. RECIRCULATING DIODE The input voltage of 24V 5% requires Schottky diodes with a reverse voltage rating greater than 30V. The next highest standard voltage rating is 40V. Selecting a 40V rated diode provides a large safety margin for the ringing of the switch node and also makes cross-referencing of diodes from different vendors easier. The next parameters to be determined are the forward current rating and case size. In this example the low duty cycle (D = 7.1 / 24 = 28%) places a greater thermal stress on D1 than on the internal power MOSFET of the LM3404. The estimated average diode current is: ID = 0.706 x 0.72 = 509 mA (40) Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 23 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com A Schottky with a forward current rating of 1A would be adequate, however reducing the power dissipation is critical in this example. Higher current diodes have lower forward voltages, hence a 2A-rated diode will be used. To determine the proper case size, the dissipation and temperature rise in D1 can be calculated as shown in the Design Considerations section. VD for a case size such as SMB in a 40V, 2A Schottky diode at 700 mA is approximately 0.3V and the JA is 75C/W. Power dissipation and temperature rise can be calculated as: PD = 0.509 x 0.3 = 153 mW TRISE = 0.153 x 75 = 11.5C (41) CB AND CF The bootstrap capacitor CB should always be a 10 nF ceramic capacitor with X7R dielectric. A 25V rating is appropriate for all application circuits. The linear regulator filter capacitor CF should always be a 100 nF ceramic capacitor, also with X7R dielectric and a 25V rating. EFFICIENCY To estimate the electrical efficiency of this example the power dissipation in each current carrying element can be calculated and summed. Electrical efficiency, , should not be confused with the optical efficacy of the circuit, which depends upon the LEDs themselves. Total output power, PO, is calculated as: PO = IF x VO = 0.706 x 7.1 = 5W (42) Conduction loss, PC, in the internal MOSFET: PC = (IF2 x RDSON) x D = (0.7062 x 0.8) x 0.28 = 112 mW (43) Gate charging and VCC loss, PG, in the gate drive and linear regulator: PG = (IIN-OP + fSW x QG) x VIN PG = (600 x 10-6 + 4 x 105 x 6 x 10-9) x 24 = 72 mW (44) Switching loss, PS, in the internal MOSFET: PS = 0.5 x VIN x IF x (tR + tF) x fSW PS = 0.5 x 24 x 0.706 x 40 x 10-9 x 4 x 105 = 136 mW (45) AC rms current loss, PCIN, in the input capacitor: PCIN = IIN(rms)2 x ESR = 0.3172 0.003 = 0.3 mW (negligible) (46) DCR loss, PL, in the inductor PL = IF2 x DCR = 0.7062 x 0.1 = 50 mW (47) Recirculating diode loss, PD = 153 mW Current Sense Resistor Loss, PSNS = 164 mW Electrical efficiency, = PO / (PO + Sum of all loss terms) = 5 / (5 + 0.687) = 88% Temperature Rise in the LM3404 IC is calculated as: 24 Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 TLM3404 = (PC + PG + PS) x JA = (0.112 + 0.072 + 0.136) x 155 = 49.2C (48) Design Example 2: LM3404HV The second example circuit will guide the user through component selection for an outdoor general lighting application. A regulated DC voltage input of 48V 10% will power ten series-connected LEDs at 500 mA 10% with a ripple current of 50 mAP-P or less. The typical forward voltage of the LED module in thermal steady state is 35V, hence the average output voltage will be 35.2V. A complete bill of materials can be found in Table 2 at the end of this datasheet. CB VIN = 48V 10% VIN CIN BOOT IF = 0.5A L1 SW LED1 RON D1 RON CO LM3404HV LED10 CS RSNS GND VCC CF Figure 15. Schematic for Design Example 2 RON and tON A low switching frequency, 225 kHz, is needed in this application, as high efficiency and low power dissipation take precedence over the solution size. RON is selected from the equation for switching frequency as follows: RON = VO 1.34 x 10-10 x fSW (49) (50) RON = 35.2 / (1.34 x 10-10 x 2.25 x 105) = 1.16 M The next highest 1% tolerance resistor is 1.18 M. The switching frequency and on-time of the circuit can then be found using the equations relating RON and tON to fSW: fSW = 35.2 / (1.18 x 106 x 1.34 x 10-10) = 223 kHz (51) tON = (1.34 x 10-10 x 1.18 x 106) / 48 = 3.3 s (52) OUTPUT INDUCTOR Since an output capacitor will be used to filter some of the AC ripple current, the inductor ripple current can be set higher than the LED ripple current. A value of 30%P-P makes a good trade-off between the current ripple and the size of the inductor: iL = 0.3 x 0.5 = 0.15A (53) With the target ripple current determined the inductance can be chosen: LMIN = VIN - VO 'iL x tON (54) Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 25 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com LMIN = [(48 - 35.2) x 3.3 x 10-6] / (0.15) = 281 H (55) The closest standard inductor value above 281 is 330 H. The average current rating should be greater than 0.5A to prevent overheating in the inductor. In this example the LM3404HV driver and the LED array share the same metal-core PCB, meaning that heat from the inductor could threaten the lifetime of the LEDs. For this reason the average current rating of the inductor used should have a de-rating of about 50%, or 1A. The inductance of the standard part chosen is 20%. With this tolerance the typical, minimum, and maximum inductor current ripples can be calculated: iL(TYP) = [(48 - 35.2) x 3.3 x 10-6] / 330 x 10-6 = 128 mAP-P (56) iL(MIN) = [(48 - 35.2) x 3.3 x 10-6] / 396 x 10-6 = 107 mAP-P (57) iL(MAX) = [(48 - 35.2) x 3.3 x 10-6] / 264 x 10-6 = 160 mAP-P (58) The peak inductor current is then estimated: IL(PEAK) = IL + 0.5 x iL(MAX) (59) IL(PEAK) = 0.5 + 0.5 x 0.16 = 0.58A (60) In the case of a short circuit across the LED array, the LM3404HV will continue to deliver rated current through the short but will reduce the output voltage to equal the CS pin voltage of 200 mV. The inductor ripple current and peak current in this condition would be equal to: iL(LED-SHORT) = [(48 - 0.2) x 3.3 x 10-6] / 264 x 10-6 = 0.598AP-P (61) IL(PEAK) = 0.5 + 0.5 x 0.598 = 0.8A (62) In the case of a short at the switch node, the output, or from the CS pin to ground the short circuit current limit will engage at a typical peak current of 1.5A. In order to prevent inductor saturation during these fault conditions the inductor's peak current rating must be above 1.5A. A 330 H off-the shelf inductor rated to 1.9A (peak) and 1.0A (average) with a DCR of 0.56 will be used. USING AN OUTPUT CAPACITOR This application uses sub-1 kHz frequency PWM dimming, allowing the use of a small output capacitor to reduce the size and cost of the output inductor. To select the proper output capacitor the equation from Buck Regulators with Output Capacitors is re-arranged to yield the following: ZC = 'iF 'iL - 'iF x rD (63) The target tolerance for LED ripple current is 50 mAP-P, and the typical value for rD is 10 with ten LEDs in series. The required capacitor impedance to reduce the worst-case steady-state inductor ripple current of 160 mAP-P is therefore: ZC = [0.05 / (0.16 - 0.05] x 10 = 4.5 26 Submit Documentation Feedback (64) Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 A ceramic capacitor will be used and the required capacitance is selected based on the impedance at 223 kHz: CO = 1/(2 x x 4.5 x 2.23 x 105) = 0.16 F (65) This calculation assumes that impedance due to the equivalent series resistance (ESR) and equivalent series inductance (ESL) of CO is negligible. The closest 10% tolerance capacitor value is 0.15 F. The capacitor used should be rated to 50V or more and have an X7R dielectric. Several manufacturers produce ceramic capacitors with these specifications in the 0805 case size. ESR values are not typically provided for such low value capacitors, however is can be assumed to be under 100 m, leaving plenty of margin to meet to LED ripple current requirement. The low capacitance required allows the use of a 100V rated, 1206-size capacitor. The rating of 100V ensures that the capacitance will not decrease significantly when the DC output voltage is applied across the capacitor. RSNS A preliminary value for RSNS was determined in selecting iL. This value should be re-evaluated based on the calculations for iF: 0.2 x L RSNS = IF x L + VO x tSNS - VIN - VO x tON 2 (66) tSNS = 220 ns, RSNS = 0.43 (67) Sub-1 resistors are available in both 1% and 5% tolerance. A 1%, 0.43 device is the closest value, and a 0.25W, 0805 size device will handle the power dissipation of 110 mW. With the resistance selected, the average value of LED current is re-calculated to ensure that current is within the 10% tolerance requirement. From the expression for average LED current: IF = 0.2 / 0.43 - (35.2 x 2.2 x 10-7) / 330 x 10-6 + 0.128 / 2 = 505 mA (68) (69) INPUT CAPACITOR Following the calculations from the Input Capacitor section, vIN(MAX) will be 48V x 2%P-P = 960 mV. The minimum required capacitance is: CIN(MIN) = (0.5 x 3.3 x 10-6) / 0.96 = 1.7 F (70) To provide additional safety margin a 2.2 F ceramic capacitor rated to 100V with X7R dielectric in an 1812 case size will be used. From the Design Considerations section, input rms current is: IIN-RMS = 0.5 x Sqrt(0.73 x 0.27) = 222 mA (71) Ripple current ratings for 1812 size ceramic capacitors are typically higher than 2A, more than enough for this design, and the ESR is approximately 3 m. Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 27 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com RECIRCULATING DIODE The input voltage of 48V requires Schottky diodes with a reverse voltage rating greater than 50V. The next highest standard voltage rating is 60V. Selecting a 60V rated diode provides a large safety margin for the ringing of the switch node and also makes cross-referencing of diodes from different vendors easier. The next parameters to be determined are the forward current rating and case size. In this example the high duty cycle (D = 35.2 / 48 = 73%) places a greater thermal stress on the internal power MOSFET than on D1. The estimated average diode current is: ID = 0.5 x 0.27 = 135 mA (72) A Schottky with a forward current rating of 0.5A would be adequate, however reducing the power dissipation is critical in this example. Higher current diodes have lower forward voltages, hence a 1A-rated diode will be used. To determine the proper case size, the dissipation and temperature rise in D1 can be calculated as shown in the Design Considerations section. VD for a case size such as SMA in a 60V, 1A Schottky diode at 0.5A is approximately 0.35V and the JA is 75C/W. Power dissipation and temperature rise can be calculated as: PD = 0.135 x 0.35 = 47 mW TRISE = 0.047 x 75 = 3.5C (73) CB AND CF The bootstrap capacitor CB should always be a 10 nF ceramic capacitor with X7R dielectric. A 25V rating is appropriate for all application circuits. The linear regulator filter capacitor CF should always be a 100 nF ceramic capacitor, also with X7R dielectric and a 25V rating. EFFICIENCY To estimate the electrical efficiency of this example the power dissipation in each current carrying element can be calculated and summed. Electrical efficiency, , should not be confused with the optical efficacy of the circuit, which depends upon the LEDs themselves. Total output power, PO, is calculated as: PO = IF x VO = 0.5 x 35.2 = 17.6W (74) Conduction loss, PC, in the internal MOSFET: PC = (IF2 x RDSON) x D = (0.52 x 0.8) x 0.73 = 146 mW (75) Gate charging and VCC loss, PG, in the gate drive and linear regulator: PG = (IIN-OP + fSW x QG) x VIN PG = (600 x 10-6 + 2.23 x 105 x 6 x 10-9) x 48 = 94 mW (76) Switching loss, PS, in the internal MOSFET: PS = 0.5 x VIN x IF x (tR + tF) x fSW PS = 0.5 x 48 x 0.5 x 40 x 10-9 x 2.23 x 105 = 107 mW (77) AC rms current loss, PCIN, in the input capacitor: PCIN = IIN(rms)2 x ESR = 0.2222 0.003 = 0.1 mW (negligible) 28 Submit Documentation Feedback (78) Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV LM3404, LM3404HV www.ti.com SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 DCR loss, PL, in the inductor PL = IF2 x DCR = 0.52 x 0.56 = 140 mW (79) Recirculating diode loss, PD = 47 mW Current Sense Resistor Loss, PSNS = 110 mW Electrical efficiency, = PO / (PO + Sum of all loss terms) = 17.6 / (17.6 + 0.644) = 96% Temperature Rise in the LM3404HV IC is calculated as: TLM3404 = (PC + PG + PS) x JA = (0.146 + 0.094 + 0.107) x 155 = 54C (80) Layout Considerations The performance of any switching converter depends as much upon the layout of the PCB as the component selection. The following guidelines will help the user design a circuit with maximum rejection of outside EMI and minimum generation of unwanted EMI. COMPACT LAYOUT Parasitic inductance can be reduced by keeping the power path components close together and keeping the area of the loops that high currents travel small. Short, thick traces or copper pours (shapes) are best. In particular, the switch node (where L1, D1, and the SW pin connect) should be just large enough to connect all three components without excessive heating from the current it carries. The LM3404/04HV operates in two distinct cycles whose high current paths are shown in Figure 16: + - Figure 16. Buck Converter Current Loops The dark grey, inner loop represents the high current path during the MOSFET on-time. The light grey, outer loop represents the high current path during the off-time. GROUND PLANE AND SHAPE ROUTING The diagram of Figure 16 is also useful for analyzing the flow of continuous current vs. the flow of pulsating currents. The circuit paths with current flow during both the on-time and off-time are considered to be continuous current, while those that carry current during the on-time or off-time only are pulsating currents. Preference in routing should be given to the pulsating current paths, as these are the portions of the circuit most likely to emit EMI. The ground plane of a PCB is a conductor and return path, and it is susceptible to noise injection just as any other circuit path. The continuous current paths on the ground net can be routed on the system ground plane with less risk of injecting noise into other circuits. The path between the input source and the input capacitor and the path between the recirculating diode and the LEDs/current sense resistor are examples of continuous current paths. In contrast, the path between the recirculating diode and the input capacitor carries a large pulsating Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV Submit Documentation Feedback 29 LM3404, LM3404HV SNVS465E - OCTOBER 2006 - REVISED FEBRUARY 2010 www.ti.com current. This path should be routed with a short, thick shape, preferably on the component side of the PCB. Multiple vias in parallel should be used right at the pad of the input capacitor to connect the component side shapes to the ground plane. A second pulsating current loop that is often ignored is the gate drive loop formed by the SW and BOOT pins and capacitor CB. To minimize this loop at the EMI it generates, keep CB close to the SW and BOOT pins. CURRENT SENSING The CS pin is a high-impedance input, and the loop created by RSNS, RZ (if used), the CS pin and ground should be made as small as possible to maximize noise rejection. RSNS should therefore be placed as close as possible to the CS and GND pins of the IC. REMOTE LED ARRAYS In some applications the LED or LED array can be far away (several inches or more) from the LM3404/04HV, or on a separate PCB connected by a wiring harness. When an output capacitor is used and the LED array is large or separated from the rest of the converter, the output capacitor should be placed close to the LEDs to reduce the effects of parasitic inductance on the AC impedance of the capacitor. The current sense resistor should remain on the same PCB, close to the LM3404/04HV. Table 1. BOM for Design Example 1 ID Part Number Type Size Parameters Qty Vendor U1 LM3404 LED Driver SO-8 42V, 1.2A 1 NSC L1 SLF10145T-470M1R4 Inductor 10 x 10 x 4.5mm 47 H, 1.4A, 120 m 1 TDK D1 CMSH2-40 Schottky Diode SMB 40V, 2A 1 Central Semi Cf VJ0805Y104KXXAT Capacitor 0805 100 nF 10% 1 Vishay Cb VJ0805Y103KXXAT Capacitor 0805 10 nF 10% 1 Vishay Cin C3225X7R1H335M Capacitor 1210 3.3 F, 50V 1 TDK Co C2012X7R1E105M Capacitor 0805 1.0 F, 25V 1 TDK Rsns ERJ8BQFR33V Resistor 1206 0.33 1% 1 Panasonic Ron CRCW08051333F Resistor 0805 133 k 1% 1 Vishay Table 2. BOM for Design Example 2 30 ID Part Number Type Size Parameters Qty U1 LM3404HV LED Driver SO-8 75V, 1.2A 1 Vendor NSC L1 DO5022P-334 Inductor 18.5 x 15.4 x 7.1mm 330 H, 1.9A, 0.56 1 Coilcraft D1 CMSH1-60M Schottky Diode SMA 60V, 1A 1 Central Semi Cf VJ0805Y104KXXAT Capacitor 0805 100 nF 10% 1 Vishay Cb VJ0805Y103KXXAT Capacitor 0805 10 nF 10% 1 Vishay Cin C4532X7R2A225M Capacitor 1812 2.2 F, 100V 1 TDK Co C3216X7R2A154M Capacitor 1206 0.15 F, 100V 1 TDK Rsns ERJ6BQFR43V Resistor 0805 0.43 1% 1 Panasonic Ron CRCW08051184F Resistor 0805 1.18 M 1% 1 Vishay Submit Documentation Feedback Copyright (c) 2006-2010, Texas Instruments Incorporated Product Folder Links: LM3404 LM3404HV PACKAGE OPTION ADDENDUM www.ti.com 24-Jan-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Qty Drawing Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (C) Top-Side Markings (3) (4) LM3404HVMA ACTIVE SOIC D 8 95 TBD CU SNPB Level-1-235C-UNLIM -40 to 125 L3404 HVMA LM3404HVMA/NOPB ACTIVE SOIC D 8 95 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 L3404 HVMA LM3404HVMAX ACTIVE SOIC D 8 2500 TBD CU SNPB Level-1-235C-UNLIM -40 to 125 L3404 HVMA LM3404HVMAX/NOPB ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 L3404 HVMA LM3404HVMR ACTIVE SO PowerPAD DDA 8 95 TBD CU SNPB Level-3-260C-168 HR -40 to 125 L3404 HVMR LM3404HVMR/NOPB ACTIVE SO PowerPAD DDA 8 95 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 L3404 HVMR LM3404HVMRX ACTIVE SO PowerPAD DDA 8 2500 TBD CU SNPB Level-3-260C-168 HR -40 to 125 L3404 HVMR LM3404HVMRX/NOPB ACTIVE SO PowerPAD DDA 8 2500 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 L3404 HVMR LM3404MA ACTIVE SOIC D 8 95 TBD CU SNPB Level-1-235C-UNLIM -40 to 125 L3404 MA LM3404MA/NOPB ACTIVE SOIC D 8 95 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 L3404 MA LM3404MAX ACTIVE SOIC D 8 2500 TBD CU SNPB Level-1-235C-UNLIM -40 to 125 L3404 MA LM3404MAX/NOPB ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 L3404 MA LM3404MR ACTIVE SO PowerPAD DDA 8 95 TBD CU SNPB Level-3-260C-168 HR -40 to 125 L3404 MR LM3404MR/NOPB ACTIVE SO PowerPAD DDA 8 95 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 L3404 MR LM3404MRX ACTIVE SO PowerPAD DDA 8 2500 TBD CU SNPB Level-3-260C-168 HR -40 to 125 L3404 MR LM3404MRX/NOPB ACTIVE SO PowerPAD DDA 8 2500 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 L3404 MR (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 24-Jan-2013 LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) Only one of markings shown within the brackets will appear on the physical device. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 17-Nov-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing LM3404HVMAX SOIC LM3404HVMAX/NOPB LM3404HVMRX SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 SO Power PAD DDA 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM3404HVMRX/NOPB SO Power PAD DDA 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM3404MAX SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM3404MAX/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM3404MRX SO Power PAD DDA 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM3404MRX/NOPB SO Power PAD DDA 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 17-Nov-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM3404HVMAX SOIC D 8 2500 349.0 337.0 45.0 LM3404HVMAX/NOPB SOIC D 8 2500 349.0 337.0 45.0 LM3404HVMRX SO PowerPAD DDA 8 2500 358.0 343.0 63.0 LM3404HVMRX/NOPB SO PowerPAD DDA 8 2500 358.0 343.0 63.0 LM3404MAX SOIC D 8 2500 349.0 337.0 45.0 LM3404MAX/NOPB SOIC D 8 2500 349.0 337.0 45.0 LM3404MRX SO PowerPAD DDA 8 2500 358.0 343.0 63.0 LM3404MRX/NOPB SO PowerPAD DDA 8 2500 358.0 343.0 63.0 Pack Materials-Page 2 MECHANICAL DATA DDA0008B MRA08B (Rev B) www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All semiconductor products (also referred to herein as "components") are sold subject to TI's terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI's terms and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily performed. TI assumes no liability for applications assistance or the design of Buyers' products. Buyers are responsible for their products and applications using TI components. To minimize the risks associated with Buyers' products and applications, Buyers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use of any TI components in safety-critical applications. In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI's goal is to help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and requirements. Nonetheless, such components are subject to these terms. No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties have executed a special agreement specifically governing such use. Only those TI components which TI has specifically designated as military grade or "enhanced plastic" are designed and intended for use in military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of non-designated products, TI will not be responsible for any failure to meet ISO/TS16949. Products Applications Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP(R) Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energy and Lighting www.ti.com/energy Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video RFID www.ti-rfid.com OMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.com Wireless Connectivity www.ti.com/wirelessconnectivity Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright (c) 2013, Texas Instruments Incorporated