Product Folder Sample & Buy Support & Community Tools & Software Technical Documents LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 LM3492HC/-Q1 Two-Channel, Individual Dimmable, LED Driver With Boost Converter and Fast Current Regulator 1 Features 2 Applications • • 1 • • Boost Converter – Automotive Grade Product, Q100 Grade-1 Qualified – Very Wide Input Voltage Range: 4.5 V to 65 V – Programmable Soft-Start Period – No Loop Compensation Required – Stable with Ceramic and Other Low ESR Capacitors with No Audible Noise – Nearly Constant Switching Frequency Programmable from 200 kHz to 1 MHz Current Regulator – Programmable LED Current: 50 mA to 250 mA – 10000:1 Contrast Ratio, 300-ns Minimum Pulse Width – Two Individual Dimmable LED Strings up to 65 V, Total 15 W (Typically 28 LEDs at 150 mA) – Dynamic Headroom Control Maximizes Efficiency – Over-Power Protection – ±3% Current Accuracy Supervisory Functions – Precision Enable – COMM I/O Pin for Diagnostic and Commands – Thermal Shutdown Protection – Thermally Enhanced PWP, 20-Pin Package • Ultra-High Contrast Ratio 6.5” to 10” LCD Display Backlight up to 28 LEDs Automotive or Marine GPS Display 3 Description The LM3492HC/-Q1 device integrates a boost converter and a two-channel current regulator to implement a highly efficient and cost effective LED driver. This device drives two individually dimmable LED strings with a maximum power of 15 W and an output voltage of up to 65 V. The boost converter employs a proprietary projected-on-time control method to give a fast transient response with no compensation required. The nearly constant switching frequency can be set to a level from 200 kHz to 1 MHz. Ceramic capacitors stabilize the application circuit and produce no audible noise on dimming. The programmable peak current limit and soft-start features reduce current surges at start-up. An integrated, 190-mΩ, 3.9-A, N-Channel MOSFET switch minimizes the solution size. The fast slew rate current regulator allows high frequency and narrow pulse width dimming signals to achieve a very high contrast ratio of 10000:1. The LED current can be set from 50 mA to 250 mA by a single resistor. Device Information(1) PART NUMBER LM3492HC PACKAGE PWP (20) LM3492HC-Q1 BODY SIZE (NOM) 6.50 mm × 4.40 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. Simplified Application L1 LM3492HC LM3492HC-Q1 VIN SW CIN RRT CDHC CCDHC VCC CVCC EN RT CFB RFB1 VOUT COUT FB RIREF RCOMM PGND GND IREF RFB2 ILIM COMM LGND DIM1/CLK IOUT1 DIM2 IOUT2 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com Table of Contents 1 2 3 4 5 6 7 8 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Description (continued)......................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 3 4 7.1 7.2 7.3 7.4 7.5 7.6 4 4 4 5 5 7 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics........................................... Typical Characteristics .............................................. Detailed Description ............................................ 11 8.1 Overview ................................................................. 11 8.2 Functional Block Diagram ....................................... 11 8.3 Feature Description................................................. 12 8.4 Device Functional Modes........................................ 17 8.5 Programming .......................................................... 18 9 Application and Implementation ........................ 19 9.1 Application Information............................................ 19 9.2 Typical Application ................................................. 19 10 Power Supply Recommendations ..................... 22 11 Layout................................................................... 22 11.1 Layout Guidelines ................................................. 22 11.2 Layout Example .................................................... 22 12 Device and Documentation Support ................. 23 12.1 12.2 12.3 12.4 12.5 Related Links ........................................................ Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 23 23 23 23 23 13 Mechanical, Packaging, and Orderable Information ........................................................... 23 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision A (May 2013) to Revision B • 2 Page Added Pin Configuration and Functions section, ESD Rating table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1 Submit Documentation Feedback Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 5 Description (continued) To maximize the efficiency, dynamic headroom control (DHC) automatically adjusts the output voltage to a minimum. The DHC also facilitates a single BOM for different number of LED in a string, which is required for back-light panels of different size, thereby reducing overall development time and cost. The LM3492HC device includes a COMM pin that serves as a bidirectional I/O pin. The versatile COMM pin interface with an external micro-controller unit (MCU) is used for the following functions: power-good, overtemperature, IOUT overvoltage and undervoltage indications, switching frequency tuning, and channel 1 disabling. Other supervisory functions of the device include precise enable, VCC undervoltage lockout, current regulator over-power protection, and thermal shutdown protection. The device is available in the thermally enhanced PWP, 20-pin package. 6 Pin Configuration and Functions PWP Package 20 Pin HTSSOP Top View EN VIN SW SW VOUT RT FB GND IOUT2 IOUT1 1 2 3 4 5 6 7 8 9 10 Exposed Thermal Pad ILIM VCC PGND PGND DIM2 DIM1/CLK LGND COMM IREF CDHC 20 19 18 17 16 15 14 13 12 11 NC – No internal connection Pin Functions PIN TYPE (1) DESCRIPTION NAME NO. CDHC 11 I Dynamic headroom control. An external capacitor connected to this pin sets the DHC sensitivity. At start-up, a 12- µA internal current source charges an external capacitor to provide a soft-start function. COMM 13 I/O Bidirectional logic communication. This pin is open drain for various indications (power-good, overtemperature, IOUT overvoltage and undervoltage) and command sending (switching frequency tuning and channel 1 disabling). DIM1/CLK 15 I/O Dimming control of channel 1. Control the on and off of the current regulator of channel 1. This pin is internally pulled low by a 5-µA current. This pin also serves as a clock signal for latching input and output data of the COMM pin. DIM2 16 I Dimming control of channel 2. Control the on and off of the current regulator of channel 2. This pin is internally pulled low by a 5-µA current. EN 1 I Enable input. Contains an internal pullup. Connect to a voltage higher than 1.63 V to provide precision enable for the device. FB 7 I Output voltage feedback. The output voltage is connected to this pin through a feedback resistor divider for output voltage regulation. The voltage of this pin is from 1.05 V to 2.5 V. GND 8 G Analog signal ground. Connect to the exposed pad directly beneath the device. ILIM 20 I Peak current limit adjust. Connecting an external resistor from the ILIM pin to the VCC pin reduces peak current limit. Connect the ILIM pin to ground to obtain the maximum current limit. IOUT1 10 I Current regulator input for channel 1. Input of the current regulator of channel 1. The regulated current is programmable (see the IREF pin). IOUT2 9 I Current regulator input for channel 2. Input of the current regulator of channel 2. The regulated current is programmable (see the IREF pin). IREF 12 I Current setting pin for the current regulators. An external resistor connected from this pin to ground programs the regulated current of the current regulator of channels 1 and 2. (1) I = Input, O = Output, G = Ground Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 3 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com Pin Functions (continued) PIN NAME NO. LGND 14 TYPE (1) 17 PGND 18 RT 6 3 SW 4 DESCRIPTION G Current regulator ground. Must be connected to the GND pin and exposed pad for normal operation. The LGND and GND pins are not internally connected. G Integrated MOSFET ground. Must be connected to the GND pin and exposed pad for normal operation. The PGND and GND pins are not internally connected. I Frequency control pin. An external resistor from the VOUT pin to this pin sets the switching frequency. I Switch node. Internally connected to the drain of the integrated MOSFET. VCC 19 O Internal LED regulator output. Nominally regulated to 5.5 V. Connect a capacitor of 0.47-μF or larger between the VCC and GND pins. VIN 2 I Input supply voltage pin. Input voltage range is from 4.5 V to 65 V. VOUT 5 I Output voltage sense pin. Senses the output voltage for nearly constant switching frequency control. G Thermal connection pad. Connect to a ground plane. Exposed Pad 7 Specifications 7.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) Input voltage Output voltage (1) VIN, RT, VOUT to GND, SW to GND MIN MAX −0.3 67 V −2 SW to GND (transient <100 ns) ILIM to GND −0.3 1 FB to GND −0.3 5 COMM, DIM1, DIM2, to GND −0.3 6 Junction temperature, TJ V 150 Storage temperature, Tstg (1) UNIT –65 °C 150 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. 7.2 ESD Ratings VALUE V(ESD) (1) (2) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) ±2000 Charged-device model (CDM), per JEDEC specification JESD22-C101 (2) ±750 UNIT V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Pins listed as ±2000 V may actually have higher performance. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Pins listed as ±750 V may actually have higher performance. 7.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) MIN NOM MAX UNIT Supply input voltage, VIN 4.5 65 V Junction temperature, TJ −40 125 °C 4 Submit Documentation Feedback Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 7.4 Thermal Information LM3492HC THERMAL METRIC PWP (HTSSOP) (1) UNIT 20 PINS RθJA Junction-to-ambient thermal resistance 36.8 °C/W RθJC(top) Junction-to-case (top) thermal resistance 21.8 °C/W RθJB Junction-to-board thermal resistance 18.3 °C/W ψJT Junction-to-top characterization parameter 0.6 °C/W ψJB Junction-to-board characterization parameter 18.1 °C/W RθJC(bot) Junction-to-case (bottom) thermal resistance 2 °C/W (1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953. 7.5 Electrical Characteristics over operating free-air temperature range, VIN = 12 V (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT CVCC = 0.47 µF, no load 4.7 5.5 6.3 V IVCC = 2 mA 4.7 5.5 6.3 V 3.56 3.78 4 V START-UP REGULATOR (VCC PIN) VVCC Output voltage VCC_UVLO VCC pin undervoltage lockout threshold (UVLO) VVCC increasing, TA = TJ = 25°C VCC_UVLO-HYS VCC pin UVLO hysteresis VVCC decreasing, TA = TJ = 25°C 310 IIN IIN operating current No switching, VFB = 0 V 3.6 5.2 mA IIN-SD IIN operating current, device shutdown VEN = 0 V 30 95 µA (1) mV IVCC VCC pin current limit VVCC = 0 V 18 30 VCC-VOUT VCC pin output voltage when supplied by VOUT VIN = Open, IVCC = 1 mA, VOUT = 18 V mA 3.5 4.1 4.7 V VEN EN pin input threshold VEN rising 1.55 1.63 1.71 V VEN-HYS EN pin threshold hysteresis VEN falling 194 mV IEN-SHUT Enable pullup current at shutdown VEN = 0 V 2 µA IEN-OPER Enable pullup current during operation VEN = 2 V 40 µA ENABLE INPUT CURRENT REGULATOR VIREF IREF pin voltage VDHC50 VDHC100 VDHC200 VIOUT under DHC VDHC250 (1) 4.5 V ≤ VIN ≤ 65 V 1.231 1.256 1.281 IOUT = 50 mA, RIREF = 25 kΩ 0.160 0.225 0.290 IOUT = 100 mA, RIREF = 12.5 kΩ 0.38 0.48 0.58 IOUT = 200 mA, RIREF = 6.25 kΩ 0.81 0.99 1.17 IOUT = 250 mA, RIREF = 5 kΩ 0.81 1.21 1.44 V V The VCC pin provides self bias for the internal gate drive and control circuits. Device thermal limitations limit external loading. Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 5 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com Electrical Characteristics (continued) over operating free-air temperature range, VIN = 12 V (unless otherwise noted) PARAMETER TEST CONDITIONS IOUT50 IOUT100 Current output under DHC IOUT200 IOUT250 IOUTOFF Leakage at maximum work voltage MIN TYP MAX VIOUT = VDHC50, RIREF = 25 kΩ, TA = TJ = 25°C 47.5 50 52.5 VIOUT = VDHC50, RIREF = 25 kΩ 46.5 50 53.5 VIOUT = VDHC100, RIREF = 12.5 kΩ, TA = TJ = 25°C 97 100 103 VIOUT = VDHC100, RIREF = 12.5 kΩ 96 100 104 VIOUT = VDHC200, RIREF = 6.25 kΩ, TA = TJ = 25°C 194 200 206 VIOUT = VDHC200, RIREF = 6.25 kΩ 192 200 208 VIOUT = VDHC250, RIREF = 5 kΩ, TA = TJ = 25°C 241.3 250 258.8 VIOUT = VDHC250, RIREF = 5 kΩ 238 250 262 VDIM = 0, VIOUT = 65 V 5 VIOUT50-MIN IOUT = 50 mA, RIREF = 25 kΩ, IOUT = 0.98 × IOUT50, TA = TJ = 25°C 0.1 0.15 VIOUT100-MIN IOUT = 100 mA, RIREF = 12.5 kΩ, IOUT = 0.98 × IOUT100, TA = TJ = 25°C 0.2 0.35 VIOUT200-MIN IOUT = 200 mA, RIREF = 6.25 kΩ, IOUT = 0.98 × IOUT200, TA = TJ = 25°C 0.4 0.65 VIOUT250-MIN IOUT = 250 mA, RIREF = 5 kΩ, IOUT = 0.98 × IOUT250, TA = TJ = 25°C 0.5 0.82 Minimum work voltage VDIM-HIGH DIM voltage HIGH VDIM-LOW DIM voltage LOW UNIT mA µA V 1.17 V 0.7 V BOOST CONVERTER ICDHC-SRC CDHC pin source current VCDHC = 1.6 V, VFB = 3 V, VIOUT = 0 V, DIM = High 60 µA ICDHC-SINK CDHC pin sink current VCDHC = 1.6 V, VFB = 3 V, VIOUT = 3 V, DIM = High 56 µA ICDHC-PULLUP CDHC pin pullup current DIM = Low, VCDHC = 2.3 V, VFB = 3 V ICL-MAX Integrated MOSFET peak current limit threshold ICL-HALF Half integrated MOSFET peak current limit threshold RILIM = 11 kΩ 2 RDS(on) Integrated MOSFET On-resistance ISW = 500 mA 0.19 VFBTH-PWRGD Power-Good FB pin threshold VFB-OVP FB pin overvoltage protection threshold FB pin OVP hysteresis VFB rising, VCDHC = 4 V IFB Feedback pin input current VFB = 3 V ON timer pulse width 200 500 nA 3.3 3.9 4.5 A VFB falling Ω V 2.76 2.88 0.1 0.215 0.323 1 V µA 1460 VIN = 24 V, VOUT = 32.5V, RRT = 300 kΩ 800 VIN = 12 V, VOUT = 65V, RRT = 100 kΩ 550 VIN = 24 V, VOUT = 32.5V, RRT = 100 kΩ 350 ns ON timer minimum pulse width at current limit 145 tOFF OFF timer pulse width 145 Submit Documentation Feedback 0.43 2.64 tON(min)ILIM 6 A 2.25 VIN = 12 V, VOUT = 65V, RRT = 300 kΩ tON 10 ns 350 ns Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 Electrical Characteristics (continued) over operating free-air temperature range, VIN = 12 V (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 5.6 6.7 7.8 V 0.7 V 5 µA COMM PIN VIOUT-OV IOUT pin overvoltage threshold COMM goes LOW during VIOUT rising, other VIOUT = 1.2 V VCOMM-LOW COMM pin at LOW 5 mA into COMM ILEAK-FAULT COMM pin open leakage VCOMM = 5 V THERMAL PROTECTION TOTM Overtemperature indication TJ rising 135 °C TOTM-HYS Over-temperature indication hysteresis TJ falling 15 °C TSD Thermal shutdown temperature TJ rising 165 °C TSD-HYS Thermal shutdown temperature hysteresis TJ falling 20 °C 7.6 Typical Characteristics Unless otherwise specified the following conditions apply: TJ = 25°C, VIN = 12 V with configuration in typical application circuit for ILED = 250 mA shown in this data sheet. Figure 1. Quiescent Current vs Input Voltage Figure 2. VCC Voltage vs VCC Ouput Current Figure 3. VCC Voltage vs Input Voltage Figure 4. Switching Frequency vs Input Voltage Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 7 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com Typical Characteristics (continued) Unless otherwise specified the following conditions apply: TJ = 25°C, VIN = 12 V with configuration in typical application circuit for ILED = 250 mA shown in this data sheet. Figure 5. LED Current Regulation vs Temperature Figure 6. MOSFET On-Resistance vs Temperature 100 1.00 0.75 -40°C 0.50 90 85 ûILED(%) EFFICIENCY (%) 95 25°C 25°C 0.25 0.00 -40°C -0.25 80 -0.50 75 125°C 70 -1.00 10 15 20 INPUT VOLTAGE (V) 25 ILED = 0.25 A ILED = 0.25 A 15 20 INPUT VOLTAGE (V) 25 Figure 8. LED Current Regulation vs Input Voltage ILED = 0.25 A Figure 9. Power-Up Waveform Submit Documentation Feedback 10 ILED = 0.25 A Figure 7. Efficiency vs Input Voltage 8 125°C -0.75 Figure 10. Enable Transient Waveform Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 Typical Characteristics (continued) Unless otherwise specified the following conditions apply: TJ = 25°C, VIN = 12 V with configuration in typical application circuit for ILED = 250 mA shown in this data sheet. ILED = 0.25 A Figure 12. LED 50% Dimming Waveforms Figure 11. Steady-State Operation ILED = 0.25 A ILED = 0.25 A Dimming frequency = 200 Hz Dimming frequency = 200 Hz Figure 14. 10000:1 LED Dimming Waveforms Figure 13. 1000:1 LED Dimming Waveforms 320 800 750 300 700 Switching Frequency (kHz) Switching Frequency (kHz) Dimming frequency = 200 Hz 650 600 550 500 450 400 VOUT = 27V VOUT = 30V VOUT = 33V VOUT = 36V 350 300 250 280 260 240 220 VOUT = 27V VOUT = 30V VOUT = 33V VOUT = 36V 200 180 200 160 6 8 10 ILED = 0.15 A 12 14 16 18 Input Voltage (V) 20 22 24 26 6 8 10 D001 RRT = 178 kΩ ILED = 0.15 A Figure 15. Switching Frequency vs Input Voltage 12 14 16 18 Input Voltage (V) 20 22 24 D001 RRT = 499 kΩ Figure 16. Switching Frequency vs Input Voltage Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 9 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com Typical Characteristics (continued) 760 300 740 295 720 Switching Frequency (kHz) Switching Frequency (kHz) Unless otherwise specified the following conditions apply: TJ = 25°C, VIN = 12 V with configuration in typical application circuit for ILED = 250 mA shown in this data sheet. 700 680 660 640 620 VIN = 10V VIN = 12V VIN = 14V VIN = 16V 600 580 560 24 26 ILED = 0.15 A 28 30 32 34 Output Voltage (V) 36 38 280 275 270 265 260 VIN = 10V VIN = 12V VIN = 14V VIN = 16V 255 245 40 240 24 26 28 D001 RRT = 178 kΩ Submit Documentation Feedback 285 250 ILED = 0.15 A Figure 17. Switching Frequency vs Output Voltage 10 290 30 32 34 Output Voltage (V) 36 38 40 D001 RRT = 499 kΩ Figure 18. Switching Frequency vs Output Voltage Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 8 Detailed Description 8.1 Overview The LM3492HC device integrates a boost converter and a two-channel current regulator to implement a highly efficient and cost effective LED driver for driving two individually dimmable LED strings with a maximum power of 15 W and an output voltage of up to 65 V. The boost converter provides power for the LED strings, and the current regulator controls the dimming of the LED strings individually. The device integrates an N-channel MOSFET switch and a two-channel current regulator to minimize the component count and solution size. The two-channel current regulator responds quickly to allow a very high contrast ratio of 10000:1. The two channels dim individually. A digital command sent through the COMM pin disables Channel 1 of the current regulator. In this case, the DIM1 pin can serve only as a clock signal for the data flow of the COMM pin. The power dissipated by the current regulator is adaptively minimized by Dynamic Headroom Control to maximize efficiency. When used in automotive LCD back-light panels, the device can operate efficiently for inputs as high as 65 V. Diagnostic functions including power good indication, over-temperature indication, output current overvoltage and undervoltage indications facilitate the interface of the device application circuit with external micro-processors (MCUs). The device does not latch off and continues to operate in the presence of the indications. Other useful features include thermal shutdown, VCC undervoltage lockout, and precision enable. 8.2 Functional Block Diagram Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 11 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com 8.3 Feature Description 8.3.1 Switching Frequency The boost converter of the LM3492HC device employs a projected-on-time (POT) control method to determine the on-time period of the MOSFET with respect to the input and output voltages and an external resistor RRT. During the on-time period, the boost inductor charges up, and the output capacitor discharges to provide power to the output. A cycle-by-cycle current limit (which is 3.9 A typically and programmable by an external resistor) protects the MOSFET. After the on-time period, the MOSFET turns off and boost inductor discharges. The next on-time period starts when the voltage of the FB pin drops below a threshold which is determined by dynamic headroom control (DHC) and operates from 1.05 V to 2 V. DHC affects the threshold when either the DIM1 pin is high or the DIM2 pin is high. During POT control operation, the boost converter maintains switching at a nearly constant frequency. During most operating conditions, the switching frequency depends on mainly the value of RRT (Figure 19) but may see some variation with changes in input or output voltage. Also, POT control operation requires no compensation circuit and offers fast transient response of the output voltage. Applications that require very wide input voltage or very wide output voltage ranges may see some variation in the switching frequency as shown in Figure 20 and Figure 21. More switching frequency graphs can be found in the Typical Characteristics section. 600 950 Switching Frequency (kHz) Switching Frequency (kHz) 560 850 750 650 550 450 350 250 520 480 440 400 360 320 280 240 150 100 200 ILED = 150 mA 300 400 500 RRT (k:) 600 700 200 800 6 8 10 12 D001 VOUT = 30 V VVIN = 12 V 14 16 18 Input Voltage (V) ILED = 150 mA Figure 19. Switching Frequency vs RT Resistance VOUT = 30 V 20 22 24 26 D001 RRT = 274 kΩ Figure 20. Switching Frequency vs Input Voltage 600 Switching Frequency (kHz) 570 540 510 480 450 420 390 360 330 300 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Output Voltage (V) D001 ILED = 150 mA RRT = 274 kΩ VVIN = 12 V Figure 21. Switching Frequency vs Output Voltage 12 Submit Documentation Feedback Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 Feature Description (continued) 8.3.2 LDO Regulator The LM3492HC device offers an integrated, 5.5-V, LDO regulator. For stability, connect an external capacitor CVCC of more than 0.47-µF between the VCC and GND pins. The current limit of the LDO is typically 30 mA. The LDO regulator can be used to pullup the open-drain COMM pin with an external resistor, and sources current to the ILIM pin to adjust the current limit of the integrated MOSFET. When the voltage on the VCC pin (VCC) is higher than the undervoltage lockout (UVLO) threshold of 3.78 V, the device becomes enabled and the CDHC pin sources a current to charge up an external capacitor (CCDHC) to provide a soft-start function. 8.3.3 Enable and Disable To enable the LM3492HC device, the voltage on the EN pin (VEN) must be higher than an enable threshold of typically 1.63 V. If the voltage on the EN pin (VEN) is lower than 1.43 V, the device shuts down. In this case, the LDO regulator turns off and the CDHC pin becomes internally grounded. The EN pin internally pulls up. After enable, a 40-µA current source pulls up the EN pin. If the EN pin is connected to low such that the device is shutdown, the pullup current is reduced to 2 µA. These advantages allow the device to effectively avoid false disabling by noise during operation, and minimize power consumption during shutdown. The enable threshold is so precise that it can support a UVLO function for the input voltage as shown in Figure 22. The input voltage can be connected to the EN pin through a resistor divider consisting of REN1 and REN2. This circuitry ensures that the device operates after the input voltage reaches a minimum require value VIN(EN), as shown in Equation 1. VIN(EN) = 1.63 V(1 + REN1/ REN2) (1) To maintain the VEN level below the absolute maximum specification, place a Zener diode (DEN) between the EN pin and GND pins. VVIN VIN REN1 EN GND REN2 DEN Figure 22. Input Voltage UVLO Implemented by Precision Enable After the EN pin is pulled low, the device performs the following functions: • resets IOUT overvoltage and undervoltage indications and the corresponding COMM bit pattern • resumes the switching frequency tuning to the normal frequency • resumes channel 1 of the current regulator if it is disabled Pulling the EN pin low for a short period of approximately 200 ns achieves these same functions with little or no effect on the operation of the boost converter and the current regulator. 8.3.4 Current Limit The current limit (ICL) of the integrated MOSFET of the LM3492HC device provides a cycle-by-cycle current limit for protection. This limit can be decreased by injecting a small signal current, IILIM into the ILIM pin. The relationship between ICL and IILIM is described in Equation 2. ICL = ICL(max) – 4290 × IILIM where • ICL(max) is the maximum current limit (3.9 A typical) (2) As shown in Figure 23, create current limit functionality by connecting a resistor (RILIM) between the VCC pin and the ILIM pin. The typical voltage on the ILIM pin is 0.7 V. To obtain the maximum current limit, connect the ILIM pin to ground. Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 13 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com Feature Description (continued) VCC RILIM CVCC ILIM GND Figure 23. Programmable Current Limit 8.3.5 Thermal Protection An internal thermal shutdown circuit provides thermal protection. The circuit activates at 165°C (typically) to disable the LM3492HC device. In this case, the LDO regulator turns off and the CDHC pin becomes internally grounded. Thermal protection helps prevent catastrophic failures from accidental device overheating. When the junction temperature of the device drops below 145°C (typical hysteresis = 20°C), the device resumes normal operation. 8.3.6 Dynamic Headroom Control, Over-Ride, and Soft-Start The LM3492HC device uses dynamic headroom control (DHC) to adjust the output voltage (VOUT) of the boost converter to reduce the power loss of the current regulator and thereby maximize efficiency. To understand this control function, consider VLED,n the forward voltage of an LED string connecting to the IOUTn pin and VIOUT,n as the voltage of the IOUTn pin (where n is 1, 2 for channels 1, 2 of the current regulator). VLED,n normally and gradually decreases (in terms of minutes) as a result of the rise of the LED die temperature during operation. The DHC adjusts the output voltage (VOUT) by adjusting a threshold that is reflected in the voltage of the FB pin with reference to VIOUT,n, (the difference between VOUT and VLED,n). The capacitor CCDHC sets the sensitivity of DHC, which affects the response time on adjusting VOUT. If the capacitance value of CCDHC is small, VOUT is more sensitive to the variation of VLED,n. Override the DHC functionality by adding internal pullup resistance or external pullup resistance by connecting the CDHC and VCC pins with a resistor. Use a value of approximately 10 MΩ. In this case, the voltage of the CDHC pin rises above 2.5 V, and the voltage of the FB pin rises until the voltage reaches the overvoltage protection threshold. Because the pullup is weak, DHC override occurs only at a low contrast ratio (approximately < 1%). The CCDHC capacitor acts to control the soft-start functionality. During the start-up period, the voltage of the CDHC pin rises from 0 V to 2.25 V at a rate that depends on the value of the CCDHC capacitor. This limitation ensures that the voltage of the FB pin (as well as the output voltage) ramps up in a controlled manner, and effectively implements a soft-start function. An internal switch grounds the CDHC pin during any of the following cases: • VVCC is below the VCC UVLO threshold • a thermal shutdown occurs • the EN pin is pulled low The CDHC pin cannot be connected to the ground externally. 8.3.7 Current Regulator The LM3492HC device integrates a two-channel current regulator for controlling the current of two LED strings. The two LED strings dim individually by applying individual dimming signals to the DIM1 and DIM2 pins for LED strings 1 and 2, which are connected from the VOUT pin to the IOUT1 and IOUT2 pins. The device pulls the DIM1 and DIM2 pins low internally. The lowest contrast ratio is 10000:1. The finest pulse width of the dimming signal for the DIM1 and DIM2 pins is 300 ns. 14 Submit Documentation Feedback Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 Feature Description (continued) The device sets the current of an LED string (ILED) from 50 mA to 250 mA by using an external resistor RIREF connected between the IREF pin and ground. Figure 24 describes the relationship between ILED and RIREF. The two channels of the current regulator can work in parallel for only one LED string by connecting the IOUT1 and IOUT2 pins together to provide an LED current of up to 500 mA. In this case, connect the DIM1 and DIM2 pins together. 250 Current Regulator Input Current (mA) 250 LED Current (mA) 200 150 100 50 200 150 100 50 0 0 5 10 15 20 Regulation Current Resistance (NŸ ) 25 Figure 24. LED Current vs Current Reference Resistance (RIREF) 0 10 20 30 40 Current Regulator Input Voltage (V) 50 Figure 25. Over-Power Protection If the voltage on the IOUTn (n = 1, 2) pin is higher than 24 V when channel n is on, the regulated current of channel n reduces linearly if the voltage further increases (as shown in Figure 25). The regulated current of another channel is not affected. This over-power protection feature avoids damaging the current regulator owing to the shorting of many LEDs in one string. 8.3.8 Output Voltage Feedback The device feeds the output voltage back to the FB pin through a feedback circuit consisting of RFB1, RFB2, and CFB as shown in Figure 26. To assist the feeback functionality, maintain a value of 10 pF for CFB. The DC component of the output voltage feedback uses RFB1 and RFB2. The voltage of the FB pin VFB can be adjusted by DHC. When VFB reaches VFB-OVP, the maximum output voltage of the boost converter VOUT(max) reaches its maximum, as shown in Equation 3. VOUT(max) = 2.88 V (1 + RFB1/ RFB2) (3) During DHC operation, maintain the output voltage at a nominal voltage but not the maximum. The nominal output voltage (VOUT(nom)) is described in Equation 4. VOUT(nom) = max (VLED,n + VIOUT,n), n = 1, 2 where • • VLED,n is the forward voltage of LED string n VIOUT,n is the voltage of the IOUTn pin, where n is 1, 2 for channels 1, 2 of the current regulator) (4) The minimum value of VIOUT,n is approximately 5 Ω × ILED. The nominal voltage of the FB pin (VFB(nom)) is recommended to be from 1.05 V to 2 V. Equation 5 describes the relation between VOUT(max), VOUT(nom), and VFB(nom): VOUT(max) = VOUT(nom) x 2.88 V / VFB(nom) Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC (5) Submit Documentation Feedback 15 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com Feature Description (continued) VOUT RFB1 CFB FB GND RFB2 Figure 26. Output Voltage Feedback Circuit 8.3.9 Overvoltage Protection When VFB is higher than the FB pin overvoltage protection (OVP) threshold VFB-OVP (typically 2.76 V and maximum 2.88 V), the on-period of the integrated MOSFET stop immediately, and the MOSFET keeps off until VFB falls back below below 2.545 V (typical hysteresis 0.215 V). An alternative method to implement OVP is to directly monitor VOUT instead of VFB. An external circuit as shown in Figure 27 is required. Current is injected to the ILIM pin to drive the LM3492HC device to the current limit mode once VOUT is higher than the avalanche voltage of the Zener diode DOVP plus 0.7 V, the typical voltage on the ILIM pin. In this case, the device imporses a maximum limit on VOUT. However, at the maximum limit of VOUT, VFB must be higher than 2.25 V to avoid affecting the start-up of the device. VOUT DOVP ILIM Figure 27. External OVP Circuit 8.3.10 Bidirectional Communication Pin The COMM pin of the LM3492HC device is an open-drain bidirectional I/O pin for interfacing with an external MCU for the following functions: • power-good indication • overtemperature indication • output current overvoltage and undervoltage indications • switching frequency tuning • channel 1 disabling Except for the power good indication and the overtemperature alerts, all data flow through the COMM pin is serial and is latched by the falling edge of the signal applying to the DIM1 pin, even when channel 1 of the current regulator is disabled. If the DIM1 pin remains only low or only high, either by an external circuit or by allowing it to open and pull low internally, data does not flow. Figure 28 and Figure 29 show timing diagrams of reading and writing a bit from and to the device through the COMM pin. Pull up the COMM pin by an MCU I/O pin, which has pullup capability, or an external resistor RCOMM connected to the VCC pin. Without this capability, the voltage of the COMM pin remains at zero. The rise time of the output signal of the COMM pin depends on the pullup power. If the rise time is long (RCOMM is too large or pullup power from the connecting MCU I/O pin is too weak), data may be ready after a longer duration after the falling edge. In this case, the design requires a longer delay between the falling edge latching and the (input or output) bit. 16 Submit Documentation Feedback Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 Feature Description (continued) Figure 28. Read from the COMM Pin Figure 29. Write to the COMM Pin 8.3.10.1 Power-Good Indication Upon start-up, the COMM pin reads low. The output voltage of the boost converter of the LM3492HC device rises until the voltage on the FB pin (VFB) reaches 2.25 V, when the COMM pin reads high to indicate powergood. The power-good indication and the signal applied on the DIM1 pin are independent. 8.3.10.2 Overtemperature Indication If the junction temperature of the LM3492HC device reaches 135°C, the COMM pin reads low, showing an overtemperature indication. The external MCU considers to either turn off or reduce the brightness of the LED strings to prevent overtemperature. The overtemperature indication and the signal applied on the DIM1 pin are independent. The COMM pin reads high if the junction temperature falls below 120°C. The device does not latch off and continues to operate in the presence of the overtemperature indication. 8.3.10.3 Output Current Undervoltage Indication The LM3492HC device gives an IOUTn (n = 1, 2) undervoltage indication if the voltage of the IOUTn pin when DIMn is high is lower than its minimum required voltage which can regulate ILED, and the voltage of the CDHC pin reaches its maximum. These conditions remain while the device applies 508 consecutive dimming signals on the DIMn pin. This means that the current of the LED string n does not reach the regulation value. In most cases, the IOUT undervoltage indication can be regarded as an open fault of the LED string n. A bit pattern (see Table 1) can be read from the COMM pin. The device does not latch off and continues to operate in the presence of the IOUT undervoltage indication. 8.3.10.4 Switching Frequency Tuning After power good, the switching frequency (fSW) of the LM3492HC device can be tuned down 20% or 40%, or resume normal by writing commands (refer to Table 2) to the COMM pin. This functionality helps avoid interfering some sensitive devices, for example radios, working nearby the device. Upon reset, the switching frequency (fSW) of the device resumes normal by default. In the presence of an overtemperature indication or any COMM bit pattern, no command can be written to the device. 8.4 Device Functional Modes There are no additional functional modes for this device. Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 17 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com 8.5 Programming 8.5.1 Output Current Overvoltage Indication The LM3492HC device gives an IOUTn (n = 1, 2) overvoltage indication if the voltage of the IOUTn pin when DIMn is higher than a threshold of typically 6.5 V. These conditions remain while the device applies 508 consecutive dimming signals on the DIMn pin. The IOUT overvoltage indication can be regarded as a short fault of the LED string n except the following two cases: • powering up the device at a very low dimming ratio such that VOUT maintains at a maximum and DHC is not fast enough to reduce VOUT • during DHC override condition, a bit pattern (see Table 1) can be read from the COMM pin The device does not latch off and continues to operate in the presence of the IOUT overvoltage indication. Table 1. COMM Indication Bit Patterns CONDITION Overvoltage Undervoltage PIN BIT PATTERN IOUT1 0001 IOUT2 0011 IOUT1 0101 IOUT2 0111 8.5.2 COMM Pin Bit Pattern Table 1 summarizes all COMM bit patterns of output current overvoltage and undervoltage indications. An existing COMM bit pattern is cleared if one of the following condition occurs: • the LM3492HC device is shutdown • the LM3492HC device is disabled by pulling the EN pin low • the overtemperature indication is appearing Apply the clock signal on both DIM1 and DIM2 pins when the COMM bit pattern is read by an external MCU. Before reading the COMM bit pattern, pull the EN pin low for approximately 200 ns to reset the COMM bit pattern. This situation does not affect the operation of the boost converter and the current regulator. After EN is reset, if the IOUT overvoltage or undervoltage condition lasts for 508 consecutive clock cycles, the COMM pin sends the COMM bit pattern for the MCU to read. In case of overtemperature, the device pulls the COMM pin low to give an overtemperature indication overriding any other pattern. After the overtemperature indication disappears, the COMM bit pattern appears before the over-temperature indication appears again. 8.5.3 Channel 1 Disable After a power good verification, channel 1 of the current regulator can be disabled by writing a command (see Table 2) to the COMM pin. If LED string 1 is malfunctioning, channel 1 can be disabled and the signal applied on the DIM1 pin can serve as only a clock signal for the data flow of the COMM pin. Channel 1 is by default enabled after reset. If the overtemperature indication or any COMM bit pattern has already presented, no command can be written to the LM3492HC device. Table 2. Channel Control Commands COMMAND 18 BIT PATTERN fSW resume normal 1111 0111 0111 0111 fSW tune down by 20% 1111 0001 0001 0001 fSW tune down by 40% 1111 0011 0011 0011 Channel 1 disable 1111 0101 0101 0101 Submit Documentation Feedback Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 9 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 9.1 Application Information The LM3429HC/-Q1 device is ideal for automotive and marine GPS display and applications that require a high contrast ratio. 9.2 Typical Application The following procedures are to design an LED driver using the LM3492HC/-Q1 device. Figure 30. Typical Application Schematic 9.2.1 Design Requirements The following procedures are to design an LED driver using the LM3492HC device with an input voltage ranged from 10 V to 24 V, and two LED strings consists of 10 LEDs each with a forward voltage of 3 V for each LED when running at 250 mA. The output power is 15 W. The switching frequency fSW is designed to be 300 kHz. 9.2.2 Detailed Design Procedure 9.2.2.1 RFB1, RFB2, and CFB The nominal voltage of the LED string with 10 LEDs is 30 V, and the minimum voltage of the IOUTn pin (n = 1, 2) is 1.25 V when ILED is 250 mA. As a result, VOUT(nom) is 31.25 V. Design VOUT(max) to be 50 V. From Equation 5, VFB(nom) is approximately 1.8 V, which falls in the recommended operation range from 1.05 V to 2 V. Also, design RFB2 to be 16.2 kΩ. From Equation 3, RFB1 is calculated to be 265.1 kΩ, and a standard resistor value of 261 kΩ is selected. CFB is selected to be 10 pF as recommended. 9.2.2.2 L1 The main parameter affected by the inductor is the peak to peak inductor current ripple (ILR). To maintain a continuous conduction mode (CCM) operation, ensure that the average inductor current IL1 is larger than half of ILR. For a boost converter, IL1 equals to the input current IIN. Hence, IIN = (VOUT(nom) × 2×ILED ) / VIN (6) Also, Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 19 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com Typical Application (continued) ton = (1 – VIN/VOUT) / fSW L1 = (VIN x ton) / 2IIN (7) (8) If VIN is maximum, which is 24 V in this example, and only one LED string is turned on (because the two channels of the LM3492HC device are individually dimmable), IIN is minimum. From Equation 6 to Equation 8, it can be calculated that IIN(MIN), ton, and L1 are 0.326 A, 0.77 µs, and 28.5 µH. However,, from Equation 6, IIN is maximum when VIN is minimum, which is 10 V in this example, and the two LED strings are turned on together. Hence IIN(max) is 1.56 A. Then, ILR is ILR = (VIN x ton) / L1 (9) From Equation 7, ton is 2.27 µs. From (9), ILR is 0.80 A. The steady-state peak inductor current IL1(PEAK) is IL1(PEAK) = IL1 + ILR / 2 (10) As a result, IL1(PEAK) is 1.96 A. A standard value of 27 µH is selected for L1, and its saturation current is larger than 1.96 A. 9.2.2.3 D1 The selection of the boost diode D1 depends on two factors. The first factor is the reverse voltage, which equals to VOUT for a boost converter. The second factor is the peak diode current at the steady state, which equals to the peak inductor current as shown in Equation 10. In this example, a 100-V 3-A schottky diode is selected. 9.2.2.4 CIN and COUT The function of the input capacitor CIN and the output capacitor COUT is to reduce the input and output voltage ripples. Experimentation is usually necessary to determine their value. The rated DC voltage of capacitors used should be higher than the maximum DC voltage applied. Owing to the concern of product lifetime, TI recommends ceramic capacitors. But ceramic capacitors with high rated DC voltage and high capacitance are rare in general. Multiple capacitors connecting in parallel can be used for CIN and COUT. In this example, two 10µF ceramic capacitor are used for CIN, and two 2.2-µF ceramic capacitor are used for COUT. 9.2.2.5 CVCC The capacitor on the VCC pin provides noise filtering and stabilizes the LDO regulator. It also prevents false triggering of the VCC UVLO. CVCC is recommended to be a 1-µF, good quality and low ESR ceramic capacitor. 9.2.2.6 CCDHC The capacitor at the CDHC pin not only affects the sensitivity of the DHC but also determines the soft-start time tSS, the time for the output voltage to rise until power good. tSS is determined from the following equation: tSS = CCDHC x 2.25V 120 PA (11) In this example, CCDHC is recommended to be a 0.47-µF good quality and low ESR ceramic capacitor. 9.2.2.7 RRT and RIREF The resistors RRT and RIREF set the switching frequency fSW of the boost converter and the LED current ILED respectively. From Figure 19, if fSW is 300 kHz, RRT is selected to be 442 kΩ. From Figure 24, if ILED is 250 mA, RIREF is selected to be 4.99 kΩ. 9.2.2.8 RCOMM Because the COMM pin is open drain, a resistor RCOMM of 52.3 kΩ is used to connect the VCC and COMM pins to act as a pullup function. 20 Submit Documentation Feedback Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 Typical Application (continued) 9.2.3 Application Curve ILED = 150 mA Dimming frequency = 1 kHz VOUT = 30 V VVIN = 12 V Trace 1 = VIOUT1 Trace 4 = channel 1 LED Figure 31. PWM Dimming Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 21 LM3492HC-Q1, LM3492HC SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 www.ti.com 10 Power Supply Recommendations Use a DC output power supply with a maximum output voltage capability greater than the maximum input voltage for the application. The current rating of the supply should be greater than the maximum input current required by the application. 11 Layout 11.1 Layout Guidelines The layout of the printed-circuit-board is critical to optimize the performance of the LM3492HC device application circuit. In general, external components should be placed as close to the device and each other as possible to make copper traces short and direct. In particular, components of the boost converter CIN, L1, D1, COUT, and the LM3492HC device should be closed. Also, the output feedback capacitor CFB should be closed to the output capacitor COUT. The ground plane connecting the GND, PGND, and LGND pins and the exposed pad of the device and the ground connection of the CIN and COUT should be placed on the same copper layer. Good heat dissipation helps optimize the performance of the device. The ground plane should be used to connect the exposed pad of the device , which is internally connected to the device die substrate. The area of the ground plane should be extended as much as possible on the same copper layer around the device. Using numerous vias beneath the exposed pad to dissipate heat of the device to another copper layer is also a good practice. 11.2 Layout Example GND CIN EN ILIM VIN VCC SW PGND SW PGND CVCC VIN L1 D1 LED+ + VOUT RRT CFB DIM2 GND RT DIM1/CLK FB LGND RCOMM RFB1 COUT RFB2 GND COMM RIREF LED- (2) - IOUT2 IREF LED- (1) - IOUT1 CDHC CCDHC THERMAL/POWER VIA Figure 32. Layout Recommendation 22 Submit Documentation Feedback Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC LM3492HC-Q1, LM3492HC www.ti.com SNVS797B – MARCH 2012 – REVISED OCTOBER 2015 12 Device and Documentation Support 12.1 Related Links Table 3 lists quick access links. Categories include technical documents, support and community resources, tools and software, and quick access to sample or buy. Table 3. Related Links PARTS PRODUCT FOLDER SAMPLE & BUY TECHNICAL DOCUMENTS TOOLS & SOFTWARE SUPPORT & COMMUNITY LM3492HC Click here Click here Click here Click here Click here LM3492HC-Q1 Click here Click here Click here Click here Click here 12.2 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 12.3 Trademarks E2E is a trademark of Texas Instruments. All other trademarks are the property of their respective owners. 12.4 Electrostatic Discharge Caution 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. 12.5 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 13 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM3492HC-Q1 LM3492HC Submit Documentation Feedback 23 PACKAGE OPTION ADDENDUM www.ti.com 29-Mar-2015 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LM3492HCMH/NOPB ACTIVE HTSSOP PWP 20 73 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LM3492 HCMH LM3492HCMHX/NOPB ACTIVE HTSSOP PWP 20 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LM3492 HCMH LM3492HCQMH/NOPB ACTIVE HTSSOP PWP 20 73 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LM3492 HCQMH LM3492HCQMHX/NOPB ACTIVE HTSSOP PWP 20 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LM3492 HCQMH (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. 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) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 29-Mar-2015 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. 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OTHER QUALIFIED VERSIONS OF LM3492HC, LM3492HC-Q1 : • Catalog: LM3492HC • Automotive: LM3492HC-Q1 NOTE: Qualified Version Definitions: • Catalog - TI's standard catalog product • Automotive - Q100 devices qualified for high-reliability automotive applications targeting zero defects Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 7-Nov-2015 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ HTSSOP PWP 20 2500 330.0 16.4 LM3492HCQMHX/NOPB HTSSOP PWP 20 2500 330.0 16.4 LM3492HCMHX/NOPB Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) Pack Materials-Page 1 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 6.95 7.1 1.6 8.0 16.0 Q1 6.95 7.1 1.6 8.0 16.0 Q1 PACKAGE MATERIALS INFORMATION www.ti.com 7-Nov-2015 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM3492HCMHX/NOPB HTSSOP PWP 20 2500 367.0 367.0 35.0 LM3492HCQMHX/NOPB HTSSOP PWP 20 2500 367.0 367.0 35.0 Pack Materials-Page 2 MECHANICAL DATA PWP0020A MXA20A (Rev C) 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. 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