LM3639A www.ti.com SNVS964 – MARCH 2013 LM3639A Single Chip 40V Backlight + 1.5A Flash LED Driver Check for Samples: LM3639A FEATURES DESCRIPTION • The LM3639A is a single-chip white LED Camera Flash Driver + LCD Display Backlight Driver. The lowvoltage, high-current flash LED driver is a synchronous boost which provides the power for a single flash LED at up to 1.5A or dual LEDs at up to 750 mA each. The high-voltage backlight driver is a dual-output asynchronous boost which powers dual LED strings at up to 40V and 30 mA per string. An adaptive regulation method in both boost converters regulates the headroom voltage across the respective source/sink to ensure the LED current remains in regulation while maximizing efficiency. The LM3639A's flash driver is a 2MHz or 4MHz fixedfrequency synchronous boost converter plus 1.5A constant current driver for a high-current white LED. The high-side current source allows for grounded cathode LED operation providing Flash current up to 1.5A. An adaptive regulation method ensures the current source remains in regulation and maximizes efficiency. 1 2 • • • • • • • • Single Chip White LED Flash and Backlight Driver 1.5A Flash LED Current Dual String Backlight Control (40V Max VOUT) 128 Level Exponential and Linear Brightness Control PWM Input for CABC Programmable Over-Voltage Protection (Backlight) Programmable Current Limit (Flash) Programmable Switching Frequency Optimized Flash Current During Low-Battery Conditions APPLICATIONS • • White LED Backlit Display Power White LED Camera Flash Power L(B) Schottky L(F) COUTB SWF SWB VIN 2.5V - 5.5V VOUTB up to 40V OVP OUTF CIN OR EN SCL SDA LM3639A COUTF STROBE BLED1 BLED2 TX FLED1 FLED2 PWM FLED2 GND FLED1 The device is controlled by an I2C-compatible interface. Features for the flash LED driver include a hardware flash enable (STROBE) allowing a logic input to trigger the flash pulse, and a TX input for synchronization to RF power amplifier events or other high current conditions. Features for the LCD backlight driver include a PWM input for content adjustable backlight control, 128 exponential or linear brightness levels, programmable over-voltage protection, and selectable switching frequency (500 kHz or 1 MHz). The device is available in a tiny 1.790 mm x 2.165 mm x 0.6 mm 20-bump, 0.4 mm pitch DSBGA package and operates over the −40°C to +85°C temperature range. 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 © 2013, Texas Instruments Incorporated LM3639A SNVS964 – MARCH 2013 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. Connection Diagram 4 4 3 3 2 2 1 1 A B C D E E Top View D C B A Bottom View Figure 1. 20-Bump, 0.4 mm Pitch DSBGA Package YFQ0020HGA PIN DESCRIPTIONS TERMINAL NAME NO. I/O DESCRIPTION FLED1 A1 Output High Side Current Source Output for Flash LED1. FLED2 B1 Output High Side Current Source Output for Flash LED2. OUTF (x2) A2/B2 Output Flash LED Boost Output. Connect a 10 µF ceramic capacitor between this pin GND. SWF (x2) A3/B3 Output Drain Connection for Internal NMOS and Synchronous PMOS Switches. Connect the Flash LED Boost Inductor to SWF. GND (x3) A4/B4/E3 Ground TX C2 Input Power Amplifier Synchronization Input. The TX pin has a 300 kΩ pull-down resistor connected to GND. STROBE C3 Input Active High Hardware Flash Enable. Drive STROBE high to turn on Flash pulse. STROBE overrides TORCH. The STROBE pin has a 300 kΩ pulldown resistor connected to GND. VIN C4 Input Input Voltage Connection. Connect IN to the input supply, and bypass to GND with a 10 µF or larger ceramic capacitor. SDA D3 Input Serial Data Input/Output. SCL D2 Input Serial Clock Input. EN C1 Input Enable Pin. High = Standby, Low = Shutdown/Reset. SWB E4 Input Drain Connection for internal NFET. Connect SWB to the junction of the backlight boost inductor and the Schottky diode anode. PWM D4 Input PWM Brightness Control Input for backlight current control. The PWM pin has a 300 kΩ pull-down resistor connected to GND. BLED1 D1 Input Input Terminal to Backlight LED String Current Sink #1 (40V max). The boost converter regulates the minimum of BLED1 and BLED2 to 400 mV. BLED2 E1 Input Input Terminal to Backlight LED String Current Sink #2 (40V max). The boost converter regulates the minimum of BLED1 and BLED2 to 400 mV. OVP E2 Input Over-Voltage Sense Input for Backlight Boost. Connect to the positive terminal of (COUTB). 2 Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 ABSOLUTE MAXIMUM RATINGS VIN (1) (2) (3) −0.3V to 6V SWF, OUTF, FLED1, FLED2, EN, PWM, SCL, SDA, TX, STROBE SWB, OVP, BLED1, BLED2 (2) (2) −0.3V to +45V −65°C to +150°C Storage Temperature Range (1) (2) (3) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits and associated test conditions, see the Electrical Characteristics table. All voltages are with respect to the potential at the GND pin. VIN can be below −0.3V if the current out of the pin is limited to 500 µA. OPERATING RATINGS (1) (2) VIN 2.5V to 5.5V −40°C to +125°C Junction Temperature (TJ) Ambient Temperature (TA) (1) (2) (3) −0.3V to the lesser of (VIN+0.3V) w/ 6V max (3) −40°C to +85°C Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits and associated test conditions, see the Electrical Characteristics table. All voltages are with respect to the potential at the GND pin. In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = +125°C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to-ambient thermal resistance of the part/package in the application (θJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (θJA × PD-MAX). THERMAL PROPERTIES Thermal Junction-to-Ambient Resistance (θJA) (1) (1) 48.8°C/W Junction-to-ambient thermal resistance (θJA) is taken from a thermal modeling result, performed under the conditions and guidelines set forth in the JEDEC standard JESD51-7. The test board is a 4-layer FR-4 board measuring 102mm x 76mm x 1.6mm with a 2 x 1 array of thermal vias. The ground plane on the board is 50mm x 50mm. Thickness of copper layers are 36μm/18μm/18μm/36μm (1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22°C in still air. Power dissipation is 1W. In applications where high maximum power dissipation exists special care must be paid to thermal dissipation issues. Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 3 LM3639A SNVS964 – MARCH 2013 www.ti.com ELECTRICAL CHARACTERISTICS (1) (2) Limits in standard typeface are for TA = +25°C. Limits in boldface type apply over the full operating ambient temperature range (−40°C ≤ TA ≤ +85°C). Unless otherwise specified, VIN = 3.6V. Symbol Parameter VIN Input Voltage Range ISHDN Shutdown Supply Current Standby Supply Current ISB Test Conditions Min Typ Max Unit 2.5 3.6 5.5 V Device Shutdown, EN = GND 1 3.5 Device Disabled via I2C EN = VIN 1 4 µA Low Voltage Boost Specifications (Flash Driver) IFLED1 + IFLED2 Current Source Accuracy 2.7V ≤ VIN ≤ 5.5V 750 mA Flash Current Setting −7% 1.5 +7% A 28.125 mA Torch Current Setting, per current source −10% 56.25 +10% mA For 750 mA Flash Current Setting 315 For 28.125 mA Torch Current Setting 180 VHR1, VHR2 Regulated Headroom Voltage VOVP Output Over-Voltage Protection Trip Point ON Threshold 4.87 5 5.10 OFF Threshold 4.71 4.88 4.98 RPMOS PMOS Switch On-Resistance IPMOS = 1A 85 RNMOS NMOS Switch On-Resistance INMOS = 1A 75 VIN = 3.6V mV V mΩ −12% 1.7 12% −12% 1.9 12% −12% 2.5 12% −12% 3.1 12% ICL Switch Current Limit VIVM Input Voltage Monitor Threshold VIN Falling −4% 2.5 4% V fSW Switching Frequency 2.5V ≤ VIN ≤ 5.5V 3.64 4.00 4.36 MHz IQ Quiescent Supply Current Device Not Switching Pass Mode, Backlight Disabled 0.6 2 mA tTX Flash to Torch LED Current Settling Time TX low to High, ILED1,2 = 750 mA to 23.44 mA 4 A µs High Voltage Boost Specification (Backlight Driver) IBLED1, IBLED2 Output Current Regulation (BLED1 or BLED2) 2.7V ≤ VIN ≤ 5.5V, Full Scale Current = 19 mA, Brightness Register = 0xFF IMATCH_HV BLED1 to BLED2 Current Matching (3) 2.7V ≤ VIN ≤ 5.5V, Full Scale Current = 19 mA, Brightness Register = 0xFF VREG_CS Regulated Current Sink Headroom Voltage ILED = 19mA 400 VHR_MIN Current Sink Minimum Headroom Voltage ILED = 95% of ILED = 19 mA 130 RDSON NMOS Switch On Resistance ISW = 500 mA ICL_BOOST NMOS Switch Current Limit VIN = 3.6V VOVP Output Over-Voltage Protection fSW Switching Frequency DMAX Maximum Duty Cycle (1) (2) (3) 4 −7% 19 7% mA 1 2.25 % mV ON Threshold, 2.7V ≤ VIN ≤ 5.5V, OVP select bits = 11 230 1 10% 38.4 40.0 41.4 Hysteresis 2.5V ≤ VIN ≤ 5.5V, Boost Frequency Select Bit = '0' mΩ −10% A V 1 465 500 94 535 kHz % All voltages are with respect to the potential at the GND pin. JESD ESD tests are applied at the ASIC level. The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin. Matching (%)= 100 × (|(ILED1 - ILED2 )| / (ILED1 + ILED2)) Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 ELECTRICAL CHARACTERISTICS (1) (2) (continued) Limits in standard typeface are for TA = +25°C. Limits in boldface type apply over the full operating ambient temperature range (−40°C ≤ TA ≤ +85°C). Unless otherwise specified, VIN = 3.6V. Symbol Parameter Test Conditions Min Typ Max Unit Logic Input Voltage Specifications (EN, STROBE, TORCH, TX, PWM) VIL Input Logic Low 2.5V ≤ VIN ≤ 5.5V 0 0.4 VIH Input Logic High 2.5V ≤ VIN ≤ 5.5V 1.2 VIN V Logic Input Voltage Specifications (SCL, SDA) VOL Output Logic Low (SDA only) ILOAD = 3 mA 400 VIL Input Logic Low 2.5V ≤ VIN ≤ 5.5V 0 0.4 VIH Input Logic High 2.5V ≤ VIN ≤ 4.2V 1.2 VIN mV V I2C-Compatible Timing Specifications (SCL, SDA) 1/t1 SCL (Clock Frequency) t2 Data In Setup Time to SCL High kHz 100 t3 Data Out Stable After SCL Low 0 t4 SDA Low Setup Time to SCL Low (Start) 100 t5 SDA High Hold Time After SCL High (Stop) 100 ns SDA SDA Figure 2. I2C Timing Diagram Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 5 LM3639A SNVS964 – MARCH 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS Unless otherwise specified: TA = 25°C; VIN = 3.6V; VEN = VIN; CIN= 10 μF, COUTF= 10 μF, COUTB = 1 μF (50V 0805 case size); LF = 1 μH; LB = 22 μH. 0.8 0.78 0.77 0.78 0.77 0.76 0.75 0.74 0.73 0.76 0.75 0.74 0.73 0.72 0.72 fSW = 2MHz 0.71 fSW = 4MHz 0.71 0.7 0.7 2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 VIN (V) 2.7 3 3.3 3.6 3.9 4.2 4.5 C004 Figure 4. Flash LED Current Line Regulation @ fSW = 4MHz 0.8 2 0.7 1.9 0.6 1.8 ICL = 1.7A 1.7 0.5 IIN (A) 0.4 0.3 D1,+25°C D2,+25°C D1,-40°C D2,-40°C D1,+85°C D2,+85°C 0.2 0.1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 1.6 1.5 1.4 0 14 15 Flash Code (#) 1.3 2MHz,+25 C 1.2 2MHz,-40 C 1.1 2MHz,+85 C 1 C006 2.5 3 3.5 4 4.5 5 VIN (V) Figure 5. Flash LED Current vs Brightness Code C008 2 ICL = 1.7A ICL = 1.9A 1.9 1.8 1.8 1.7 1.7 1.6 1.6 IIN (A) IIN (A) 5.5 Figure 6. Input Current vs Input Voltage, IFLASH = 1.5A 2 1.9 1.5 1.4 1.5 1.4 1.3 4MHz,+25 C 1.3 2MHz,+25 C 1.2 4MHz,-40 C 1.2 2MHz,-40 C 4MHz,+85 C 1.1 2MHz,+85 C 1.1 1 1 2.5 3 3.5 4 VIN (V) 4.5 5 5.5 2.5 3 3.5 4 VIN (V) C008 Figure 7. Input Current vs Input Voltage, IFLASH = 1.5A 6 4.8 VIN (V) C004 Figure 3. Flash LED Current Line Regulation @ fSW = 2MHz ILED (A) D1, +25°C D2, +25°C D1, +85°C D2, +85°C D1, -40°C D2, -40°C 0.79 ILED (A) ILED (A) 0.8 D1, +25°C D2, +25°C D1, +85°C D2, +85°C D1, -40°C D2, -40°C 0.79 4.5 5 5.5 C008 Figure 8. Input Current vs Input Voltage, IFLASH = 1.5A Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified: TA = 25°C; VIN = 3.6V; VEN = VIN; CIN= 10 μF, COUTF= 10 μF, COUTB = 1 μF (50V 0805 case size); LF = 1 μH; LB = 22 μH. 2 3 ICL = 1.9A 1.8 2.6 2MHz,-40 C 1.7 2.4 2MHz,+85 C 1.6 2.2 1.5 1.4 2 1.3 4MHz,+25 C 1.6 1.2 4MHz,-40 C 1.4 1.1 4MHz,+85 C 1.2 1 2.5 3 3.5 4 4.5 5 VIN (V) 5.5 2.5 3 3.5 4 4.5 5 VIN (V) C008 Figure 9. Input Current vs Input Voltage, IFLASH = 1.5A 5.5 C008 Figure 10. Input Current vs Input Voltage, IFLASH = 1.5A 3 3 ICL = 2.5A 2.8 4MHz,+25 C 2.6 4MHz,-40 C 2.6 2.4 4MHz,+85 C 2.4 ICL = 3.1A 2.8 2.2 IIN (A) IIN (A) ICL = 2.5A 1.8 1 2 2MHz,+25 C 2.2 2MHz,-40 C 2 1.8 1.8 1.6 1.6 1.4 1.4 1.2 1.2 1 2MHz,+85 C 1 2.5 3 3.5 4 4.5 5 VIN (V) 5.5 2.5 3 3.5 4 4.5 5 VIN (V) C008 Figure 11. Input Current vs Input Voltage, IFLASH = 1.5A 5.5 C008 Figure 12. Input Current vs Input Voltage, IFLASH = 1.5A 3 100% ICL = 3.1A 2.8 fSW = 2MHz 2.6 90% 2.4 4MHz,+25 C (%) 2.2 4MHz,-40 C 2 4MHz,+85 C 1.8 80% LED IIN (A) 2MHz,+25 C 2.8 IIN (A) IIN (A) 1.9 70% 1.6 TA = +25 C 1.4 60% TA = +85 C 1.2 TA = -40 C 1 50% 2.5 3 3.5 4 VIN (V) 4.5 5 5.5 2.7 Figure 13. Input Current vs Input Voltage, IFLASH = 1.5A 3 3.3 3.6 3.9 4.2 4.5 VIN (V) C008 4.8 C016 Figure 14. Flash LED Efficiency vs Input Voltage Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 7 LM3639A SNVS964 – MARCH 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified: TA = 25°C; VIN = 3.6V; VEN = VIN; CIN= 10 μF, COUTF= 10 μF, COUTB = 1 μF (50V 0805 case size); LF = 1 μH; LB = 22 μH. 0.25 100% fSW = 4MHz 0.24 ILED (A) 90% LED (%) 80% 0.23 0.22 D1, +25°C D2, +25°C D1, +85°C D2, +85°C D1, -40°C D2, -40°C 70% 0.21 TA = +25 C 60% TA = +85 C 0.2 TA = -40 C 2.7 3 3.3 fSW = 2MHz 3.6 50% 2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 VIN (V) 3.9 4.2 4.5 VIN (V) 4.8 C004 C016 Figure 15. Flash LED Efficiency vs Input Voltage Figure 16. Torch Current Line Regulation 0.25 0.3 0.25 0.24 ILED (A) ILED (A) 0.2 0.23 0.22 D1, +25°C D2, +25°C D1, +85°C D2, +85°C D1, -40°C D2, -40°C 0.21 0.2 2.7 3 0.05 fSW = 4MHz 0 3.3 3.6 3.9 4.2 4.5 0 4.8 0.0196 0.0196 0.0194 0.0194 0.0192 0.0192 ILED (A) ILED (A) 0.02 0.0198 0.019 0.0186 D1, +85°C 3 6 7 C006 D1, +25°C D2, +25°C D1, +85°C D2, +85°C D1, -40°C D2, -40°C 0.0184 D1, -40°C 5 0.019 0.0188 0.0186 fSW = 500kHz 11 LEDs 0.0182 4 Figure 18. Flash LED Torch Current vs Brightness Code 0.02 D1, +25°C 2 Torch Code (#) 0.0198 0.0188 1 C004 Figure 17. Torch Current Line Regulation 0.0184 D1,+25°C D2,+25°C D1,-40°C D2,-40°C D1,+85°C D2,+85°C 0.1 VIN (V) 0.0182 0.018 fSW = 1MHz 2x7 LEDs 0.018 2.5 2.8 3.1 3.4 3.7 4 4.3 4.6 4.9 5.2 VIN (V) 5.5 2.5 3 3.5 4 4.5 5 VIN (V) C004 Figure 19. Backlight LED Current Line Regulate Single String 8 0.15 5.5 C004 Figure 20. Backlight LED Current Line Regulate Dual String Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified: TA = 25°C; VIN = 3.6V; VEN = VIN; CIN= 10 μF, COUTF= 10 μF, COUTB = 1 μF (50V 0805 case size); LF = 1 μH; LB = 22 μH. 0.035 0.035 D1, -40 C D1, -40 C 0.03 D2, -40 C 0.025 D1, +25 C 0.025 0.02 D2, +25 C 0.02 ILED (A) ILED (A) 0.03 D1, +85 C 0.015 D2, -40 C D1, +25 C D2, +25 C D1, +85 C 0.015 D2, +85 C D2, +85 C 0.01 0.01 0.005 0.005 0 0 0 16 32 48 64 80 96 112 Brightness Code (#) 128 0 96 112 128 C020 (%) 90% 85% 80% 75% ILED = 19mA fSW = 500kHz. 65% 60% 85% 80% 2x4 LEDs 75% 2x5 LEDs 70% 2x6 LEDs 65% 2x7 LEDs ILED = 19mA fSW = 500kHz. 60% 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VIN (V) 5.5 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VIN (V) C022 Figure 23. Backlight Efficiency vs Input Voltage Single String 5.5 C022 Figure 24. Backlight Efficiency vs Input Voltage Dual String 100% 100% ILED = 19mA 6 LEDs 95% ILED = 19mA 8 LEDs 95% 90% 85% 85% (%) 90% 80% CONVERTER (%) 80 95% 70% CONVERTER 64 100% CONVERTER CONVERTER (%) 90% 48 Figure 22. Backlight LED Current vs Brightness Code Linear 6 LEDs 8 LEDs 10 LEDs 95% 32 Brightness Code (#) Figure 21. Backlight LED Current vs Brightness Code Exponential 100% 16 C020 75% 70% 500 kHz. 65% 80% 75% 70% 500 kHz. 65% 60% 60% 1 MHz. 55% 1 MHz. 55% 50% 50% 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VIN (V) 5.5 2.7 Figure 25. Backlight Efficiency vs Input Voltage Single String - 6 LEDs 3.1 3.5 3.9 4.3 4.7 5.1 VIN (V) C022 5.5 C022 Figure 26. Backlight Efficiency vs Input Voltage Single String - 8 LEDs Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 9 LM3639A SNVS964 – MARCH 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified: TA = 25°C; VIN = 3.6V; VEN = VIN; CIN= 10 μF, COUTF= 10 μF, COUTB = 1 μF (50V 0805 case size); LF = 1 μH; LB = 22 μH. 100% 100% 95% 90% 85% (%) 85% 80% 80% CONVERTER (%) 90% CONVERTER 95% ILED = 19mA 10 LEDs 75% 70% ILED = 19mA 2x4 LEDs 75% 70% 65% 500 kHz. 65% 500 kHz. 60% 60% 55% 1 MHz. 55% 50% 50% 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VIN (V) 5.5 2.7 3.9 100% 95% 95% 90% 90% 85% 85% (%) 100% 80% ILED = 19mA 2x5 LEDs 70% 4.3 500 kHz. 65% 5.5 C022 ILED = 19mA 2x6 LEDs 80% 75% 70% 500 kHz. 60% 1 MHz. 55% 1 MHz. 55% 50% 50% 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VIN (V) 5.5 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 VIN (V) C022 Figure 29. Backlight Efficiency vs Input Voltage Dual String - 2x5 LEDs C022 Figure 30. Backlight Efficiency vs Input Voltage Dual String - 2x6 LEDs 100 100% ILED = 19mA 2x7 LEDs 95% Duty-Cycle = 50% ILED = 19mA 90% 10 85% ILED RIPPLE (mA) (%) 5.1 65% 60% CONVERTER 4.7 Figure 28. Backlight Efficiency vs Input Voltage Dual String - 2x4 LEDs CONVERTER (%) CONVERTER 3.5 VIN (V) Figure 27. Backlight Efficiency vs Input Voltage Single String - 10 LEDs 75% 3.1 C022 80% 75% 70% 500 kHz. 65% 60% 0.1 1 MHz. 55% 1 50% 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VIN (V) 5.5 C022 0.01 1.E+0 1.E+1 1.E+2 1.E+3 1.E+4 1.E+5 fPWM (Hz) Figure 31. Backlight Efficiency vs Input Voltage Dual String - 2x7 LEDs 10 Submit Documentation Feedback 1.E+6 C033 Figure 32. PWM Input Filter Response Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified: TA = 25°C; VIN = 3.6V; VEN = VIN; CIN= 10 μF, COUTF= 10 μF, COUTB = 1 μF (50V 0805 case size); LF = 1 μH; LB = 22 μH. 0.020 0.014 0.012 0.010 0.008 D1, -40C D2, -40C D1, +25C D2, +25C D1, +85C D2, +85C 0.0105 ILED (A) 0.016 ILED (A) 0.0110 500Hz 1kHz 5kHz 10kHz 25kHz 50kHz 100kHz 500kHz 0.018 0.006 0.0100 Duty-Cycle = 50% fPWM = 50kHz ILED-MAX = 19mA 0.0095 0.004 0.002 0.000 0.0090 0 20 40 60 80 2.7 100 Duty Cycle (%) 3.5 3.9 4.3 4.7 5.1 VIN (V) Figure 33. LED Current vs PWM Duty-Cycle 5.5 C034 Figure 34. LED Current vs Input Voltage w/ PWM Enabled 0.0008 0.0008 PWM OFFSET CURRENT (A) +25C 0.0007 PWM Offset Current (A) 3.1 C035 +85C 0.0006 -40C 0.0005 0.0004 0.0003 ILED-MAX = 19mA Brightness Code = 127 PWM Pin = GND 0.0002 0.0001 0.0007 0.0006 0.0005 0.0004 0.0003 ILED-MAX = 5mA 0.0002 ILED-MAX = 19mA 0.0001 ILED-MAX = 29.5mA 0 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VIN (V) 5.5 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VIN (V) C036 Figure 35. PWM Offset Current vs Input Voltage Tri-Temp 5.5 C037 Figure 36. PWM Offset Current vs Input Voltage Different Max. LED Current, Brightness Code = 127 2.5 2.5 TA = +25°C 2 2 TA = +85°C 1.5 ISB ( A) ISD ( A) TA = +85°C 1 1.5 TA = -40°C 1 TA = +25°C and -40°C 0.5 0.5 0 0 2.5 3 3.5 4 4.5 5 VIN (V) 5.5 2.5 C001 Figure 37. Shutdown Current vs. VIN EN = 0V 3 3.5 4 4.5 5 VIN (V) Product Folder Links: LM3639A C001 Figure 38. Standby Current vs. VIN EN = VIN Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated 5.5 11 LM3639A SNVS964 – MARCH 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified: TA = 25°C; VIN = 3.6V; VEN = VIN; CIN= 10 μF, COUTF= 10 μF, COUTB = 1 μF (50V 0805 case size); LF = 1 μH; LB = 22 μH. 16 TA = +25°C 14 TA = -40°C 12 ISB ( A) 10 8 6 4 TA = +85°C 2 0 2.5 3 3.5 4 4.5 5 VIN (V) 5.5 C001 Figure 39. Standby Current vs. VIN EN = 1.8V FUNCTIONAL DESCRIPTION Flash and Backlight Enable (EN) The LM3639A operates from a 2.5V to 5.5V input voltage (IN). EN must be pulled high to bring the LM3639A out of shutdown. Once EN is high the flash driver and backlight driver can be enabled via the I2C-compatible interface. Thermal Shutdown The LM3639A features a thermal shutdown. When the die temperature reaches 140°C the flash boost, backlight boost, flash LED current sources, and backlight current sinks shut down. Flash LED Boost Operation The LM3639A’s low-voltage boost provides the power for a single flash LED at up to 1.5A or dual flash LEDs at up to 750 mA each. The device incorporates a 2MHz or 4MHz constant frequency-synchronous boost converter, and two high-side current sources to regulate the LED currents from a 2.5V to 5.5V input voltage range. The boost converter switches and maintains at least VHR across each of the current sources (FLED1 and FLED2). This minimum headroom voltage ensures that the current source remains in regulation. If the input voltage is above the LED voltage + current source headroom voltage, the device does not switch and turns the PFET on continuously (Pass mode). In Pass mode the difference between (VIN – ILED x RPMOS) and the voltage across the LED is dropped across each of the current sources. The LM3639A has a hardware Flash Enable input (STROBE) and a Flash Interrupt input (TX) designed to interrupt the flash pulse during high battery current conditions. Both logic inputs have internal 300 kΩ (typ.) pull-down resistors to GND. Additional features of the LM3639A include an input voltage monitor that can reduce the Flash current (during VIN under voltage conditions). Control of the LM3639A’s flash driver is done via the I2C-compatible interface. Startup (Enabling the FLASH LED Boost) On startup, when VOUT is less than VIN, the internal synchronous PFET turns on as a current source and delivers 200 mA (typ.) to the output capacitor. During this time the current source (LED) is off. When the voltage across the output capacitor reaches 2.2V (typ.) the current sources will turn on. At turn-on the current sources will step through each FLASH or TORCH level until the target LED current is reached. This gives the device a controlled turn-on and limits inrush current from the VIN supply. 12 Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 Pass Mode The LM3639A starts up in Pass Mode and stays there until Boost Mode is needed to maintain regulation. If the voltage difference between VOUT and VLED falls below VHR, the device switches to Boost Mode. In Pass Mode the boost converter does not switch, and the synchronous PFET turns fully on bringing VOUT up to VIN – ILED x RPMOS. Flash Mode Currents There are 16 programmable flash current levels for FLED1 and FLED2 from 46.875 mA to 750 mA. Flash mode is activated via the I2C-compatible interface or by pulling the STROBE pin HIGH (LOW if configured as ActiveLow). Once the Flash sequence is activated the current sources will ramp up to their programmed Flash current by stepping through all current steps until the programmed current is reached. Table 1. Flash Current vs. Code Code 0000 = 46.875 mA Code 0001 = 93.75 mA Code 0010 =140.625 mA Code 0011 = 187.5 mA Code 0100 = 234.375 mA Code 0101 = 281.25 mA Code 0110 = 328.125 mA Code 0111 = 375 mA Code 1000 = 421.875 mA Code 1001 = 468.75 mA Code 1010 = 515.625 mA Code 1011 = 562.5 mA Code 1100 = 609.375 mA Code 1101 = 656.25 mA Code 1110 = 703.125 mA Code 1111 = 750 mA Torch Mode Torch mode is activated through the I2C-compatible interface setting or by the hardware STROBE input when the Strobe EN bit is set to '1'. Once Torch mode is enabled the current sources will ramp up to the programmed Torch current level. Table 2. Torch Current vs. Code Code 000 = 28.125 mA Code 001 = 56.25 mA Code 010 = 84.375 mA Code 011 = 112.5 mA Code 100 = 140.625 mA Code 101 = 168.75 mA Code 110 = 196.875 mA Code 111 = 225 mA Independent LED Control The part has the ability to independently turn on and turn off the FLED1 or FLED2 current sources. The LED current is adjusted by writing to the Torch Brightness or Flash Brightness Registers. Both the FLED1 or FLED2 use the same target current level stored in the Torch Brightness and the Flash Brightness Registers. Both LED outputs use the same LED ramp step time. Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 13 LM3639A SNVS964 – MARCH 2013 www.ti.com Power Amplifier Synchronization (TX) The TX pin is a Power Amplifier Synchronization input. This is designed to reduce the flash LED currents and thus limit the battery-current during high battery current conditions such as PA transmit events. When the LM3639A is engaged in a Flash event and the TX pin is pulled high, the LED current is forced into Torch mode at the programmed Torch current setting. If the TX pin is then pulled low before the Flash pulse terminates, the LED current will return to the previous Flash current level. At the end of the Flash time-out, whether the TX pin is high or low, the LED current will turn off. The TX pin has a 300 kΩ pull-down resistor connected to GND. Input Voltage Flash Monitor (IVFM) The LM3639A has the ability to adjust the flash current based upon the voltage level present at the VIN pin utilizing an Input Voltage Flash Monitor. The adjustable VIN Monitor threshold ranges from 2.5V to 3.2V in 100 mV steps. Depending on the option, the LM3639A will either transition the LED current to the programmed Torch current or shut down completely when the Input Voltage Monitor detects an input voltage drop lower than the threshold value. Flash LED Fault/Protections Flash Timeout The Flash Timeout period sets the maximum amount of time that the Flash Currents is sourced from each of the current source (FLED1 and FLED2). The LM3639A has 32 timeout levels ranging 32 ms to 1024 ms in 32 ms steps. Flash Timeout only applies to the Flash Mode operation. In I2C-compatible Flash Mode, the flash period is equal to the timeout value. In Strobe Flash Mode, the flash period is set by the active duration of the Strobe pin if the duration is less than the timeout value. If the Strobe event lasts longer than the set flash timeout value, the flash event will terminate upon reach the timeout period. Over-Voltage Protection (OVP) The output voltage is limited to typically 5.0V (see VOVP Spec). In situations such as an open LED, the LM3639A will raise the output voltage in order keep the LED current at its target value. When VOUTF reaches 5.0V (typ.) the over-voltage protection (OVP) comparator will trip and turn off the internal NFET. When VOUTF falls below the “VOVP Off Threshold”, the LM3639A will begin switching again. The mode bits in the Enable Register (0x0A) are not cleared upon an OVP event. Current Limit The LM3639A features selectable inductor current limits. When the inductor current limit is reached, the LM3639A will terminate the charging phase of the switching cycle. Since the current limit is sensed in the NMOS switch, there is no mechanism to limit the current when the device operates in Pass Mode. In Boost mode or Pass mode, if OUTF falls below 2.3V, the part stops switching, and the PFET operates as a current source limiting the current to 200 mA. This prevents damage to the LM3639A and excessive current draw from the battery during output short-circuit conditions. Pulling additional current from the OUTF node during normal operation is not recommended. LED and/or OUTF Fault The LM3639A determines an LED open condition if the OVP threshold is crossed at the OUTF pin while the device is in Flash or Torch mode. An LED short condition is determined if the voltage at LED goes below 500 mV (typ.) while the device is in Torch or Flash mode. There is a delay of 256 μs deglitch time before the LED flag is valid and 2.048 ms before the VOUT flag is valid. This delay is the time between when the Flash or Torch current is triggered and when the LED voltage and the output voltage are sampled. Backlight Boost Operation The high-voltage boost converter provides power for the two current sinks (BLED1 and BLED2). The backlight boost operates using a 10 µH to 22 µH inductor and a 1µF output capacitor. The selectable 500 kHz or 1 MHz switching frequency allows use of small external components and provides for high boost converter efficiency. When there are different voltage requirements in both high-voltage LED strings, the LM3639A’s backlight boost will regulate the feedback point of the highest voltage string to 400 mV and drop the excess voltage of the lower voltage string across its current sink. 14 Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 Backlight Over-Voltage Protection The output voltage protection is limited to typically 16V, 24V, 32V or 40V (see VOVP Spec). In situations such as an open LED, the LM3639A will raise the output voltage in order to keep the LED current at its target value. When VOUTB reaches the selected OVP level, the over-voltage comparator will trip and turn off the internal NFET. When VOUT falls below the “VOVP Off Threshold”, the LM3639A will begin switching again. By default, the Backlight OVP flag in the Flag Register (0x0B, Bit7) will not be set upon hitting an OVP condition. To enable this reporting feature, the BL Flag Report bit (Register 0x09, Bit7) must be set to a '1'. The BL Flag Report function is intended for use in a factory environment to check for LED connectivity and is not intended for use during normal operation. Backlight LED Short Detection The LM3639A features a Backlight LED short flag that indicates whether either of the BLEDx pins rise above (VIN - 1V). This detection block can help detect whether one or more of the LEDs in a string have experienced a short when operating in a balanced dual-string LED configuration (ex: 2 strings of 5 is balanced. One string of 5 and one string of 4 is unbalanced). If one or more of the LEDs in a string become shorted, and either of the BLEDx pins rise above (VIN - 1V), the BLED1/2 Flag in the Flag register (0x0B, Bit2) will be set to a '1'. By default this detection block is disabled. To enable this reporting feature, the BL Flag Report bit (Register 0x09, Bit7) must be set to a '1'. The BL Flag Report function is intended for use in a factory environment to check for LED connectivity and is not intended for use during normal operation. Backlight Current Sinks (BLED1 and BLED2) BLED1 and BLED2 control the current in the backlight boost LED strings. Each current sink has 3-bit full-scale current programmability and 7-bit brightness control. Either current sink can have its current set through a dedicated brightness register and be controlled via the PWM input. Backlight Boost Switching Frequency The LM3639A’s backlight boost converter can have a 500 kHz or 1 MHz switching frequency. For the 500 kHz switching frequency selection the inductor must be 22 µH. For the 1 MHz switching frequency selection the inductor can be 10 µH or 22 µH. PWM Input There is a single PWM input which can control the current in the backlight current sinks (BLED1/2). When the PWM input is enabled, the current becomes a function of the full-scale current, the brightness code, and the PWM input duty cycle. The PWM pin has a 300 kΩ pull-down resistor connected to GND. PWM Polarity The PWM input can be programmed to have active high or active low polarity. Full-Scale Current There are 8 (3-bit) separate full-scale current settings for the backlight current. The full-scale current is the maximum backlight current when the brightness code is at 100% (Code 0x7F). The full-scale current vs full-scale current code is given by: ILED Fullscale = 5mA + (CODE × 3.5 mA) (1) Table 3. Full-Scale Current vs. Code Code Full Scale Current 000 5 mA 001 8.5 mA : : 100 19 mA : : 110 26 mA 111 29.5 mA Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 15 LM3639A SNVS964 – MARCH 2013 www.ti.com LED Current Mapping Modes The backlight current can be programmed for either exponential or linear mapping modes. These modes determine the transfer characteristic of backlight code to LED current. The brightness code selected for linear will always be forced to be equal to the exponential value. The brightness code for exponential will always be mapped to the linear code as well. Exponential Mapping In exponential mapping mode the brightness code to backlight current transfer function is given by the equation: ª §Code + 1 ·º «44 - ¨¨ ¸¸» © 2 . 91 ¹»¼ ILED = ILED_FULLSCALE x DPWM x 0.85 «¬ (2) 30186911 where ILED_FULLSCALE is the full-scale LED current setting, Code is the backlight code in the brightness register, and DPWM is the PWM input duty cycle. In exponential mapping mode the current ramp (either up or down) appears to the human eye as a more uniform transition then the linear ramp. This is due to the logarithmic response of the eye. NOTE: Code '0' does not enable the boost or the current sinks and should not be used. Linear Mapping In linear mapping mode the brightness code to backlight current has a linear relationship and follows the equation: ILED = ILED_FULLSCALE x 1 x Code x DPWM 127 (3) where ILED_FULLSCALE is the full-scale LED current setting, Code is the backlight code in the brightness register, and DPWM is the PWM input duty cycle. NOTE: Code '0' does not enable the boost or the current sinks and should not be used. LED Current Ramping Ramp-Up/Ramp-Down Step Time The Ramp-Up step time is the time the LM3639A spends at each current step during the ramping up of the backlight LED current. The Ramp-Down step time is the time the LM3639A spends at each current step during the ramping down of the backlight LED current. There are 8 different Ramp-Up and 8 different Ramp-Down step times. The Ramp-Up and Ramp-Down step times are independently programmable, but not independently programmable for each backlight current sink. For example, programming a Ramp-Up or Ramp-Down time programs the same ramp time for the current in both BLED1 and BLED2. Table 4. Ramp Times 16 Code Ramp-Up Step Time Ramp-Down Step Time 000 32 µs 32 µs 001 4.096 ms 4.096 ms 010 8.192 ms 8.192 ms 011 16.384 ms 16.384 ms 100 32.768 ms 32.768 ms 101 65.536 ms 65.536 ms 110 131.072 ms 131.072 ms 111 262.144 ms 262.144 ms Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 APPLICATION INFORMATION Register Map (7-Bit I2C Chip Address = 0x39) 0x00 [7:0] Device ID 0x01 [7:0] Check sum 0x00 0001 0001 0x01 0000 1001 BACKLIGHT CONFIGURATION REGISTERS [7] N/A 00 = 16V [6:5] 01 = 24V (default) BLED OVP 10 = 32V 11 = 40V 0x02 [4] BLED Mapping mode 0 = Exponential 1 = Linear (default) [3] BLED PWM configuration 0 = Active high (default) 1 = Active low 000 - 5 mA [2:0] BLED Max Current 100 19 mA Default 111 - 29.5 mA 0x03 [7] RFU [6] BLED SW Frequency 1 = 1 Mhz BLED Brightness Ramp Fall Rate 000 = 32 µs per step ~ 111 = 262 ms per step [2:0] BLED Brightness Ramp rise Rate 000 = 32 µs per step ~ 111 = 262 ms per step N/A - BLED Brightness control 128 step (7-bit) (Exponential) N/A - BLED Brightness control 128 step (7-bit) (Linear) [6:0] [7] 0x05 0 = 500 kHz (default) [5:3] [7] 0x04 Must ALWAYS be set to a '0' [6:0] Any code written to Register 0x04 will be mapped to 0x05. Any code written to Register 0x05 will be mapped to 0x04 Writing a '0' to either Register 0x04 or 0x05 is not recommended as the LM3639A will remain off. FLASH CONFIGURATION REGISTERS 7 N/A 000 = 28.125 mA [7:4] FLED LED1/2 Torch current 0x06 ~ 111 = 225 mA 0000 = 46.875 mA [3:0] FLED LED1/2 strobe Current ~ 1111 = 750 mA Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 17 LM3639A SNVS964 – MARCH 2013 [7] www.ti.com 0 = 2 MHz (default) FLED SW Frequency 1 = 4 MHz 00 = 1.7A 0x07 [6:5] 01 = 1.9A FLED Current Limit 10 = 2.5A (default) 11 = 3.1A 00000 = 32 ms [4:0] FLED Strobe Time-Out 01111 = 512 ms (default) 11111 = 1024 ms [7:3] N/A 000 = 2.5V 0x08 001 = 2.6V [2:0] FLED VIN monitor ... 110 = 3.1V 111 = 3.2V I/O CONTROL REGISTER 1 = Backlight OVP and BLED1/2 Short Flag Reporting ACTIVE [7] Backlight Flag Reporting [6] PWM ENABLE [5] STROBE POLARITY [4] STROBE EN [3] TX POLARITY [2] TX Enable [1] VIN Monitor Mode [0] VIN Monitor EN 0x09 0 = Backlight OVP and BLED1/2 Short Flag Reporting DISABLED (default) 1= PWM Enabled 0 = PWM Ignored 1 = Active High 0 = Active Low 1 = Strobe Flash 0 = I2C Flash 1 = Active High 0 = Active Low 1 = Tx Enabled 0 = Tx Ignored 1 = Standby 0 = Torch 1 = VIN Monitor Enabled 0 = Disabled ENABLE REGISTER [7] Software Reset [6] FLED1 EN [5] FLED2 EN [4] BLED1 EN [3] BLED2 EN [2] Torch/Flash [1] FLASH EN [0] BACKLIGHT EN 0x0A 18 1 = RESET 0 = disable (auto) 1 = Flash LED1 On 0 = Disabled 1 = Flash LED2 On 0 = Disabled 1 = Backlight LED1 On 0 = Disabled 1 = Backlight LED2 On 0 = Disabled 1 = FLASH 0 = TORCH 1 = Enable FLASH 0 = Off 1 = Enable Backlight 0 = Off Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 Setting both "FLED1 EN" and "FLED2 EN" to '0' when "FLASH EN" is '1' is not recommended as the flash boost will run in OVP Setting both "BLED1 EN" and "BLED2 EN" to '0' when "BACKLIGHT EN" is '1' is not recommended backlight boost will run in OVP. See Notes for more configuration details. FLAGS REGISTER 1 = FAULT [7] BACKLIGHT OVP [6] FLASH OVP [5] FLASH OUTPUT SHORT [4] VIN MONITOR [3] TX INTERRUPT [2] FLED1/2 SHORT [1] BLED1/2 SHORT [0] THERMAL SHUTDOWN 0 = NORMAL 1 = FAULT 0 = NORMAL 1 = FAULT 0 = NORMAL 1 = VIN Monitor Threshold Crossed 0 = Normal 0x0B 1 = TX Event Occurred 0 = Normal 1 = FAULT 0 = NORMAL 1 = FAULT 0 = NORMAL 1 = Thermal Shutdown 0 = Normal Notes 1. To initiate a flash event, the Flash EN bit must be set via I2C (Reg 0x0A, bit 1 = ‘1’). Upon the termination of a flash event (I2C Controlled or Strobe Controlled), the Flash EN bit in register 0x0A will automatically clear itself to ‘0’. To restart a flash event, the Flash EN bit must be reset to a ‘1’ via an I2C write. 2. During Backlight Operation, registers 0x02 and 0x03 become READ-ONLY. To adjust the values of registers 0x02 and 0x03, the Backlight EN bit in register 0x0A must be set to a ‘0’ first. 3. During Flash Operation, register 0x07 becomes READ-ONLY. To adjust the values of register 0x07, the Flash EN bit in register 0x0A must be set to a ‘0’ first. 4. If a single Backlight string is used, the string must be connected to BLED1, and the BLED2 EN bit must be set to ‘0’. BLED2 in this configuration should be left floating. 5. If a single Flash LED is going to be used without shorting FLED1 to FLED2, FLED1 must be used and the FLED2 EN bit must be set to a ‘0’. FLED2 in this configuration should be left floating. Applications Information: Backlight Backlight Inductor Selection The LM3639A is designed to work with a 10 µH to 22 µH inductor. When selecting the inductor, ensure that the saturation rating is high enough to accommodate the applications peak inductor current. The inductance value must also be large enough so that the peak inductor current is kept below the LM3639A's switch current limit. Table 5 lists various inductors that can be used with the LM3639A. The inductors with higher saturation currents are more suitable for applications with higher output currents or voltages (multiple strings). The smaller devices are geared toward single string applications with lower series LED counts. NOTE For high LED count single string applications (greater than 9 LEDs), the 500 kHz switching frequency and a 22 µH inductor must be used. For dual string applications with a maximum LED count of two strings of 7 LEDs, a 22 µH inductor is required for use with the 500kHz switching frequency, whereas a 10 µH or a 22 µH inductor can be used with the 1 MHz switching frequency. Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 19 LM3639A SNVS964 – MARCH 2013 www.ti.com Table 5. Inductors Manufacturer Part Number Value Size Current Rating DC Resistance TDK VLF403212MT-220M 22µH 4 mm × 3.2 mm × 1.2 mm 600 mA 0.59Ω TDK VLS252010T-100M 10 µH 2.5 mm × 2 mm × 1 mm 590 mA 0.712Ω TDK VLS2012ET-100M 10 µH 2 mm × 2 mm × 1.2 mm 695 mA 0.47Ω TDK VLF301512MT-100M 10 µH 3.0 mm × 2.5 mm × 1.2mm 690 mA 0.25Ω TDK VLF4010ST-100MR80 10 µH 2.8 mm × 3 mm × 1 mm 800 mA 0.25Ω TDK VLS252012T-100M 10 µH 2.5 mm × 2 mm × 1.2mm 810 mA 0.63Ω TDK VLF3014ST-100MR82 10 µH 2.8 mm × 3 mm × 1.4mm 820 mA 0.25Ω TDK VLF4014ST-100M1R0 10 µH 3.8 mm × 3.6 mm × 1.4 mm 1000 mA 0.22Ω Coilcraft XPL2010-103ML 10 µH 1.9 mm × 2 mm × 1 mm 610 mA 0.56Ω Coilcraft LPS3010-103ML 10 µH 2.95 mm × 2.95 mm × 0.9 mm 550 mA 0.54Ω Coilcraft LPS4012-103ML 10 µH 3.9mm × 3.9mm × 1.1mm 1000 mA 0.35Ω Coilcraft LPS4012-223ML 22 µH 3.9 mm × 3.9 mm × 1.1 mm 780 mA 0.6Ω Coilcraft LPS4018-103ML 10 µH 3.9 mm × 3.9 mm × 1.7 mm 1100 mA 0.2Ω Coilcraft LPS4018-223ML 22 µH 3.9 mm × 3.9 mm × 1.7 mm 700 mA 0.36Ω Backlight Output Capacitor Selection The LM3639A’s output capacitor has two functions: to filter the boost converter's switching ripple, and to ensure feedback loop stability. As a filter, the output capacitor supplies the LED current during the boost converter's on time and absorbs the inductor's energy during the switch's off time. This causes a sag in the output voltage during the on time and a rise in the output voltage during the off time. Because of this, the output capacitor must be sized large enough to filter the inductor current ripple that could cause the output voltage ripple to become excessive. As a feedback loop component, the output capacitor must be at least 1 µF and have low ESR; otherwise, the LM3639A's boost converter can become unstable. This requires the use of ceramic output capacitors. Table 6 lists part numbers and voltage ratings for different output capacitors that can be used with the LM3639A. NOTE For all LED applications, it is required that at least 0.4 µF of capacitance is present at the output of the backlight boost converter. Please refer to the output capacitor data sheets to find the effective capacitance (taking into account the DC Bias effect) of the capacitors at the target application output voltage. Table 6. Output Capacitors 20 Manufacturer Part Number Value Size Rating Description TDK CGA4J3X7R1H105K 1 µF 0805 50V COUT Murata GRM21BR71H105KA12 1 µF 0805 50V COUT Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 Backlight Diode Selection The diode connected between SW and OUT must be a Schottky diode and have a reverse breakdown voltage high enough to handle the maximum output voltage in the application. Table 7 lists various diodes that can be used with the LM3639A. Table 7. Diodes Manufacturer Part Number Value Size Rating Diodes Inc. B0540WS Schottky SOD-323 40V/500 mA Diodes Inc. SDM20U40 Schottky SOD-523 (1.2 mm × 0.8 mm × 0.6 mm) 40V/200 mA On Semiconductor NSR0340V2T1G Schottky SOD-523 (1.2 mm × 0.8 mm × 0.6 mm) 40V/250 mA On Semiconductor NSR0240V2T1G Schottky SOD-523 (1.2 mm × 0.8 mm × 0.6 mm) 40V/250 mA Backlight Layout Guidelines The LM3639A contains an inductive boost converter which sees a high switched voltage (up to 40V) at the SWB pin, and a step current (up to 1A) through the Schottky diode and output capacitor each switching cycle. The high switching voltage can create interference into nearby nodes due to electric field coupling (I = CdV/dt). The large step current through the diode and the output capacitor can cause a large voltage spike at the SW pin and the OVP pin due to parasitic inductance in the step current conducting path (V = LdI/dt). Board layout guidelines are geared towards minimizing this electric field coupling and conducted noise. Figure 40 highlights these two noise generating components. Voltage Spike VOUT + VF Schottky Pulsed voltage at SW Current through Schottky Diode and COUT IPEAK IAVE = IIN Current through inductor Paracitic Circuit Board Inductances Affected Node due to capacitive coupling Cp1 L(B) Lp1 D1 Lp2 2.7V to 5.5V VLOGIC SW IN 10 k: Up to 40V COUTB Lp3 10 k: SCL OVP SDA LM3639A LCD Display BLED1 BLED2 GND Figure 40. LM3639A's Boost Converter Showing Pulsed Voltage at SW (High dV/dt) and Current Through Schottky and COUT (High dI/dt) Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 21 LM3639A SNVS964 – MARCH 2013 www.ti.com The following lists the main (layout sensitive) areas of the LM3639A in order of decreasing importance: Output Capacitor • Schottky Cathode to COUTB+ • COUTB− to GND Schottky Diode • SWB Pin to Schottky Anode • Schottky Cathode to COUTB+ Inductor • SWB Node PCB capacitance to other traces Input Capacitor • CIN+ to VIN pin • CIN− to GND Backlight Output Capacitor Placement The output capacitor is in the path of the inductor current discharge current. As a result, COUTB sees a high current step from 0 to IPEAK each time the switch turns off and the Schottky diode turns on. Typical turn-off/turnon times are around 5 ns. Any inductance along this series path from the cathode of the diode through COUTB and back into the LM3639A's GND pin will contribute to voltage spikes (VSPIKE = LPX × dI/dt) at SWB and OUTB which can potentially over-voltage the SWB pin, or feed through to GND. To avoid this, COUTB+ must be connected as close as possible to the cathode of the Schottky diode, and COUT− must be connected as close as possible to the LM3639A's GND bump. The best placement for COUTB is on the same layer as the LM3639A to avoid any vias that will add extra series inductance. Schottky Diode Placement The Schottky diode is in the path of the inductor current discharge. As a result the Schottky diode sees a high current step from 0 to IPEAK each time the switch turns off and the diode turns on. Any inductance in series with the diode will cause a voltage spike (VSPIKE = LPX × dI/dt) at SW and OUT which can potentially over-voltage the SW pin, or feed through to VOUT and through the output capacitor and into GND. Connecting the anode of the diode as close as possible to the SW pin and the cathode of the diode as close as possible to COUT+ will reduce the inductance (LPX) and minimize these voltage spikes. Backlight Inductor Placement The node where the inductor connects to the LM3639A’s SW bump presents two challenges. First, a large switched voltage (0 to VOUT + VF_SCHOTTKY) appears on this node every switching cycle. This switched voltage can be capacitively coupled into nearby nodes. Second, there is a relatively large current (input current) on the traces connecting the input supply to the inductor and connecting the inductor to the SW bump. Any resistance in this path can cause large voltage drops that will negatively affect efficiency. To reduce the capacitively coupled signal from SWB into nearby traces, the SW bump-to-inductor connection must be minimized in area. This limits the PCB capacitance from SW to other traces. Additionally, other nodes need to be routed away from SWB and not directly beneath. This is especially true for high-impedance nodes that are more susceptible to capacitive coupling such as (SCL, SDA, EN, PWM). A GND plane placed directly below SWB will help isolate SWB and dramatically reduce the capacitance from SW into nearby traces. To limit the trace resistance of the VBATT-to-inductor connection and from the inductor-to-SW connection, use short, wide traces. Input Capacitor Selection and Placement The input bypass capacitor filters the inductor current ripple, and the internal MOSFET driver currents, during turn-on of the power switch. The driver current requirement can be a few hundred mAs with 5 ns rise and fall times. This will appear as high dI/dt current pulses coming from the input capacitor each time the switch turns on. Close placement of the input capacitor to the IN pin and to the GND pin is critical since any series inductance between VIN and CIN+ or CIN− and GND can create voltage spikes that could appear on the VIN supply line and in the GND plane. 22 Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com SNVS964 – MARCH 2013 Close placement of the input bypass capacitor at the input side of the inductor is also critical. The source impedance (inductance and resistance) from the input supply, along with the input capacitor of the LM3639A, form a series RLC circuit. If the output resistance from the source (RS) is low enough the circuit will be underdamped and will have a resonant frequency (typically the case). Depending on the size of LS the resonant frequency could occur below, close to, or above the LM3639A's switching frequency. This can cause the supply current ripple to be: • approximately equal to the inductor current ripple when the resonant frequency occurs well above the LM3639A's switching frequency; • greater then the inductor current ripple when the resonant frequency occurs near the switching frequency; or • less then the inductor current ripple when the resonant frequency occurs well below the switching frequency. Figure 41 shows the series RLC circuit formed from the output impedance of the supply and the input capacitor. The circuit is re-drawn for the AC case where the VIN supply is replaced with a short to GND, and the LM3639A + Inductor is replaced with a current source (ΔIL). Equation 1 is the criteria for an underdamped response. Equation 2 is the resonant frequency. Equation 3 is the approximated supply current ripple as a function of LS, RS, and CIN. As an example, consider a 3.6V supply with 0.1Ω of series resistance connected to CIN through 50 nH of connecting traces. This results in an underdamped input filter circuit with a resonant frequency of 712 kHz. Since the switching frequency lies near to the resonant frequency of the input RLC network, the supply current is probably larger then the inductor current ripple. In this case, using Equation 3 from Figure 41, the supply current ripple can be approximated as 1.68 times the inductor current ripple. Increasing the series inductance (LS) to 500 nH causes the resonant frequency to move to around 225 kHz and the supply current ripple to be approximately 0.25 times the inductor current ripple. 'IL ISUPPLY RS L LS SW IN + LM3639A CIN - VIN Supply ISUPPLY RS LS 'IL CIN 2 1. RS 1 > L S x C IN 4 x L S2 2. f RESONANT = 3. 1 2S LS x CIN 1 2S x 500 kHz x CIN I SUPPLYRIPPLE | ' I L x 2 RS § · 1 ¨2S x 500 kHz x LS ¸ ¨ ¸ x x S 500 kHz C 2 IN ¹ © 2 Figure 41. Input RLC Network Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 23 LM3639A SNVS964 – MARCH 2013 www.ti.com Applications Information: Flash Output Capacitor Selection The LM3639A's flash boost converter is designed to operate with a ceramic output capacitor of at least 10 µF. When the boost converter is running, the output capacitor supplies the load current during the boost converter's on-time. When the NMOS switch turns off, the inductor energy is discharged through the internal PMOS switch, supplying power to the load and restoring charge to the output capacitor. This causes a sag in the output voltage during the on-time and a rise in the output voltage during the off-time. The output capacitor is therefore chosen to limit the output ripple to an acceptable level depending on load current and input/output voltage differentials and also to ensure the converter remains stable. Larger capacitors such as a 22 µF or capacitors in parallel can be used if lower output voltage ripple is desired. To estimate the output voltage ripple considering the ripple due to capacitor discharge (ΔVQ) and the ripple due to the capacitors ESR (ΔVESR) use the following equations: For continuous conduction mode, the output voltage ripple due to the capacitor discharge is: 'VQ = ILED x (VOUT - VIN) fSW x VOUT x COUT (4) The output voltage ripple due to the output capacitors ESR is found by: 'VESR = R ESR x § © where 'IL = I LED x VOUT· ¹ VIN + 'I L VIN x (VOUT - VIN ) 2 x f SW x L x VOUT (5) In ceramic capacitors the ESR is very low so the assumption is that 80% of the output voltage ripple is due to capacitor discharge and 20% from ESR. Table 8 lists different manufacturers for various output capacitors and their case sizes suitable for use with the LM3639A. Input Capacitor Selection Choosing the correct size and type of input capacitor helps minimize the voltage ripple caused by the switching of the LM3639A’s boost converter, and reduces noise on the boost converter's input terminal that can feed through and disrupt internal analog signals. In the Typical Application Circuit a 10 µF ceramic input capacitor works well. It is important to place the input capacitor as close as possible to the LM3639A’s input (IN) terminal. This reduces the series resistance and inductance that can inject noise into the device due to the input switching currents. The table below lists various input capacitors recommended for use with the LM3639A. Table 8. Recommended Flash Input/Output Capacitors (X5R/X7R Dielectric) Manufacturer Part Number Value Case Size Voltage Rating GRM155R60J106ME44D 10 µF 0402 (1mm × 0.5mm × 0.5mm) 6.3V TDK Corporation C1608JB0J106M 10 µF 0603 (1.6 mm × 0.8 mm × 0.8 mm) 6.3V TDK Corporation C2012JB1A106M 10 µF 0805 (2 mm × 1.25 mm × 1.25 mm) 10V Murata GRM188R60J106M 10 µF 0603 (1.6 mm x 0.8 mm x 0.8 mm) 6.3V Murata GRM21BR61A106KE19 10 µF 0805 (2 mm × 1.25 mm × 1.25 mm) 10V Murata Inductor Selection The LM3639A's flash boost is designed to use a 1 µH or 0.47 µH inductor. Table 9 below lists various inductors and their manufacturers that work well with the LM3639A. When the device is boosting (VOUT > VIN) the inductor will typically be the largest area of efficiency loss in the circuit. Therefore, choosing an inductor with the lowest possible series resistance is important. Additionally, the saturation rating of the inductor should be greater than the maximum operating peak current of the LM3639A. This prevents excess efficiency loss that can occur with inductors that operate in saturation. For proper inductor operation and circuit performance, ensure that the inductor saturation and the peak current limit setting of the LM3639A are greater than IPEAK in the following calculation: 24 Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A LM3639A www.ti.com IPEAK = SNVS964 – MARCH 2013 I LOAD VOUT V x (VOUT - VIN) x + 'IL where 'IL = IN K VIN 2 x f SW x L x VOUT (6) where ƒSW = 4 MHz or 2MHz, and efficiency can be found in the Typical Performance Characteristics plots. Table 9. Recommended Inductors Manufacturer L TOKO 1µH Part Number Dimensions (LxWxH) ISAT RDC DFE201612C-H-1R0M 2 mm x 1.6 mm x 1.2 mm 3.1A 68 mΩ DFE252010C 2.5 mm x 2 mm x 1 mm 3.4A 60 mΩ DFE252012C 2.5 mm x 2 mm x 1.2 mm 3.8A 45 mΩ Flash Layout Recommendations The high switching frequency and large switching currents of the LM3639A make the choice of layout important. The following steps should be used as a reference to ensure the device is stable and maintains proper LED current regulation across its intended operating voltage and current range. 1. Place CIN on the top layer (same layer as the LM3639A) and as close to the device as possible. The input capacitor conducts the driver currents during the low-side MOSFET turn-on and turn-off and can see current spikes over 1A in amplitude. Connecting the input capacitor through short, wide traces to both the VIN and GND terminals will reduce the inductive voltage spikes that occur during switching which can corrupt the VIN line. 2. Place COUTF on the top layer (same layer as the LM3639A) and as close as possible to the OUTF and GND terminals. The returns for both CIN and COUTF should come together at one point, as close to the GND pin as possible. Connecting COUTF through short, wide traces will reduce the series inductance on the OUTF and GND terminals that can corrupt the VOUTF and GND lines and cause excessive noise in the device and surrounding circuitry. 3. Connect the inductor on the top layer close to the SWF pin. There should be a low-impedance connection from the inductor to SWF due to the large DC inductor current, and at the same time the area occupied by the SW node should be small to reduce the capacitive coupling of the high dV/dt present at SW that can couple into nearby traces. 4. Avoid routing logic traces near the SWF node to avoid any capacitively coupled voltages from SW onto any high-impedance logic lines such as STROBE, EN, TX, PWM, SDA, and SCL. A good approach is to insert an inner layer GND plane underneath the SWF node and between any nearby routed traces. This creates a shield from the electric field generated at SW. 5. Terminate the Flash LED cathodes directly to the GND pin of the LM3639A. If possible, route the LED returns with a dedicated path to keep the high amplitude LED currents out of the GND plane. For Flash LEDs that are routed relatively far away from the LM3639A, a good approach is to sandwich the forward and return current paths over the top of each other on two layers. This will help reduce the inductance of the LED current paths. Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated Product Folder Links: LM3639A 25 PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (°C) Top-Side Markings (3) (4) LM3639AYFQR ACTIVE DSBGA YFQ 20 3000 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85 363A LM3639AYFQT ACTIVE DSBGA YFQ 20 250 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85 363A (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) Multiple Top-Side Markings will be inside parentheses. Only one Top-Side 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 Top-Side Marking for that 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 1 Samples MECHANICAL DATA YFQ0020xxx D 0.600±0.075 E TMD20XXX (Rev D) D: Max = 2.19 mm, Min = 2.13 mm E: Max = 1.815 mm, Min =1.755 mm 4215083/A NOTES: A. All linear dimensions are in millimeters. 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