LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 LM3501 Synchronous Step-up DC/DC Converter for White LED Applications Check for Samples: LM3501 FEATURES APPLICATIONS • • • • • • 1 2 • • • • • • • • • • • Synchronous Rectification, High Efficiency and no External Schottky Diode required Uses Small Surface Mount Components Can Drive 2-5 White LEDs in Series (May Function with More Low VF LEDs) 2.7V to 7V Input Range True Shutdown Isolation, no LED Leakage Current DC Voltage LED Current Control Input Undervoltage Lockout Internal Output Over-Voltage Protection (OVP) Circuitry, with no External Zener Diode Required LM3501-16: 15.5V OVP; LM3501-21: 20.5V OVP. Requires Only a Small 16V (LM3501-16) or 25V (LM3501-21) Ceramic Capacitor at the Input and Output Thermal Shutdown 0.1µA shutdown Current Small 8-Bump Thin DSBGA Package LCD Bias Supplies White LED Back-Lighting Handheld Devices Digital Cameras Portable Applications DESCRIPTION The LM3501 is a fixed-frequency step-up DC/DC converter that is ideal for driving white LEDs for display backlighting and other lighting functions. With fully integrated synchronous switching (no external schottky diode required) and a low feedback voltage (515 mV), power efficiency of the LM3501 circuit has been optimized for lighting applications in wireless phones and other portable products (single cell Li-Ion or 3-cell NiMH battery supplies). The LM3501 operates with a fixed 1 MHz switching frequency. When used with ceramic input and output capacitors, the LM3501 provides a small, low-noise, low-cost solution. Typical Application Circuit L 22 PH VIN 2.7V - 5.5V Voltage Control B1 VIN A3 CIN 1PF Ceramic CNTRL LM3501-16 >1.1V <0.3V A2 C2 VSW VOUT COUT 1PF Ceramic C1 B3 SHDN FB AGND GND C3 A1 R2 24: Figure 1. Typical 3 LED Application 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 © 2003–2013, Texas Instruments Incorporated LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 www.ti.com DESCRIPTION (CONTINUED) Two LM3501 options are available with different output voltage capabilities. The LM3501-21 has a maximum output voltage of 21V and is typically suited for driving 4 or 5 white LEDs in series. The LM3501-16 has a maximum output voltage of 16V and is typically suited for driving 3 or 4 white LEDs in series (maximum number of series LEDs dependent on LED forward voltage). If the primary white LED network should be disconnected, the LM3501 uses internal protection circuitry on the output to prevent a destructive overvoltage event. A single external resistor is used to set the maximum LED current in LED-drive applications. The LED current can easily be adjusted by varying the analog control voltage on the control pin or by using a pulse width modulated (PWM) signal on the shutdown pin. In shutdown, the LM3501 completely disconnects the input from output, creating total isolation and preventing any leakage currents from trickling into the LEDs. Connection Diagram A2 A1 A3 B1 B3 C1 C3 C2 Figure 2. 8-Bump DSBGA Top View 2 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 PIN DESCRIPTIONS Pin Name Function A1 AGND B1 VIN C1 VOUT PMOS source connection for synchronous rectification. C2 VSW Switch pin. Drain connections of both NMOS and PMOS power devices. C3 GND Power Ground. B3 FB A3 CNTRL Analog LED current control. A2 SHDN Shutdown control pin. Analog ground. Analog and Power supply input. Output voltage feedback connection. AGND (pin A1): Analog ground pin The analog ground pin should tie directly to the GND pin. VIN (pin B1): Analog and Power supply pin Bypass this pin with a capacitor, as close to the device as possible, connected between the VIN and GND pins. VOUT (pin C1): Source connection of internal PMOS power device Connect the output capacitor between the VOUT and GND pins as close as possible to the device. VSW (pin C2): Drain connection of internal NMOS and PMOS switch devices Keep the inductor connection close to this pin to minimize EMI radiation. GND (pin C3): Power ground pin Tie directly to ground plane. FB (pin B3): Output voltage feedback connection Set the primary White LED network current with a resistor from the FB pin to GND. Keep the current setting resistor close to the device and connected between the FB and GND pins. CNTRL (pin A3): Analog control of LED current A voltage above 125 mV will begin to regulate the LED current. Decreasing the voltage below 75 mV will turn off the LEDs. SHDN (pin A2): Shutdown control pin Disable the device with a voltage less than 0.3V and enable the device with a voltage greater than 1.1V. The white LED current can be controlled using a PWM signal at this pin. There is an internal pull down on the SHDN pin, the device is in a normally off state. 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. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 3 LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 Absolute Maximum Ratings www.ti.com (1) (2) VIN −0.3V to 7.5V VOUT (LM3501-16) (3) −0.3V to 16V VOUT (LM3501-21) (3) VSW −0.3V to 21V (3) −0.3V to VOUT+0.3V −0.3V to 7.5V FB Voltage −0.3V to VIN+0.3V SHDN Voltage −0.3V to 7.5V CNTRL Maximum Junction Temperature 150°C Lead Temperature (Soldering 10 sec.) 300°C Vapor Phase (60 sec.) 215°C Infrared (15 sec.) ESD Ratings 220°C (4) Human Body Model 2kV Machine Model (1) (2) (3) (4) 200V Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended to be functional, but device parameter specifications may not be specified. For specifications and test conditions, see the Electrical Characteristics. Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. This condition applies if VIN < VOUT. If VIN > VOUT, a voltage greater than VIN + 0.3V should not be applied to the VOUT or VSW pins. 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. Operating Conditions Junction Temperature (1) −40°C to +125°C Supply Voltage 2.7V to 7V CNTRL Max. (1) 2.7V The maximum allowable power dissipation is a function of the maximum operating junction temperature, TJ(MAX), the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. See the Thermal Properties section for the thermal resistance. The maximum allowable power dissipation at any ambient temperature is calculated using: PD (MAX) = (TJ(MAX) − TA)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature. Thermal Properties Junction to Ambient Thermal Resistance (θJA) (1) 4 (1) 75°C/W Junction-to-ambient thermal resistance (θJA) is highly application and board-layout dependent. The 75ºC/W figure provided was measured on a 4-layer test board conforming to JEDEC standards. In applications where high maximum power dissipation exists, special care must be paid to thermal dissipation issues when designing the board layout. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 Electrical Characteristics Specifications in standard type face are for TA = 25°C and those in boldface type apply over the Operating Temperature Range of TA = −10°C to +85°C. Unless otherwise specified VIN = 2.7V and specifications apply to both LM3501-16 and LM3501-21. Symbol IQ VFB Parameter Conditions Min (1) Typ Max 0.95 1.2 2 2.5 0.1 2 (2) (1) Quiescent Current, Device Not Switching FB > 0.54V Quiescent Current, Device Switching FB = 0V Shutdown SHDN = 0V Feedback Voltage CNTRL = 2.7V, VIN = 2.7V to 7V 0.485 0.515 0.545 CNTRL = 1V, VIN = 2.7V to 7V 0.14 0.19 0.24 0.1 0.5 Units mA µA V ΔVFB Feedback Voltage Line Regulation VIN = 2.7V to 7V ICL Switch Current Limit (LM3501-16) VIN = 2.7V, Duty Cycle = 80% 275 400 480 VIN = 3.0V, Duty Cycle = 70% 255 400 530 VIN = 2.7V, Duty Cycle = 70% 420 640 770 VIN = 3.0V, Duty Cycle = 63% 450 670 800 45 200 nA 7.0 V Switch Current Limit (LM3501-21) FB Pin Bias Current VIN Input Voltage Range RDSON NMOS Switch RDSON VIN = 2.7V, ISW = 300 mA PMOS Switch RDSON VOUT = 6V, ISW = 300 mA Duty Cycle Limit (LM3501-16) FB = 0V Duty Cycle Limit (LM3501-21) FB = 0V DLimit FB = 0.5V FSW Switching Frequency ISD SHDN Pin Current ICNTRL IL UVP OVP (1) (2) (3) (4) (4) CNTRL Pin Current (4) mA (3) IB %/V 2.7 0.43 1.3 Ω 2.3 80 87 85 94 0.85 1.0 1.15 1.8 4 SHDN = 2.7V 1 2.5 SHDN = GND 0.1 VCNTRL = 2.7V 10 20 VCNTRL = 1V 4 15 % SHDN = 5.5V Switch Leakage Current (LM3501-16) VSW = 15V 0.01 0.5 Switch Leakage Current (LM3501-21) VSW = 20V 0.01 2.0 Input Undervoltage Lockout ON Threshold 2.4 2.5 2.6 OFF Threshold 2.3 2.4 2.5 Output Overvoltage Protection (LM3501-16) ON Threshold 15 15.5 16 OFF Threshold 14 14.6 15 Output Overvoltage Protection (LM3501-21) ON Threshold 20 20.5 21 OFF Threshold 19 19.5 20 MHz µA µA µA V V V All limits specified at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are production tested, specified through statistical analysis or specified by design. All limits at temperature extremes are specified via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25°C and represent the most likely norm. Feedback current flows out of the pin. Current flows into the pin. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 5 LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 www.ti.com Electrical Characteristics (continued) Specifications in standard type face are for TA = 25°C and those in boldface type apply over the Operating Temperature Range of TA = −10°C to +85°C. Unless otherwise specified VIN = 2.7V and specifications apply to both LM3501-16 and LM3501-21. Symbol IVout IVL Parameter Min (1) Typ Max (2) (1) VOUT Bias Current (LM3501-16) VOUT = 15V, SHDN = 1.5V 260 400 VOUT Bias Current (LM3501-21) VOUT = 20V, SHDN = 1.5V 300 460 PMOS Switch Leakage Current (LM3501-16) VOUT = 15V, VSW = 0V 0.01 3 PMOS Switch Leakage Current (LM3501-21) VOUT = 20V, VSW = 0V 0.01 3 CNTRL Threshold SHDN Threshold Conditions µA µA LED power off 75 LED power on 125 SHDN low 0.65 SHDN High Units 1.1 mV 0.3 0.65 V Specifications in standard type face are for TJ = 25°C and those in boldface type apply over the full Operating Temperature Range (TJ = −40°C to +125°C). Unless otherwise specified VIN =2.7V and specifications apply to both LM3501-16 and LM3501-21. Symbol IQ VFB Parameter Conditions Min (1) Typ Max 0.95 1.2 2 2.5 0.1 2 (2) Quiescent Current, Device Not Switching FB > 0.54V Quiescent Current, Device Switching FB = 0V Shutdown SHDN = 0V Feedback Voltage CNTRL = 2.7V, VIN = 2.7V to 7V 0.485 0.515 0.545 CNTRL = 1V, VIN = 2.7V to 7V 0.14 0.19 0.24 0.5 Feedback Voltage Line Regulation VIN = 2.7V to 7V 0.1 ICL Switch Current Limit (LM3501-16) VIN = 3.0V, Duty Cycle = 70% 400 Switch Current Limit (LM3501-21) VIN = 3.0V, Duty Cycle = 63% 670 IB FB Pin Bias Current FB = 0.5V VIN Input Voltage Range RDSON NMOS Switch RDSON VIN = 2.7V, ISW = 300 mA PMOS Switch RDSON VOUT = 6V, ISW = 300 mA Duty Cycle Limit (LM3501-16) FB = 0V Duty Cycle Limit (LM3501-21) FB = 0V FSW Switching Frequency ISD SHDN Pin Current (1) (2) (3) (4) 6 (4) Units mA ΔVFB DLimit (1) V %/V mA (3) 45 2.7 200 nA 7.0 V 0.43 1.3 2.3 Ω 87 % 94 0.8 1.0 1.2 1.8 4 SHDN = 2.7V 1 2.5 SHDN = GND 0.1 SHDN = 5.5V µA MHz µA All limits specified at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are production tested, specified through statistical analysis or specified by design. All limits at temperature extremes are specified via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25°C and represent the most likely norm. Feedback current flows out of the pin. Current flows into the pin. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 Specifications in standard type face are for TJ = 25°C and those in boldface type apply over the full Operating Temperature Range (TJ = −40°C to +125°C). Unless otherwise specified VIN =2.7V and specifications apply to both LM3501-16 and LM3501-21. Symbol ICNTRL IL UVP OVP IVout IVL CNTRL Pin Current (4) Max VCNTRL = 2.7V 10 20 VCNTRL = 1V 4 15 Conditions Min (1) (2) (1) Switch Leakage Current (LM3501-16) VSW = 15V 0.01 0.5 Switch Leakage Current (LM3501-21) VSW = 20V 0.01 2.0 Input Undervoltage Lockout ON Threshold 2.4 2.5 2.6 OFF Threshold 2.3 2.4 2.5 Output Overvoltage Protection (LM3501-16) ON Threshold 15 15.5 16 OFF Threshold 14 14.6 15 Output Overvoltage Protection (LM3501-21) ON Threshold 20 20.5 21 OFF Threshold 19 19.5 20 VOUT Leakage Current (LM3501-16) VOUT = 15V, SHDN = 1.5V 260 400 VOUT Leakage Current (LM3501-21) VOUT = 20V, SHDN = 1.5V 300 460 PMOS Switch Leakage Current (LM3501-16) VOUT = 15V, VSW = 0V 0.01 3 PMOS Switch Leakage Current (LM3501-21) VOUT = 20V, VSW = 0V 0.01 3 CNTRL Threshold SHDN Threshold Typ Parameter LED power on 125 SHDN low 0.65 1.1 V V mV 0.3 0.65 Submit Documentation Feedback Product Folder Links: LM3501 µA µA 75 Copyright © 2003–2013, Texas Instruments Incorporated µA µA LED power off SHDN High Units V 7 LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics 8 Switching Quiescent Current vs. VIN Non-Switching Quiescent Current vs. VIN Figure 3. Figure 4. 2 LED Efficiency vs. Load Current L = Coilcraft DT1608C-223, Efficiency = 100*(PIN/(2VLED*ILED)) 3 LED Efficiency vs. Load Current L = Coilcraft DT1608C-223, Efficiency = 100*(PIN/(3VLED*ILED)) Figure 5. Figure 6. 4 LED Efficiency vs. Load Current L = Coilcraft DT1608C-223, Efficiency = 100*(PIN/(4VLED*ILED)) Output Power vs. VIN (LM3501-16, L = Coilcraft DT1608C-223) Figure 7. Figure 8. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 Typical Performance Characteristics (continued) Output Power vs. Temperature (LM3501-16, L = Coilcraft DT1608C-223) FB Pin Current vs. Temperature Figure 9. Figure 10. SHDN Pin Current vs. SHDN Pin Voltage CNTRL Pin Current vs. CNTRL Pin Voltage Figure 11. Figure 12. FB Voltage vs. CNTRL Voltage Switch Current Limit vs. VIN (LM3501-16) Figure 13. Figure 14. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 9 LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) Switch Current Limit vs. Temperature (LM3501-16, VOUT = 8V) Switch Current Limit vs. Temperature (LM3501-16, VOUT = 12V) Figure 15. Figure 16. Switch Current Limit vs. VIN (LM3501-21) Switch Current Limit vs. Temperature (LM3501-21, VOUT = 8V) 1300 1100 1200 VOUT = 8V 900 UT VO 800 =1 2V CURRENT LIMIT (mA) CURRENT LIMIT (mA) 1000 700 600 UT =1 5V VO 500 400 VOUT = 18V 3.0 3.5 4.0 4.5 5.0 5.5 6.0 1000 VIN = 4.2V 900 800 700 600 300 200 2.5 VIN = 5.5V 1100 VIN = 3.0V 500 -40 6.5 -15 INPUT VOLTAGE (V) 35 60 Figure 17. Figure 18. Switch Current Limit vs. Temperature (LM3501-21, VOUT = 12V) Switch Current Limit vs. Temperature (LM3501-21, VOUT = 18V) 850 85 440 800 420 VIN = 5.5V V IN = 5.5V 400 750 CURRENT LIMIT (mA) CURRENT LIMIT (mA) 10 TEMPERATURE (ºC) 700 650 VIN = 4.2V 600 550 V IN = 3.0V 380 360 340 V IN = 4.2V 320 300 280 500 450 -40 VIN = 3.0V -15 10 35 260 60 85 -15 10 35 60 85 TEMPERATURE °C TEMPERATURE (ºC) Figure 19. 10 240 -40 Figure 20. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 Typical Performance Characteristics (continued) Oscillator Frequency vs. VIN VOUT DC Bias vs. VOUT Voltage (LM3501-16) Figure 21. Figure 22. FB Voltage vs. Temperature FB Voltage vs. Temperature Figure 23. Figure 24. FB Voltage vs. VIN NMOS RDSON vs. VIN (ISW = 300 mA) Figure 25. Figure 26. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 11 LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) PMOS RDSON vs. Temperature Typical VIN Ripple 3 LEDs, RLED = 22Ω, VIN = 3.0V, CNTRL = 2.7V 1) SW, 10 V/div, DC 3) IL, 100 mA/div, DC 4) VIN, 100 mV/div, AC T = 250 ns/div Figure 28. Figure 27. Start-Up (LM3501-16) SHDN Pin Duty Cycle Control Waveforms 3 LEDs, RLED = 22Ω, VIN = 3.0V, CNTRL = 2.7V 1) SHDN, 1 V/div, DC 2) IL, 100 mA/div, DC 3) ILED, 20 mA/div, DC T = 100 µs/div LM3501-16, 3 LEDs, RLED = 22Ω, VIN = 3.0V, SHDN frequency = 200 Hz 1) SHDN, 1 V/div, DC 2) IL, 100 mA/div, DC 3) ILED, 20 mA/div, DC 4) VOUT, 10 V/div, DC T = 1 ms/div Figure 30. Figure 29. Typical VOUT Ripple, OVP Functioning (LM3501-16) Typical VOUT Ripple, OVP Functioning (LM3501-21) T 1 VOUT open circuit and equals approximately 15V DC, VIN = 3.0V 3) VOUT, 200 mV/div, AC T = 1 ms/div Figure 31. 12 VOUT open circuit and equals approximately 20V DC, VIN = 3.0V 1) VOUT, 200 mV/div, AC T = 400 µs/div Figure 32. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 Operation L VIN B1 VIN C2 UVP REF UVP COMP THERMAL SHUTDOWN + REF + OVP COMP LIGHT LOAD COMP VSW VOUT C1 + - OVP REF x CIN FB B3 COUT Reset Reset Reset Reset DriveP - LOGIC PWM COMP + EAMP + Reset SET Reset DriveN Reset Body Diode Control + Current Sense osc FB R LED CNTRL A3 + Dlimit A1 Duty Limit Comp SHUTDOWN COMP - A2 AGND SHDN C3 GND Figure 33. LM3501 Block Diagram The LM3501 utilizes a synchronous Current Mode PWM control scheme to regulate the feedback voltage over almost all load conditions. The DC/DC controller acts as a controlled current source ideal for white LED applications. The LM3501 is internally compensated thus eliminating the requirement for any external compensation components providing a compact overall solution. The operation can best be understood referring to the block diagram in Figure 33. At the start of each cycle, the oscillator sets the driver logic and turns on the NMOS power device conducting current through the inductor and turns off the PMOS power device isolating the output from the VSW pin. The LED current is supplied by the output capacitor when the NMOS power device is active. During this cycle, the output voltage of the EAMP controls the current through the inductor. This voltage will increase for larger loads and decrease for smaller loads limiting the peak current in the inductor minimizing EMI radiation. The EAMP voltage is compared with a voltage ramp and the sensed switch voltage. Once this voltage reaches the EAMP output voltage, the PWM COMP will then reset the logic turning off the NMOS power device and turning on the PMOS power device. The inductor current then flows through the PMOS power device to the white LED load and output capacitor. The inductor current recharges the output capacitor and supplies the current for the white LED branches. The oscillator then sets the driver logic again repeating the process. The Duty Limit Comp is always operational preventing the NMOS power switch from being on more than one cycle and conducting large amounts of current. The LM3501 has dedicated protection circuitry active during normal operation to protect the IC and the external components. The Thermal Shutdown circuitry turns off both the NMOS and PMOS power devices when the die temperature reaches excessive levels. The LM3501 has a UVP Comp that disables both the NMOS and PMOS power devices when battery voltages are too low preventing an on state of the power devices which could conduct large amounts of current. The OVP Comp prevents the output voltage from increasing beyond 15.5V (LM3501-16) and 20.5V (LM3501-21) when the primary white LED network is removed or if there is an LED failure, allowing the use of small (16V for LM3501-16 and 25V for LM3501-21) ceramic capacitors at the output. This comparator has hysteresis that will regulate the output voltage between 15.5V and 14.6V typically for the LM3501-16, and between 20.5V and 19.5V for the LM3501-21. The LM3501 features a shutdown mode that reduces the supply current to 0.1 uA and isolates the input and output of the converter. The CNTRL pin can be used to change the white LED current. A CNTRL voltage above 125 mV will enable power to the LEDs and a voltage lower than 75 mV will turn off the power to the LEDs. Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 13 LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 www.ti.com APPLICATION INFORMATION ADJUSTING LED CURRENT The maximum White LED current is set using the following equation: ILED = VFB(MAX)/RLED (1) The LED current can be controlled using an external DC voltage. The recommended operating range for the voltage on the CNTRL pin is 0V to 2.7V. When CNTRL is 2.7V, FB = 0.515V (typ.) The FB voltage will continue to increase if CNTRL is brought above 2.7V (not recommended). The CNTRL to FB voltage relationship is: FB = 0.191*CNTRL (2) The LED current can be controlled using a PWM signal on the SHDN pin with frequencies in the range of 100 Hz (greater than visible frequency spectrum) to 1 kHz. For controlling LED currents down to the µA levels, it is best to use a PWM signal frequency between 200-500 Hz. The LM3501 LED current can be controlled with PWM signal frequencies above 1 kHz but the controllable current decreases with higher frequency. The maximum LED current would be achieved using the equation above with 100% duty cycle, ie. the SHDN pin always high. Applying a voltage greater than 125 mV to the CNTRL pin will begin regulating current to the LEDs. A voltage below 75 mV will prevent application or regulation of the LED current. LED-DRIVE CAPABILITY The maximum number of LEDs that can be driven by the LM3501 is limited by the output voltage capability of the LM3501. When using the LM3501 in the typical application configuration, with LEDs stacked in series between the VOUT and FB pins, the maximum number of LEDs that can be placed in series (NMAX) is dependent on the maximum LED forward voltage (VF-MAX), the voltage of the LM3501 feedback pin (VFB-MAX = 0.545V), and the minimum output overvoltage protection level of the chosen LM3501 option (LM3501-16: OVPMIN = 15V; LM350121: OVPMIN = 20V). For the circuit to function properly, the following inequality must be met: (NMAX x VF-MAX) + 0.545V ≤ OVPMIN (3) When inserting a value for maximum LED VF, LED forward voltage variation over the operating temperature range should be considered. The table below provides maximum LED voltage numbers for the LM3501-16 and LM3501-21 in the typical application circuit configuration (with 3, 4, 5, 6, or 7 LEDs placed in series between the VOUT and FB pins). Maximum LED VF # of LEDs (in series) LM3501-16 LM3501-21 3 4.82V 6.49V 4 3.61V 4.86V 5 2.89V 3.89V 6 X 3.24V 7 X 2.78V For the LM3501 to operate properly, the output voltage must be kept above the input voltage during operation. For most applications, this requires a minimum of 2 LEDs (total of 6V or more) between the FB and VOUT pins. OUTPUT OVERVOLTAGE PROTECTION The LM3501 contains dedicated circuitry for monitoring the output voltage. In the event that the primary LED network is disconnected from the LM3501-16, the output voltage will increase and be limited to 15.5V (typ.). There is a 900 mV hysteresis associated with this circuitry which will cause the output to fluctuate between 15.5V and 14.6V (typ.) if the primary network is disconnected. In the event that the network is reconnected regulation will begin at the appropriate output voltage. The 15.5V limit allows the use of 16V 1 µF ceramic output capacitors creating an overall small solution for white LED applications. 14 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 In the event that the primary LED network is disconnected from the LM3501-21, the output voltage will increase and be limited to 20.5V (typ.). There is a 1V hysteresis associated with this circuitry which will cause the output to fluctuate between 20.5V and 19.5V (typ.) if the primary network is disconnected. In the event that the network is reconnected regulation will begin at the appropriate output voltage. The 20.5V limit allows the use of 25V 1 µF ceramic output capacitors. RELIABILITY AND THERMAL SHUTDOWN The maximum continuous pin current for the 8 pin thin DSBGA package is 535 mA. When driving the device near its power output limits the VSW pin can see a higher DC current than 535 mA (see INDUCTOR SELECTION section for average switch current). To preserve the long term reliability of the device the average switch current should not exceed 535 mA. The LM3501 has an internal thermal shutdown function to protect the die from excessive temperatures. The thermal shutdown trip point is typically 150°C. There is a hysteresis of typically 35°C so the die temperature must decrease to approximately 115°C before the LM3501 will return to normal operation. INDUCTOR SELECTION The inductor used with the LM3501 must have a saturation current greater than the cycle by cycle peak inductor current (see Table 1 below). Choosing inductors with low DCR decreases power losses and increases efficiency. The minimum inductor value required for the LM3501-16 can be calculated using the following equation: L> VIN RDSON D -1 D' 0.29 (4) The minimum inductor value required for the LM3501-21 can be calculated using the following equation: L> VIN RDSON D -1 D' 0.58 (5) For both equations above, L is in µH, VIN is the input supply of the chip in Volts, RDSON is the ON resistance of the NMOS power switch found in Typical Performance Characteristics in ohms and D is the duty cycle of the switching regulator. The above equation is only valid for D greater than or equal to 0.5. For applications where the minimum duty cycle is less than 0.5, a 22 µH inductor is the typical recommendation for use with most applications. Bench-level verification of circuit performance is required in these special cases, however. The duty cycle, D, is given by the following equation: VIN =1-D D' = V OUT (6) where VOUT is the voltage at pin C1. Table 1. Typical Peak Inductor Current (mA) (1) VIN (V) # LEDs (in series) 2.7 3.3 (1) LED Current 15 mA 20 mA 30 mA 40 mA 50 mA 60 mA 2 82 100 134 160 204 234 3 118 138 190 244 294 352 4 142 174 244 322 X X 5 191 232 319 413 X X 2 76 90 116 136 172 198 3 110 126 168 210 250 290 4 132 158 212 270 320 X 5 183 216 288 365 446 X CIN = COUT = 1 μF, L = 22 μH, 160 mΩ DCR max. Coilcraft DT1608C-2232 and 3 LED applications: LM3501-16 or LM3501-21; LED VF = 3.77V at 20mA; TA = 25°C4 LED applications: LM3501-16 or LM3501-21; LED VF = 3.41V at 20mA; TA = 25°C5 LED applications: LM3501-21 only; LED VF = 3.28V at 20mA; TA = 25°C Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 15 LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 www.ti.com Table 1. Typical Peak Inductor Current (mA)(1) (continued) LED Current VIN (V) # LEDs (in series) 4.2 2 64 3 102 4 122 5 179 15 mA 20 mA 30 mA 40 mA 50 mA 60 mA 76 96 116 142 162 116 148 180 210 246 146 186 232 272 318 206 263 324 388 456 The typical cycle-by-cycle peak inductor current can be calculated from the following equation: IPK | IOUT KD' + VIND 2LFSW (7) where IOUT is the total load current, FSW is the switching frequency, L is the inductance and η is the converter efficiency of the total driven load. A good typical number to use for η is 0.8. The value of η can vary with load and duty cycle. The average inductor current, which is also the average VSW pin current, is given by the following equation: IL(AVE) | IOUT KD' (8) The maximum output current capability of the LM3501 can be estimated with the following equation: IOUT | KD' ICL - VIND 2LFSW (9) where ICL is the current limit. Some recommended inductors include but are not limited to: Coilcraft DT1608C series Coilcraft DO1608C series TDK VLP4612 series TDK VLP5610 series TDK VLF4012A series CAPACITOR SELECTION Choose low ESR ceramic capacitors for the output to minimize output voltage ripple. Multilayer X7R or X5R type ceramic capacitors are the best choice. For most applications, a 1 µF ceramic output capacitor is sufficient. Local bypassing for the input is needed on the LM3501. Multilayer X7R or X5R ceramic capacitors with low ESR are a good choice for this as well. A 1 µF ceramic capacitor is sufficient for most applications. However, for some applications at least a 4.7 µF ceramic capacitor may be required for proper startup of the LM3501. Using capacitors with low ESR decreases input voltage ripple. For additional bypassing, a 100 nF ceramic capacitor can be used to shunt high frequency ripple on the input. Some recommended capacitors include but are not limited to: TDK C2012X7R1C105K Taiyo-Yuden EMK212BJ105 G LAYOUT CONSIDERATIONS The input bypass capacitor CIN, as shown in Figure 33, must be placed close to the device and connect between the VIN and GND pins. This will reduce copper trace resistance which effects the input voltage ripple of the IC. For additional input voltage filtering, a 100 nF bypass capacitor can be placed in parallel with CIN to shunt any high frequency noise to ground. The output capacitor, COUT, should also be placed close to the LM3501 and connected directly between the VOUT and GND pins. Any copper trace connections for the COUT capacitor can increase the series resistance, which directly effects output voltage ripple and efficiency. The current setting 16 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 resistor, RLED, should be kept close to the FB pin to minimize copper trace connections that can inject noise into the system. The ground connection for the current setting resistor should connect directly to the GND pin. The AGND pin should connect directly to the GND pin. Not connecting the AGND pin directly, as close to the chip as possible, may affect the performance of the LM3501 and limit its current driving capability. Trace connections made to the inductor should be minimized to reduce power dissipation, EMI radiation and increase overall efficiency. It is good practice to keep the VSW routing away from sensitive pins such as the FB pin. Failure to do so may inject noise into the FB pin and affect the regulation of the device. See Figure 34 and Figure 35 for an example of a good layout as used for the LM3501 evaluation board. Figure 34. Evaluation Board Layout (2X Magnification) Top Layer Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 17 LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 www.ti.com Figure 35. Evaluation Board Layout (2X Magnification) Bottom Layer (as viewed from the top) L 22 PH VIN 2.7V - 5.5V Voltage Control B1 VIN A3 CIN 1PF Ceramic C2 VSW CNTRL LM3501-16 >1.1V <0.3V A2 VOUT COUT 1PF Ceramic C1 B3 SHDN FB AGND GND C3 A1 R2 24: Figure 36. 2 White LED Application 18 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 L 22 PH VIN 2.7V - 5.5V Voltage Control B1 C2 VIN A3 CIN 1 PF Ceramic VSW COUT 1 PF Ceramic VOUT C1 CNTRL LM3501-16 >1.1V <0.3V A2 B3 SHDN FB AGND GND C3 A1 Control with DC voltage, NMOS FET switch, or tie directly to ground. R2 R1 24: Figure 37. Multiple 2 LED String Application L 22 PH VIN 2.7V - 5.5V Voltage Control B1 C2 VIN A3 CIN 1 PF Ceramic >1.1V <0.3V A2 VSW CNTRL VOUT LM3501-16 C1 COUT 1 PF Ceramic B3 SHDN FB AGND GND C3 A1 R1 24: R2 24: Figure 38. Multiple 3 LED String Application Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 19 LM3501 SNVS230C – DECEMBER 2003 – REVISED MAY 2013 www.ti.com L 22 PH VIN 2.7V - 5.5V Voltage Control B1 C2 VIN A3 CIN 1 PF Ceramic >1.1V <0.3V A2 VSW CNTRL VOUT LM3501-21 C1 COUT 1 PF Ceramic B3 SHDN FB AGND GND A1 C3 R2 24: Figure 39. LM3501-21 5 LED Application 20 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 LM3501 www.ti.com SNVS230C – DECEMBER 2003 – REVISED MAY 2013 REVISION HISTORY Changes from Revision B (May 2013) to Revision C • Page Changed layout of National Data Sheet to TI format .......................................................................................................... 20 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated Product Folder Links: LM3501 21 PACKAGE OPTION ADDENDUM www.ti.com 16-Oct-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) LM3501TL-16/NOPB ACTIVE DSBGA YZR 8 250 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85 S 19 LM3501TL-21/NOPB LIFEBUY DSBGA YZR 8 250 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85 S 30 LM3501TLX-21/NOPB LIFEBUY DSBGA YZR 8 3000 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85 S 30 (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. 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 Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 16-Oct-2015 continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 2-Sep-2015 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) LM3501TL-16/NOPB DSBGA YZR 8 250 178.0 8.4 LM3501TL-21/NOPB DSBGA YZR 8 250 178.0 LM3501TLX-21/NOPB DSBGA YZR 8 3000 178.0 2.08 2.08 0.76 4.0 8.0 Q1 8.4 2.08 2.08 0.76 4.0 8.0 Q1 8.4 2.08 2.08 0.76 4.0 8.0 Q1 Pack Materials-Page 1 W Pin1 (mm) Quadrant PACKAGE MATERIALS INFORMATION www.ti.com 2-Sep-2015 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM3501TL-16/NOPB DSBGA YZR 8 250 210.0 185.0 35.0 LM3501TL-21/NOPB DSBGA YZR 8 250 210.0 185.0 35.0 LM3501TLX-21/NOPB DSBGA YZR 8 3000 210.0 185.0 35.0 Pack Materials-Page 2 MECHANICAL DATA YZR0008xxx D 0.600±0.075 E TLA08XXX (Rev C) D: Max = 1.972 mm, Min =1.911 mm E: Max = 1.972 mm, Min =1.911 mm 4215045/A NOTES: A. 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