TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 CONSTANT CURRENT LED DRIVER WITH DIGITAL AND PWM BRIGHTNESS CONTROL • • • FEATURES • • • • • • • • • • • • LED Driver With Integrated Overvoltage and Short-Circuit Protection 2.7-V to 6.0-V Input Voltage Range 500-mV/250-mV Feedback Voltage TPS61060 Powers Up to 3 LEDs TPS61061 Powers Up to 4 LEDs TPS61062 Powers Up to 5 LEDs PWM Brightness Control on Enable Digital Brightness Control on ILED 1.0-MHz Fixed Switching Frequency 400-mA Internal Power MOSFET Switch LEDs Disconnected During Shutdown Operates With Small-Output Capacitors Down to 220 nF Up to 80% Efficiency 8-Pin NanoFree™Package (Chipscale, CSP) 3 × 3-mm QFN Package APPLICATIONS • • • • • White LED Driver Cellular Phones PDA, Pocket PC, and Smart Phones Digital Still Camera Handheld Devices DESCRIPTION The TPS61060/61/62 is a high-frequency, synchronous boost converter with constant current output to drive up to 5 white LEDs. For maximum safety, the device features integrated overvoltage and an advanced short-circuit protection when the output is shorted to ground. The device operates with 1-MHz fixed switching frequency to allow small external components and to simplify possible EMI problems. The device comes with three different overvoltage protection thresholds (14 V/18 V/23 V) to allow inexpensive and small-output capacitors with lower voltage ratings. The LED current is initially set with the external sense resistor Rs, and the feedback voltage is regulated to 500 mV or 250 mV, depending on the ILED pin configuration. Digital brightness control is implemented by applying a simple digital signal to the ILED pin. Alternatively, a PWM signal up to 1 kHz can be applied to the enable pin to control the LED brightness. During shutdown, the output is disconnected from the input to avoid leakage current through the LEDs. TYPICAL APPLICATION C2 220 nF VIN 2.7 V to 6 V L1 22 H C1 1 F VIN SW EN OUT ILED FB GND PGND RS 12 Figure 1. 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. NanoFree, PowerPAD are trademarks of Texas Instruments. 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 © 2004, Texas Instruments Incorporated TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 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. ORDERING INFORMATION OVERVOLTAGE PROTECTION (OVP) TA –40 to 85°C (1) PACKAGE PACKAGE MARKING NanoFree QFN NanoFree (1) QFN (2) 14 V (min) TPS61060YZF TPS61060DRB AKX AQP 18 V (min) TPS61061YZF TPS61061DRB AKY AQQ 22.2 V (min) TPS61062YZF TPS61062DRB AKZ AQR The YZF package is available in tape and reel. Add R suffix (TPS61060YZFR) to order quantities of 3000 parts per reel or add T suffix (TPS61060YZFT) to order 250 parts per reel. The DRB package is available in tape and reel. Add R suffix (TPS61060DRBR) to order quantities of 3000 parts per reel. (2) 8-Pin NanoFree Package Top View 8-Pin 3x3-mm QFN Package Top View Pin A1 1 Index 2 8 Vin GND 1 3 EN 2 ILED 3 A FB 4 Exposed Thermal DiePad 7 OUT 6 SW 5 PGND B C TERMINAL FUNCTIONS TERMINAL NAME NO. I/O DESCRIPTION CSP QFN VIN B1 8 I Input supply pin of the device EN A2 2 I Enable pin. This pin needs to be pulled high to enable the device. To allow brightness control of the LEDs a PWM signal up to 1 kHz can be applied. This pin has an internal pulldown resistor. GND A1 1 Analog ground PGND C3 5 Power ground FB B3 4 I This is the feedback pin of the device. The feedback pin regulates the LED current through the sense resistor by regulating the voltage across Rs. The feedback voltage is set by the ILED pin. ILED=GND sets the feedback voltage to 500 mV. ILED=high sets the feedback voltage to 250 mV. Refer to digital brightness control section for more information. OUT C1 7 O Output of the device SW C2 6 I Switch pin of the device I Digital brightness control input. When this pin is grounded the digital brightness control is disabled. When this pin is connected to high then the feedback voltage is reduced to typically 250 mV and the digital brightness control is enabled. Refer to digital brightness control section for more information. ILED PowerPAD™ 2 A3 3 – – The PowerPAD™ (exposed thermal diepad) is only available on the QFN package. The PowerPAD™ needs to be connected and soldered to analog ground (GND). TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 FUNCTIONAL BLOCK DIAGRAM SW Q2 Pre-Charge Current/PWM Short-Circuit Detection VIN 50-mS Turnoff Delay EN Bias Vref = 1.22 V Thermal Shutdown UVLO OUT OVP Oscillator 1 MHz Error Amplifier EN Vref Control Logic Gate Drive Circuit FB EN Comparator EN Σ EN Q1 Current Limit Current Sense Ramp Compensation GND PGND Vref = 1.22 V ILED = High VFB = 250 mV ILED = Low VFB = 500 mV ILED Programmed VFB = 15.6 mV to 500 mV 5-Bit DAC 15.6 mV/Step Digital Interface ILED ABSOLUTE MAXIMUM RATINGS (1) over operating free-air temperature range (unless otherwise noted) UNIT VIN (2) Supply voltages on pin –0.3 V to 7 V EN, ILED, FB (2) Voltages on pins –0.3 V to 7 V OUT (2) Voltage on pin SW (2) Voltage on pin Continuous power dissipation (2) 33 V See Dissipation Rating Table Operating junction temperature range –40°C to 150°C Storage temperature range –55°C to 150°C Lead temperature (soldering, 10 sec) (1) 33 V 260°C Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. All voltage values are with respect to network ground terminal. 3 TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 DISSIPATION RATINGS (1) (2) (3) (4) PACKAGE RθJA TA≤ 25°C POWER RATING TA = 70° C POWER RATING TA = 85°C POWER RATING QFN (1) 270°C/W 370 mW 204 mW 148 mW QFN (2) 60°C/W 1.6W 916mW 666mW CSP (3) 220°C/W 454 mW 250 mW 181 mW CSP (4) 110°C/W 909 mW 500mW 363 mW Soldered PowerPAD on a standard 2-layer PCB without vias for thermal pad. Soldered PowerPAD on a standard 4-layer PCB with vias for thermal pad. Rθ is based on a 1-layer PCB according to JEDEC standard. Rθ is based on a 2-layer PCB according to JEDEC standard. Refer to application section on how to improve thermal resistance RθJA. RECOMMENDED OPERATING CONDITIONS MIN TYP L Inductor (1) CI Input capacitor (1) CO Output capacitor (1) TA Operating ambient temperature -40 85 °C TJ Operating junction temperature -40 125 °C MAX UNIT 0.22 6.0 UNIT Input voltage range (1) 2.7 MAX VI V 22 µH 1 µF 1 µF Refer to application section for further information ELECTRICAL CHARACTERISTICS Vin = 3.6 V, EN = VIN, TA= –40°C to 85°C, typical values are at TA = 25°C (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP SUPPLY CURRENT VIN Input voltage range IQ Operating quiescent current into Vin Device not switching 2.7 ISD Shutdown current EN = GND VUVLO Undervoltage lockout threshold VIN falling VHYS Undervoltage lockout hysteresis 6.0 V 1 mA 1 10 µA 1.65 1.8 50 V mV ENABLE AND ILED VEN Enable high-level voltage VIN = 2.7 V to 6.0 V VEN Enable low-level voltage VIN = 2.7 V to 6.0 V REN Enable pulldown resistor tshtdn Enable-to-shutdown delay (1) EN = high to low tPWML PWM low-level signal time (1) PWM signal applied to EN VILED ILED high-level voltage VIN = 2.7 V to 6.0 V VILED ILED low-level voltage VIN = 2.7 V to 6.0 V IILED ILED input leakage current ILED = GND or VIN DAC resolution 5 Bit tup Increase feedback voltage one step ILED = high to low 1 75 us tdown Decrease feedback voltage one step ILED = high to low 180 300 us tdelay Delay time between up/down steps ILED = low to high 1.5 us toff Digital programming off, VFB=500mV ILED = high to low 720 us (1) 4 1.2 V 0.4 200 300 V kΩ 50 ms 25 ms 1.2 V 0.4 0.1 3 15.6 V µA mV A PWM low signal applied to EN for a period of time (≥25 ms) could cause a device shutdown. After a period of ≥50 ms the device definitely enters shutdown mode. TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 1 1.5 uA FEEDBACK FB IFB Feedback input bias current VFB = 500 mV VFB Feedback regulation voltage ILED = GND, after start-up 485 500 515 mV VFB Feedback regulation voltage ILED = High, after start-up 240 250 260 mV POWER SWITCH SYNCHRONOUS RECTIFIER AND CURRENT LIMIT (SW) P-channel MOSFET on-resistance VO = 10 V, Isw = 10 mA 2.5 3.7 Ω N-channel MOSFET on-resistance VIN = VGS = 3.6 V, Isw = 100 mA 0.6 0.9 Ω N-channel MOSFET on-resistance VIN = VGS = 2.7 V, Isw = 100 mA 0.7 1.0 Ω Iswleak Switch leakage current VIN = VSW=6.0 V, VOUT = GND, EN=GND 0.1 2 µA ISW N-Channel MOSFET current limit VO = 10 V 325 400 475 mA 0.8 1.0 1.2 MHz rDS(ON) RDS(ON) OSCILLATOR fs Switching frequency OUTPUT Vovp Output overvoltage protection VO rising; TPS61060 14 14.5 16 V Vovp Output overvoltage protection VO rising; TPS61061 18 18.5 19.8 V Vovp Output overvoltage protection VO rising; TPS61062 22.2 23.5 25 V Vovp Output overvoltage protection hysteresis TPS61060/61/62, VO falling Vo Output voltage threshold for short-circuit detection Vo Output voltage threshold for short-circuit detection 0.7 V VO falling VIN–0.7 V VO rising VIN–0.3 V Start-up, EN = low to high, OUT = GND Ipre Pre-charge current and short circuit current VIN = 6 V VIN = 3.6 V 180 VIN = 2.7 V D mA 95 65 Maximum duty cycle 95% TYPICAL CHARACTERISTICS Table of Graphs FIGURE η Efficiency vs LED current; 2 LEDs, ILED = high 2 vs LED current; 3 LEDs, ILED = low 3 vs LED current; 3 LEDs, ILED = high 4 vs LED current; 4 LEDs, ILED = low 5 vs LED current; 4 LEDs, ILED = high 6 vs LED current; 5 LEDs, ILED = high 7 PWM dimming 8 Digital brightness control Feedback voltage vs ILED programming step 9 LED current vs PWM duty cycle 10 Soft-start operation 11 Short-circuit protection 12 Overvoltage protection 13 Input voltage ripple 14 5 TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 EFFICIENCY vs LED CURRENT EFFICIENCY vs LED CURRENT 90 90 80 3 LEDS, ILED = Low, VOUT = 10.9 V 80 VIN = 4.2 V VIN = 4.2 V VIN = 3.6 V VIN = 3 V 60 50 40 VIN = 3 V 60 50 40 2 LEDS, ILED = High, VOUT= 7.33 V 30 20 VIN = 3.6 V 70 Efficiency − % Efficiency − % 70 0 10 20 30 40 50 30 20 0 60 10 90 Figure 2. Figure 3. EFFICIENCY vs LED CURRENT EFFICIENCY vs LED CURRENT VIN = 4.2 V 4 LEDS, ILED = Low, VOUT = 14.3 V 80 VIN = 3.6 V 60 50 50 30 30 20 20 LED Current − mA Figure 4. 6 60 40 10 30 40 VIN = 4.2 V VIN = 3 V 40 0 40 VIN = 3.6 V 70 VIN = 3 V Efficiency − % Efficiency − % 70 20 30 90 3 LEDS, ILED = High, VOUT = 10.8 V 80 20 LED Current − mA LED Current − mA 0 5 10 15 20 LED Current − mA Figure 5. 25 30 TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 EFFICIENCY vs LED CURRENT EFFICIENCY vs LED CURRENT 90 90 4 LEDS, ILED = High, VOUT = 14.3 V 80 VIN = 4.2 V 80 VIN = 3.6 V 60 50 30 30 10 15 20 LED Current − mA 25 VIN = 3 V 50 40 5 VIN = 3.6 V 60 40 0 VIN = 4.2 V 70 VIN = 3 V Efficiency − % Efficiency − % 70 20 5 LEDS, ILED = High, VOUT = 17.8 V 20 30 0 5 10 15 LED Current − mA 20 Figure 6. Figure 7. PWM DIMMING DIGITAL BRIGHTNESS CONTROL FEEDBACK VOLTAGE vs ILED PROGRAMMING STEP 25 600 550 C1 Frequency 199.9991 Hz Low Signal Amplitude Inductor Current 100 mA/div LED Current 20 mA/div 1 ms/div 500 VFB − Voltage Feedback − mV EN 2 V/div Stepsize typ = 15.6 mV 450 400 350 300 250 200 150 100 50 0 Figure 8. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 ILED − Programming Step Figure 9. 7 TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 LED CURRENT vs PWM DUTY CYCLE SOFT-START OPERATION 22 20 EN 2 V/div LED Current − mA 18 16 14 f = 1 kHz LED Current 20 mA/div 12 10 8 f = 500 Hz 6 Inductor Current 100 mA/div 4 f = 100 Hz 2 0 100 s/div 0 10 20 30 40 50 60 70 80 90 100 PWM − Duty Cycle − % Figure 10. Figure 11. SHORT-CIRCUIT PROTECTION OVERVOLTAGE PROTECTION TPS61062 SW 20 V/div SW 20 V/div Output Voltage 20 V/div Inductor Current 200 mA/div Output Voltage 2 V/div 17 V DC Offset 20 s/div Figure 12. 8 500 s/div Figure 13. TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 INPUT VOLTAGE RIPPLE SW 10 V/div Input Voltage 20 mV/div 500 ns/div Figure 14. DETAILED DESCRIPTION OPERATION The TPS61060/61/62 family is a constant-frequency, PWM current-mode converter with integrated N-channel MOSFET switch and synchronous P-channel MOSFET rectifier. The device operates in pulse width modulation (PWM) with a fixed switching frequency of 1 MHz. Operation is understood best by referring to the block diagram. The duty cycle of the converter is set by the error amplifier and the sawtooth ramp applied to the comparator. Because the control architecture is based on a current-mode control, a compensation ramp is added to allow stable operation for duty cycles larger than 50%. The converter is a fully integrated synchronous boost converter operating always in continuous conduction mode. This allows low noise operation and avoids ringing on the switch pin as it would be seen on a converter when entering discontinuous conduction mode. START-UP To avoid high inrush current during start-up, special care is taken to control the inrush current. When the device is first enabled, the output capacitor is charged with a constant precharge current of typically 100 mA until the output voltage is typically 0.3 V below Vin. The the device starts with a reduced analog controlled current limit for typically 40 µs. After this time period, the device enters its normal regulation with full current limit. The start-up current waveform is shown in Figure 11. The fixed precharge current during start-up allows the device to start up without problems when driving LEDs because the LED only starts to conduct current when the forward voltage is reached. If, for any reason a resistive load is driven, the maximum start-up load current needs to be smaller, or equal to, the precharge current. SHORT-CIRCUIT PROTECTION The TPS6106x family has an advanced short-circuit protection in case the output of the device is shorted to ground. Because the device is configured as a current source even when the LEDs are shorted, the maximum current is controlled by the sense resistor Rs. As an additional safety feature, the TPS6106x series also protects the device and inductor when the output is shorted to ground. When the output is shorted to ground, the device enters precharge mode and limits the maximum current to typically 100 mA. 9 TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 DETAILED DESCRIPTION (continued) OVERVOLTAGE PROTECTION (OVP) As with any current source, the output voltage rises when the output gets high impedance or disconnected. To prevent the output voltage exceeding the maximum switch voltage rating (33 V) of the main switch, an overvoltage protection circuit is integrated. As soon as the output voltage exceeds the OVP threshold, the converter stops switching and the output voltage falls down. When the output voltage falls below the OVP threshold, the converter continues operation until the output voltage exceeds the OVP threshold again. To allow the use of inexpensive low-voltage output capacitors, the TPS6106x series has different OVP levels that need to be selected according to the number of external LEDs and their maximum forward voltage. ENABLE PWM DIMMING The enable pin allows disabling and enabling of the device as well as brightness control of the LEDs by applying a PWM signal up to typically 1 kHz. When a PWM signal is applied, the LED current is turned on when the EN is high and off when EN is pulled low. Changing the PWM duty cycle therefore changes the LED brightness. To allow higher PWM frequencies on the enable pin, the device continues operation when a PWM signal is applied. As shown in the block diagram, the EN pin needs to be pulled low for at least 50 ms to fully turn the device off. The enable input pin has an internal 300-kΩ pulldown resistor to disable the device when this pin is floating. DIGITAL BRIGHTNESS CONTROL (ILED) The ILED pin features a simple digital interface to allow digital brightness control. This can save processor power and battery life. Using the digital interface to control the LED brightness does not required a PWM signal all the time, and the processor can enter sleep mode if available. To save signal lines, the ILED pin can be connected to the enable pin to allow digital programming and enable/disable function at the same time with the same signal. Such a circuit is shown in Figure 22. The ILED pin basically sets the feedback regulation voltage (VFB); thus, it sets the LED current. When the ILED pin is connected to GND, the digital brightness control is disabled and the feedback is regulated to VFB = 500 mV. When the ILED pin is pulled high, the digital brightness control is enabled starting at its midpoint where the feedback is regulated to VFB = 250 mV. The digital brightness control is implemented by adjusting the feedback voltage in digital steps with a typical maximum voltage of VFB = 500 mV. For this purpose, a 5-bit DAC is used giving 32 steps equal to a 15.6-mV change in feedback voltage per step. To increase or decrease the internal reference voltage, the ILED pin needs to be pulled low over time as outlined in Table 1 and specified in the electrical table. When the internal DAC is programmed to its highest or lowest value, it stays at this value until it gets programmed in the opposite direction again. Table 1. Increase/Decrease Internal Reference Voltage FEEDBACK VOLTAGE 10 TIME ILED LOGIC LEVEL Increase 1 µs to 75 µs Low Decrease 180 µs to 300 µs Low Brightness control disabled ≥550 µs Low Delay between steps 1.5 µs High TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 Between each cycle the ILED pin needs to be pulled high for 1.5 µs. td High ILED Low tup td tdown td toff Brightness Control Disabled Brightness Brightness Control Control Disabled Enabled Figure 15. ILED Timing Diagram Using the digital interface on the ILED pin allows simple implementation of a two-step brightness control by pulling the ILED either high or low. For full LED current with VFB = 500 mV, the ILED needs to be pulled low and to program half the LED current with VFB = 250 mV, the ILED pin needs to be pulled high. EFFICIENCY AND FEEDBACK VOLTAGE The feedback voltage has a direct effect on the converter efficiency. Because the voltage drop across feedback resistor does not contribute to the output power (LED brightness), the lower the feedback voltage higher the efficiency. Especially when powering only three or less LEDs, the feedback voltage impacts efficiency around 2% depending on the sum of the forward voltage of the LEDs. To take advantage of this, ILED pin can be connected to VIN, setting the feedback voltage to 250 mV. the the the the UNDERVOLTAGE LOCKOUT An undervoltage lockout prevents mis-operation of the device at input voltages below typical 1.65 V. When the input voltage is below the undervoltage threshold the device remains off and both internal MOSFETs are turned off providing isolation between input and output. THERMAL SHUTDOWN An internal thermal shutdown is implemented and turns off the internal MOSFETs when the typical junction temperature of 160°C is exceeded. The thermal shutdown has a hysteresis of typically 15°C. CHIPSCALE PACKAGE DIMENSIONS The TPS6106x is available in Chipscale package and has the following mechanical dimensions: E=D=1.446mm (typ), E=D=1.424mm (min), E=D=1.5mm (max). Please refer to mechanical drawing of the package (YZF). 11 TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 APPLICATION INFORMATION INDUCTOR SELECTION The device requires typically a 22-µH or 10-µH inductance. When selecting the inductor, the inductor saturation current should be rated as high as the peak inductor current at maximum load, and respectively, maximum LED current. Because of the special control loop design, the inductor saturation current does not need to be rated for the maximum switch current of the converter. The maximum converter switch current usually is not reached even when the LED current is pulsed by applying a PWM signal to the enable pin. The maximum inductor peak current, as well as LED current, is calculated as: Duty Cycle : D 1 Vin Vout (1) Maximum LED current : I LED D (1 D) Isw 2 Vin ƒs L (2) I Inductor peak current : i Lpeak Vin D LED 2 ƒs L (1 D) (3) with: fs = Switching frequency (1 MHz typ) L = Inductor value η = Estimated converter efficiency (0.75) Isw = Minimum N-channel MOSFET current limit (325 mA) Using the expected converter efficiency is a simple approach to calculate maximum possible LED current as well as peak inductor current. The efficiency can be estimated by taking the efficiency numbers out of the provided efficiency curves or to use a worst-case assumption for the expected efficiency, e.g., 75%. EFFICIENCY The overall efficiency of the application depends on the specific application conditions and mainly on the selection of the inductor. A physically smaller inductor usually shows lower efficiency due to higher switching losses of the inductor (core losses, proximity losses, skin effect losses). A trade-off between physical inductor size and overall efficiency has to be made. The efficiency can typically vary around ±5% depending on the selected inductor. Figures 2 to 7 can be used as a guideline for the application efficiency. These curves show the typical efficiency with a 22 µH inductor (muRata LQH32CN220K23). Figure 23 shows a basic setup where the efficiency is taken/measured as: V I LED LED V I in in (4) Table 2. Inductor Selection INDUCTOR VALUE COMPONENT SUPPLIER DIMENSIONS 10 µH TDK VLF3012AT-100MR49 2,6 mm × 2,8 mm × 1,2 mm 10 µH Murata LQH32CN100K53 3,2 mm × 2,5 mm × 1,55 mm 10 µH Murata LQH32CN100K23 3,2 mm × 2,5 mm × 2,0 mm 22 µH TDK VLF3012AT-220MR33 2,6 mm × 2,8 mm × 1,2 mm 22 µH Murata LQH32CN220K53 3,2 mm × 2,5 mm × 1,55 mm 22 µH Murata LQH32CN220K23 3,2 mm × 2,5 mm × 2,0 mm OUTPUT CAPACITOR SELECTION The device is designed to operate with a fairly wide selection of ceramic output capacitors. The selection of the output capacitor value is a trade-off between output voltage ripple and capacitor cost and form factor. In general, capacitor values of 220 nF up to 4.7 µF can be used. When using a 220-nF output capacitor, it is recommended 12 TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 to use X5R or X7R dielectric material to avoid the output capacitor value falling far below 220 nF over temperature and applied voltage. For systems with wireless or RF sections, EMI is always a concern. To minimize the voltage ripple in the LED string and board traces, the output capacitor needs to be connected directly from the OUT pin of the device to ground rather than across the LEDs. A larger output capacitor value reduces the output voltage ripple. Table 3 shows possible input and/or output capacitors. INPUT CAPACITOR SELECTION For good input voltage filtering low ESR ceramic capacitors are recommended. A 1-µF ceramic input capacitor is sufficient for most of the applications. For better input voltage filtering and EMI reduction this value can be increased. The input capacitor should be placed as close as possible to the input pin of the converter. Table 3 shows possible input and/or output capacitors. Table 3. Capacitor Selection VOLTAGE RATING FORM FACTOR COMPONENT SUPPLIER (1) 10 V 0603 Tayo Yuden LMK107BJ105 220 nF 16 V 0603 Tayo Yuden EMK107BJ224 TPS61060 220 nF 50 V 0805 Tayo Yuden UMK212BJ224 TPS61060/61/62 470 nF 35 V 0805 Tayo Yuden GMK212BJ474 TPS61060/61/62 1 µF 16 V 0805 Tayo Yuden EMK212BJ105 TPS61060 1 µF 35 V 1206 Tayo Yuden GMK316BJ105 TPS61060/61/62 1 µF 25 V 1206 TDK C3216X7R1E105 TPS61060/61/62 CAPACITOR COMMENTS INPUT CAPACITOR 1 µF OUTPUT CAPACITOR (1) Similar capacitors are also available from TDK and other suppliers. LAYOUT CONSIDERATIONS As for all switching power supplies, the layout is an important step in the design, especially at high peak currents and switching frequencies. If the layout is not carefully done, the regulator might show noise problems and duty cycle jitter. The input capacitor should be placed as close as possible to the input pin for good input voltage filtering. The inductor should be placed as close as possible to the switch pin to minimize the noise coupling into other circuits. The output capacitor needs to be placed directly from the OUT pin to GND rather than across the LEDs. This reduces the ripple current in the trace to the LEDs. The GND pin needs to be connected directly to the PGND pin. When doing the PCB layout, the bold traces (Figure 16) should be routed first, as well as placement of the inductor, input and output capacitors. VIN 2.7 V to 6 V C1 1 F Keep These Traces as Short as Possible L1 VIN SW EN OUT ILED C2 220 nF FB GND PGND RS 12 Traces in Bold Need to be Routed First and Should be Kept as Short as Possible Figure 16. Layout Considerations 13 TPS61060 TPS61061 TPS61062 SLVS538 – NOVEMBER 2004 www.ti.com THERMAL CONSIDERATIONS The TPS6106x comes in a thermally enhanced QFN package. The package includes a thermal pad that improves the thermal capabilities of the package. Also see QFN/SON PCB Attachment Application Note (SLUA271). The thermal resistance junction-to-ambient RθJA of the QFN package greatly depends on the PCB layout. Using thermal vias and wide PCB traces improves the thermal resistance RθJA. The thermal pad needs to be soldered to analog ground on the PCB. For the NanoFree package, similar guidelines apply as for the QFN package. The thermal resistance RθJA depends mainly on the PCB layout. 14 TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 TYPICAL APPLICATIONS C2 220 nF VIN 2.7 V to 6 V L1 22 H C1 1 F VIN SW EN OUT ILED FB RS 12 GND PGND Figure 17. TPS61060 Powering Two White LEDs C2 220 nF VIN 2.7 V to 6 V L1 22 H C1 1 F VIN SW EN OUT ILED FB RS 12 GND PGND Figure 18. TPS61060 Powering Three White LEDs C2 220 nF VIN 2.7 V to 6 V L1 22 H C1 1 F VIN SW EN OUT ILED FB GND PGND RS 12 Figure 19. TPS61061 Powering Four White LEDs 15 TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 TYPICAL APPLICATIONS (continued) C2 220 nF VIN 3 V to 6 V L1 22 H C1 1 F VIN SW EN OUT FB ILED GND PGND RS 12 Figure 20. TPS61062 Powering Five White LEDs C2 220 nF VIN 3 V to 6 V L1 22 H C1 1 F VIN SW EN OUT FB ILED GND PGND RS 25 R1 25 Figure 21. TPS61060 Powering Six White LEDs C2 220 nF VIN 2.7 V to 6 V L1 22 H C1 1 F Digital Brightness Control VIN SW EN OUT ILED FB GND PGND RS 12 Figure 22. TPS61061 Digital Brightness Control (2) (2) 16 This circuit combines the enable with the digital brightness control pin, allowing the digital signal applied to ILED to also enable and disable the device. TPS61060 TPS61061 TPS61062 www.ti.com SLVS538 – NOVEMBER 2004 TYPICAL APPLICATIONS (continued) ILED C2 220 nF VIN 2.7 V to 6 V L1 22 H VLED Iin C1 1 F Vin VIN SW EN OUT ILED FB GND PGND RS 12 Figure 23. Efficiency Measurement Setup 17 PACKAGE OPTION ADDENDUM www.ti.com 14-Mar-2005 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TPS61060DRBR ACTIVE SON DRB 8 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS61060DRBRG4 ACTIVE SON DRB 8 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS61060YZFR ACTIVE DSBGA YZF 8 3000 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM TPS61060YZFT ACTIVE DSBGA YZF 8 250 SNAGCU Level-1-260C-UNLIM TPS61061DRBR ACTIVE SON DRB 8 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS61061DRBRG4 ACTIVE SON DRB 8 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS61061YZFR ACTIVE DSBGA YZF 8 3000 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM TPS61061YZFT ACTIVE DSBGA YZF 8 250 SNAGCU Level-1-260C-UNLIM TPS61062DRBR ACTIVE SON DRB 8 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS61062DRBRG4 ACTIVE SON DRB 8 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS61062YZFR ACTIVE DSBGA YZF 8 3000 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM TPS61062YZFT ACTIVE DSBGA YZF 8 250 SNAGCU Level-1-260C-UNLIM Green (RoHS & no Sb/Br) Green (RoHS & no Sb/Br) Green (RoHS & no Sb/Br) Lead/Ball Finish MSL Peak Temp (3) (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 - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. None: Not yet available Lead (Pb-Free). 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. Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens, including bromine (Br) or antimony (Sb) above 0.1% of total product weight. (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder temperature. 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 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Amplifiers amplifier.ti.com Audio www.ti.com/audio Data Converters dataconverter.ti.com Automotive www.ti.com/automotive DSP dsp.ti.com Broadband www.ti.com/broadband Interface interface.ti.com Digital Control www.ti.com/digitalcontrol Logic logic.ti.com Military www.ti.com/military Power Mgmt power.ti.com Optical Networking www.ti.com/opticalnetwork Microcontrollers microcontroller.ti.com Security www.ti.com/security Telephony www.ti.com/telephony Video & Imaging www.ti.com/video Wireless www.ti.com/wireless Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright 2005, Texas Instruments Incorporated