TPS61166 www.ti.com.......................................................................................................................................................................................... SLVS991 – SEPTEMBER 2009 WHITE LED DRIVER WITH INTEGRATED POWER DIODE AND FAST BURST MODE DIMMING FEATURES 1 • • • • • • • • • • DESCRIPTION IC Supply Range: 2.5-V to 6-V Power Stage Input Range: 4.5-V to 10-V Integrated 1.1-A / 20-V Internal Switch FET and Power Diode Drive up to 5 LEDs in Series Fast on/off LED Current Within 1-µs in Brightness Dimming Burst PWM Dimming Method With Frequency Range From 60-Hz to 40-kHz Built-in Soft Start-up Over Load Protection Over Voltage Protection 2.5 × 2.5 × 0.8 mm SON Package The TPS61166 is a boost converter with a 20-V rated integrated switch FET and power diode that drives up to 5 LEDs in series. This device integrates a high side switch FET that can turn on/off the LED current within 1-µs of the applied external PWM signal. The high side switch also provides input-to-output isolation during IC shutdown. The default white LED current is set with the external sensor resistor R1, and the feedback voltage is regulated to 200-mV, as shown in the typical application circuit. The LED current can be adjusted using a pulse width modulation (PWM) signal through the PWM pin. The LED current is synchronized to the PWM signal. The device does not discharge the output ceramic capacitor during dimming, thus reducing audible noise when dimming. APPLICATIONS • • • • • Separating the IC input (VIN pin) and power stage input (VBAT pin) makes the device flexible enough to support single- or two-cell Li-ion battery applications. Other protection features include 1.1-A peak-to-peak over current protection (OCP), over voltage protection (OVP), over load protection (OLP), and thermal shutdown. The TPS61166 is available in a 2.5 mm × 2.5 mm SON package with thermal pad. Small Form Factor LCD Backlight Mobile Phone Digital Camera Personal Camcorder Single Lens Reflex Vin 2.5 V to 6 V L1 4.7 mH C1 4.7 mF TPS61166 VBAT 15 kHz / 50% duty cycle SW VIN VO NC OUT EN PWM C2 4.7 mF FB GND R1 8 Figure 1. Single Cell Li-Ion Battery Typical Application 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. 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 © 2009, Texas Instruments Incorporated TPS61166 SLVS991 – SEPTEMBER 2009.......................................................................................................................................................................................... www.ti.com L1 Vin 4.5 V to 10 V 4.7 mH C1 4.7 mF TPS61166 VBAT C3 15 kHz / 50% duty cycle VIN VO NC OUT EN C2 4.7 mF SW FB PWM GND R1 8 Figure 2. Two Cell Li-Ion Battery Typical Application ORDERING INFORMATION (1) (1) (2) PART NUMBER OVER VOLTAGE PROTECTION PACKAGE MARKING TPS61166DSK (2) 18V (TYP) OAO For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI web site at www.ti.com The DSK package is available in tape and reel. Add R suffix (TPS61166DSKR) to order quantities of 3000 parts per reel, or add T suffix (TPS61166DSKT) to order 250 parts per reel. ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range (unless otherwise noted) (1) VALUE / UNITS Supply voltage on pin VBAT (2) Voltage on pins VIN, EN, and PWM –0.3 V to 10 V (2) –0.3 V to 7 V Voltage on pins SW, VO, and OUT (2) –0.3 V to 20 V Voltage on pin FB (2) –0.3 V to 3 V HBM ESD rating (3) 2 kV Operating temperature range, TA –40°C to 85°C Maximum operating junction temperature, TJ 150°C Storage temperature, Tst (1) (2) (3) –55°C to 150°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 The Human body model (HBM) is a 100-pF capacitor discharged through a 1.5-kΩ resistor into each pin. The testing is done according JEDECs EIA/JESD22-A114 DISSIPATION RATINGS (1) 2 PACKAGE THERMAL RESISTANCE θJA (1) THERMAL RESISTANCE θJP THERMAL RESISTANCE θJC POWER RATING TA ≤ 25°C (1) DERATING FACTOR ABOVE TA = 25°C (1) DSK 60.6°C/W 6.3°C/W 40°C/W 1650 mW 17 mW/°C Thermal ratings are determined assuming a high K PCB design according to JEDEC standard JESD51-7. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 TPS61166 www.ti.com.......................................................................................................................................................................................... SLVS991 – SEPTEMBER 2009 RECOMMENDED OPERATING CONDITIONS over operating free-air temperature range (unless otherwise noted) MIN NOM MAX UNIT VBAT Battery input voltage range 4.5 10 V Vin IC Input voltage range 2.5 6 V Vo Output voltage at VO pin L Inductor (1) fdim PWM signal frequency Cin Input capacitor Co Output capacitor at VO pin (1) C3 Pre-regulator capacitor at VIN pin (2) 0.1 TJ Operating junction temperature –40 125 °C TA Operating free-air temperature –40 85 °C (1) (2) 2.2 4.7 0.06 17 V 10 µH 40 kHz µF 4.7 1 4.7 10 µF µF These values are recommended values that have been successfully tested in several applications. Other values may be acceptable in other applications but should be fully tested by the user. For a two cell Li-ion battery application or input supply above 6 V as shown in Figure 2, C3 is needed for the internal pre-regulator. Otherwise, C3 is not needed as shown in Figure 1. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 3 TPS61166 SLVS991 – SEPTEMBER 2009.......................................................................................................................................................................................... www.ti.com ELECTRICAL CHARACTERISTICS VIN=3.6V, EN=VIN, TA = –40°C to 85°C, typical values are at TA = 25°C (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT SUPPLY CURRENT VIN IC input voltage range, VIN 2.5 VBAT Battery input voltage range, VBAT IQ Operating quiescent current into VIN Device PWM switching no load ISD Shutdown current EN = GND, VIN = 6 V UVLO Undervoltage lockout threshold VIN falling Vhys Undervoltage lockout hysterisis 6 4.5 0.9 1.5 V 10 V 1.5 mA 1 µA 1.55 50 V mV ENABLE AND PWM CONTROL VENH EN and PWM logic high voltage VIN = 2.5 V to 6 V VENL En and PWM logic low voltage VIN = 2.5 V to 6 V REN EN and PWM pull down resistor Toff EN pulse width to shutdown 1.2 V 0.3 400 800 EN high to low V 1600 kΩ 1 ms 206 mV 200 nA 1.4 MHz VOLTAGE CONTROL VREF Voltage feedback regulation voltage IFB Voltage feedback input bias current fS Oscillator frequency Dmax Maximum duty cycle Tmin_on Minimum on pulse width 194 VFB = 0.1 V, TA = 85°C 200 1.0 1.2 90% 93% 65 ns POWER SWITCH, ISOLATION FET RDS(ON)N N-channel MOSFET on-resistance VIN = 3 V 0.25 0.4 Ω RDS(ON)iso Isolation FET on-resistance VO = 5 V 2.5 4 Ω VO = 3.5 V 4.5 ILN_N N-channel leakage current VDS = 20 V, TA = 25°C 1 µA ILN_iso Isolation FET leakage current VDS = 20 V, TA = 25°C 1 µA VF Power diode forward voltage Current = 500 mA 0.8 V OC, ILIM, OVP SC AND SS ILIM N-Channel MOSFET current limit Vovp Over voltage protection threshold Vovp_hys Over voltage protection hysteresis IOL Over load protection Measured on the VO pin 0.9 1.1 18 19 1.5 A 0.6 V 200 300 mA V THERMAL SHUTDOWN Tshutdown Thermal shutdown threshold 150 °C Thysteresis Thermal shutdown hysteresis 15 °C 4 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 TPS61166 www.ti.com.......................................................................................................................................................................................... SLVS991 – SEPTEMBER 2009 DEVICE INFORMATION PIN ASSIGNMENTS TOP VIEW VO GND VIN VBAT SW Thermal Pad OUT NC FB EN PWM 10-PIN 2.5mm x 2.5mm QFN PIN FUNCTIONS PIN NAME NO. I/O DESCRIPTION VIN 2 I IC Supply voltage input. VO 10 O Output of the boost converter. When the output voltage exceeds the over voltage protection (OVP) threshold, the power switch turns off until VO drops below the over voltage protection hysteresis. OUT 8 O Isolation switch is between this pin and the VO pin. Connect the anode of the LED to this pin. GND 1 – Ground of the IC. VBAT 3 I Battery supply voltage input. It can be tied with VIN pin when using a signal Li-ion battery. EN 5 I Enable pin (HIGH = enable). When the pin is pulled low for 1 ms, the IC turns off and consumes less than 1-µA current. For a 2-cell battery application, a logic high signal turns on the internal pre-regulator and enables the IC. Therefore, do not connect the EN pin to the VIN pin in the Figure 2 application. PWM 6 I Control LED on/off. A PWM signal from 60 Hz to 40 kHz connects to the pin for LED brightness control. FB 7 I Cathode of the LED connects to this pin. Its voltage is regulated at 0.2 V. An external resistor connected to this pin programs the LED current. SW 9 I Switching node of the IC where the PWM switching operates. NC 4 – No connect pin. Connect to ground is recommended, or can float. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 5 TPS61166 SLVS991 – SEPTEMBER 2009.......................................................................................................................................................................................... www.ti.com FUNCTIONAL BLOCK DIAGRAM FB EN VBAT SW NC OUT VO Soft Startup Ref . EN Preregulator VIN OVP OLP EA Gate Driver Gate Driver PWM Control EN Precharge On/off control Oscillator Ramp Generator + Current Sensor GND VIN PWM TYPICAL CHARACTERISTICS TABLE OF GRAPHS (Figure 1), L = TOKO #A915_Y-4R7M, VIN = 3.6 V, LOAD = 4 LEDS unless otherwise noted FIGURE η LED Efficiency vs Led current; Five LEDs (14.5 V) 3 η LED Efficiency vs Led current; Four LEDs (11.5 V) 4 η LED Efficiency vs Led current; Three LEDs (8.5 V) 5 VFB FB voltage vs Input voltage 6 VFB FB voltage vs VBAT voltage 7 VFB FB voltage vs Free-air temperature 8 Switch current limit vs Free-air temperature 9 PWM dimming operation 1 kHz with 30% duty cycle 10 PWM dimming operation 15 kHz with 10% duty cycle 11 PWM switch operation 15 kHz with 10% duty cycle 12 PWM dimming linearity 100 Hz, 1 kHz, 40 kHz; 13 PWM dimming linearity (zoom in) 100 Hz, 1 kHz, 40 kHz; 14 6 Over voltage protection 15 Soft start up in PWM dimming 16 Soft start up with EN and PWM tied together 17 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 TPS61166 www.ti.com.......................................................................................................................................................................................... SLVS991 – SEPTEMBER 2009 LED EFFICIENCY vs LED CURRENT LED EFFICIENCY vs LED CURRENT 100 100 5 LEDs = 14.5 V 4 LEDs = 11.5 V VI = 8 V 80 80 VI = 5 V VI = 2.7 V 70 70 VI = 3.6 V 60 Efficiency - % Efficiency - % VI = 5 V 90 90 50 40 VI = 2.7 V 60 VI = 3.6 V 50 40 30 30 20 20 10 10 0 0 1 10 100 1 1000 10 100 1000 Load - mA Figure 4. Load - mA Figure 3. LED EFFICIENCY vs LED CURRENT FB VOLTAGE vs INPUT VOLTAGE 200.5 100 3 LEDs = 8.5 V 90 VI = 5 V 80 200 VI = 2.7 V 60 VI = 3.6 V VFB - mV Efficiency - % 70 50 40 199.5 30 199 20 10 198.5 0 1 10 100 1000 2.5 Load - mA Figure 5. 3 3.5 4 4.5 5 VI - Input Voltage - V 5.5 6 Figure 6. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 7 TPS61166 SLVS991 – SEPTEMBER 2009.......................................................................................................................................................................................... www.ti.com FB VOLTAGE vs FREE-AIR TEMPERATURE 200.5 0.202 200 0.201 VFB - V VFB - mV FB VOLTAGE vs VBAT VOLTAGE 199.5 199 198.5 4.5 0.2 0.199 5 5.5 6 6.5 7 7.5 8 VBAT - V 8.5 9 9.5 10 0.198 -40 -20 0 20 40 60 80 100 TA - Free-Air Temperature - ºC Figure 7. Figure 8. SWITCH CURRENT LIMIT vs FREE-AIR TEMPERATURE 1-kHz PWM DIMMING WITH DUTY=30% 1.3 120 VO 100 mV; AC 1.2 LED Current 50 mA/div ILIM - A 1.1 1 Inductor Current 500 mA/div 0.9 0.8 -40 -20 0 20 40 60 80 100 120 t - Time = 400 ms/div TA - Free-Air Temperature - ºC Figure 9. 8 Figure 10. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 TPS61166 www.ti.com.......................................................................................................................................................................................... SLVS991 – SEPTEMBER 2009 15-kHz PWM DIMMING WITH DUTY=10% 15-kHz PWM DIMMING WITH DUTY=10% VO 100 mV; AC VO 100 mV; AC LED Current 50 mA/div LED Current 50 mA/div Inductor Current 500 mA/div Inductor Current 500 mA/div t - Time = 20 ms/div t - Time = 2 ms/div Figure 11. Figure 12. PWM DIMMING LINEARITY PWM DIMMING LINEARITY 8 80 70 1 kHz 6 60 LED Current - mA LED Current - mA 1 kHz 50 40 100 Hz 40 kHz 30 100 Hz 40 kHz 4 2 20 10 0 0 0 10 20 30 40 50 60 70 Duty Cycle - % Figure 13. 80 90 100 1 2 3 4 5 6 7 Duty Cycle - % 8 9 10 Figure 14. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 9 TPS61166 SLVS991 – SEPTEMBER 2009.......................................................................................................................................................................................... www.ti.com OVER VOLTAGE PROTECTION SOFT START UP IN PWM DIMMING VO 1 V/div, 18 V offset VO 5V/div LED Current 50 mA/div Inductor Current 100 mA/div Inductor Current 200 mA/div t - Time = 2 ms/div t - Time = 4 ms/div Figure 15. Figure 16. SOFT START UP VO 5 V/div LED Current 50 mA/div Inductor Current 200 mA/div t - Time = 400 ms/div Figure 17. DETAILED DESCRIPTION OPERATION The TPS61166 adopts peak current-mode control with a constant pulse-width-modulation (PWM) frequency of 1.2-MHz. PWM operation turns on the PWM switch at the beginning of each switching cycle. The input voltage is applied across the inductor and the inductor current ramps up. In this mode, the output capacitor is discharged by the load current. When the inductor current hits the threshold set by the error amplifier output, the PWM switch is turned off, and the power diode is forward-biased. The inductor transfers its stored energy to replenish the output capacitor. This operation repeats in the next switching cycle. The error amplifier compares the FB pin voltage with an internal reference, and its output determines the duty cycle of the PWM switching. This closed-loop system requires frequency compensation for stable operation. The device has a built-in compensation circuit that can accommodate a wide range of input and output voltages. To avoid the sub-harmonic oscillation intrinsic to current-mode control, the IC also integrates the slope compensation, which adds an artificial slope to the current ramp. 10 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 TPS61166 www.ti.com.......................................................................................................................................................................................... SLVS991 – SEPTEMBER 2009 The device integrates a high side switch FET between the VO pin and the OUT pin to turn LEDs on/off quickly. The LED current is synchronous with the external PWM signal that is applied to the PWM pin. The delay between the PWM signal and the rising/falling edge of the LED current is less than 1-µs. The IC’s isolation switch prevents the output capacitor from discharging during dimming, thus reducing the ceramic output capacitor’s audible noise to neglible levels. STARTUP AND SHUTDOWN The TPS61166 starts to turn on the isolation FET and PWM switch when the EN pin is pulled high. In the boost power stage, the IC ramps up the over-current limit of the PWM switch to 1.1-A in 8 steps, and each step takes 213-µs. This ensures that the VO pin voltage rises slowly to reduce input inrush current. The Vgs of the isolation switch is self-clamped by the VO pin voltage, so that the high on-resistance of the switch during startup limits the output current. When the EN pin is pulled low for 1-ms, the IC stops the PWM switch and turns off the isolation switch, providing isolation between input and output. In the shutdown mode, less than 1-µA input current is consumed by the IC. UNDER VOLTAGE LOCKOUT (UVLO), OVER LOAD PROTECTION (OLP), AND OVER VOLTAGE PROTECTION (OVP) An under voltage lockout circuit prevents improper operation of the device for input voltages below 1.55-V. When the input voltage is below the undervoltage threshold, both the PWM switch and isolation switch remain off. If the current passing through the isolation switch is above the over load limit of 300-mA (IOL,typ) for 1.5-µs, the TPS61166 is switched off until the fault clears and the EN pin toggles. Over load protection is disabled until the over current limit ramp is completed during startup. To prevent the PWM switch and the output capacitor from exceeding maximum voltage ratings, an over votlage protection circuit turns off the boost switch as soon as the output voltage at the VO pin exceeds the OVP threshold. Simultaneously, the isolation switch opens. The regulator resumes PWM switching after the VO pin voltage falls 0.6 V below the threshold. This function provides protection for open LED protection as well. THERMAL SHUTDOWN An internal thermal shutdown turns off the isolation and PWM switches when the typical junction temperature of 150°C is exceeded. The thermal shutdown has a hysteresis of 15°C, typical. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 11 TPS61166 SLVS991 – SEPTEMBER 2009.......................................................................................................................................................................................... www.ti.com APPLICATION INFORMATION SWITCH DUTY CYCLE The maximum switch duty cycle (D) of the TPS61166 is 90% (MIN). The duty cycle of a boost converter in continuous conduction mode (CCM) is given by: Vout + 0.8 V - Vin D= Vout + 0.8 V (1) where Vout = ∑VFWD(LED)+200mV. The duty cycle must be lower than the specification in the application; otherwise the output voltage cannot be regulated. LED CURRENT PROGRAMMING The FB voltage is regulated to a low 0.2-V reference voltage. LED current is programmed externally using a current sense resistor R1 in series with the LED string. The value of R1 is calculated using Equation 2: 200 mV ILED = R1 (2) The output current tolerance depends on FB accuracy and current sensor resistor accuracy. Maximum LED current can be calculated using Equation 3. DIL Iout_MAX = (ILIM ) ´ (1 - D) 2 1 DIL = é æ 1 1 öù + êL ´ fSW ´ ç ÷ú è VO + 0.8 V - VIN VIN ø û ë (3) Where ΔIL = Inductor peak to peak current; L = Selected inductor value; fSW = Converter switching frequency (typically 1.2-MHz); For instance, the TPS61166 can support 4 LEDs (equivalent output voltage of 14-V) with 160-mA output current at 3.3-V input supply at typical conditions. LED BRIGHTNESS DIMMING A PWM signal applied to the PWM pin can adjust the LED brightness. The signal controls whether the isolation switch is on or off; therefore LED current is directly proportion to the duty cycle of the PWM signal. During the on periods, LED current is defined by the value as described in Equation 2. The recommended PWM signal frequency range is 60-Hz to 40-kHz. The IC needs several µ-seconds to settle the LED current after the isolation switch turns on. This settling time affects the LED current linearity at low duty cycle. A 1% duty cycle is the minimum recommended duty cycle for a PWM dimming signal with 1-kHz frequency, and 0.1% is recommended for a 100-Hz frequency. The isolation switch ON time determines the maximum PWM frequency. The ON time must be at least twice as long as one switch cycle of 2/fs(max) = 2/1.4MHz = 1.2-µs. A PWM dimming frequency above 40 kHz may be acceptable, but needs to be fully tested by the user. INDUCTOR SELECTION Because the selection of the inductor affects steady state operation, transient behavior, and loop stability, the inductor is the most important component in power regulator design. There are three important inductor specifications: inductor value, saturation current, and dc resistance. Considering inductor value alone is not enough. The saturation current of the inductor should be higher than the peak switch current as calculated in the following equations: 12 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 TPS61166 www.ti.com.......................................................................................................................................................................................... SLVS991 – SEPTEMBER 2009 IL_peak = IL_DC + IL_DC = DIL 2 Vout ´ Iout Vin ´ h (4) Where IL_DC = Inductor average current η = Estimated converter efficiency The inductor value should not be outside the 2.2 µH to 10 µH range listed in the recommended operating conditions table, otherwise internal slope compensation and loop compensation are ineffective.Table 1 lists the recommended inductors for the TPS61166. Table 1. Recommended Inductors for the TPS61166 PART NUMBER L (µH) DCR MAX (mΩ) SATURATION CURRENT (A) SIZE (L×W×H mm) VENDOR #A915_Y-4R7M 4.7 #A915_Y-100M 10 45 1.5 5.2x5.2x3.0 Toko 90 1.09 5.2x5.2x3.0 VLS4012-4R7M 4.7 Toko 132 1.1 4.0x4.0x1.2 TDK VLS4012-100M 10 240 0.82 4.0x4.0x1.2 TDK CDRH3D23/HP 4.7 95.5 1.6 4.0x4.0x2.5 Sumida LPS4012-472ML 4.7 175 1.6 4.0x4.0x1.2 Coilcraft INPUT AND OUTPUT CAPACITOR SELECTION The output capacitor is mainly selected to meet the requirements for output ripple and loop stability. This ripple voltage is related to the capacitor’s capacitance and its equivalent series resistance (ESR). Assuming a ceramic capacitor with zero ESR, the minimum capacitance needed for a given ripple can be calculated by Equation 5: D ´ Iout Cout = Fs ´ Vripple (5) where, Vripple = peak to peak output ripple. The ESR impact on the output ripple must be considered if tantalum or electrolytic capacitors are used. Care must be taken when evaluating a ceramic capacitor’s derating under dc bias, aging, and ac signal. For example, larger form factor capacitors (in 1206 size) have their self resonant frequencies in the range of the switching frequency. So the effective capacitance is significantly lower. The dc bias can also significantly reduce capacitance. A ceramic capacitor can loose as much as 50% of its capacitance at its rated voltage. Therefore, always leave margin on the voltage rating to ensure adequate capacitance at the required output voltage. At least a 4.7-µF input capacitor is recommended. The output requires a capacitor in the range of 1 µF to 10 µF. The output capacitor affects the loop stability of the boost regulator. If the output capacitor is below the range, the boost regulator can potentially become unstable. The popular vendors for high value ceramic capacitors are: • TDK (http://www.component.tdk.com/components.php) • Murata (http://www.murata.com/cap/index.html) LAYOUT CONSIDERATIONS As for all switching power supplies, especially those running at high switching frequency and high currents, layout is an important design step. If layout is not carefully performed, the regulator could suffer from instability as well as noise problems. To maximize efficiency, switch rise and fall times are very fast. To prevent radiation of Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 13 TPS61166 SLVS991 – SEPTEMBER 2009.......................................................................................................................................................................................... www.ti.com high frequency noise (e.g., EMI), proper layout of the high frequency switching path is essential. Minimize the length and area of all traces connected to the SW pin and always use a ground plane under the switching regulator to minimize interplane coupling. The high current path including the switch and output capacitor contains nanosecond rise and fall times and should be kept as short as possible. The input capacitor needs not only to be close to the VIN pin, but also to the GND pin in order to reduce input supply ripple. L1 C2 C1 Vin VO GND Th VIN SW er LED + m VBAT OUT al LED - Pa NC Minimize the area of SW trace FB d EN PWM PWM EN R1 Place enough VIAs around thermal pad to enhace thermal performance GND THERMAL CONSIDERATIONS The maximum IC junction temperature should be restricted to 125°C under normal operating conditions. This restriction limits the power dissipation of the TPS61166. Calculate the maximum allowable dissipation, PD(MAX) and keep the actual dissipation less than or equal to PD(MAX). The maximum-power-dissipation limit is determined using Equation 6: 125 °C - TA PD(MAX) = RqJA (6) where TA = Maximum ambient temperature for the application. RθJA = Thermal resistance junction-to-ambient listed in the dissipation ratings table. The TPS61166 is available in a thermally enhanced QFN package. This package includes a thermal pad that improves the thermal capabilities of the package. The RθJA of the QFN package greatly depends on the PCB layout and thermal pad connection. The thermal pad must be soldered to the analog ground on the PCB. Using thermal vias underneath the thermal pad as illustrated in the layout example. Also, see the QFN/SON PCB Attachment application report (SLUA271). 14 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 TPS61166 www.ti.com.......................................................................................................................................................................................... SLVS991 – SEPTEMBER 2009 ADDITIONAL APPLICATION Multiple LED Strings Bar Application Vin 5 V L1 4.7 mH C1 4.7 mF C2 4.7 mF TPS61166 VBAT Total LED current = 300 mA SW VIN VO NC OUT EN FB PWM GND R1 LED Efficiency Measurement Application Vin 4.5 V to 10 V L1 A V 4.7 mH C1 4.7 mF C3 C2 4.7 mF TPS61166 VBAT VIN VO NC OUT EN PWM V SW FB GND A R1 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS61166 15 PACKAGE OPTION ADDENDUM www.ti.com 12-Oct-2009 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TPS61166DSKR ACTIVE SON DSK 10 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM TPS61166DSKT ACTIVE SON DSK 10 250 CU NIPDAU Level-1-260C-UNLIM 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 - 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. 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. 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