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Summary of Contents for Texas Instruments tps61040EVM-002
- Page 1 TPS61040EVM 002 White Light LED Bias Supply Evaluation Module User’s Guide September 2004 PMP EVMs SLVU068A...
- Page 2 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:...
- Page 3 EVM IMPORTANT NOTICE Texas Instruments (TI) provides the enclosed product(s) under the following conditions: This evaluation kit being sold by TI is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not considered by TI to be fit for commercial use. As such, the goods being provided may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including product safety measures typically found in the end product incorporating the goods.
- Page 4 EVM schematic located in the EVM User’s Guide. When placing measurement probes near these devices during operation, please be aware that these devices may be very warm to the touch. Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright 2004, Texas Instruments Incorporated...
- Page 5 This user’s guide describes the characteristics, operation, and use of the TPS61040EVM−002 white light LED bias supply evaluation module (EVM). This EVM is a Texas Instruments high-efficiency boost converter configured to supply 20 mA of bias current to four white light LEDs, from a single-cell Li-ion battery.
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Page 7: Table Of Contents
Contents Contents Introduction ..............Background . - Page 8 Contents Figures 2−1 Start-up Waveforms ............2−2 Output Ripple Current .
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Page 9: Introduction
Chapter 1 Introduction This chapter contains background information for the TPS61040 and support documentation for the TPS61040EVM-002 evaluation module. Topic Page Background .......... -
Page 10: Background
Background 1.1 Background The TPS61040EVM uses the TPS61040 boost converter to provide 20 mA of bias current to a four-element white LED from a single-cell Li-ion battery (3 V to 4.2 V). The EVM operates over an input voltage range of 1.8 V to 6.0 V, but has been optimized over a 3-V to 4.2-V input range. -
Page 11: Setup And Test Results
Chapter 2 Setup and Test Results This chapter describes how to properly connect, set up, and use the TPS61040EVM−002. It also presents the test results for the EVM. All test results are measured with the EVM driving four white light LEDs. Topic Page Input/Output Connections... -
Page 12: Input/Output Connections
Input/Output Connections 2.1 Input/Output Connections The TPS61040EVM−002 PWB has several connections, which are described in Table 2−1. Table 2−1. Input/Output Connections Reference Name Description Designator This is the positive connection to the input power supply. Input supply leads (Vin and GND) should be a twisted pair and kept as short as possible. This is the return connection for the input power supply. -
Page 13: Analog Dimming With Pwm Voltage
EVM Operation seen at the FB pin, which lowers the LED current. If the resistor values are chosen correctly, the analog control voltage varies the output current between 0 mA and maximum programmed current. This dimming method is the default configuration of the EVM, and is accomplished by injecting an analog voltage into the DIM1 pin on J3. -
Page 14: Pwm Dimming Using Enable
Setup 2.2.3 PWM Dimming Using Enable The third method for dimming the LEDs is to inject a PWM voltage into the EN pin of the TPS61040. When the EN pin is high, the supply turns on and the output current is at the programmed maximum current. When the EN pin is low, the supply turns off and the output current goes to 0 mA. -
Page 15: Start-Up
Start-up 2.4 Start-up When enabled, the EVM goes through its programmed three-stage soft-start sequence to reduce inrush current at turnon. Figure 2−1 shows the startup sequence of the EVM when powered from a 4.0-V Li-ion battery. The top oscilloscope trace is the input current and the bottom trace is the output current. -
Page 16: Led Ripple Current
LED Ripple Current 2.5 LED Ripple Current Figure 2−2 shows the output ripple current with Iout = 20 mA. The top oscilloscope trace shows the ripple with 3.6-V input, and the bottom trace shows the ripple with a 4.2-V input. The difference in switching frequency between the two traces is expected and is explained in the data sheet. -
Page 17: Switching Waveforms
Switching Waveforms 2.6 Switching Waveforms Figure 2−3 shows the switching waveform at the SW pin of the TPS61040. When the internal FET turns on, the voltage at the SW pin is pulled to ground until the inductor current reaches 400 mA. When the inductor current reaches 400 mA, the FET turns off and the voltage at the SW pin rises to the output voltage plus the forward voltage drop of the diode. -
Page 18: Efficiency
Efficiency 2.7 Efficiency Figure 2−4 shows the measured efficiency of the TPS61040. Figure 2−4. Typical Efficiency V I = 6 V V I = 4.2 V V I = 3.6 V V I = 2.5 V 12.5 17.5 I O − Output Current − mA 2.8 Analog Dimming With Analog Voltage Data The EVM was modified to generate a 0 mA to 20 mA output when the control voltage is varied from 3.3 V to 0 V. -
Page 19: Analog Dimming With Pwm Voltage Data
Analog Dimming With PWM Voltage Data 2.9 Analog Dimming With PWM Voltage Data For the Analog Dimming With PWM Voltage method, the EVM is configured identically with the Analog Dimming With Analog Voltage method with the exception that the control voltage is injected into the DIM2 pin on J3. R1 and C2 are chosen to be 10 kΩ... -
Page 20: Pwm Dimming Using Enable Data
PWM Dimming Using Enable Data 2.10 PWM Dimming Using Enable Data For the PWM Dimming Using Enable method, the EVM is configured with R2= open and R3 = short. Setting R4 = 61.9 Ω programs the maximum output current to 20 mA. Figure 2−7 shows input current and output current with the PWM frequency set to 100 Hz and 50% duty cycle. -
Page 21: Output Current Vs Duty Cycle For Pwm Dimming Using Enable
PWM Dimming Using Enable Data Figure 2−8. Output Current vs Duty Cycle for PWM Dimming Using Enable Duty Cycle − % Setup and Test Results 2-11... -
Page 22: Pwm Dimming Using Injected Voltage On Fb Data
PWM Dimming Using Injected Voltage on FB Data 2.11 PWM Dimming Using Injected Voltage on FB Data For the PWM Dimming Using Injected Voltage on FB method, a 0-V to 3.3-V control voltage is used to program a maximum LED current of 20 mA. Use the equations found in the Analog Dimming Using Analog Voltage section to calculate the resistor values. -
Page 23: Output Current Vs Duty Cycle
PWM Dimming Using Injected Voltage on FB Data Figure 2−10. Output Current vs Duty Cycle 20 kHz 10 kHz 5 kHz 1 kHz 100 Hz Duty Cycle − % Setup and Test Results 2-13... - Page 24 This page intentionally left blank 2-14...
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Page 25: Board Layout
Chapter 3 Board Layout This chapter provides the TPS61040EVM-002 board layout and illustrations. Topic Page Board Layout .......... -
Page 26: Board Layout
Board Layout 3.1 Board Layout Board layout is critical for all switch mode power supplies. Figures 3−1, 3−2, and 3−3 show the board layout for the TPS61040EVM−002 PWB. The nodes with a high switching frequency are short and are isolated from the noise-sensitive feedback circuitry. -
Page 27: Bottom Layer Routing
Board Layout Figure 3−3. Bottom Layer Routing Board Layout... - Page 28 This page intentionally left blank...
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Page 29: Schematic And Bill Of Materials
Chapter 4 Schematic and Bill of Materials This chapter provides the TPS61040EVM-002 schematic and bill of materials. Topic Page Schematic ........... . -
Page 30: Schematic
Schematic 4.1 Schematic 10 µ H MBR0530 LED ANODE TPS61040DBV 0.1µ F 4.7µ F MMBZ5254BLT1 LED CATHODE 147 kΩ 249 kΩ 100 Ω DIM1 DIM2 10 kΩ 1 µ F Open 4.2 Bill of Materials Reference Description Size Part Number Designator Capacitor, ceramic, 1.0 µF, 6.3 V, Murata... - Page 31 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Texas Instruments TPS61040EVM-002...
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