User’s Guide September 2002 PMP EVMs SLLU053
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.
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.
EVM WARNINGS AND RESTRICTIONS It is important to operate this EVM within the input voltage range of 1.8 V to 6.0 V. Exceeding the specified input range may cause unexpected operation and/or irreversible damage to the EVM. If there are questions concerning the input range, please contact a TI field representative prior to connecting the input power. Applying loads outside of the specified output range may result in unintended operation and/or possible permanent damage to the EVM.
Related Documentation From Texas Instruments Preface About This Manual This user’s guide describes the characteristics, operation, and use of the TPS61042EVM–226 white light LED bias supply evaluation module (EVM). This EVM is a Texas Instruments high-efficiency boost converter that is configured to supply 20 mA of bias current to four white light LEDs, from a 1.8 V to 6 V input voltage. The user’s guide includes a schematic diagram and bill of materials (BOM).
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Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 2 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Input/Output Connections .
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Chapter 1 This chapter contains background information for the TPS61042 and support documentation for the TPS61042EVM–226 evaluation module. Topic 1.1 Page Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Background 1.1 Background This TPS61042EVM uses the TPS61042 boost converter to provide 20 mA of bias current to a four-element white LED from a 1.8 V to 6 V input. This EVM may be modified to drive more or less than four LEDs. It may also be modified to deliver a higher or lower output current to the LEDs. Refer to the data sheet for more information on adjusting the rated output current. The EVM includes a CTRL pin and an ADJ pin that allows the user to dim the LEDs.
Chapter 2 This chapter describes how to properly connect, set up, and use the TPS61042EVM-226. Topic Page 2.1 Input/Output Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 2.2 EVM Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 2.3 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input/Output Connections 2.1 Input/Output Connections The TPS61042EVM–226 PWB has several connections, which are described in Table 2–1. Table 2–1. Input/Output Connections Reference Designator Name Description J1 Vin This is the positive connection to the input power supply. The leads to the input supply should be twisted and kept as short as possible.
EVM Operation - Io_min is the minimum output current - Io_max is the maximum output current - Reference designators correspond to the EVM schematic shown in Chapter 4 R2 + V V R1 + ref ǒIo_max R3 * Io_min R3 ) Vadj_min * Vadj_maxǓ ǒVref * Vadj_minǓ ) Io_max ǒVadj_max * VrefǓ I o_min R3 ) V ref I o_min R2 * V R2 adj_max ref R3 * V ) V adj_max ref If Vref = 0.25 V, Vadj_min = 0 V, Vadj_max = 3.3 V, Io_min = 0 A, Io_max = 20 mA, and R3 = 121 kΩ, R2 is calculated to be 9.
Setup 2.2.3 PWM Dimming Using CTRL The third method for dimming the LEDs is to inject a PWM voltage into the CTRL pin of the TPS61042. The LED current is proportional to the CRTL pin duty cycle. Refer to the TPS61042 data sheet for more information on this dimming method. For this dimming method, R2 and R3 are not needed. R2 may be shorted and R3 may be removed if desired. R1 is calculated by the following equation where Vref is the reference voltage of the TPS61042 (0.
Chapter 3 This chapter provides the TPS61042EVM-226 board layout and illustrations. Topic 3.1 Page Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Layout 3.1 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 TPS61042EVM–226 PWB. The nodes with a high switching frequency are short and are isolated from the noise sensitive feedback circuitry. Careful attention has been given to the routing of high frequency current loops. Refer to the data sheet for specific layout guidelines. Figure 3–1. Assembly Layer Figure 3–2.
Layout Figure 3–3.
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Chapter 4 This chapter provides the TPS61042EVM–226 schematic and bill of materials. Topic Page 4.1 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 4.2 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Schematic 4.
Bill of Materials 4.2 Bill of Materials Table 4–1. TPS61042EVM-226 Bill of Materials Count Ref Des Description Size MFR Part Number 1 C1 Capacitor, ceramic, 4.7 µF, 6.3 V, X5R, 10% 805 Murata GRM21BR60J475KA11 1 C2 Capacitor, ceramic, 0.1 µF, 25 V, X7R, 10% 603 Murata GRM188R71E104KA01 1 D1 Diode, Schottky, 400 mA, 40 V SOD323 Zetex ZHCS400 4 D2, D3, D4, D5 Diode, LED, white, 30 mA 1210 Lumex SML–LX2832UWC–TR 3 J1, J2, J3 Header, 2-pin, 100 mil spacing, (36-pin strip) 0.
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