!" # " $ " User’s Guide February 2002 PMP EVMs SLLU037
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 This EVM is designed to operate over an input voltage range of 4.0 V to 6.0 V, and over a load range of 0 A to 3 A. It is important to operate this EVM within the specified input and output ranges described in the EVM User’s Guide. 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.
Contents Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Performance Specification Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Contents Figures 1–1 2–1 2–2 2–3 2–4 2–5 2–6 2–7 2–8 2–9 2–10 2–11 2–12 3–1 3–2 3–3 3–4 4–1 Frequency Trimming Resistor Selection Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 Connection Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 Measured Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 1 Introduction This chapter contains background information for the TPS54310 and support documentation for the TPS54310 evaluation module. The EVM performance specifications are also given. Topic Page 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1.2 Performance Specification Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1.3 Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Background 1.1 Background The TPS54310 evaluation module (EVM) uses the TPS54310 synchronous buck regulator to provide a 3.3-V output over an input range of 4.0 V to 6.0 V, and over a load range of 0 A to 3 A. Less than 0.55 square inches of board space is occupied by the electrical components of the TPS54310 circuit. Additional pads support multiple input and ouput capacitors. A jumper allows the switching frequency to be easily changed from 350 kHz to 550 kHz.
Performance Specification Summary 1.3 Modifications 1.3.1 General The TPS54310 EVM is designed to demonstrate the small amount of board space taken up by the TPS54310 electrical components. In addition, the EVM can be used to evaluate different output filters by substituting an alternate inductor for L1, or by using the optional pads for capacitors C2 and C11 (see Figure 3–1). When changing the output filter, the compensation values must also be changed to ensure that stability is maintained.
Performance Specification Summary 1.3.3 Output Voltage The output voltage of the TPS54310 EVM can be adjusted to any value down to 0.9 V by changing only one component value (R4). The value of R4 for a specific output voltage can be calculated by using equation 1–1. Table 1–2 lists the value of R4 for some common bus voltages. R 4 + 10 kW 0.891 V V –0.891 V O (1–1) Table 1–2. Output Voltage Programming 1.3.4 Output Voltage (V) R4 (kΩ) 0.9 1000 1.2 28.7 1.5 14.7 1.8 9.76 2.5 5.49 3.3 3.
Performance Specification Summary Table 1–3. Alternate Compensation for Improved Transient Response Reference Designator Component Value R2 15 kΩ R4 3.74 kΩ R5 10 kΩ R6 1.
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Chapter 2 Test Setup and Results This chapter describes how to properly connect, setup, and use the TPS54310 EVM. It also presents the test results and covers efficiency, output voltage regulation, load transients, loop response, output ripple, input ripple, and start-up. Topic Page 2.1 Input/Output Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 2.2 Loop Characterization Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 2.
Input/Output Connections 2.1 Input/Output Connections The TPS54310 EVM has the following four input/output connections: J1 (Vin and GND) and J3 (Vout and GND). A diagram showing the connection points is shown in Figure 2–1. Connect a power supply capable of supplying 3 A to J1 through a pair of 20 AWG wires. Connect the load to J3 through a pair of 20 AWG wires. Minimize wire lengths to reduce losses in the wires.
Loop Characterization Setup 2.2 Loop Characterization Setup The TPS54310 EVM contains a 49.9 Ω resistor (R7) in the feedback path for use in measuring the loop response. Test points on either side of R7 (TP5 and TP7) provide connection points for network analyzer signals. By injecting a small ac signal across R7, the loop gain and phase can be measured from one side of R7 to the other.
Thermal Performance Figure 2–3. Measured Board Losses 1.2 TA = 25°C VI = 5 V 1 Losses – W 0.8 0.6 0.4 0.2 0 0 0.5 1 1.5 2 IL – Load Current – A 2.5 3 2.4 Thermal Performance The junction temperature is plotted versus the load current with a 5-V input voltage and a 25°C ambient temperature in Figure 2–4. The low junction-tocase thermal resistance of the PWP package, along with a good board layout, helps to keep the junction temperature low at high output currents.
Output Voltage Regulation 2.5 Output Voltage Regulation The output voltage load regulation, with a 5-V input and a 25°C ambient temperature, is shown in Figure 2–5. Over the load range of 0 A to 3 A, the output voltage varies less than 0.2%. Figure 2–5. Measured Load Regulation 1.01 TA = 25°C VI = 5 V 1.008 VO – Output Voltage – V (Normalized to 1.5 A Load) 1.006 1.004 1.002 1 0.998 0.996 0.994 0.992 0.99 0 0.5 1 1.5 2 2.
Load Transients 2.6 Load Transients The TPS54310 EVM response to load transients is shown in Figure 2–6. The load transient in Figure 2–6 transitions between 0 A and 3 A. The output voltage deviates approximately –95 mV (–2.9%) and 75 mV (2.3%) from its average value as a result of these transients. In Figure 2–6, the output voltage returns to a ±2% regulation band within 30 µs. Using the alternate feedback compensation described in Section 1.3.
Loop Characteristics 2.7 Loop Characteristics The loop gain and phase for a 5.0-V input and a 3.0-A load is shown in Figure 2–8. The loop crossover frequency is approximately 30 kHz, and the phase margin is approximately 75°. Figure 2–9 shows the loop response using the alternate compensation described in Section 1.3.5 Improving Transient Response. With the alternate feedback compensation, the loop crossover frequency is approximately 75 kHz, and the phase margin is approximately 72°. Figure 2–8.
Output Voltage Ripple 2.8 Output Voltage Ripple The output ripple voltage is plotted in Figure 2–10 with an input voltage of 5.0 V and a load current of 3 A. The TPS54310 EVM has a typical output voltage ripple of less than 33 mVpp. If the switching frequency is reduced, the output ripple voltage is higher. The output ripple voltage can be decreased by using a larger inductor, or by reducing the equivalent series resistance of the output capacitor.
Input Ripple Voltage 2.9 Input Ripple Voltage The input ripple voltage for a 3-A load is shown in Figure 2–11. With an input voltage of 5.0 V, the input ripple is approximately 120 mVpp. The input ripple voltage can be made lower by adding capacitance to the input. Figure 2–11.
Start-Up 2.10 Start-Up Figure 2–12 shows the start-up voltage waveform of the TPS54310 EVM with C1 left open. The input voltage is displayed on channel 3, the output voltage on channel 1, and the power good signal on channel 2. Once the input voltage rises above the 2.9-V start-up threshold, the output voltage begins to rise linearly to 3.3 V in 3.6 ms. When the output voltage has reached its final value, the open-drain power good signal rises to a high state.
Chapter 3 Board Layout This chapter provides a description of the TPS54310 EVM board layout and layer illustrations. Topic 3.1 Page Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Layout 3.1 Layout The top-side layer for the TPS54310 EVM is shown in Figure 3–1. The input capacitors (C8 and C9), bias decoupling capacitor (C3), and bootstrap capacitor (C7), are all located as close to the IC as possible. In addition, the feedback compensation components are also kept close to the IC. The compensation circuit ties to the output voltage at the point of regulation (TP7). The TPS54310 EVM PWB consists of two layers of 1.5 oz. copper.
Layout Figure 3–2.
Layout Figure 3–3.
Layout Figure 3–4.
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Chapter 4 Schematic and Bill of Materials The EVM schematic and bill of materials are presented in this chapter. Topic Page 4.1 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 4.2 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Schematic 4.1 Schematic Figure 4–1. TPS54310 EVM Schematic J1 VIN GND TP1 VIN 2 1 + C2 JP1 R3 TP2 71.5 kΩ 20 19 J2 18 SYNCH SS/ENA GND PWRGD 17 4 C1 C3 0.1 µF 3 2 1 R1 10 kΩ VIN TP3 C4 100 pF 4-2 R4 3.74 kΩ VIN C8 10 µF 16 15 VIN VIN 14 10 PH VBIAS 9 PWRGD PH 8 PH COMP/NC 7 PH 6 PH 5 VSENSE BOOT 13 PGND 12 ANAGND PGND 11 PGND SYNCH TP4 L1 1.2 µH SS/ENA TP7 + C7 TP5 R6 R7 2700 pF 732 Ω 49.9 Ω R5 + C10 TP8 C6 10 kΩ C9 180 µF 4V TP6 J3 0.
Bill of Materials 4.2 Bill of Materials Table 4–1. TPS54310 EVM BIll of Materials Count Ref Des Description Size MFR Part Number 1 C1 Open 603 1 C11 Capacitor, ceramic, 1000 pF, 25 V, X7R, 10% 603 Vishay VJ0603Y102KXXAT 2 C2, C10 Open 7343 (D) 1 C3 Capacitor, ceramic, 0.
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