TPA005D02 Class D Stereo Audio Power Amplifier Evaluation Module User’s Guide October 1998 Mixed-Signal Products SLOU032A
IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete.
Preface Related Documentation From Texas Instruments J J TI Plug-N-Play Audio Amplifier Evaluation Platform (literature number SLOU011) provides detailed information on the evaluation platform and its use with TI audio evaluation modules. TPA005D02 CLASS D STEREO AUDIO POWER AMPLIFIER (literature number SLOS227) This is the data sheet for the TPA005D02 audio amplifier integrated circuit. FCC Warning This equipment is intended for use in a laboratory test environment only.
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Running Title—Attribute Reference Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Feature Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.
Running Title—Attribute Reference Figures 1–1 The TI TPA005D02 Class D Stereo Audio Amplifier Evaluation Module . . . . . . . . . . . . . . . 1-3 2–1 Quick Start Platform Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 3–1 The TI Plug-N-Play Audio Amplifier Evaluation Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 3–2 TPA005D02 Class D EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 1 Introduction This chapter provides an overview of the Texas Instruments (TI) TPA005D02 Class D Stereo Audio Amplifier Evaluation Module (SLOP223). It includes a list of EVM features, a brief description of the module illustrated with a pictorial diagram, and a list of EVM specifications. Topic Page 1.1 Feature Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2 1.2 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Feature Highlights 1.
Description 1.2 Description The TPA005D02 Class D Stereo Audio Power Amplifier Evaluation Module is a complete, 2-Watt per channel stereo audio power amplifier. It consists of the TI TPA005D02 Class D Stereo Audio Power Amplifier IC along with a small number of other parts mounted on a circuit board that measures approximately 2 1/4 inches by 1 3/4 inches (Figure 1–1). Figure 1–1.
TPA005D02 Class D EVM Specifications 1.3 TPA005D02 Class D EVM Specifications Supply voltage range, VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 V to 5.5 V Supply current, IDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 A max Continuous output power per channel, PO: 4-Ω BTL, VDD = 5 V . . . . . . . . . . . . . . . . . . . . . . 2 W . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2 Quick Start Follow the steps in this chapter to quickly prepare the TPA005D02 Class D Stereo Audio Amplifier EVM for use. Using the TPA005D02 class D EVM with the TI Plug-N-Play Audio Amplifier Evaluation Platform is a quick and easy way to connect power, signal and control inputs, and signal outputs to the EVM using standard connectors.
Precautions 2.1 Precautions Power Supply Input Polarity and Maximum Voltage Always ensure that the polarity and voltage of the external power connected to VCC power input connector J1, J2, and/or VDD power input connector J6 are correct. Overvoltage or reverse-polarity power applied to these terminals can open onboard soldered-in fuses and cause other damage to the platform, installed evaluation modules, and/or the power source.
Quick Start List for Platform 2.2 Quick Start List for Platform Follow these steps when using the TPA005D02 class D EVM with the TI PlugN-Play Audio Amplifier Evaluation Platform (see the platform user’s guide, SLOU011, for additional details). Numbered callouts for selected steps are shown in Figure 2–1 and details appear in Chapter 3. - Platform Preparations 1) Ensure that all external power sources are set to OFF and that the platform power switch S1 is set to OFF.
Quick Start List for Stand-Alone 2.3 Quick Start List for Stand-Alone Follow these steps to use the TPA005D02 class D EVM stand-alone or to connect it into existing circuits or equipment. Connections to the TPA005D02 module header pins can be made via individual sockets, wire-wrapping, or soldering to the pins, either on the top or the bottom of the module circuit board. - Power supply 1) Ensure that all external power sources are set to OFF.
Chapter 3 Details This chapter provides details on the TPA005D02 IC, the evaluation module, and the steps in the Quick-Start List, a discussion on class D amplifiers, additional application information, a parts list for the TPA005D02 class D evaluation module, module performance graphs, and module PCB layer illustrations. Topic Page 3.1 Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 3.
Precautions 3.1 Precautions Power Supply Input Polarity and Maximum Voltage Always ensure that the polarity and voltage of the external power connected to VCC power input connector J1, J2, and/or VDD power input connector J6 are correct. Overvoltage or reverse-polarity power applied to these terminals can open onboard soldered-in fuses and cause other damage to the platform, installed evaluation modules, and/or the power source.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2 The TPA005D02 Audio Power Amplifier Evaluation Module The TPA005D02 Class D Stereo Audio Power Amplifier Evaluation Module is powered by a TPA005D02 class D stereo power amplifier integrated circuit capable of delivering greater than 2 W of continuous power per channel into 4-Ω loads. The amplifier IC operates in the bridge-tied load mode for maximum efficiency.
The TPA005D02 Audio Power Amplifier Evaluation Module Figure 3–3. TPA005D02 Class D EVM Schematic Diagram VDD VDD S2 2 3 Mute C7 LIN+ LIN– C6 1 µF 5 1 µF 4 C8 6 470 pF 7 C2 RIN+ C3 RIN– 1 µF 44 1 µF C4 45 470 pF 43 17 19 30 C5 470 pF 48 47 46 20 C19 C21 0.047 µF 1 µF 22 28 26 23 24 25 C20 0.047 µF 3.2.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2.2 Overview of Class D Audio Amplifiers Class D audio amplifiers are very similar in operation to switch-mode power supplies in that both compare an input signal with a reference to create an error voltage that controls a pulse-width modulator (PWM) circuit. The PWM then produces an output signal at constant frequency and with a duty cycle that varies according to the input signal.
The TPA005D02 Audio Power Amplifier Evaluation Module The H-bridge circuit consists of DMOS power transistors for supplying the heavy currents which are required by the load. These transistors operate in either the cutoff or saturation regions rather than the linear region in which class AB amplifiers operate.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2.3 EVM Design Considerations Circuit design and layout plays a large role in the creation or reduction of distortion in class D amplifiers, and the high frequency switching characteristics of class D audio power amplifier output stages offer some interesting design challenges over conventional class AB amplifiers. The main goal of the design of this EVM is to offer the best performance with the smallest components, without sacrificing performance.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2.3.2 Output Filter Class D amplifiers require special filtering at the output to remove the high-frequency switching component and accurately reconstruct the audio signal. The output filter is a low-pass filter (LPF) which sets the high frequency –3-dB point of the bandwidth. The major consideration here is how to choose the components and set the desired –3-dB point. Filter Design Goals A second-order low-pass filter is used for the output filter.
The TPA005D02 Audio Power Amplifier Evaluation Module The transfer function is easily derived by using a voltage divider equation with the load voltage being a parallel combination of RL and CL. This transfer function is V (s) O V (s) I + S2 ) 1 LC 1 R C L L L S ) LC1 L The next step is to set the terms of the circuit transfer function equal to the terms of the normalized 2nd-order Butterworth low-pass filter and solve for L and CL in terms of RL.
The TPA005D02 Audio Power Amplifier Evaluation Module The component equations adjusted for bridged amplifiers are + Ǹ2 Ǹ2 L + BTL 2 C 1 R L BTL ω0 R L ω0 To find component values, let fc = 30 kHz, which yields ω0 = 188495.6 radians/ second. If a 4-Ω speaker is used, RL = 4 Ω. This yields LBTL = 15 µH and CBTL = 0.94 µF. Additional capacitors can be added from each side of RL to ground to provide a high-frequency short to ground. These additional capacitors should be approximately 10% of 2CBTL.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2.3.3 Power Filtering Power supply considerations include power supply decoupling and high frequency bypass loops. Electrolytic capacitors are used for decoupling and ceramic or mica capacitors are used for high frequency bypass applications. Decoupling capacitors serve to smooth the input voltage and assist the amplifier by providing current when needed.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2.3.4 Ground Plane Experimentation with several types of ground planes has shown that a solid ground plane works as well as methods that split the analog and power ground planes when good layout practices are followed. This allows a much simpler design that requires less time and is less prone to layout errors.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2.3.6 Control and Indicator Circuits The shutdown circuit, the mute circuit, and the fault indicator circuit are all low-current circuits and are not as critical in the layout design as the circuits mentioned previously. Shutdown The shutdown control (IC pin 1) is activated by a logic low. Shutdown limits the supply current of the TPA005D02 to 400 µA to conserve power in low power applications.
The TPA005D02 Audio Power Amplifier Evaluation Module Fault Indicator The TPA005D02 IC has two fault indicator pins (IC pins 41 and 42) to indicate an under-voltage condition or a thermal fault. When the device is operating normally, both pins are pulled up to the supply voltage through R6/D2 and R7/D3. If the power supply voltage drops too low, the charge pump voltage drops below the operational threshold and the low-side transistors short to ground.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2.4 Efficiency of Class D vs. Linear Operation Amplifier efficiency is defined as the ratio of output power delivered to the load to power drawn from the supply. In the efficiency equation below, PL is power across the load and PSUP is the supply power. Efficiency + h + PP L SUP A high-efficiency amplifier has a number of advantages over one with lower efficiency.
The TPA005D02 Audio Power Amplifier Evaluation Module Figures 3–10 and 3–11 show the currents and voltages of the half-bridge circuit. When transistor M1 is on and M2 is off, the inductor current is approximately equal to the supply current. When M2 switches on and M1 switches off, the supply current drops to zero, but the inductor keeps the inductor current from dropping. The additional inductor current is flowing through M2 from ground.
The TPA005D02 Audio Power Amplifier Evaluation Module Given these plots, the efficiency of the class D device can be calculated and compared to an ideal linear amplifier device. In the derivation below, a sine wave of peak voltage (VP) is the output from an ideal class D and linear amplifier and the efficiency is calculated.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2.4.2 Losses in a Real-World Class D Amplifier Losses make class D amplifiers nonideal, and reduce the efficiency below 100%. These losses are due to the output transistors having a nonzero RDS(on), and rise and fall times that are greater than zero. The loss due to a nonzero RDS(on) is called conduction loss, and is the power lost in the output transistors at nonswitching times, when the transistor is ON (saturated).
The TPA005D02 Audio Power Amplifier Evaluation Module Losses due to rise and fall times are called switching losses. A plot of the output, showing switching losses, is shown in Figure 3–14. Figure 3–14. Output Switching Losses 1 f SW tSWon + tSWoff = tSW Rise and fall times are greater than zero for several reasons. One is that the output transistors cannot switch instantaneously because (assuming a MOSFET) the channel from drain to source requires a specific period of time to form.
The TPA005D02 Audio Power Amplifier Evaluation Module There is a minor power supply savings with a class D amplifier versus a linear amplifier when amplifying sine waves. The difference is much larger when the amplifier is used strictly for music. This is because music has much lower RMS output power levels, given the same peak output power (Figure 3–15); and although linear devices are relatively efficient at high RMS output levels, they are very inefficient at mid-to-low RMS power levels.
The TPA005D02 Audio Power Amplifier Evaluation Module 3.2.4.4 Class D Effect on Battery Life Battery operations for class D amplifiers versus linear amplifiers have similar power supply savings. The essential contributing factor to longer battery life is lower RMS supply current. Figure 3–17 compares the TPA005D02 supply current to the supply current of the TPA0202, a 2-W linear device, while playing music at different peak voltage levels. Figure 3–17.
Using The TPA005D02 Class D EVM With the Plug-N-Play Platform 3.3 Using The TPA005D02 Class D EVM With the Plug-N-Play Platform The TPA005D02 Class D Stereo Audio Amplifier Evaluation Module was designed to be used with the TI Plug-N-Play Audio Amplifier Evaluation Platform. It simply plugs into socket U2. The following paragraphs provide additional details for using the TPA005D02 class D EVM with the platform. 3.3.
Using The TPA005D02 Class D EVM With the Plug-N-Play Platform 3.3.2 Module Switches The TPA005D02 Class D Stereo Audio Amplifier Evaluation Module is equipped with two pushbutton switches that allow the module shutdown and mute functions to be manually activated. 3.3.2.1 S1 — Shutdown To have the module amplifier IC enter the shutdown mode, press the Shutdown switch (S1) on the module. S1 connects the amplifier IC SHUTDOWN pin to ground, forcing it into a low-power state.
Using The TPA005D02 Class D EVM With the Plug-N-Play Platform 3.3.3 Signal Routing Signal flow on the platform is controlled by two signal routing switches, as shown in Figure 3 – 18. Figure 3–18. Platform Signal Routing and Outputs Off + Audio Input R R R U1 Signal Conditioning S2 – U2 TPA005D02 Amplifier EVM – L L L J7, J8, J9 Speaker Outputs + On U2 – U4 R U5 Stereo Headphone Amplifier R S3 + – J10 Headphone Output – GND L L + U5 3.3.3.
Using The TPA005D02 Class D EVM With the Plug-N-Play Platform 3.3.4 Mute The TPA005D02 class D EVM is equipped with a mute control input pin. When this input is tied to GND, the TPA005D02 amplifier IC on the module enters the mute mode and dissipates very little power. When the EVM control input is tied to VDD or allowed to float, amplifier operation resumes.
Power Requirements 3.3.5 Power Requirements The TPA005D02 Class D Stereo Audio Power Amplifier Evaluation Module is designed to operate from a supply voltage between 4.5 V and 5.5 V. For best performance (highest output power with lowest distortion), the module should be operated on at least 5 V.
Inputs and Outputs 3.3.6 Inputs and Outputs The TI Plug-N-Play Audio Amplifier Evaluation Platform is equipped with several standard conectors for audio inputs and outputs. 3.3.6.1 Inputs In most cases, audio signals enter the platform through either a pair of RCA phono jacks (J3 and J5) or a miniature (1/8″) stereo phone jack (J4). Certain signal conditioning and amplifier EVMs, however, may have additional signal input connectors mounted on the module circuit board.
Using The TPA005D02 Class D EVM Stand-Alone 3.4 Using The TPA005D02 Class D EVM Stand-Alone Using the TPA005D02 Class D Stereo Audio Power Amplifier Evaluation Module stand-alone is much the same as using it with the platform. The same 4.5-V to 5.5-V power supply range and the isolated OUT+ and OUT– lines for BTL operation requirement exists. Power can be connected to either VDD pin on the module.
TPA005D02 Audio Power Amplifier Evaluation Module Parts List 3.5 TPA005D02 Audio Power Amplifier Evaluation Module Parts List Table 3–3. TPA005D02 Class D EVM Parts List Reference Description Size EVM Qty. Manufacturer/ Part Number C1, C2, C3, C6 C7, C9, C12, C13, C16, C17, C18, C19 Capacitor, Ceramic, 1 µF, 16 V, Y5V, +80% –20% 0805 12 muRata GRM40Y5V105Z16 C4, C5, C8 Capacitor, Ceramic, 470 pF, 50 V, X7R, 10% 0603 3 muRata GRM39X7R471K50 C20, C21 Capacitor, Ceramic, 0.
TPA005D02 Class D EVM Measured Characteristics 3.6 TPA005D02 Class D EVM Measured Characteristics The TPA005D02 Class D Stereo Audio Power Amplifier EVM was tested using an Audio Precision 2322, a 5-V regulated DC power supply, the TI PNP Audio Power Amplifier Evaluation Platform set up as described in Chapter 2, and 4-W speaker loads. The results are shown in Figures 3–22 through 3–25.
TPA005D02 Class D EVM Measured Characteristics Total harmonic distortion plus noise (THD+N) versus output power is shown in Figure 3–23. A lower power levels (less than 40 mW), most of the distortion is contributed by the class D amplifier device. Distortion at mid and high power levels (40 mW to 1.9 W) is a function of the output filter components, particularly the inductors. A slight increase in supply voltage over 5 V substantially reduces the harmonic distortion at power levels above 500 mW.
TPA005D02 Class D EVM Measured Characteristics THD+N versus frequency is shown in Figure 3–24, and correlates with the data shown in Figure 3–23. The rise in distortion at higher frequencies is due primarily to the increase in crosstalk with frequency (Figure 3–25). The crosstalk was measured at full output power, which is the worst-case scenario. Crosstalk may be reduced by using shielded inductors in the output filter. Figure 3–24.
TPA005D02 Class D EVM PCB Layers 3.7 TPA005D02 Class D EVM PCB Layers The following illustrations depict the TPA005D02 class D EVM PCB layers. These drawings are not to scale. Gerber plots can be obtained from any TI Sales Office. Figure 3–26.
TPA005D02 Class D EVM PCB Layers Figure 3–28. TPA005D02 Class D EVM 2nd Layer Figure 3–29.
TPA005D02 Class D EVM PCB Layers Figure 3–30.
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