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Summary of Contents for Texas Instruments APA100
- Page 1 APA100 100−W Analog Input Class-D Amplifier TPA2001D1/TAS5111 User’s Guide August 2004 Audio Power Amplifiers SLOU170...
- 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:...
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Page 3: Read This First
About This Manual This user’s guide describes the characteristics, operation, and the use of the APA100 reference design board. It covers all pertinent areas involved to properly use this reference design board along with the devices that it supports. The physical PCB layout, schematic diagram, and circuit descriptions are included. - Page 4 Related Documentation From Texas Instruments This is an example of a warning statement. A warning statement describes a situation that could potentially cause harm to you. The information in a caution or a warning is provided for your protection. Read each caution and warning carefully.
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Page 5: Table Of Contents
EVM Overview ..............Features . - Page 6 APA100 Efficiency vs Output Power With 4-W Load 5−8 APA100 Gain vs Frequency With 4-W and 8-W Load 5−9 APA100 Supply Ripple Rejection Ratio vs Frequency With 8-W Load Tables 2−1 Parts List ..............
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Page 7: Evm Overview
This reference design demonstrates how to make the TPA2001D1 and the TAS5111 into a 100-W class-D amplifier. The user’s guide discusses how the TPA2001D1 is used as an analog input class-D modulator. The analog modulator is input to the TAS5111, which is an H-bridge that effectively extends the supply range from the TPA2001D1’s 3-V rails to 29.5 V with the TAS5111. -
Page 8: Features
TAS5111, and TLV2464A. For simplicity, this EVM is referred to as the APA100 EVM to cover all parts that are supported in this user’s guide. The APA100 EVM is an evaluation module designed for a quick and easy way to evaluate the functionality and performance of the 100−W analog input class−D... -
Page 9: Tpa2001D1 And Tlv2464A Supply Voltage (3-V Reference)
(DUT). 1.3 EVM Basic Function/Block Diagram The APA100 EVM uses the TPA2001D1 as the analog modulator. The TAS5111 level shifts the 3-V, peak-to-peak output to the 18-V to 29.5-V, peak-to-peak output level of the TAS5111 enabling high−power output. The TLV2464A is used for the input gain stage, to provide a buffered midsupply voltage (1.5 V) and as feedback. -
Page 10: Apa100 Evm Block Diagram
EVM Basic Function/Block Diagram Figure 1−2. APA100 EVM Block Diagram Audio Input (TLV2464) Feedback Gain Integrator (TLV2464) Analog Input Class-D H-Bridge Modulator (TAS5111) TPA2001D1 Audio Output... -
Page 11: Pcb Design
This chapter gives layout guidelines for the APA100 reference design. Topic PCB Layout .......... -
Page 12: Pcb Layout
Figure 2−1 shows the top layer labeled with Analog Section and H-Bridge Section to demonstrate how the board is split. The bottom layer is split along the same line, as shown in Figure 2−2. Figure 2−1. APA100 Split Plane Top Layout... -
Page 13: H-Bridge Layout
Figure 2−2. APA100 Split Plane Bottom Layout 2.1.2 H-Bridge Layout The H-bridge is laid out based on recommendations from the TAS5111 data sheet and follows the same pattern as the DAVREF100 EVM board. 1) Keep local decoupling and bootstrap capacitors and resistors close to pins. -
Page 14: Pcb Layers
2.1.4 PCB Layers The APA100 EVM board is constructed on a two-layer printed−circuit board using a copper-clad FR-4 laminate material. The printed−circuit board has a dimension of 3.4 inch (86,36 mm) X 2.5 inch (63,5 mm), and the board thickness is 0.062 inch (1,57 mm). -
Page 15: Bottom Copper And Silkscreen
Figure 2−4. Bottom Copper and Silkscreen Figure 2−5. Drill Drawing 3.4 INCH PCB Layout SIZE QTY STM PLTD PLTD PLTD PLTD PLTD PLTD PLTD PCB Design... -
Page 16: Bill Of Materials
Yageo 9C12063A1R50FKHFT Yageo 9C12063A20R0JLHFT Yageo 9C12063A1002FKHFT DB Tech DB1320 Onsemi MMSZ4686T1 Diodes Inc. SMAJ33A IPC SM-782 STD PB-SUR-4P Texas Instruments TAS5111 Heavy MEtal #230 Screws Wakefield Wakefield 126 Texas Instruments TLV2464A Texas Instruments TPA2001D1 Infineon SMBT3904E6327 Description 50 V, size 603, COG, 5%... -
Page 17: Schematic
Schematic 2.3 Schematic PCB Design... -
Page 19: Evm Operation
This chapter covers in detail the operation of the APA100 EVM to guide the user in evaluating the audio power amplifier and in interfacing the APA100 EVM to an audio input and power supply. Topic Quick Start ........... -
Page 20: Quick Start
3.1 Quick Start Follow these steps to use the APA100 EVM. APA100 audio input connection can be made via a phono jack (J1), or by sol- dering to its pins. The power supply and outputs can be connected with banana connectors or wires via screw terminals. -
Page 21: Power−Up/Down Sequence
3.4 Error Signals The APA100 board has test points to monitor the error signals from the TAS5111. Test points SD and OTW gives TAS5111 state information as described in Table 3−1. -
Page 22: Changing The Gain
Changing the Gain 3.5 Changing the Gain The APA100 EVM is set with a gain of 31.4 dB, but can be adjusted. The front-end has a gain of 4.4 dB (−1.667 V/V), and a back-end gain of 27 dB (−22.4 V/V), for a total of 31.4 dB (37.3 V/V). The back-end gain needs to be kept constant, because it is set by the control-loop feedback system with the TLV2464A, TPA2001D1, and TAS5111. -
Page 23: Technical Information
Technical Information This chapter goes into the details of the design of the 100-W amplifier. The design comprises the modulator, H-bridge, operational amplifier, feedback loop, LC filter, and thermal. Topic Feedback System Design ........TPA2001D1 (Class-D Modulator) TAS5111 (H-Bridge) . -
Page 24: Feedback System Design
Feedback System Design 4.1 Feedback System Design The APA100 EVM uses feedback to lower distortion, increase supply ripple rejection, and make the gain not change with supply voltage. This section goes through the following steps to close the loop. 1) Take feedback at TAS5111 outputs before the LC filter, so that it is unnec- cary to cancel two poles of the LC filter. -
Page 25: Open- And Closed-Loop Frequency Response
operational amplifier (R22, R23, C20, C23, and C24) was eventually reduced from 400 kHz to 252 kHz to optimize performance; compensation for this is discussed later. Notice that in Figure 4−8, the switching frequency of each output is 250 kHz, but the differential frequency is 500 kHz. The poles greater than 400−kHz from the low-pass filters do not affect the stability because they are ten times the corner frequency. -
Page 26: Open- And Closed-Loop Frequency Response With Tpa2001D1 Pole And Canceling Zero
18 V/3 V = 6 V/V to 29.5 V/3 V = 9.8 V/V (17 dB to 29 dB). Adding the gains of each stage in dB: Open−loop gain = Integrator gain + 18 dB + 17 dB to 20 dB. Figure 4−4. APA100 Integrator Design Input Amplifier... - Page 27 The closed−loop gain is set to 27 dB to allow enough gain from the 3−V signal to the A+ voltage range. This leaves sufficient low−frequency correction. Figure 4−4 shows the circuit used for the APA100 feedback. Equation (2) shows the closed−loop response.
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Page 28: Pspice Circuit For Simulating The Feedback
First, resistor R18 was removed to give an open−loop response, with the APA100 output being simulated by the output of the RC filter after the third op amp. Taking the gain and phase after the RC filter takes into account the 252−kHz filtering before the feedback op amp. -
Page 29: Tpa2001D1 (Class-D Modulator)
Figure 4−6. PSPICE Simulation of Open−Loop Response −0 −100 −200 −300 4.2 TPA2001D1 (Class-D Modulator) The TPA2001D1 was chosen as an excellent performance, low-cost analog class-D modulator. A class-D modulator takes an analog input signal and outputs a pulse width modulated (PWM) signal. The TPA2001D1 was selected over other class-D amplifiers because of the following reasons. -
Page 30: Tpa2001D1 Inputs And Outputs With 20-Khz Sine Wave
TPA2001D1 (Class-D Modulator) Figure 4−7. TPA2001D1 Block Diagram Pre-Amp Gain Adj. Gain Adj. Input GAIN1 Buffers Biases GAIN0 References Gain COSC ROSC BYPASS Figure 4−8 shows the output PWM signal and the input signal of the TPA2001D1. Figure 4−8. TPA2001D1 Inputs and Outputs With 20−kHz Sine Wave Differential AGND Integrator... -
Page 31: Tas5111 (H-Bridge)
For more information concerning the TPA2001D1 operation and modulation scheme, see the TPA2001D1 data sheet http://focus.ti.com/docs/prod/folders/print/tpa2001d1.html 4.3 TAS5111 (H-Bridge) The TAS5111 converts the PWM signal from the 3-V peak-to-peak outputs of the TPA2001D1 to 18-V to 29.5-V peak-to-peak. This allows the output power to increase from 1 W with just the TPA2001D1 to 100 W with the TAS5111 H-bridge. -
Page 32: Lc Filter
The inductor must have 8 µH of inductance or more at 15 A, for overcurrent (OC) protection to be effective. The TAS5111 data sheet recommends 5 µH of inductance, but that is for a switching frequency of 380 kHz. The APA100 switches at 250 kHz and needs more inductance to protect the device. -
Page 33: Thermal
4.6 Thermal The APA100 thermal issues lie with the TAS5111. The following thermal calculations and tables are taken from the TAS5111 data sheet. The TAS5111 is designed to be interfaced directly to a heatsink using a thermal interface compound (for example, Wakefield Engineering type 126 thermal grease.) The heatsink then absorbs heat from the ICs and couples it to the local air. - Page 34 0.002 inch thick, the required heatsink thermal resistance changes to 2.4°C/W. The large heatsink used for the APA100 EVM is required for full output power sine waves over temperature. A smaller heatsink can be used for music, which requires much less average power.
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Page 35: Measured Results
This chapter shows the performance of the APA100 reference design. An Audio Precision analyzer was used to produce the graphs in this chapter. Topic Total Harmonic Distortion + Noise Output Power .......... -
Page 36: Total Harmonic Distortion + Noise
Total Harmonic Distortion + Noise 5.1 Total Harmonic Distortion + Noise The APA100 has excellent total harmonic distortion + noise (THD+N). Figure 5−1 and Figure 5−2 show the THD+N versus frequency, and Figure 5−3 and Figure 5−4 show THD+N vs output power. A 30-kHz bandwidth limit was used on the audio precision to limit switching frequency from affecting the measurement. -
Page 37: Apa100 Thd+N Vs Output Power With 4-W Load
Figure 5−3. APA100 THD+N vs Output Power With 4-W Load 0.05 0.01 10 m Figure 5−4. APA100 THD+N vs Output Power With 8-W Load 0.05 0.01 10 m f = 1 kHz, = 15 V, 18 V, 20 V, 24 V, 28 V, 29.5 V... -
Page 38: Output Power
Output Power 5.2 Output Power The APA100 can output over 100 W into 4 Ω. The curves in Figure 5−5 and Figure 5−6 show the output power versus supply voltage. Figure 5−5. APA100 Output Power vs Supply Voltage With 4-W Load Figure 5−6. -
Page 39: Efficiency
5.3 Efficiency The APA100 is a highly efficient class-D audio power amplifier. The efficiency is greater than 85% efficient with 4- or 8-Ω load. The efficiency plot is shown in Figure 5−7. Figure 5−7. APA100 Efficiency vs Output Power With 4-W Load... -
Page 40: Gain And Phase Response
Figure 5−8. APA100 Gain vs Frequency With 4-W and 8-W Load 5.5 Signal-to-Noise Ratio (SNR) The APA100 has low noise and a wide output swing. The noise does not increase with output power making the signal-to-noise ratio (SNR) just before clipping good for this type of amplifier. -
Page 41: Supply Ripple Rejection
5.6 Supply Ripple Rejection The APA100 uses a closed loop which keeps the gain from changing with supply voltage and improves the supply ripple rejection ratio (k open−loop class-D amplifier. The supply ripple rejection ratio versus frequency curve is shown in Figure 5−9.
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