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AP A100 100−W Analog Input Class-D Amplifier TP A2001D1/T AS5111 August 2004 Audio Power Amplifiers User ’ s G uide SLOU170.
IMPORT ANT NOTICE T exas 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.
Information About Cautions and Warnings iii Preface Read This First About This Manual This user ’s guide describes the characteristics, operation, and the use of the AP A100 reference design board. It covers all pertinent areas involved to properly use this reference design board along with the devices that it supports.
Related Documentation From T exas Instruments iv This is an example of a warning statement. A warning statement describes a situation that could potentially cause harm to you . Th e information in a caution or a warning is provided for your protection.
Contents v Contents 1 EVM Overview 1-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Features 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Contents vi Figures 1−1 THD+N vs Output Power (a), THD+N vs Frequency (b) 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1−2 AP A100 EVM Block Diagram 1-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1 EVM Overview EVM Overview This reference design demonstrates how to make the TP A2001D1 and the T AS51 1 1 into a 100-W class-D amplifier . The user’s guide discusses how the TP A2001D1 is used as an analog input class-D modulator .
Features 1-2 1.1 Features This reference design or evaluation module (EVM) features the TP A2001D1, T AS51 1 1, and TL V2464A. For simplicity , this EVM is referred to as the AP A100 EVM to cover all parts that are supported in this user ’ s guide.
EVM Basic Function/Block Diagram 1-3 EVM Overview an d NPN transistor circuit is used to create the 3-V supply for the TP A2001D1 and TL V2464A; therefore, the user only needs to apply the single-supply voltage.
EVM Basic Function/Block Diagram 1-4 Figure 1−2. AP A100 EVM Block Diagram Audio Input Gain (TL V2464) Feedback and Integrator (TL V2464) Audio Output Analog Input Class-D Modulator TP A2001D1 H-Bri.
2-1 PCB Design PCB Design This chapter gives layout guidelines for the AP A100 reference design. T opic Page 2.1 PCB Layout 2-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Bill of Materials 2-6 .
PCB Layout 2-2 2.1 PCB Layout The critical part of the design lies particularly in the layout process. The EVM layout should be followed exactly for optimal performance. The main concern is the placement of components and the proper routing of signals.
PCB Layout 2-3 PCB Design Figure 2−2. AP A100 Split Plane Bottom Layout 2.1.2 H-Bridge Layout The H-bridge is laid out based on recommendations from the T AS51 1 1 data sheet and follows the same pattern as the DA VREF100 EVM board. 1) Keep local decoupling and bootstrap capacitors and resistors close to pins.
PCB Layout 2-4 3) Us e a split ground plane to keep high switching ground currents from the operational amplifier circuitry . 4) Place decoupling capacitors close to the TL V2464A and TP A2001D1 5) Pl.
PCB Layout 2-5 PCB Design Figure 2−4. Bottom Copper and Silkscreen Figure 2−5. Drill Drawing SIZE QTY STM PL TD 18 4 PL TD 28 40 PL TD 42 21 PL TD 89 3 PL TD 1 16 6 PL TD 140 4 PL TD 3.
Bill of Materials 2-6 2.2 Bill of Materials T able 2−1. Parts List Reference Qty V alue Manufacturer Part Number Description C23,24 2 22 pF TDK C1608C0G1H220J 50 V , size 603, COG, 5% C13,19,20,R25 .
Schematic 2-7 PCB Design 2.3 Schematic.
2-8.
3-1 EVM Operation EVM Operation This chapter covers in detail the operation of the AP A100 EVM to guide the user in evaluating the audio power amplifier and in interfacing the AP A100 EVM to an audio input and power supply . T opic Page 3.1 Quick Start 3-2 .
Quick Start 3-2 3.1 Quick Start Follow these steps to use the AP A100 EVM. AP A100 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.
Power−Up/Down Sequence 3-3 EVM Operation Power Up 6) Press and hold the RESET button (S1) 7) V erify correct voltage and input polarity , and set the external power supply to on . 8) Depress the RESET button (S1). The EVM begins operation. 9) Adjust the signal source level as needed.
Changing the Gain 3-4 3.5 Changing the Gain The AP A100 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.
4-1 T echnical Information T echnical 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. T opic Page 4.1 Feedback System Design 4-2 .
Feedback System Design 4-2 4.1 Feedback System Design The AP A100 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.
Feedback System Design 4-3 T echnical Information 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 dif ferential frequency is 500 kHz.
Feedback System Design 4-4 Figure 4−3. Open− and Closed−Loop Frequency Response With TP A2001D1 Pole and Canceling Zero Open Loop Gain Closed Loop Gain Fc = 40 kHz 0 Degrees −90 Degrees Phase .
Feedback System Design 4-5 T echnical Information Th e 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 AP A100 feedback.
Feedback System Design 4-6 Instead of calculating the bandwidth, PSPICE was used with a linearized circuit (see Figure 4−5) to simulate and adjust the component values to approximately 40-kHz bandwidth. Then, Equations 7 and 8 were used to set the poles and zeros.
TP A2001D1 (Class-D Modulator) 4-7 T echnical Information Figure 4−6. PSPICE Simulation of Open−Loop Response f − Frequency − Hz T AS51 1 1 Output (dB) Integrator Output (dB) 200 100 −0 −100 −200 −300 100 1 k 10 k 100 k 1 M Phase ( 5 ) 4.
TP A2001D1 (Class-D Modulator) 4-8 Figure 4−7. TP A2001D1 Block Diagram _ + Gain Adj. _ + + _ cmv Gain Adj. Rs2 Rs1 _ + _ + Cint2 Cint1 _ + Deglitch Logic Deglitch Logic Comparator Integrator Pre-Am.
T AS51 1 1 (H-Bridge) 4-9 T echnical Information For more information concerning the TP A2001D1 operation and modulation scheme, see the TP A2001D1 data sheet http://focus.ti.com/docs/prod/folders/print/tpa2001d1.html 4.3 T AS51 1 1 (H-Bridge) The T AS51 1 1 converts the PWM signal from the 3-V peak-to-peak outputs of the T P A2001D1 to 18-V to 29.
LC Filter 4-10 4.5 LC Filter The LC filter serves two purposes in this design. 1) Reduces EMI 2) Enables overcurrent (OC) protection. Th e outputs of the T AS51 1 1 are square waves with fast rise and fall times. The square waves produce harmonics up to 500 MHz.
Thermal 4-1 1 T echnical Information 4.6 Thermal The AP A100 thermal issues lie with the T AS51 1 1. The following thermal calculations and tables are taken from the T AS51 1 1 data sheet.
Thermal 4-12 As an indication of the importance of keeping the thermal grease layer thin, if the thermal grease layer increases to 0.002 inch thick, the required heatsink thermal resistance changes to 2.4 ° C/W . The large heatsink used for the AP A100 EVM is required for full output power sine waves over temperature.
5-1 Measured Results Measured Results This chapter shows the performance of the AP A100 reference design. An Audio Precision analyzer was used to produce the graphs in this chapter . T opic Page 5.1 T otal Harmonic Distortion + Noise 5-2 . . . . . . .
T otal Harmonic Distortion + Noise 5-2 5.1 T otal Harmonic Distortion + Noise The AP A100 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 .
T otal Harmonic Distortion + Noise 5-3 Measured Results Figure 5−3. AP A100 THD+N vs Output Power With 4- W Load 20 5 1 0.5 0.1 0.05 0.01 10 m 1 2 10 20 100 200 THD+N − T otal Harmonic Distortion + Noise − % P O − Output Power − W f = 1 kHz, PV DD = 15 V , 18 V , 20 V , 24 V , 28 V , 29.
Output Power 5-4 5.2 Output Power The AP A100 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.
Efficiency 5-5 Measured Results 5.3 Efficiency The A P A100 is a highly ef ficient class-D audio power amplifier . The ef ficiency is greater than 85% efficient with 4- or 8- Ω load.
Gain and Phase Response 5-6 5.4 Gain and Phase Response Th e A P A100 is a closed−loop, class-D audio power amplifier with an LC output filter . The output filter and the 39-kHz loop bandwidth limit the bandwidth of the AP A100 reference design. The gain versus frequency curve is shown in Figure 5−8.
Supply Ripple Rejection 5-7 Measured Results 5.6 Supply Ripple Rejection The AP A100 uses a closed loop which keeps the gain from changing with supply voltage and improves the supply ripple rejection ratio (k SRR ) over an open−loop class-D amplifier .
5-8.
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