|TAS5704||20-W Stereo Digital Audio Power Amplifier With Feedback|
|TAS5704 Datasheet PDF : 34 Pages |
SLOS563 – MARCH 2008
The circuit is designed for a CBYP value of 1 µF for best pop performance. The input capacitors should have the
same value. A ceramic or tantalum low-ESR capacitor is recommended.
USING LOW-ESR CAPACITORS
Low-ESR capacitors are recommended throughout this application section. A real (as opposed to ideal) capacitor
can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this resistor
minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this resistance,
the more the real capacitor behaves like an ideal capacitor.
PRINTED-CIRCUIT BOARD (PCB) LAYOUT
Because the TAS5704 is a class-D amplifier that switches at a high frequency, the layout of the printed-circuit
board (PCB) should be optimized according to the following guidelines for the best possible performance.
• Decoupling capacitors—The high-frequency 0.1-µF decoupling capacitors should be placed as close to the
PVCC, VR_DIG, and AVCC terminals as possible. The BYPASS capacitor and VCLAMP_XX capacitors
should also be placed as close to the device as possible. Large (220-µF or greater) bulk power-supply
decoupling capacitors should be placed near the TAS5704 on the PVCCx terminals. For single-ended
operation, a 220 µF capacitor should be placed on each PVCC pin. For Bridge-tied operation, a single 220
µF, capacitor can be shared between A and B or C and D.
• Grounding—The AVCC decoupling capacitor and BYPASS capacitor should each be grounded to analog
ground (AGND). The PVCCx decoupling capacitors and VCLAMP_xx capacitors should each be grounded to
power ground (PGND). Analog ground and power ground should be connected at the thermal pad, which
should be used as a central ground connection or star ground for the TAS5704.
• Output filter—The reconstruction LC filter should be placed as close to the output terminals as possible for the
best EMI performance. The capacitors should be grounded to power ground.
• Thermal pad—The thermal pad must be soldered to the PCB for proper thermal performance, audio
performance, and optimal reliability. The dimensions of the thermal pad and thermal land are described in the
mechanical section at the back of the data sheet. See TI Technical Briefs SLMA002 and SLOA120 for more
information about using the thermal pad. For recommended PCB footprints, see figures at the end of this data
For an example layout, see the TAS5704 Evaluation Module (TAS5704EVM) User Manual, (SLOU189). Both the
EVM user manual and the thermal pad application note are available on the TI Web site at http://www.ti.com.
BASIC MEASUREMENT SYSTEM
This section focuses on methods that use the basic equipment listed below:
• Audio analyzer or spectrum analyzer
• Digital multimeter (DMM)
• Twisted-pair wires
• Signal generator
• Power resistor(s)
• Linear regulated power supply
• Filter components
• EVM or other complete audio circuit
Figure 31 shows the block diagrams of basic measurement systems for class-AB and class-D amplifiers. A sine
wave is normally used as the input signal because it consists of the fundamental frequency only (no other
harmonics are present). An analyzer is then connected to the audio power amplifier (APA) output to measure the
voltage output. The analyzer must be capable of measuring the entire audio bandwidth. A regulated dc power
supply is used to reduce the noise and distortion injected into the APA through the power pins. A System Two™
audio measurement system (AP-II) by Audio Precision™ includes the signal generator and analyzer in one
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TAS5704
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