SDAA313A March   2026  – May 2026 INA1650-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Automotive Hi-Fi Headphone Audio System Overview
    1. 2.1 Key Technical Specifications of Automotive Hi-Fi Audio Systems
    2. 2.2 Design Requirements for Automotive Hi-Fi Headphone Audio Systems
  6. 3Automotive Hi-Fi Headphone Audio System Working Principle and Circuit Design
    1. 3.1 DAC Circuit Design
    2. 3.2 Differential-to-Single-Ended Circuit Design
  7. 4Simulation
    1. 4.1 Transient Response Simulation
    2. 4.2 Noise Analysis
    3. 4.3 Power Consumption Simulation and Thermal Calculation
  8. 5Experimental Test
  9. 6Summary
  10. 7References
  11. 8Revision History

2.1 Key Technical Specifications of Automotive Hi-Fi Audio Systems

The core technical specifications of an automotive Hi-Fi audio system include Signal-to-Noise Ratio (SNR) and Total Harmonic Distortion plus Noise (THD+N).

Signal-to-Noise Ratio (SNR) is defined as the ratio of the output signal power to the output noise power of an audio device at the same reference point, typically expressed in decibels (dB), as shown in Equation (2). In the formula, Psignal represents the output signal power and Pnoise denotes the output noise power. A higher SNR value indicates a lower level of noise superimposed on the audio signal, which corresponds to a higher sound reproduction quality, and vice versa. For automotive Hi-Fi audio systems, the SNR specification is typically required to be above 105db.

Equation 2. N R d B = 10 l o g ( P s i g n a l P n o i s e )

Total Harmonic Distortion plus Noise (THD+N) is a critical performance parameter for characterizing audio reproduction quality, and its predicted value can be calculated per Equation 3, where V n represents the RMS value of the total output noise voltage and V f denotes the RMS value of the fundamental frequency output voltage. The THD+N performance of an audio system is determined by multiple design factors, including a high-quality audio signal source, DACs and operational amplifiers with ultra-low noise and distortion, ultra-low noise power supplies, and optimized PCB layout and routing. For automotive Hi-Fi audio systems, the typical specification requires THD+N < 0.001%. Equation 3 mathematically shows that THD + N is defined as the ratio of the harmonic power measurements summed together to the power of the fundamental frequency.

Equation 3. T H D + N % = 100 % × ∑ i = 2 ∞ ( V i 2 + V n 2 ) V f 2

Where:

Vi RMS voltage of the i-th harmonic of the fundamental (i=2,3,4…)

Vn RMS noise voltage of the circuit

Vf RMS voltage of the fundamental

In addition, automotive applications impose stringent and detailed requirements for Electromagnetic Interference (EMI) performance of chips. The core requirement is compliance with international and industry standards, as well as adaptation to the complex electromagnetic environment of vehicles. Automotive chips are typically required to operate at an ambient temperature of 85°C. Therefore, the EMI performance and thermal characteristics of devices adopted in the Hi-Fi system must be considered in the design. Automobiles are generally powered by a 12V battery, so TI recommends that the supply voltage of the Hi-Fi system be less than 12V with a unipolar power supply configuration.