SLAAEI4 August 2024 TAC5111-Q1 , TAC5212-Q1 , TAC5311-Q1 , TAC5312-Q1 , TAC5411-Q1 , TAC5412-Q1 , TAD5212-Q1
The TAx5xxx-Q1 family of audio converters are used in automotive applications that can experience exposure to high temperature conditions and sudden fluctuations in battery supply voltage (VBAT). The TAx5xxx-Q1 generation of Texas Instruments' audio converters introduces a Distortion Limiter, Brown-out Protector, and Thermal Foldback feature that monitors battery voltage and die temperature levels. This monitor function helps protect the device from these adverse factors by automatically attenuating the output signal.
The Distortion Limiter reduces the peak of the output signal and the Brown-out Protector applies a constant gain reduction to the output signal as a function of supply voltage. In addition,Thermal Foldback automatically attenuates the output signal, by reducing the gain, if the temperature of the die exceeds a programmable limit while audio is still present at the output.
The Distortion Limiter, Brown-out, and Thermal Foldback features are algorithms within the limiter bank of the DAC signal chain present in TAx5xxx-Q1 devices. This application note describes how to configure these features for the following devices:
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Maximizing efficiency in battery-powered applications is paramount for extending battery life and maintaining high-quality audio. Audio signals that approach the limits of the dynamic range of the DAC can create distortion in the output signal and audio clipping. TAx5xxx-Q1 devices mitigate the risk of distortion and improve power consumption by allowing the user to map VBAT to the output peak because the device is continuously monitoring the output signal level with the limiter bank algorithm.
A droop in VBAT reduces the supply headroom needed to prevent audio clipping and the ability of the device to supply current is limited when the battery voltage continues to decrease. If an audio converter continues to drive significant current into a speaker, or speaker amplifier, the system battery voltage can dip below normal system operating levels. This continuous dip in voltage can potentially cause electrical damage to devices sharing the same supply, or result in the system shutting down. This type of event is commonly known as Brown Out. Texas Instruments' audio option for this problem is to incorporate a Brown-out Protector and Distortion Limiter to reduce the peak or gain of the output signal. These features grant the user control over attenuation levels based on supply voltage, which effectively manages device power consumption.
Automotive audio applications require that devices are fully-operational in high ambient temperature conditions. This device family has an overtemperature detection circuit that can enable the shutdown of input channels, MICBIAS, and on-chip boost in the DAC_FLT_CFG (P1_R80) and INT_CFG register (P0_R66) upon fault detection. The Thermal Foldback feature attenuates the audio signal based on a programmed temperature limit with audio playing to further prevent damage to the device.