Headset Detection for TAx52xx Family

Abstract

A common feature in most of today's electronic devices – including cell phone, PDAs, notebooks, handheld media players, game systems, and so on, is the provision for connecting to external accessories. The devices therefore include dedicated logic circuitry that can detect not only the presence of an accessory, but also the type.

The TAx5x1x includes extensive capability to monitor a headphone, microphone (mic), or headset jack, determine if an audio plug has been inserted, and then detect what type of headset is wired to the plug. This application note mainly discusses the headset detection scheme for two different headset output configurations: pseudo-differential (capacitor-less) output, and ac-coupled output. The content of this document applies to the TAD5212, TAD5112, TAC5212, TAC5112, TAC5211, TAC5111, TAD5212-Q1, TAD5112-Q1, TAC5212-Q1, TAC5112-Q1, and TAC5111-Q1

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1 Headset Plugs and Connection Diagrams

Figure 1-1 Different Configurations of 4-Conductor Headset Plug

Figure 1-2 Connection Diagrams for Various Headsets

1.1 Part I: Pseudo-Differential (Capacitor-less) Headset Output Configuration

Figure 1-3 shows one configuration of the device that enables detection and determination of headset type when a pseudo-differential (capacitor-less) stereo headphone output connection is used. Note that for best results, it is recommended to select a MICBIAS value as high as possible, and to program the output driver common-mode level at a 1.6-V or 1.5-V level.

Figure 1-3 Device With a Pseudo-Differential (Capacitor-less) Headset Output Connection

Figure 1-4 demonstrates the internal circuitry that implements the detection logic. The two comparators in this figure is used for headphone and jack detection.

Figure 1-4 Circuit Diagram of Detection Scheme for Capacitor-less Interface