Driver ICs
STMicroelectronics introduces a headset and speaker driver IC for mobile phones that includes an audio amplifier and digital volume control. The TS4851 offers controllable gain for left and right audio channels, plus a separate mono input for a microphone without a gain control. The TS4855 has an additional gain path that can be used for another input, such as a hands-free microphone. The TS4851 includes an audio amplifier that can deliver a typical 400 mW of continuous RMS output power into an 8 Ω load with 1% THD+N. A headset driver will drive a typical 30 mW of continuous average power into each channel of a stereo 32 Ω bridged-tied load with 0.5% THD+N, given a 3.3 V supply. The TS4855 includes an audio amplifier that can deliver a typical 1.1 W of continuous RMS output power into an 8 Ω speaker with 1% THD+N. A headset driver will drive a typical 85 mW of continuous average power into each channel of a stereo 32 Ω bridged-tied load with 0.5% THD+N, given a 5 V supply. Both parts have a 32-step digital volume control and eight output modes, which control the combination of headset channels, speaker, inputs and volume that is used. The digital volume and output modes are controlled through a three-wire SPI bus interface. Both parts support rail to rail inputs and outputs, and include pop and click reduction circuitry. Both work from a supply voltage of between 3 V and 5 V. The current drain when they are in shutdown mode is a typical 0.1 μA. The parts feature thermal shutdown protection.
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