Audio acquires the "write" touch

Wolfson Microelectronic's $6.64 (1000) WM9712L builds on the foundations of its WM9705 forerunner, which you can find in the latest generation of Dell (www.dell.com) and Toshiba (www.toshiba.com) Pocket PCs. This power-stingy combination of an audio codec and touchscreen-interface controller now comprises a differential or two-channel microphone input with automatic level control, a two-channel audio-line input, a separate monophonic-audio input, a PC-"beep" input, and an audio DAC that connects to the AC'97 Version 2.2 system interface. Whereas the previous generation chip's audio outputs were unamplified, Wolfson now includes a 45-mW, 16 to 32Ω, dual-channel-headset output with presence detection; a mono-phonic, 300-mW, 8Ω speaker driver; a monophonic, 30-mW, 32Ω earpiece driver; and an S/PDIF (Sony/Philips-digital-interface) digital-output capability.

Between the audio inputs and outputs, you find a multistage mixer and tone controls, a flexible sample-rate converter operating from the system clock and supporting independent ADC and DAC rates, and bass-boost and surround-sound virtualization-processing circuits. The WM9712L operates at voltages ranging from 1.8 to 3.6V, and the digital core operates as low as 1.42V. The device consumes 10 µW in sleep mode and 20 mW in headphone-playback mode. Its touchpad digitizer has 12-bit resolution and pen-down detection even if the chip is in sleep mode; the digitizer also now supports both four- and five-wire panels. Two analog inputs with comparators and a third analog input and companion ADC, let you monitor battery status and other system parameters, and five general-purpose I/Os, most of which multiplex with other functions, deliver chip-to-chip control and communication. Now available, the WM9712L comes in 7×7-mm QFN and 48-lead TQFP packages.

If your chip needs are audiocentric or your system lacks an AC-Link interface, you might instead consider the company's $4.98 (1000) WM8750L. It operates as a master or a slave and supports a variety of clock frequencies, including 12 or 24 MHz for USB and standard sampling frequencies, such as 12.288 and 24.576 MHz. The integrated DAC delivers a 98-dB, A-weighted SNR with –95 dB THD, and the ADC has a 95-dB SNR and –90-dB THD, all at 3.3V and a 48-kHz sampling rate. Estimated power-consumption is 7 mW for two-channel playback and 14 mW for two-channel simultaneous recording and playback. Also now available, the WM8750L comes in a 5×5-mm QFN package (Picture).

Wolfson Microelectronics, 1-858-676-5090, www.wolfsonmicro.com.