Consumer ICs
Volume 9, Issue 1 YOUR SEMICONDUCTOR SOLUTIONS RESOURCE

Low Voltage Touch Screen Controller Reduces Noise with On-Chip Filters

The AD7879 is a 12-bit successive approximation ADC with a synchronous serial interface and low on-resistance switches for driving 4-wire resistive touch screens. It works with a very low power supply—single 1.6 V to 3.6 V—and features throughput rates of 105 kSPS. The device includes a shutdown mode that reduces its current consumption to less than 6 µA.

To reduce the effects of noise from LCDs and other sources, the AD7879 contains a postprocessing block that consists of a median and an averaging filter. The combination provides a more robust solution, discarding the spurious noise in the signal and keeping only the data of interest. The size of both filters is programmable. Other userprogrammable conversion controls include variable acquisition time and first conversion delay. Up to 16 averages can be taken per conversion. The AD7879 can run in either slave mode or standalone mode using an automatic conversion sequencer and timer.

It has a programmable pin that can operate as either an auxiliary input to the ADC, as a battery monitor, or as a GPIO. The device is available with either an SPI or I2C interface.

AD7879

AD7879 Features

  • 12-bit, 105 kSPS ADC
  • Trimode programmable interrupt output (INT, PENIRQ, DAV)
  • Temperature, touch pressure measurement capabilities
  • Package options
    • 12-lead, 1.6 mm × 2 mm WLCSP
    • 16-lead, 4 mm × 4 mm LFCSP

Stereo Audio Codecs Deliver Best Audio Experience with Lowest Power Dissipation

Consumers expect portable devices to deliver longer battery life without compromising audio quality. The ADAU1361 and ADAU1761 24-bit audio codecs are ideally suited to meet these demands. The ADAU1361 achieves greater than 100 dB SNR, while dissipating less than 5 mW in stereo playback mode. The ADAU1761 audio codec adds a SigmaDSP® digital audio processor for customizing the end user's audio experience. ADI's SigmaStudio™ graphical development tool allows the easy combination and integration of ADI's algorithm suite, customer developed algorithms, and/or branded third-party audio algorithms.

Both devices include stereo audio ADCs and DACs that support sample rates from 8 kHz to 96 kHz. They also offer a digital volume control. The analog input stage supports a stereo line input, a stereo analog microphone interface, and a circuit to supply the microphone bias voltage. It also supports new standards in high performance, low noise digital microphones.

As part of a complete portable audio signal chain, the devices interface to any analog microphone or PDM digital microphone, including ADI's ADMP401 analog and ADMP421 digital MEMS microphones. The codecs also match well with both stereo and mono Class-D audio amplifiers, such as ADI's SSM2315, SSM2317, and SSM2306 Class-D power amplifiers.

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ADAU1361, ADAU1761

Click here to view full size image ADAU1761 ADAU1361

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