Programmable analog converter yields flexible filters

Allen, Texas–Using the QF4A512 four-channel Programmable Signal Converter from Quickfilter Technologies, designers can design, implement, and modify low-frequency conversion and filtering using a single, small IC. The analog front end provides four channels of conversion using its single 16-bit analog/digital converter, with built-in x1 to x8 programmable gain amplifiers (PGA). This is followed by four independent FIR filters, each with up to 512 taps per filter; you can achieve “brick-wall” filters with 1-kHz cutoff, 10-Hz transition band, and 80-dB rejection, for example.

The user establishes via download the filter topology, such as lowpass, highpass, bandstop, notch, as well as parameters such as rolloff, 3 dB frequency, and attenuation; the configuration and filter coefficients are stored in internal EEPROM. There is also user storage for serial number, model number, and other unique or non-filter data.

Using this programmable analog device, a single IC can serve multiple models and systems. In addition, the filter can be modified in-circuit, to adapt to different conditions and application regimes. Input range is 2V, with bandwidth of DC to 500 kHz. Each channel's A/D function is preceded by a programmable antialiasing filter, using a 3rd-order Bessel function. Set-up and data I/O uses and SPI port; the IC requires 1.8 and 3.3V supplies and a single 20-MHz clock source. The 32-lead LQFP device (9×9 mm) is priced at $9.89 (1000 pieces). The development kit, at $199, includes PCB and connectors, support components, software, USB interface, cables, and filter examples and templates.

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Quickfilter Technologies Inc, 214-547-0460, www.

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