Analog Angle Article

Broadband active-filter family drives ADCs; targets wireless, signal-processing needs

Milpitas, Calif.‚Analog filters: for so many anti-aliasing and signal-processing applications, you can't live with them, but you certainly can't live without them. A new series of active, broadband lowpass filters from Linear Technology Corp. includes single- and dual-channel devices spanning 2.5 to 14 MHz, and also provides buffering and drive for the subsequent analog/digital converter (ADC) stage, to ease the challenge. Target applications include femtocells and I/Q demodulation (WiMax, CDMA-2000, W-CDMA, and LTE), RFID readers, imaging, and sonar designs.

The LTC6603 ($7.50/1000 pieces) has dual, matched, 9th -order switched-capacitor, linear-phase filters, with a low-pass cutoff frequency which the designer can set (up to 2.5 MHz) via the SPI port or using hard-wired pin-strapping. The designer can also fine-tune the frequency using an external DAC, over a 100:1 range.

The LTC6601-1 ($3.95/1000 pieces) is a low-noise, 2nd -order, linear-phase Butterworth filter (5 to 28 MHz). Its internal RC components, which set operating parameters such as cutoff frequency, Q, and gain, are factory-trimmed to provide 0.5% tolerance; these components are “pinned out” of the IC so users have access and can set up different combinations.
The LTC6605-7 , LTC6605-10 , and LTC6605-14 ($6.95/1000 pieces) provide fixed-frequency, dual-channel, matched lowpass filtering with 7, 10, and 14-MHz bandwidths, respectively, with tight matching of critical gain and phase characteristics.

Key specifications and features for the ICs in the family are shown in the Table :

(Click on image to enlarge)

Availability : All the ICs in the LTC66xx family are available now.

For more information : contact Linear Technology Corp.,‚Bill Schweber

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