Broadband active filters
18 November 2008
Single and dual high performance, wide bandwidth lowpass active filter/ADC driver amplifiers launched.
For filtering applications in broadband wireless communications and signal processing equipment, Linear Technology has introduced a family of five single and dual high performance, wide bandwidth lowpass active filter/ADC driver amplifiers.
The LTC6603 features a dual matched programmable ninth order switched capacitor linear-phase filter and ADC driver. The filter’s lowpass cut-off frequency up to 2.5MHz and its gain are adjustable via a serial SPI port, or can be fixed by pin-strapping. Fine frequency control over 100:1 frequency range can be implemented using an external DAC to vary the device’s master reference clock. The LTC6603’s programmability and sharp filter roll-off frequency response make it suitable as a baseband filter for I/Q demodulators in CDMA-2000, W-CDMA and LTE (Long-Term Evolution) Femto-cell basestations, repeaters, RFID readers, imaging, sonar scan receivers and a range of industrial signal processing instruments, and comes in a 4mm x 4mm 24-lead QFN package.
The LTC6601-1 is a low noise 0.5% tolerance low-pass active filter and ADC driver with configurable bandwidth from 5MHz to 28MHz. The filter has a second order linear phase Butterworth response. It has differential inputs and outputs. The filter’s on-chip resistors and capacitors that form its cut-off frequency, Q (quality factor of a filter) and gain are laser trimmed at the factory to an absolute tolerance of 0.5% typical. These resistors and capacitors are pinned out, allowing users to pin strap wide combinations of filter response and gain. Additionally, the amplifier’s frequency response is also laser trimmed, resulting in a highly accurate and repeatable filter response from device to device. Higher order filters can be attained by cascading multiple stages of the LTC6601-1. Furthermore, the amplifier has a robust output stage to directly drive many high sampling speed A/D converters. Each filter comes in a 4mm x 4mm 20-lead QFN package.
Finally, the LTC6605-7, 10 and 14 are fixed frequency second order linear phase dual matched low-pass active filters with bandwidths of 7MHz, 10MHz and 14MHz, respectively. Each filter pairs are tested and guaranteed to offer tight matching of phase and gain characteristics. These filters are suitable for I/Q demodulator channel filtering in WiMAX and broadband wireless access equipment including point-to-point microwave links. The matched filter performance is also suitable for driving multi-channel signal processing and pre-filtering for high speed ADCs. The LTC6605 family comes in a 6mm x 3mm, 22 leads DFN package.
All filters are available in C grade specified for 0°C to 70°C, and I-grade specified for -40°C to 85°C operation.
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