The ISL5216 Quad Programmable Digital Downconverter
(QPDC) is designed for high dynamic range applications
such as cellular basestations where multiple channel
processing is required in a small physical space. The QPDC
combines into a single package a set of four channels which
include: digital mixers, a quadrature carrier NCO, digital
filters, a resampling filter, a Cartesian-to-polar coordinate
converter and an AGC loop.
The ISL5216 accepts four channels of 16-bit fixed or up to
14-bit mantissa/3-bit exponent floating point real or complex
digitized IF samples which are mixed with local quadrature
sinusoids. Each channel carrier NCO frequency is set
independently by the microprocessor. The output of the
mixers are filtered with a CIC and FIR filters, with a variety of
decimation options. Gain adjustment is provided on the
filtered signal. The digital AGC provides a gain adjust range
of up to 96dB with programmable thresholds and slew rates.
A cartesian to polar coordinate converter provides
magnitude and phase outputs. A frequency discriminator is
also provided to allow FM demodulation. Selectable outputs
include I samples, Q samples, Magnitude, Phase,
Frequency and AGC gain. The output resolution is
selectable from 4-bit fixed point to 32-bit floating point.
Output bandwidths in excess of 1MHz are achievable using
a single channel. Wider bandwidths are available by
cascading or polyphasing multiple channels.

Features
• Up to 95MSPS Input
• Four Independently Programmable Downconverter
Channels in a single package
• Four Parallel 17-Bit Inputs providing 16-bit fixed or one of
several 17-bit floating point formats
• 32-Bit Programmable Carrier NCO with > 115dB SFDR
• 110dB FIR Out of Band Attenuation
• Decimation from 4 to >65536
• 24-bit Internal Data Path
• Digital AGC with up to 96dB of Gain Range
• Filter Functions
- 1- to 5-Stage CIC Filter
- Halfband Decimation and Interpolation FIR Filtering
- Programmable FIR Filtering
- Resampling FIR Filtering
• Cascadable Filtering for Additional Bandwidth
• Four Independent Serial Outputs
• 2.5V Core, 3.3V I/O Operation
• Pb-Free Plus Anneal Available (RoHS Compliant)

Applications
• Narrow-Band TDMA through IS-95 CDMA Digital Software
Radio and Basestation Receivers
• Wide-Band Applications: W-CDMA and UMTS Digital
Software Radio and Basestation Receivers