The AFE8220 implements the intermediate frequency (IF) sampling and processing functions of a digital radio receiver system. It is designed to be used with TIs digital radio baseband processors and AM/FM tuners. The AFE8220 can also be programmed by the baseband processor for use in conventional AM/FM and digital radio. This unit includes two IF inputs with associated filtering and digital processing circuitry.
The receive circuit oversamples the radio tuner IF output to reduce noise and improve dynamic range. The IF analog-to-digital converter (ADC) oversamples the IF input at rates up to 75 MHz. The AFE8220 then digitally mixes, filters, and decimates the signal to provide in-phase (I) and quadrature (Q) output signals to the baseband processor. A clock oscillator circuit is provided that can be used with an appropriate third-overtone crystal and external tank circuit to generate the sampling clock for the IF ADCs.
The AFE8220 also includes a real-time clock and associated low-power oscillator circuit. Two auxiliary digital-to-analog converters (DACs) are included for system control functions. Other features include eight general-purpose input/output (GPIO) lines and programmable interrupt generators.
The AFE8220 is available in a TQFP-100 (14 mm × 14 mm) package and uses a 3.3-V and a 1.8-V power supply. An onboard voltage regulator is included to optionally generate the 1.8-V digital supply for the AFE8220.
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