AD6649EBZ datasheet(3/40 Pages) AD

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AD6649

Rev. 0 | Page 3 of 40

ADC data outputs are internally connected directly to the digital

downconverter (DDC) of the receiver. The digital receiver has

two channels and provides processing flexibility. Each receive

channel has four cascaded signal processing stages: a 32-bit

frequency translator (numerically controlled oscillator (NCO)),

an optional sample rate converter, a fixed FIR filter, and an fS/4

fixed-frequency NCO.

In addition to the receiver DDC, the AD6649 has several

functions that simplify the automatic gain control (AGC)

function in the system receiver. The programmable threshold

detector allows monitoring of the incoming signal power using

the fast detect output bits of the ADC. If the input signal level

exceeds the programmable threshold, the fast detect indicator goes

high. Because this threshold indicator has low latency, the user

can quickly turn down the system gain to avoid an overrange

condition at the ADC input.

After digital processing, data is routed directly to the 14-bit

output port. These outputs operate at ANSI or reduced swing

LVDS signal levels.

The AD6649 receiver digitizes a wide spectrum of IF frequencies.

Each receiver is designed for simultaneous reception of the main

channel and the diversity channel. This IF sampling architecture

greatly reduces component cost and complexity compared with

traditional analog techniques or less integrated digital methods.

In diversity applications, the output data format is real due to

the final NCO, which shifts the output center frequency to fS/4.

Flexible power-down options allow significant power savings,

when desired.

Programming for setup and control is accomplished using a 3-pin

SPI-compatible serial interface.

The AD6649 is available in a 64-lead LFCSP and is specified over

the industrial temperature range of −40°C to +85°C. This

product is protected by a U.S. patent.

PRODUCT HIGHLIGHTS

1. Integrated dual, 14-bit, 250 MSPS ADCs.

2. Integrated wideband filter and 32-bit complex NCO.

3. Fast overrange and threshold detect.

4. Proprietary differential input maintains excellent SNR

performance for input frequencies of up to 400 MHz.

5. SYNC input allows synchronization of multiple devices.

6. 3-pin, 1.8 V SPI port for register programming and register

readback.

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