AD6655 데이터 시트보기 (PDF) - Analog Devices

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AD6655

IF Diversity Receiver

Analog Devices 

AD6655

GENERAL DESCRIPTION

The AD6655 is a mixed-signal intermediate frequency (IF) receiver

consisting of dual 14-bit, 80 MSPS/105 MSPS/125 MSPS/150 MSPS

ADCs and a wideband digital downconverter (DDC). The AD6655

is designed to support communications applications where low

cost, small size, and versatility are desired.

The dual ADC core features a multistage, differential pipelined

architecture with integrated output error correction logic. Each

ADC features wide bandwidth differential sample-and-hold

analog input amplifiers supporting a variety of user-selectable

input ranges. An integrated voltage reference eases design consid-

erations. A duty cycle stabilizer is provided to compensate for

variations in the ADC clock duty cycle, allowing the converters

to maintain excellent performance.

ADC data outputs are internally connected directly to the digital

downconverter (DDC) of the receiver, simplifying layout and

reducing interconnection parasitics. 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)), a half-

band decimating filter, a fixed FIR filter, and an fADC/8 fixed-

frequency NCO.

In addition to the receiver DDC, the AD6655 has several

functions that simplify the automatic gain control (AGC)

function in the system receiver. The fast detect feature allows

fast overrange detection by outputting four bits of input level

information with short latency.

In addition, the programmable threshold detector allows

monitoring of the incoming signal power using the four fast

detect bits of the ADC with low latency. If the input signal level

exceeds the programmable threshold, the coarse upper threshold

indicator goes high. Because this threshold indicator has low

latency, the user can quickly turn down the system gain to avoid

an overrange condition.

The second AGC-related function is the signal monitor. This

block allows the user to monitor the composite magnitude of the

incoming signal, which aids in setting the gain to optimize the

dynamic range of the overall system.

After digital processing, data can be routed directly to the two

external 14-bit output ports. These outputs can be set from 1.8 V

to 3.3 V CMOS or as 1.8 V LVDS. The CMOS data can also be

output in an interleaved configuration at a double data rate using

only Port A.

The AD6655 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.

Flexible power-down options allow significant power savings,

when desired.

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

SPI-compatible serial interface.

The AD6655 is available in a 64-lead LFCSP and is specified over

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

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