The AD6643 is an 11-bit, 250MSPS, dual-channel intermediate frequency (IF) receiver specifically designed to support multiantenna systems in telecommunication applications where high dynamic range performance, low power, and small size are desired.
The device consists of two high performance analog-to-digital converters (ADCs) and noise shaping requantizer (NSR) digital blocks. Each ADC consists of a multistage, differential pipelined architecture with integrated output error correction logic. The ADC features a wide bandwidth switched-capacitor sampling network within the first stage of the differential pipeline. An integrated voltage reference eases design considerations. A duty cycle stabilizer (DCS) compensates for variations in the ADC clock duty cycle, allowing the converters to maintain excellent performance.
Each ADC output is connected internally to an NSR block. The integrated NSR circuitry allows for improved SNR performance in a smaller frequency band within the Nyquist bandwidth. The device supports two different output modes selectable via the external MODE pin or the SPI.
With the NSR feature enabled, the outputs of the ADCs are processed such that the AD6643 supports enhanced SNR performance within a limited portion of the Nyquist bandwidth while maintaining an 11-bit output resolution. The NSR block can be programmed to provide a bandwidth of either 22% or 33% of the sample clock. For example, with a sample clock rate of 185 MSPS, the AD6643 can achieve up to 75.5 dBFS SNR for a 40 MHz bandwidth in the 22% mode and up to 73.7 dBFS SNR for a 60 MHz bandwidth in the 33% mode.
With the NSR block disabled, the ADC data is provided directly to the output with a resolution of 11 bits. The AD6643 can achieve up to 66.5 dBFS SNR for the entire Nyquist bandwidth when operated in this mode. This allows the AD6643 to be used in telecommunication applications such as a digital predistortion observation path where wider bandwidths are desired.
After digital signal processing, multiplexed output data is routed into two 11-bit output ports such that the maximum data rate is 500Mbps (DDR). These outputs are set at 1.8 V LVDS and support ANSI-644 levels.
The AD6643 receiver digitizes a wide spectrum of IF frequencies. Each receiver is designed for simultaneous reception of a separate antenna. 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. Programming for device setup and control is accomplished using a 3-wire SPI-compatible serial interface with numerous modes to support board-level system testing.APPLICATIONS
|Title||Content Type||File Type|
|AD6643: Dual IF Receiver Datasheet (Rev C, 11/2012) (pdf, 1342 kB)||Data Sheets|
|AN-1142: Techniques for High Speed ADC PCB Layout (pdf, 392 kB)||Application Notes|
|AN-878: High Speed ADC SPI Control Software (pdf, 585 kB)||Application Notes|
|AN-282: Fundamentals of Sampled Data Systems (pdf, 2131 kB)||Application Notes|
|AN-737: How ADIsimADC Models an ADC (pdf, 373 kB)||Application Notes|
|AN-807: Multicarrier WCDMA Feasibility (pdf, 969 kB)||Application Notes|
AN-808: Multicarrier CDMA2000 Feasibility
(pdf, 1535 kB)
The goal of this application note is to determine the feasibility of implementing a multicarrier CDMA2000 transceiver and what the major subsystem performances must be.
|AN-827: A Resonant Approach to Interfacing Amplifiers to Switched-Capacitor ADCs (pdf, 203 kB)||Application Notes|
|AN-877: Interfacing to High Speed ADCs via SPI (pdf, 1594 kB)||Application Notes|
|AN-905: VisualAnalog Converter Evaluation Tool Version 1.0 User Manual (pdf, 2124 kB)||Application Notes|
|AN-935: Designing an ADC Transformer-Coupled Front End (pdf, 363 kB)||Application Notes|
|AN-835: Understanding High Speed ADC Testing and Evaluation (pdf, 985 kB)||Application Notes|
AN-586: LVDS Outputs for High Speed A/D Converters
(pdf, 207 kB)
High Speed ADCs Uses LVDS (Low-Voltage Differential Signaling) to Minimize Performance Limitations In ADC Applications When Providing High Speed Data Output
AN-812: MicroController-Based Serial Port Interface (SPI) Boot Circuit (pdf, 452,449 bytes)
(pdf, 441 kB)
This application note describes the operation of a general-purpose, microcontroller-based Serial Port Interface (SPI) boot circuit.
|AN-851: A WiMax Double Downconversion IF Sampling Receiver Design (pdf, 262 kB)||Application Notes|
|AN-742: Frequency Domain Response of Switched-Capacitor ADCs (pdf, 401 kB)||Application Notes|
|AN-715: A First Approach to IBIS Models: What They Are and How They Are Generated (pdf, 370 kB)||Application Notes|
AN-345: Grounding for Low-and-High-Frequency Circuits
(pdf, 455 kB)
Know Your Ground and Signal Paths for Effective Designs. Current Flow Seeks Path of Least Impedance-Not Just Resistance....
|AN-756: Sampled Systems and the Effects of Clock Phase Noise and Jitter (pdf, 291 kB)||Application Notes|
AN-501: Aperture Uncertainty and ADC System Performance
(pdf, 227 kB)
A Key Concern in IF Sampling is that of Aperture Uncertainty (Jitter)
|AN-741: Little Known Characteristics of Phase Noise (pdf, 1679 kB)||Application Notes|
|UG-293: Evaluating the AD9643/AD9613/AD6649/AD6643 Analog-to-Digital Converters (pdf, 2740 kB)||User Guides|
|Glossary of EE Terms||Glossary||HTML|
|Title||Content Type||File Type|
ADIsimADC is Analog Devices' Analog-to-Digital Behavioral Model that accurately models the typical performance characteristics of many of our High Speed Converters. The model faithfully reproduces the errors associated with both static and dynamic features such as AC linearity, clock jitter, and many other product specific anomalies.
|ADIsim Design/Simulation Tools||HTML|
|AD6643 IBIS Model||IBIS Models||HTML|
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