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Analog Angle Article

IF-to-digital micromodule minimizes signal-chain design challenge

Milpitas, Calif—With the announcement of the LTM9001 receiver subsystem, Linear Technology Corp. (LTC) is continuing its migration up the “value chain” from ICs and into modules. It is designed for applications such as base stations, satellite communications, test equipment, and spectrum analyzers. This IF/baseband receiver subsystem encompasses the “front end-to-digital out” signal chain, incorporating a 16-bit, 130 Msps A/D converter, as well as the requisite antialiasing filter and fixed-gain ADC driver.

Based on the μModule™ technology already used by LTC in their family of dc/dc converters, and suitable for applications with a 300-MHz IF range, the modules are built on a four-layer, BT-grade circuit board and use existing LTC ICs. Impedance matching, filter design, converter-input and digital-output drive, bypassing, and layout issues are all resolved and specified in this 11.25×11.25 mm LGA-package device.




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In the LTM9001-AA, the front-end's low-noise, low-distortion amplifier has fixed gain of 20 dB, a noise figure as low as 5.9 dB, and differential input impedance of 200 Ω. The 16-bit A/D converter specifies signal-to-noise ratio (SNR) of 72 dB and spur free dynamic range (SFDR) of 82 dB, and a 50-MHz bandpass filter is centered at 162.5 MHz.

Digital outputs are parallel LVDS and CMOS compatible, and feature an optional “data randomizer” to reduce the impact of multiple digital transitions on sensitive analog signals and paths. The module accepts a differential, user-supplied clock via its 100 Ω input termination.

As an added benefit, the design has the potential for customization with modest turn times for both samples and production runs, and at low-to-moderate volumes. For example, the converter can be replaced by slower, lower-cost, pin-compatible devices (down to 10 Msps); amplifiers with different fixed-gain values (8, 14, 20, or 26 dB) can be used, and the internal filter can be modified by using different passive components.

The module operates from a single 3.3 V supply with nominal dissipation of 1.65 W, and with independent rails for the analog and digital subsections to accommodate designs which separate VCC and VDD supplies.–Bill Schweber

Price and availability : The LTM9001-AA, full production now, $82.00 (1000 piece)

For more information : Linear Technology Corp., www.linear.com

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