Octal LNA/VGA/AAF/ADC and Crosspoint Switch

The AD9271 is designed for low cost, low power, small size, and ease of use. It contains eight channels of a variable gain amplifier (VGA) with low noise preamplifier (LNA); an antialiasing filter (AAF); and a 12-bit, 10 MSPS to 50 MSPS analog-to-digital converter (ADC).

Each channel features a variable gain range of 30 dB, a fully differential signal path, an active input preamplifier termination, a maximum gain of up to 40 dB, and an ADC with a conversion rate of up to 50 MSPS. The channel is optimized for dynamic performance and low power in applications where a small package size is critical.

The LNA has a single-ended-to-differential gain that is selectable through the SPI. The LNA input noise is typically 1.2 nV/√Hz, and the combined input-referred noise of the entire channel is 1.4 nV/√Hz at maximum gain. Assuming a 15 MHz noise bandwidth (NBW) and a 15.6 dB LNA gain, the input SNR is roughly 86 dB. In CW Doppler mode, the LNA output drives a transconductance amp that is switched through an 8 × 6 differential crosspoint switch. The switch is programmable through the SPI.

APPLICATIONS

* Medical imaging/ultrasound

* Automotive radar

* 8 channels of LNA, VGA, AAF, and ADC

* Low noise preamplifier (LNA)

Input-referred noise = 1.1 nV/√Hz @ 5 MHz typical, gain = 18 dB

SPI-programmable gain = 14 dB/15.6 dB/18 dB

Single-ended input; VIN maximum = 400 mVP-P/333 mV p-p/250 mVP-P

Dual-mode active input impedance matching

Bandwidth (BW) > 70 MHz

Full-scale (FS) output = 2 VP-P differential