Octal Ultrasound AFE with Digital Demodulator, JESD204B

The AD9671 is designed for low cost, low power, small size, and ease of use for medical ultrasound applications. It contains eight channels of a VGA with an LNA, a CW harmonic rejection I/Q demodulator with programmable phase rotation, an AAF, an ADC, and a digital demodulator and decimator for data processing and bandwidth reduction.

Each channel features a maximum gain of up to 52 dB, a fully differential signal path, and an active input preamplifier termination. The channel is optimized for high 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 serial port interface (SPI). Assuming a 15 MHz noise bandwidth (NBW) and a 21.6 dB LNA gain, the LNA input SNR is 94 dB. In CW Doppler mode, each LNA output drives an I/Q demodulator that has independently programmable phase rotation with 16 phase settings.

Power-down of individual channels is supported to increase battery life for portable applications. Standby mode allows quick power-up for power cycling. In CW Doppler operation, the VGA, AAF, and ADC are powered down. The ADC contains several features designed to maximize flexibility and minimize system cost, such as a programmable clock, data alignment, and programmable digital test pattern generation. The digital test patterns include built-in fixed patterns, built-in pseudorandom patterns, and custom user defined test patterns entered via the SPI.

Applications

* Medical imaging/ultrasound

* Nondestructive testing (NDT)

* 8 channels of LNA, VGA, AAF, ADC, and digital demodulator/decimator

* Low power: 150 mW per channel, time gain compensation (TGC) mode, 40 MSPS

62.5 mW per channel, continuous wave (CW) mode; <30 mW in power-down mode

* 10 mm × 10 mm, 144-ball CSPBGA

* TGC channel input referred noise: 0.82 nV/√Hz, maximum gain

* Flexible power-down modes

* Fast recovery from low power standby mode: <2 μs

* Low noise preamplifier (LNA)

* Input referred noise: 0.78 nV/√Hz, gain = 21.6 dB

* Programmable gain: 15.6 dB/17.9 dB/21.6 dB

* 0.1 dB compression: 1000 mV p-p/750 mV p-p/450 mV p-p

* Flexible active input impedance matching

* Variable gain amplifier (VGA)

* Attenuator range: 45 dB, linear-in-dB gain control

* Postamplifier (PGA) gain: 21 dB/24 dB/27 dB/30 dB

* See data sheet for additional features