The AD9674 is designed for low cost, low power, small size, and ease of use for medical ultrasound. 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, a digital HPF, and RF decimation by 2.
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)
### Features and Benefits
8 channels of LNA, VGA, AAF, ADC, and digital RF decimator
Low power: 150 mW per channel, TGC mode, 40 MSPS; 62.5 mW per channel, CW mode; <30 mW in power-down
Time gain compensation (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 voltage: 0.78 nV/√Hz, gain = 21.6 dB
Programmable gain: 15.6 dB/17.9 dB/21.6 dB
0.1 dB compression: 1.00 V p-p/0.75 V p-p/0.45 V p-p
Flexible active input impedance matching
Variable gain amplifier (VGA)
Attenuator range: 45 dB, linear in dB gain control
