Maxim introduced the industry’s first fully integrated SiGe variable gain amplifier (VGA) max2036 / max2038 with on-chip continuous wave Doppler (CWD) beamformer. The device is designed for high-performance ultrasonic imaging applications. Max2036 / max2038 8 8-channel VGA with CWD beamformer, together with the existing max2034 4 4-channel low noise amplifier (LNA), can provide higher integration, sensitivity, dynamic range and lower output reference noise than competitive integration schemes. In addition, max2036 / max2038 is the only solution with fully integrated CWD beamformer in the market, without external phase conversion IC, delay line, analog switch and mixer.

Performance characteristics and application analysis of Maxim SiGe variable gain amplifier

Max2036 / max2038 has the same excellent linearity and noise performance as the previously released MAX2035 / max2037 VGA. On this basis, an on-chip 8-channel orthogonal mixer array and a programmable Lo phase generator are added. During normal operation, max2036 / max2038 can be configured to enable VGA channel and turn off mixer array (VGA mode); Or enable the quadrature mixer array and turn off the VGA path (CW mode). In CW mode, the lo phase splitter can be set to 4, 8 or 16 orthogonal phases to optimize the beamforming resolution.

Max2036 / max2038 have the dynamic range and noise performance required for detecting Doppler frequency offset signals within 100kHz to 1kHz. Mixer and lo generator have extremely low thermal noise and jitter noise. It is – 155dbc / Hz when 900mvp-p, 1.25mhz carrier signal and 1kHz frequency offset. This excellent noise performance is very important to detect the weak low-speed Doppler frequency offset signal generated by flowing blood. In ultrasonic system, it is difficult to detect these low-speed Doppler frequency offset signals due to the existence of very strong blocking signals (commonly known as clutter). Doppler measurement must be carried out in the presence of continuous wave transmission signal. The clutter signal generated by solid-state tissue and bone reflection and crosstalk between transmission and reception on the sensor can be up to 200mvp-p at the input of the receiver. These clutter signals reduce the ability of the receiver to accurately detect weak low-speed Doppler signals (i.e. those near CW carriers). The excellent near carrier noise performance of max2036 / max2038 makes it have great advantages in these difficult to detect low-speed blood flow measurement applications.

Combined with max2034 4 4-channel LNA, max2036 / max2038 has very low cascade output reference noise (only 20nv /) in VGA mode, which is half of the competitive chipset schemes of the same kind. Another key feature of this series of VGAs is that they are customized to support 10 bit or 12 bit ADC. Max2036 is optimized for 10 bit ADC to meet higher variable gain range requirements. Max2038 is optimized for 12 bit ADC and is suitable for applications that need to use the initial resolution of ADC to achieve excellent dynamic range.

The max2036 / max2038 are available in a 100 pin TQFP lead-free package.

Responsible editor: GT

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