AFE5818 - 16-Channel Ultrasound Analog Front End With Passive CW Mixer, 0.75 nV/rtHz, 124mW/Channel

The AFE5818 is a highly-integrated, analog front-end (AFE) solution specifically designed for ultrasound systems where high performance and small size are required. The device integrates a complete time-gain-control (TGC) imaging path and a continuous wave Doppler (CWD) path. The device also allows various power and noise combinations to be selected to optimize system performance. Therefore, the AFE5818 is a suitable ultrasound AFE solution for high-end and portable systems

The AFE5818 has a total of 16 channels, with each channel consisting of a voltage-controlled amplifier (VCA), a simultaneous sampling 14-bit and 12-bit analog-to-digital converter (ADC), and a continuous wave (CW) mixer. The VCA includes a low-noise amplifier (LNA), a voltage-controlled attenuator (VCAT), a programmable gain amplifier (PGA), and a low-pass filter (LPF). LNA gain is programmable and supports 250-mV_PP to 1-V_PP input signals and programmable active termination. The ultra-low noise VCAT provides an attenuation control range of 40 dB and improves overall low-gain SNR, which benefits harmonic and near-field imaging. The PGA provides gain options of 24 dB and 30 dB. In front of the ADC, an LPF can be configured at 10 MHz, 15 MHz, 20 MHz, 30 MHz, 35 MHz, or 50 MHz to support ultrasound applications with different frequencies.

The AFE5818 also integrates a low-power passive mixer and a low-noise summing amplifier to create an on-chip CWD beamformer. 16 selectable phase delays can be applied to each analog input signal. Furthermore, a unique third- and fifth-order harmonic suppression filter is implemented to enhance CW sensitivity

The high-performance, 14-bit ADC achieves 75-dBFS SNR. This ADC ensures excellent SNR at low-chain gain. The device can operate at maximum speeds of 65 MSPS and 80 MSPS, providing a 14-bit and a 12-bit output, respectively.

The ADC low-voltage differential signaling (LVDS) outputs enable a flexible system integration that is desirable for miniaturized systems.

The AFE5818 also allows various power and noise combinations to be selected to optimize system performance. Therefore, the AFE5818 is a suitable ultrasound AFE solution for both high-end and portable systems.

The AFE5818 is available in a 15-mm × 15-mm NFBGA-289 package (ZBV package, S-PBGA-N289) and are specified for operation from –40°C to 85°C. The devices are also pin-to-pin compatible with the AFE5816 device family.

• 16-Channel, Complete Analog Front-End:
  • LNA, VCAT, PGA, LPF, ADC, and CW Mixer
• LNA with Programmable Gain:
  • Gain: 24 dB, 18 dB, and 12 dB
  • Linear Input Range:
    0.25 V_PP, 0.5 V_PP, and 1 V_PP
  • Input-Referred Noise:
    0.63 nV/√Hz, 0.7 nV/√Hz, and 0.9 nV/√Hz
  • Programmable Active Termination
• Voltage-Controlled Attenuator (VCAT): 40 dB
• Programmable Gain Amplifier (PGA):
  24 dB and 30 dB
• Total Signal Chain Gain: 54 dB (max)
• 3rd-Order, Linear-Phase LPF:
  • 10 MHz, 15 MHz, 20 MHz, 30 MHz, 35 MHz, and 50 MHz
• Analog-to-Digital Converter (ADC):
  • 14-Bit ADC: 75-dBFS SNR at 65 MSPS
  • 12-Bit ADC: 72-dBFS SNR at 80 MSPS
• LVDS Interface Maximum Speed of 1 Gbps
• Noise and Power Optimizations (Full-Channel):
  • 140 mW/Ch at 0.75 nV/√Hz, 65 MSPS
  • 91.5 mW/Ch at 1.1 nV/√Hz, 40 MSPS
  • 80 mW/Ch at CW Mode
• Excellent Device-to-Device Gain Matching:
  • ±0.5 dB (typical) and ±1.1 dB (max)
• Low Harmonic Distortion
• Fast and Consistent Overload Recovery
• Passive Mixer for CWD:
  • Low Close-In Phase Noise:
    –156 dBc/Hz at 1 kHz Off 2.5-MHz Carrier
  • Phase Resolution: λ / 16
  • Supports 16X, 8X, 4X, and 1X CW Clocks
  • 12-dB Suppression on 3rd and 5th Harmonics
  • CWD High-Pass Filter Rejects Undesired Low-Frequency Signals < 1 kHz
• Small Package: 15-mm × 15-mm NFBGA-289