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TI公司的AFE5804是八路超声波模拟前端,每路的功耗仅为120mW,12位,取样速率高达40MSPS,噪音为0.92nV/√Hz. AFE5804包括了低噪音放大器(LNA),电压控制的衰减器(VCA),可编程增益放大器(PGA),低通滤波器(LPF)以及采用低压差分信号(LVDS)输出的12位模数转换器(ADC). AFE5804广泛用在医疗图像和超声波,手提设备以及以电池为能源的系统.本文介绍了AFE5804的主要特性, 方框图和功能方框图, 采用电流相加和无源延迟线的CW多普勒信号图以及超声波系统方框图.

AFE5804:FULLY-INTEGRATED, 8-CHANNEL ANALOG FRONT-END FOR ULTRASOUND 0.92nV/√Hz, 12-Bit, 40MSPS, 102mW/Channel
The AFE5804 is a complete analog front-end device specifically designed for ultrasound systems that require low power and small size.
The AFE5804 consists of eight channels, including a low-noise amplifier (LNA), voltage-controlled attenuator (VCA), programmable gain amplifier (PGA), low-pass filter (LPF), and a 12-bit analog-to-digital converter (ADC) with low voltage differential signaling (LVDS) data outputs.

The LNA gain is set for 20dB gain and has excellent noise and signal handling capabilities, including fast overload recovery. VCA gain can vary over a 46dB range with a 0V to 1.2V control voltage common to all channels of the AFE5804.

The PGA can be programmed for gains of 20dB, 25dB, 27dB, and 30dB. The internal low-pass filter can also be programmed to 12.5MHz or 17.5MHz.

The LVDS outputs of the ADC reduce the number of interface lines to an ASIC or FPGA, thereby enabling the high system integration densities desired for portable systems. The ADC can either be operated with internal or external references. The ADC also features a signal-to-noise ratio (SNR) enhancement mode that can be useful at high gains.

The AFE5804 is available in a 15mm × 9mm, 135-ball BGA package that is Pb-free (RoHS-compliant) and green. It is specified for operation from 0°C to +70°C.

主要特性:
8-Channel Complete Analog Front-End:
LNA, VCA, PGA, LPF, and ADC
Mode Control for Power/Noise Optimization:
Low Noise (Full-Channel):
0.92nV/√Hz (TGC Mode I)
1.25nV/√Hz (TGC Mode II)
1.10nV/√Hz (CW and PW Modes)
Ultra-Low Power:
102mW/Channel (TGC Mode II)
65mW/Channel (CW Mode)
Low-Noise Pre-Amp (LNA):
0.75nV/√Hz
20dB Fixed Gain
280mVPP Linear Input Range

Variable-Gain Amplifier:
Gain Control Range: 46dB
PGA Gain Settings: 20dB, 25dB, 27dB, 30dB
Low-Pass Filter:
Selectable BW: 12.5MHz, 17.5MHz
2nd-Order, Bessel
Gain Error: ±0.5dB
Channel Matching: ±0.25dB
Distortion, HD2: -47dBc at 0.2VPP Input
Clamping
Fast Overload Recovery
Rapid Power-Up/Power-Down ≤ 2µs
12-Bit Analog-to-Digital Converter:
10MSPS to 50MSPS
69dB SNR at 10MHz
Serial LVDS Interface
Integrated CW Switch Matrix
15mm × 9mm, 135-BGA Package:
Pb-Free (RoHS-Compliant) and Green

主要应用:
Medical Imaging, Ultrasound
Portable Systems
Battery-Powered Systems



图1. AFE5804方框图



图2. AFE5804功能方框图



图3.采用电流相加和无源延迟线的CW多普勒信号图
SYSTEM BLOCK DIAGRAMS