ADI AD9277低成本低功耗醫(yī)療超聲解決方案

作者：時間：2012-04-09 來源：網絡

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ADI公司的AD9277是低成本低功耗小型容易使用的8路14位ADC,包括8路可變增益放大器(VGA)和低噪音放大器(LNA),抗混淆濾波器(AAF)和14位10MSPS到50MSPS本世紀末ADC以及可編相位旋轉的I/Q解調器,主要用在醫(yī)療圖像和超聲波圖像以及汽車雷達.本文介紹了AD9277主要特性和產品亮點,方框圖, 超聲波系統(tǒng)方框圖以及AD9277評估板主要特性,評估板連接圖,電路圖,PCB布局圖和材料清單.此外還介紹了ADI醫(yī)療超聲解決方案方框圖和信號鏈接圖.

本文引用地址：http://m.butianyuan.cn/article/199335.htm

The AD9277 is designed for low cost, low power, small size, and ease of use. It contains eight channels of a variable gain amplifier (VGA) with a low noise preamplifier (LNA); an anti-aliasing filter (AAF); a 14-bit, 10 MSPS to 50 MSPS analog-to-digital converter (ADC); and an I/Q demodulator with programmable phase rotation.

Each channel features a variable gain range of 42 dB, a fully differ-ential signal path, an active input preamplifier termination, a maximum gain of up to 52 dB, and an ADC with a conversion rate of up to 50 MSPS. The channel is optimized for 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 SPI. The LNA input noise is typically 0.75 nV/√Hz at a gain of 21.3 dB, and the combined input-referred noise of the entire channel is 0.85 nV/√Hz at maximum gain. Assuming a 15 MHz noise bandwidth (NBW) and a 21.3 dB LNA gain, the input SNR is roughly 92 dB. In CW Doppler mode, each LNA output drives an I/Q demodulator. Each demodulator has inde-pendently programmable phase rotation through the SPI with 16 phase settings.
The AD9277 requires a LVPECL-/CMOS-/LVDS-compatible sample rate clock for full performance operation. No external reference or driver components are required for many applications.

The ADC automatically multiplies the sample rate clock for the appropriate LVDS serial data rate. A data clock (DCO±) for capturing data on the output and a frame clock (FCO±) trigger for signaling a new output byte are provided.

Powering down individual channels is supported to increase battery life for portable applications. A standby mode option allows quick power-up for power cycling. In CW Doppler opera-tion, the VGA, AAF, and ADC are powered down. The power of the TGC path scales with selectable ADC speed power modes.

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 pseudo-random patterns, and custom user-defined test patterns entered via the serial port interface.
Fabricated in an advanced CMOS process, the AD9277 is available in a 16 mm × 16 mm, RoHS compliant, 100-lead TQFP. It is specified over the industrial temperature range of −40°C to +85°C.

AD9277產品亮點:

Small Footprint. Eight channels are contained in a small, space-saving package. Full TGC path, ADC, and I/Q demodulator contained within a 100-lead, 16 mm × 16 mm TQFP.

Low Power. In TGC mode, low power of 207 mW per channel at 50 MSPS. In CW mode, ultralow power of 94 mW per channel.

Integrated High Dynamic Range I/Q Demodulator with Phase Rotation.

Ease of Use. A data clock output (DCO±) operates up to 480 MHz and supports double data rate (DDR) operation.

User Flexibility. Serial port interface (SPI) control offers a wide range of flexible features to meet specific system requirements.

Integrated Second-Order Antialiasing Filter. This filter is placed before the ADC and is programmable from 8 MHz to 18 MHz.

AD9277主要特性:

8 channels of LNA, VGA, AAF, ADC, and I/Q demodulator

Low noise preamplifier (LNA)

Input-referred noise: 0.75 nV/√Hz typical at 5 MHz (gain = 21.3 dB)

SPI-programmable gain: 15.6 dB/17.9 dB/21.3 dB

Single-ended input: VIN maximum = 733 mV p-p/ 550 mV p-p/367 mV p-p

Dual-mode active input impedance matching

Bandwidth (BW) > 100 MHz

Full-scale (FS) output: 4.4 V p-p differential

Variable gain amplifier (VGA)

Attenuator range: −42 dB to 0 dB

Postamp gain: 21 dB/24 dB/27 dB/30 dB

Linear-in-dB gain control

Antialiasing filter (AAF)

Programmable second-order LPF from 8 MHz to 18 MHz

Programmable HPF

Analog-to-digital converter (ADC)

14 bits at 10 MSPS to 50 MSPS

SNR: 73 dB

SFDR: 75 dB

Serial LVDS (ANSI-644, IEEE 1596.3 reduced range link)

Data and frame clock outputs

CW mode I/Q demodulator

Individual programmable phase rotation

Output dynamic range per channel >160 dBFS/√Hz

Low power: 207 mW per channel at 14 bits/50 MSPS (TGC), 94 mW per channel for CW Doppler

Flexible power-down modes

Overload recovery in 10 ns

Fast recovery from low power standby mode: 2 μs

100-lead TQFP_EP

AD9277應用:

Medical imaging/ultrasound

Automotive radar

圖1. AD9277功能方框圖

圖2. 簡化超聲波系統(tǒng)方框圖

圖3. 簡化超聲波系統(tǒng)單路方框圖
AD9277評估板

AD9277評估板主要特性:

Full featured evaluation board for the AD9276 and the AD9277

SPI and alternate clock options

Internal and external reference options

VisualAnalog and SPI Controller software interfaces

EQUIPMENT NEEDED

Analog signal source and antialiasing filter

2 switching power supplies (6.0 V, 2.5 A) CUI EPS060250UH-PHP-SZ, provided

Linear bench top dc voltage source (0 V to 1.6 V), not required for CW Doppler mode

PC running Windowsreg; 98 (2nd edition), Windows 2000, Windows ME, or Windows XP

USB 2.0 port, recommended (USB 1.1 compatible)

AD9276 and AD9277 evaluation board

HSC-ADC-EVALCZ FPGA-based data capture kit

For CW Doppler mode: spectrum analyzer

圖4. AD9276-65EBZ/AD9276-80KITZ/AD9277-50EB評估板和HSC-ADC-EVALCZ數據采集板外形圖

圖5. AD9277評估板連接框圖

圖6. AD9277評估板電路圖(1)

圖7. AD9277評估板電路圖(2)

圖8. AD9277評估板電路圖(3)

圖9. AD9277評估板電路圖(4)

圖10. AD9277評估板電路圖(5)

圖11. AD9277評估板電路圖(6)

圖12. AD9277評估板PCB頂層布局圖

AD9277評估板材料清單:

ADI醫(yī)療超聲解決方案

超聲系統(tǒng)可以通過向人體發(fā)射聲學能量，然后接收并處理回波，從而產生內部器官和結構的圖像，繪制血液流動和組織運動圖，以及提供高度精確的血流速度信息。

超聲系統(tǒng)包含傳感器、高壓開關、高壓發(fā)射電路、發(fā)射(Tx)/接收(Rx)開關、接收通道模擬前端(AFE)、波束形成器、波束形成后的數字信號處理電路、顯示處理電路和外設。AFE包括低噪聲放大器(LNA)、可變增益放大器(VGA)、抗混疊濾波器(AAF)和模數轉換器(ADC)。針對不同應用，波束形成可以分為兩類：數字波束形成和模擬波束形成。

醫(yī)療超聲系統(tǒng)設計考慮和主要挑戰(zhàn)

• AFE電路性能，如噪聲性能、信噪比(SNR)和動態(tài)范圍(DR)等，動態(tài)范圍的典型要求如下：B模式70 dB，PWD(脈沖波多普勒)140 dB，CWD(連續(xù)波多普勒)160 dB。

• 發(fā)射電壓——為提高信號穿透率以及進行諧波成像，需要很高的發(fā)射電壓。聲功率隨著發(fā)射電壓增大而提高，但發(fā)射聲功率不能超過美國食品和藥品管理局(FDA)等機構規(guī)定的安全要求限制。

• 波束形成器的復雜度——要獲得高圖像質量，就要求采用大量波束形成通道。復雜度增加進而導致功耗升高，并且需要更多成像通道來實施。

• 散熱——隨著設備向小型化發(fā)展，尤其是在還要提高圖像質量的時候，散熱問題顯得非常重要。