TI公司的ADS1299是8路低噪音同時取樣的24位delta-sigma ADC,并內置了可編程增益放大器(PGA),基準電壓和振蕩器,集成了腦電圖(EEG)所需的通用特性.器件具有非常低的輸入參考噪音:1.0 μVPP (70-Hz BW),沒路的功耗5mW,輸入偏置電流300pA,數據速率250SPS到16kSPS,C1.0 μVPP (70-Hz BW),CMMR為-110dB,可編程增益為1, 2, 4, 6, 8, 12或24,單極或雙極電源工作,主要用在醫療儀器如EEG和ECG,聽覺誘發電位(EAP),腦電雙頻譜指數(BIS),睡眠研究監測等,高精度多路信號采集.本文介紹了ADS1299主要特性,功能框圖,單電源和雙極電源工作電路,以及評估板ADS1299EEG-FE主要特性,框圖,電路圖,材料清單和PCB布局圖.

The ADS1299 is a low-noise, multichannel, simultaneous-sampling, 24-bit, delta-sigma (ΔΣ) analog-to-digital converter (ADC) with a built-in programmable gain amplifier (PGA), internal reference, and an onboard oscillator. The ADS1299 incorporates all commonly-required features for electroencephalogram (EEG) applications.

With its high levels of integration and exceptional performance, the ADS1299 enables the creation of 23scalable medical instrumentation systems at  significantly reduced size, power, and overall cost.

The ADS1299 has a flexible input multiplexer per channel that can be independently connected to the  internally-generated signals for test, temperature, and lead-off detection. Additionally, any configuration of  input channels can be selected for derivation of the patient bias output signal. The ADS1299 operates at  data rates from 250 SPS to 16 kSPS. Lead-off detection can be implemented internal to the device,  either with an external pull-up or pull-down resistor or an excitation current sink or source.

Multiple ADS1299 devices can be cascaded in high channel count systems in a daisy-chain configuration.

The ADS1299 is offered in a TQFP-64 package  specified from –40℃ to +85℃.

ADS1299主要特性:

• Eight Low-Noise PGAs and Eight High- Resolution Simultaneous-Sampling ADCs

• Very Low Input-Referred Noise:

1.0 μVPP (70-Hz BW)

• Low Power: 5 mW/channel

• Input Bias Current: 300 pA

• Data Rate: 250 SPS to 16 kSPS

• CMRR: –110 dB

• Programmable Gain: 1, 2, 4, 6, 8, 12, or 24

• Unipolar or Bipolar Supplies:

– Analog: 4.75 V to 5.25 V

– Digital: 1.8 V to 3.6 V .

• Built-In Bias Drive Amplifier,

Lead-Off Detection, Test Signals

• Built-In Oscillator

• Internal or External Reference

• Flexible Power-Down, Standby Mode

• Pin-Compatible with the ADS1298IPAG

• SPI™-Compatible Serial Interface

• Operating Temperature Range: –40℃ to +85℃

ADS1299應用:

• Medical Instrumentation (EEG and ECG) Including:

– EEG, Bispectral index (BIS), Evoked audio potential (EAP), Sleep study monitor

• High-Precision, Simultaneous, Multichannel Signal Acquisition

圖1.ADS1299功能框圖

圖2.多個ADS1299器件配置圖

圖3.ADS1299單電源工作電路圖

圖4.ADS1299雙極電源工作電路圖

腦電圖(EEG)前端性能演示板ADS1299EEG-FE

This user’s guide describes the characteristics, operation, and use of the ADS1299EEG-FE. This EVM is an evaluation module for the ADS1299, an eight-channel, 24-bit, low-power; integrated analog front-end (AFE) designed for electroencephalography (EEG) applications. The ADS1299ECG-FE is intended for prototyping and evaluation. This user’s guide includes a complete circuit description, schematic diagram, and bill of materials.

The ADS1299EEG-FE is intended for evaluating the ADS1299 low-power, low noise 24-bit, simultaneously sampling, eight-channel front-end for EEG applications. The digital SPI™ control interface is provided by the MMB0 Modular EVM motherboard (Rev. D or higher) that connects to the ADS1299EEG FE evaluation board (Rev A). The ADS1299EEG-FE is NOT a reference design for EEG applications; rather, its purpose is to expedite evaluation and system development. The output of the ADS1299 yields a raw, unfiltered EEG signal.

The MMB0 motherboard allows the ADS1299EEG-FE to be connected to the computer via an available USB port. This manual shows how to use the MMB0 as part of the ADS1299EEG-FE, but does not provide technical details about the MMB0 itself.

Throughout this document, the abbreviation EVM and the term evaluation module are synonymous with the ADS1299EEG-FE.

ADS1299EEG-FE支持的特性:

Hardware Features:

• Configurable for bipolar or unipolar supply operation

• Configurable for internal and external clock and reference via jumper settings

• Configurable for dc-coupled inputs

• External bias electrode drive

• Option to provide a common reference to all channels negative terminals.

• Option to select any electrode as reference electrode

• Option to choose any electrode as bias electrode

• External shield drive amplifier

Software Features:

• Analysis tools including a virtual oscilloscope, histogram, FFT.

• Data export for post-processing of raw EEG data

圖5.ADS1299EEG-FE外形圖

ADS1299EEG-FE 包括:

• ADS1299EEG FE printed circuit board (PCB), Rev A

• MMB0 (Modular EVM motherboard, Rev D or higher)

• Universal ac to dc wall adapter, 120V to 240V ac to +6V dc

圖6.ADS1299 EEG-FE前端框圖

圖7.ADS1299EEG-FC電路圖

圖8.ADS1299EEG-FC跨接器電路圖

圖9.ECG電源

圖10.外接基準驅動器(未安裝)

圖11.ECG MDK板接口適配器電路
ADS1299 EEG-FE材料清單(BOM):



圖12.ADS1299EEG-FE PCB布局圖(頂層)

圖13.ADS1299EEG-FE PCB布局圖(中間層1)

圖14.ADS1299EEG-FE PCB布局圖(中間層2)

圖15.ADS1299EEG-FE PCB布局圖(底層)

圖16.ADS1299EEG-FE底層元件布局圖
詳情請見:
http://www.ti.com/litv/pdf/sbas499a
和
http://www.ti.com/lit/ug/slau443/slau443.pdf