Maxim MAX30001超低功耗生物电势和阻抗AFE的解决方案详解

电子工程师 2018-06-18 7923

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描述

Maxim公司的MAX30001是超低功耗单路生物电势（ECG，R-R，节奏检测）和生物阻抗（BioZ）模拟前端（AFE）。生物电势通路提供心电图（ECG）波形，心率和起搏器边沿检测，而生物阻抗通路则能够测量呼吸。两个通路具有ESD保护，EMI滤波，内部电极偏压，DC导联脱落检测，超低功耗，待机模式导联连接检测和内置自测校准电压以及高输入阻抗，低噪音，高CMRR，可编增益，各种低通和高通滤波器选择和高分辨率模数转换器。主要用在心律不齐检测的单导联事件监测器，住院/门诊监测的单引线无线贴片，健身胸带心率监视器，呼吸和水化监视器，基于阻抗的心率检测，生物认证和按需ECG应用。本文介绍了MAX30001主要优势和特性，功能框图，应用电路，以及评估板MAX30001 EVS主要特性，电路图，材料清单和PCB设计图。

The MAX30001 is a complete， biopotential and bioimpedance （BioZ）， analog front-end （AFE） solution for wearable applications. It offers high performance for clinical and fitness applications， with ultra-low power for long battery life. The MAX30001 is a single biopotential channel providing electrocardiogram （ECG） waveforms， heart rate and pacemaker edge detection， and a single bioimpedance channel capable of measuring respiration.

The biopotential and bioimpedance channels have ESD protection， EMI filtering， internal lead biasing， DC leads-off detection， ultra-low-power， leads-on detection during standby mode， and extensive calibration voltages for built-in self-test. Soft power-up sequencing ensures no large transients are injected into the electrodes. Both channels also have high input impedance， low noise， high CMRR， programmable gain， various low-pass and high-pass filter options， and a high resolution analog-to-digital converter. The biopotential channel is DC coupled， can handle large electrode voltage offsets， and has a fast recovery mode to quickly recover from overdrive conditions， such as defibrillation and electro-surgery. The bioimpedance channel includes integrated programmable current drive， works with common electrodes， and has the flexibility for 2 or 4 electrode measurements. It also has AC lead off detection.The MAX30001 is available in a 28-pin TQFN and 30-bump wafer-level package （WLP）， operating over the0℃ to +70℃ commercial temperature range.

MAX30001主要优势和特性：

Clinical-Grade ECG and BioZ AFE with High Resolution Data Converter15.9 Bits ENOB with 3.1μVPP （typ） Noise for ECG

17 Bits ENOB with 1.1μVPP Noise for BioZ

Better Dry Starts Due to Much Improved Real World CMRR and High Input ImpedanceFully Differential Input Structure with CMRR 》 100dB

Offers Better Common-Mode to Differential Mode Conversion Due to High Input Impedance

High Input Impedance 》 1GΩ for Extremely Low Common-to-Differential Mode

Minimum Signal Attenuation at the Input During Dry Start Due to High Electrode Impedance

High DC Offset Range of ±650mV （1.8V， typ） Allows to Be Used with Wide Variety of Electrodes

High AC Dynamic Range of 65mVPP for ECG and 100mVPP for BioZ Will Help Prevent Saturation in the Presence of Motion/Direct Electrode Hits

Longer Battery Life Compared to Competing Solutions85μW at 1.1V Supply Voltage for ECG

158μW at 1.1V Supply Voltage for BioZ

Leads-On Interrupt Feature Allows to KeepμC in Deep Sleep Mode Until Valid Lead Condition is DetectedLead-On Detect Current： 0.7μA （typ）

Built-In Heart Rate Detection with Interrupt Feature Eliminates the Need to Run HR Algorithm on the μControllerRobust R-R Detection in High Motion Environment at Extremely Low Power

Configurable Interrupts Allows the μC Wake-Up Only on Every Heart Beat Reducing the Overall System Power

High Accuracy Allows for More Physiological Data Extractions

32-Word ECG and 8-Word BioZ FIFOs Allows the MCU to Stay Powered Down for 256ms with Full Data Acquisition

High-Speed SPI Interface

Shutdown Current of 0.5μA （typ）

MAX30001应用：

Single-Lead Event Monitors for Arrhythmia Detection

Single-Lead Wireless Patches for In-Patient/Out-Patient Monitoring

Chest Band Heart Rate Monitors for Fitness Applications

Bio Authentication and ECG-On-Demand Applications

Respiration and Hydration Monitors

Impedance Based Heart Rate Detection

AFE

图1.MAX30001功能框图

AFE

图2.MAX30001应用电路图：两电极ECG和呼吸监视器

AFE

图3.MAX30001应用电路图：四电极ECG和呼吸监视器

评估板MAX30001 EVS

The MAX30001 evaluation system （EV system） provides a single platform to evaluate the functionality and features of the MAX30001 with Biopotential （ECG， R-to-R， and Pace Detection） and Bioimpedance （BioZ） measurement capabilities. The EV system includes a MAX30001 evaluation kit （EV kit） and a MAX32630FTHR Cortex-M4F microcontroller for wearables. The MAX32630FTHR provides power to the MAX30001 EV kit and contains the firmware necessary to use the EV kit GUI program. The EV kit ships with jumpers installed and supply voltages set to typical operating values. Optional connections exist which can be shunted to make use of different functionalities.

评估板MAX30001 EVS主要特性：

Convenient Platform to Evaluate the MAX30001

Many Easy-to-Reach Test Points

Measure Individual Supply Currents

Touchproof Cable Connectors

Windows® 7/8/10 Compatible GUI software

Fully Assembled and Tested

Facilitates IEC 60601-2-47 Compliance Testing

Ultra-Low-Power Design

评估板MAX30001 EVS包括：

MAX30001 EV kit

MAX32630FTHR