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驾驶状态标尺上的芯片

关键词:MEMS传感器,可穿戴式传感器,数据采集,微控制器MCU

时间:2015-08-27 13:09:09      来源:网络

国际即时新闻(原文:英文)

Driving a Health Meter on a Chip

A key driver for wearable sensors is health monitoring, and miniaturization has been a key enabler of this technology. Being able to integrate multiple sensors and the data acquisition subsystems on the same device as the microcontroller is giving designers the ability to miniaturize the design of their equipment to fit into more form-factors.

The latest wearable health monitor from PulseOn, for example, uses a customized micromachined MEMS sensor from STMicroelectronics along with its STM32L microcontroller. This provides accurate continuous heart-rate measurement and the algorithms running on the microcontroller turn the data into meaningful personalized feedback for each individual.

The MEMS accelerometer maintains the heart-rate measurement accuracy and reliability at the level delivered by an electrocardiogram and has been tested in a wide range of conditions, from physical inactivity up to high levels of cardio-intensive activities. The accelerometer does this by tracking hand motion and vibration in the system to eliminate the noise in optical blood-flow detection so that the system can distinguish between the signal that represents the actual heart pulse and which is just noise caused by hand movements. The accelerometer also determines the wearer’s level of physical activity.

Image of PulseOn's smart wearable health monitor

Figure 1: PulseOn's smart wearable health monitor uses a MEMS accelerometer and highly integrated controller from STMicroelectronics to increase the accuracy of blood pressure measurements.

“The precision and performance of the chips has enabled us to apply the strictest scientific standards to the PulseOn heart-rate measurement technology, producing reliable results that includes the beat-to-beat accuracy during rest,” said Jari Nousiainen, Head of Engineering at PulseOn. “Equally important, the minuscule dimensions and energy budget of the devices have been a competitive advantage by contributing to the creation of the market’s smallest and most accurate wrist-worn heart-rate monitor.”

Another way to miniaturize the health monitor is to integrate as much of the data capture on one chip. The ADuCM350 from Analog Devices is a high precision meter-on-a-chip that is designed to run from a coin cell in portable device applications such as point-of-care diagnostics and wearable devices. By combining the amperometric, voltametric, and impedometric measurement capabilities in the analog front-end with a flexible switch matrix, a wide range of sensors can be used in the minimum footprint to reduce the overall size of the system. This uses a 16-bit, precision, 160 kSPS analog-to-digital converter (ADC); 0.17% precision voltage reference; 12-bit, no missing codes digital-to-analog converter (DAC); and the reconfigurable ultralow leakage switch matrix. There is also a temperature sensor with an accuracy of ±1°C from 0°C to 50°C.

The chip also includes a low-power ARM Cortex-M3-based processor, 384 kB of embedded flash memory, 32 kB of system SRAM and 16 kB of flash-configured EEPROM, as well as I/O to support portable meters with display, USB communication, and active sensors. The AFE is connected to the ARM Cortex-M3 via a high-performance bus (AHB) slave interface, as well as direct memory access (DMA) and interrupt connections.

Image of Analog Devices ADuCM350 diagram

Figure 2: The ADuCM350 integrates all the elements needed for a health monitor onto a single chip in chip-scale packaging.

To keep the size of the system down, all this is packaged in a 120-lead, 8 mm × 8 mm chip-scale ball grid array (CSP_BGA) that operates from -40°C to +85°C to meet the needs of many different environments.

Power, of course, is a vital consideration in miniaturization of the system, as lower power allows for smaller batteries.  As a result, the ADuCM350 has a range of power modes such as dynamic and software-controlled clock and power gating. 

Freescale Semiconductor's MK50DX256CLK10 similarly is aimed at miniaturized sensor applications, with a wide range of integrated peripherals. These include two 16-bit successive approximation SAR ADCs, a programmable gain amplifier (PGA) (up to x64) integrated in each ADC, as well as two operational amplifiers and two transimpedance amplifiers. For data output, there are two 12-bit DACs, with three analog comparators (CMP) containing a 6-bit DAC and programmable reference input and a voltage reference, all allowing the system to be more highly integrated.

Communication interfaces include a USB full-/low-speed On-the-Go controller with on-chip transceiver, two SPI modules and two I2C modules for linking to digital sensors in the system, as well as four UART modules to link to other serial sensors. There is also an I2S module to link to other controllers in the system and a low-power hardware touch sensor interface (TSI) for display management.

All of this is controlled by an ARM Cortex-M4 core with DSP instructions, delivering 1.25 Dhrystone MIPS per MHz and running at up to 100 MHz to minimize the power consumption. Memory support includes up to 512 KB of program flash memory, 56 KB FlexNVM of non-volatile memory and up to 128 KB of RAM. A 16-channel DMA controller supports up to sixty-three request sources and allows data to be captured from sensors and stored without having to wake up the microcontroller core, reducing the overall power consumption and helping to reduce the size of the design.

Image of Freescale MK50DX256CLK10 diagram

Figure 3: Freescale's MK50DX256CLK10 is used in a heart rate measuring patch by integrating the data capture functions from simple electrodes.

The MK50DX256CLK10 can be used for applications such as a wearable heart-monitoring patch, where the signals from the electrodes are boosted by the operational amplifier and converted to a digital signal by the SAR ADCs to a resolution of 12 bits. The M4 core can then process the signals or send them to a wireless transceiver that links to a base unit. All of this can be integrated into a simple adhesive patch with a flexible lithium ion battery that sits comfortably on a patient's chest to monitor activity without complex chest straps and lots of different wires. This level of miniaturization increases the efficiency of operations in hospitals and makes life more comfortable for the patient.

However, it is not just 32-bit controllers that can be used to miniaturize sensor systems that are monitoring health. The MSP430 16-bit family from Texas Instruments has focused on low power and integration to provide a platform for sensor systems. Applications such as glucose meters for monitoring diabetes and heart rate monitors are targeted by the MSP430 family, making use of the on-chip data converters. The MSP430AFE2x3 is an ultra-low-power mixed-signal microcontroller that integrates three independent 24-bit sigma-delta ADCs, one 16-bit timer, one 16-bit hardware multiplier, USART communication interface, watchdog timer, and eleven I/O pins.

Again, ultra-low power is a key consideration for minimizing the size of the design, and the architecture has five low-power modes so that it can be optimized for extended battery life in portable measurement applications. The device features a 16-bit RISC CPU with 16-bit registers and constant generators that contribute to maximum code efficiency, and so allow for a smaller, more power efficient design. A digitally-controlled oscillator (DCO) allows wake-up from low-power modes to active mode in less than 1 µs.

Image of MSP430AFE family from Texas Instruments

Figure 4: The MSP430AFE family from Texas Instruments integrates sigma delta analog to digital converters with a 16-bit RISC controller for compact, low power health monitor designs.

Conclusion

The advanced integration of modern microcontrollers is contributing dramatically to the miniaturization of health monitors, approaching the point where the vast majority of the functionality is combined on a single chip. System developers will always want separate sensors in order to differentiate their designs, but miniaturizing the data capture and analog front-end of the system design is allowing more health monitoring functions to be included in ever smaller form-factors. The ability to manage the power consumption carefully also allows for a sufficient battery life but also means that a smaller battery can be used to further reduce the size of the system.

Having data acquisition peripherals on a flexible bus also helps reduce the system size, as multiple sensors can be linked to the same data converters. As long as the functionality is orthogonal and the sensors will not be used at the same time, the flexibility allows for a smaller pinout and therefore, a smaller footprint.

However, the example of PulseOn shows that increasingly sensors are being used together – the MEMS accelerometer is used at the same time as the optical blood flow sensor to improve the quality of the end data. This presents more challenges for the designer who is aiming to reduce the layout to the smallest possible system size but provides opportunities for both shrinking the size of a health monitor and improving the quality of the information.









中文自动翻译,供参考

驾驶状态标尺上的芯片

用于可穿戴式传感器的一个关键驱动程序是健康监测,和小型化一直是一个关键推动这种技术。如果能够在同一台设备上的多个传感器和数据采集子系统集成的微控制器为设计人员提供小型化的设备的设计,以适应更多的形式因素的能力。

从PulseOn最新的可穿戴式健康监测,例如,采用意法半导体定制的微机械MEMS传感器以及它的STM32L微控制器。这提供了准确的连续心脏率测量和在微控制器上运行的算法把数据到为每个单独的有意义的个性化反馈。

所述MEMS加速计保持心脏率测量的准确性和可靠性,在由心电图输送的水平,并在广泛的条件进行了测试,从体力活动到高水平的有氧密集的活动。加速计通过跟踪手的移动和振动系统中,以消除在光血液流量探测的噪声,以便系统可以表示实际心脏脉搏和这是刚刚噪声引起的手部动作的信号区分这一点。加速度计还确定身体活动的穿用者的水平。

PulseOn的智能可穿戴式健康监测的图像

图1:PulseOn的智能可穿戴的健康显示器采用了MEMS加速计和高度集成的控制器,意法半导体,增加血压测量的准确性。

“精度和芯片的性能,使我们能够在严格的科学标准适用于PulseOn心脏速率测量技术,生产可靠的结果,其中包括在休息的节奏心跳的准确性,”杰瑞诺西艾宁,工程负责人说,在PulseOn。 “同样重要的是,该器件的微小尺寸和能量的预算已经由有助于创造了市场上最小和最准确的腕戴心脏速率监测的是一个竞争优势。”

另一种方法是小型化的健康监测是尽可能多的数据采集整合在一个芯片上。来自Analog Devices的ADuCM350是一种高精度流量计上的单芯片被设计成从在便携式设备的应用,如护理点诊断和可穿戴设备纽扣电池运行。通过组合在模拟前端的安培,伏安,和impedometric测量能力具有灵活开关矩阵,可以在最足迹可以使用多种传感器来降低系统的整体尺寸。这里使用的16位,精密,160 kSPS的模拟 - 数字转换器(ADC); 0.17%高精度电压参考; 12位,无失码数字 - 模拟转换器(DAC);和可重构超低漏电开关矩阵。还有一个温度传感器,±1℃下从0℃的精确度至50℃。

该芯片还包括一个低功耗的ARM Cortex-M3架构的处理器,384 KB的嵌入式闪存,32 KB系统SRAM和闪存配置EEPROM 16 KB,以及I / O支持便携式仪表与显示屏, USB通信,以及主动式传感器。在AFE被连接到ARM Cortex-M3的经由高性能总线(AHB)从接口,以及直接存储器存取(DMA)和中断连接。

ADI公司ADuCM350图的图像

图2:ADuCM350集成了所有需要的健康监测到的芯片级封装在单一芯片中的元素。

为了保持系统的大小了,这一切都被打包在一个120引脚,8毫米×8毫米芯片级球栅阵列(CSP_BGA),工作温度范围为-40°C至+ 85°C,以满足需求许多不同的环境。

功率,当然,是在该系统的小型化的一个重要的考虑,因为较低的功率允许使用更小的电池。其结果是,该ADuCM350有一系列的功率模式,例如动态和软件控制的时钟和电源门控。

飞思卡尔半导体公司的MK50DX256CLK10同样是针对小型化传感器应用,具有广泛的集成外设。这些包括两个16位逐次逼近SAR ADC的,可编程增益放大器(PGA)(最多64)集成在每个ADC,以及两个运算​​放大器和两个互阻抗放大器。对于数据输出,有两个12位DAC,用含有6位DAC和可编程参考输入端和参考电压,三个模拟比较器(CMP)的所有允许系统更加高度集成。

通讯接口包括USB全速/低速这去控制器,带有片上收发器,两个SPI模块和两个I2C模块连接到数字传感器系统,以及4个UART模块链接到其他串口传感器。此外,还有一个I2S模块在系统和一个低功率的硬件触摸传感器接口(TSI)用于表示管理链接到其他控制器。

所有这一切都是由ARM的Cortex-M4内核带DSP指令控制,提供1.25 Dhrystone MIPS的每兆赫和高达100 MHz的运行,以最大限度地降低功耗。内存支持包括高达512 KB的闪存程序存储器中,非易失性存储器56 KB的FlexNVM和高达128 KB的RAM。一个16通道DMA控制器支持多达63请求源,并且允许将数据从传感器捕获和存储,而不必以唤醒微控制器核心,从而降低整体功耗并有助于减少设计的尺寸。

飞思卡尔MK50DX256CLK10图的图像

图3:飞思卡尔MK50DX256CLK10用在心脏速率由从简单的电极集成的数据捕捉功能测量补丁。

该MK50DX256CLK10可用于应用如可穿戴心脏监测贴剂,其中,来自所述电极的信号由运算放大器升压并转换成数字信号由特区ADC以12位的分辨率。然后在M4芯可以处理的信号或将其发送到无线收发信机链接到一个基本单元。所有这一切都可以集成到一个灵活的锂离子电池,坐在舒适的在患者的胸部监控活动无需复杂的胸带和许多不同的电线简单的粘贴片。小型化这一水平提高操作的效率在医院,使生活更舒适的病人。

但是,它不是可用于小型化正在监视健康传感器系统只是32位控制器。该MSP430 16位系列德州仪器一直专注于低功耗和集成提供了一个平台,传感器系统。应用程序,如血糖仪监测糖尿病和心脏率监测仪是由MSP430系列有针对性的,利用芯片上的数据转换器。该MSP430AFE2x3是一款超低功耗混合信号微控制器,集成了三个独立的24位Σ-Δ型ADC,1个16位定时器,一个16位硬件乘法器,USART通信接口,看门狗定时器及11个I / O引脚。

再次,超低功耗是一个关键考虑因素最小化设计的大小和结构有五个低功耗模式,以便它可以延长电池寿命在便携式测量应用进行优化。该设备具有16位RISC CPU与16位寄存器和常数发生器有助于最大代码效率,并因此允许更小,更省电的设计。数字控制振荡器(DCO)允许唤醒从低功耗模式至运行模式,在不到1微秒。

MSP430AFE家庭德州仪器的图像

图4:MSP430AFE家庭德州仪器集成Σ-Δ模数转换器具有一个16位RISC控制器结构紧凑,低功耗的健康监测器的设计。

结论

现代微控制器的先进的集成极大地促进健康显示器的小型化,快到那里的功能绝大部分是结合在一块芯片上的点。系统开发人员总是希望独立的传感器,以差异化的设计,但小型化的系统设计的数据采集和模拟前端是让更多的健康监测功能将包含在更小的外形尺寸。来管理功耗的功能仔细还允许充分的电池寿命,但也意味着较小的电池可用于进一步降低系统的尺寸。

具有数据获取外围的柔性总线上也有助于降低系统的大小,作为多个传感器可以连接到相同的数据转换器。只要功能是正交和传感器不会同时使用,该灵活性允许一个较小的引出线,因此,更小的体积。

然而,PulseOn的例子表明,越来越多的传感器被一起使用 - 所述MEMS加速计被用来同时作为光血流传感器来改善最终数据的质量。这为谁的目标是减少的布局到尽可能小的系统尺寸,但提供了机会,既缩小一个健康监视器的尺寸和改进的信息质量设计者更多的挑战。

 

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