FAQ Analog Front End and Sensors

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FAQ Analog Front End and Sensors [Copy link]

Analog front end and sensor category (17 questions and answers in total, compiled and provided by Haroad Chen, a member of TI Expert Committee)

1. Do the wearable devices we wear have anti-interference algorithms when we are exercising? How to ensure the battery life?

A: Anti-motion interference algorithms are indeed very important, and they also require good sensor data to support them. TI does not provide relevant algorithms, but we work with third parties to support customers.

2. Can TI provide sensor algorithms?

A: Currently, TI does not provide relevant algorithms, and customers need to develop them themselves. If there is a business need, TI can provide support with a third party partner.

3. How to improve the accuracy of heart rate detection? It is not accurate when the human body sweats. How to improve it?

A: If photoelectric PPG is used for measurement, sweat may cause more light reflection, resulting in a larger DC signal offset. TI's AFE4404 can support real-time calibration provided by the algorithm to reduce the impact of DC.

4. How long will it take for wearable devices to have medical-grade measurement accuracy?

A: Many of our customers have used TI products to make wearable devices that have passed CFDA and FDA medical certifications.

5. For ECG measurement in wearable applications, which one is more suitable, ADS1291 or ADS1292?

A: TI has a whole series of ECG measurement AFE products, supporting from 1 to 12 leads, and respiratory monitoring, PACE monitoring functions, etc. Whether to use ADS1291 or ADS1292 depends mainly on how many leads you need to collect. If it is a single lead, ADS1291 can be used.

6. Is there respiratory monitoring?

A: TI's ADS129XR can provide respiratory monitoring function. For details, please refer to: 查看详情

7. How do I verify the accuracy of the AFE44XX? Do I need TI to calibrate it?

A: Generally speaking, accuracy is related to many factors, such as optics, structure, size of photoelectric tube, performance of AFE, etc. When debugging, customers can first connect the engineering sample to TI's EVM, analyze real-time data, and optimize in real time by combining register settings.

8. Help analyze the application selection considerations of the AFE440x series

A: It is recommended to refer to 查看详情 for a very detailed comparison.

9. What is the power consumption performance of AFE4404 and AFE4405?

A: Under normal working conditions, the current of AFE4405 itself is about 200uA. The main current consumption is on the LED, which mainly depends on the switching frequency and duty cycle of the LED. Compared with other analog front ends, TI's AFE440X is very flexible in LED control and can minimize the power consumption of the entire system.

10. Can the AFE44XX integrated analog front end measure heart rate and calorie consumption at the same time? The operating temperature range of AFE4403/04/05 is -20~70 degrees. Will the measurement accuracy be affected at lower temperatures, such as -30 degrees?

A: FE440X mainly measures PPG signals, not calories. At low temperatures such as -30 degrees, it is recommended to use AFE4490, which can reach -40 degrees. However, at -30 degrees, the impact on skin and blood flow should be greater.

11. Does TI have other ECG solutions?

A: TI has a wide range of ECG AFE products and solutions, ranging from 1-lead to 12-lead. For details, please refer to: 查看详情

12. What is the operating range of the LMT70?

A: The temperature range is -55 - 150 degrees. The operating voltage range is 2V to 5.5V. For details, please refer to the LMT70 data sheet: 查看详情 ·

13. How can LMT70 replace NTC in thermometers? How can we prevent uneven temperature measurement in the temperature measuring head?

A: Generally speaking, NTC requires a high-precision voltage or current source. LMT70 directly outputs a voltage signal proportional to the temperature, and the power supply requirement is not high, and it can be powered by the IO port of the MCU. For the uniformity of temperature measurement, it mainly requires that the temperature measuring head is well wrapped, and LMT70 also needs to be well wrapped with thermal conductive glue in the temperature measuring head.

14. How much power does LMT70 consume when in operation?

Answer: <12uA. For details, please refer to the LMT70 data sheet: 查看详情

15. What parts of the body are mainly used to measure the temperature of the LMT70? How to solve the problem that traditional mercury thermometers are inconvenient to measure, especially when infants and young children do not cooperate? If dynamic body temperature monitoring is required, is there any solution?

A: LMT70 is a contact thermometer. For accuracy, we recommend placing it under the armpit. Generally speaking, the package of LMT70 is very small, so you can use thermal conductive glue, put it in a very small metal cap, and then measure the temperature against the skin.

16. Currently, heart rate monitoring of wearable devices is restricted by the correctness of wearing the wearable devices. On the other hand, continuous monitoring consumes too much power. Does TI's new solution have any improvement measures to address these problems?

A: In normal operation, the current of AFE4405 itself is about 200uA. The main current consumption is on the LED, which mainly depends on the switching frequency and duty cycle of the LED. Compared with other analog front ends, TI's AFE440X is very flexible in LED control and can minimize the power consumption of the entire system.

17. Can DRV2625 be used for small eccentric motors? Can the speed be controlled?

A: Yes, in fact, the intensity corresponds to the rotation speed.

alan000345

Nice sharing. Wearable devices are still very popular now, and sensors are indeed very important.