According to the micro-network news, the vehicle steering wheel ECG system can realize the timely judgment and early warning of the driver's ECG detection, abnormal heart rhythm detection, fatigue driving and emotional detection; the car seat ECG system can realize real-time monitoring and attention to the family's heart health, and at the same time provide long-term ECG monitoring data to help increase the doctor's judgment accuracy in the medical diagnosis of heart disease... These are typical application scenarios for in-vehicle health monitoring technology. With the promotion and popularization of intelligent cockpits, on-board health monitoring technology, which is an important part, has also developed rapidly in recent years. However, the complexity of the on-board electromagnetic environment and the diversity of various operating conditions (such as speed, bumps, vibrations) make the accurate acquisition of weak ECG signals more challenging, and these factors put forward higher requirements for both the hardware and software systems of the ECG system.
(Block diagram of typical applications of automotive ECG)
System-on-chip supplier Analogysemi's latest ADX923Q series of self-defined automotive-grade ECG analog front-end chips for professional Holter detection has enabled many improvements from the hardware level to the challenge factors of the above-mentioned automotive applications.
With the development of big data and AI intelligent health software applications, software ECG-related algorithms have made great progress in precision, diversity, reliability and cloud diagnostic technology. Correspondingly, more innovations and breakthroughs are needed at the hardware system level.
It is understood that in the ECG hardware system, AFE ECG chip is the key to the entire system, how to design to meet the vehicle ECG system AFE ECG chip, you need to solve the following important problems, including:
1. The application of vehicle gauge has higher requirements in terms of temperature -40°C - 105/125°C (the maximum temperature requirements of each car company are different);
2. Vehicle regulations are applied to have higher requirements for anti-electromagnetic interference and ESD protection;
3. Various interferences of on-board working conditions;
4. The sensitivity of the vehicle ECG system in the contact of dry electrodes is detected by the hand;
5. Functional safety design requirements for vehicle specification chips;
6. The on-board steering wheel electrode module supports L2 and above autopilot HOD function.
It is reported that the new automotive grade AFE ECG chip ADX923Q product launched by Analog Semiconductor can meet the above-mentioned automotive ECG chip needs. The basic features of the ADX923Q product include a multichannel, synchronous sampling, 24-bit, Δ-Σ (ΔΣ) analog-to-digital converter (ADC) with an internal programmable gain amplifier (PGA), internal reference, and on-board oscillator that includes all the features typically required in automotive steering wheels, seats, portable, low power medical electrocardiograms (ECG), and sports and fitness applications. At the same time, the high level of integration and superior performance enables the creation of scalable medical instrumentation systems with significantly reduced size, power consumption, and overall cost, with a flexible input multiplexer for each channel that can be independently connected to internally generated signals for testing, temperature, and lead shedding detection, and can be selected for any input channel configuration to export right-leg drive (RLD) output signals.
In addition, the ADX923Q operates at data rates up to 8 kSPS and can use the device's internal excitation current sink or current source for lead-off DC detection and internal DDS excitation source for lead-off AC detection. The ADX923Q version also includes fully integrated breath impedance measurement, and the ADX923Q version also includes integrated analog pace detection, single-channel 3-way detection, and configurable low-frequency noise signal filtering, all of which support fault diagnosis detection required for automotive functional safety features. These devices are available in a 4 mm x 4 mm, 32-pin leadless square flat package (QFN with Wettable flank) package and are specified for operation from –40°C to +125°C.
It is worth mentioning that in order to meet the challenges of vehicle specification applications, the analog ADX923Q has made a series of design implementations at the chip level, including:
1. Products from the process, design, packaging and testing, mass production to meet a series of requirements of the vehicle standard level, support the vehicle specification functional safety requirements and meet the AEC-Q100 Grade1 standard. Specifically, all PIN ESD HBM in the chip family support +/-4 kV, and the power SUPPLY PIN ESD HBM reaches +/- 8kV.
2. Improved input impedance and increased differential impedance coefficient, with 64 dc off-hand detection current selection, while chip DC off-hand detection comes with 50Hz/60Hz power frequency filter function, saving software power frequency filtering overhead.
3. For the detection challenges of dry electrodes, the analogy introduces a hardware AC off-hand detection scheme, which supports 4KHz and 500Hz 2 kinds of AC excitation source hardware algorithm AC detection, and supports software AC excitation source software algorithm detection from 125Hz to 8KHz, and based on the AC off-hand detection principle, it can be applied to the current L2 and above automatic driving HOD detection.
4. The chips support three configurable low-frequency noise filtering functions to filter out noise interference in most operating conditions.
5. Support communication ECG data and equipment command word CRC check to ensure the reliability of communication link transmission; support PGA input overrange detection, clock fault diagnosis, data and command word transmission error diagnosis, illegal command word detection, power-on chip fault self-test, output PIN short-circuit and short-circuit power supply detection, communication timeout reset communication interface and data frame loss detection and other functional safety features.
6. For seat ECG applications, Analog Semiconductor has innovatively introduced Electrode Rotation (ERM), enabling sampling and monitoring of triple-conducted ECG data using only a single channel ADC.
7. The chip supports FIFOs up to 12 depths, and has the ability to locally store 24 sets of ECG data, which can balance the adaptation of communication and data processing rates while reducing the time occupied by μC devices.
8. The chip has a built-in analog PACE detection circuit, which can realize the detection of the pacing pulse signal, which can eliminate the components of the peripheral discrete pacing circuit, optimize the board-level circuit design and reduce cost.
It is reported that at present, the product has cooperated with a number of domestic automobile manufacturers and Tier1, and has been sent to mass production.
(Proofreading/Sami)