ADI integrated heart rate monitoring analog front end focuses on system-level design solutions

A few days ago, ADI launched a low-power, single-lead heart rate monitor analog front end (AFE) AD8232. Compared with similar solutions, the size of the AD8232 AFE is reduced by 50%, and power consumption is reduced by as much as 20%. With advantages in power consumption, size, and integration, designers can use the AD8232 to develop heart rate and heart monitor equipment needed for daily health care, such as personal health management and remote health monitoring.

It is understood that the so-called single lead requires at least 2 or 3 electrodes to achieve (in the case of 3 electrodes, one of them is used for driving the right leg). Unlike the topology used in many current integrated solutions, the AD8232's highly flexible analog filter configuration uses a bipolar high-pass filter, combined with the on-chip instrumentation amplifier architecture and unconstrained operational (gain) amplifier, allowing users to use multi-pole low Pass filter technology to eliminate line noise and other interference. Similar products are usually derived from existing clinical heart monitor solutions, while the AD8232 AFE is specifically designed to meet the ECG signal conditioning requirements of emerging fitness equipment, portable / wearable monitoring equipment, and remote health monitoring equipment, which can be used for running Mobile phones, smart phones, gaming peripherals, automotive electronics and even the military field.

Figure ADI's low-power, single-lead heart rate monitor analog front end (AFE) AD8232 internal structure diagram

AD8232 function configuration

Wang Sheng, marketing manager of ADI Asia Pacific medical industry, introduced that ADI has discrete solutions to achieve similar functions, and this AFE launched this time is pure analog conditioning integration, and is really focused on system-level design solutions. Considering that the devices in the target application scenario (such as smart phones, automobiles, etc.) already have DSP / MCU, and also have ADC function, and are usually multi-channel, from the performance to fully meet the AFE needs, so there is no need to integrate DSP / MCU, ADC, but share these devices with the system, thereby eliminating the cost, area, power consumption of integration, and achieve greater flexibility.

By performing high-gain and high-pass signal conditioning in a single stage in the analog domain, the AD8232 can adapt to electrode DC offset when operating on a single supply voltage without affecting performance or signal quality. Through the analog output, the AD8232 can be paired with a discrete ADC or a microcontroller with an embedded ADC. It provides system designers with the flexibility to raise the value and performance of fitness and medical monitoring to a new level .

In addition to the instrument and gain amplifier, the AD8232 heart rate monitor AFE also integrates the reference buffer, right leg drive circuit, and shutdown function. The AD8232 also includes a user-selectable AC or DC lead off detection circuit, which will send an alarm signal to the system when it is monitored that the electrode is disconnected from the user. In addition, this new heart rate monitor AFE provides an innovative fast recovery mode. When the user temporarily disconnects the electrode during exercise or other activities, when the lead is reconnected, this chip can quickly and automatically recover the ECG signal, thereby Significantly improve the quality of user experience.

The market's demand for fixed, portable, and even wearable heart rate monitors is increasing, including vital sign measurements for athlete training, home fitness equipment, or remote health monitoring. This level of non-diagnostic monitoring needs to consider a series of unique design factors. ADI hopes that the AD8232 can provide manufacturers with a more reasonable and balanced signal processing architecture. From the perspective of back-end component selection and filter design, it has greater flexibility, which simplifies system design and is simpler, more reliable, and more accurate than existing solution designs. AD8232 is currently priced at US $ 1.36 / piece (a thousand-piece order quantity), and it has certain competitiveness in terms of price.