24 bit 32kSPS analog front-end GX1291 software and hardware 100% replacement ADS1291 applied to heart rate band

In the field of sports and health, heart rate bands are commonly used devices for monitoring exercise status. The heart rate band collects human electrocardiogram signals through skin electrodes to calculate real-time parameters such as heart rate and heart rate variability (HRV), providing data reference for adjusting exercise intensity and evaluating health status. However, the surface electrocardiogram signals collected by the heart rate band are weak, susceptible to motion interference and environmental interference, and the device requires low-power design to support long-term wear. GXSC, a single channel 24 bit high-precision analog front-end chip GX1291, is an ideal choice for heart rate and electrocardiogram signal acquisition.

The amplitude of the electrocardiogram signal in the heart rate band is generally low. The small waveform amplitude of GX1291 requires the acquisition system to have high resolution and low noise, with 24 bit high resolution, and advanced low-noise design. The internal integrated programmable gain amplifier (PGA) and digital filter can effectively suppress noise interference. GX1291 is designed for ECG application scenarios, with functions such as right leg drive, lead detachment detection, pacing detection, WCT, etc. It can switch to internal clock and internal reference, simplifying the ECG peripheral circuit and significantly reducing the size, power consumption, and cost of the application product. It is very suitable for skin worn heart rate band applications.

For the application scenarios of wearable products, the GX1291 chip provides ULP mode, with a power consumption of only 0.475mW per channel, greatly improving battery life. Its data caching function can reduce the number of MCU interrupts, helping to save system power consumption. And it has lead detection function based on excitation current trap/current source, with a current range of 6nA~399nA, which can be selected and adjusted according to product requirements. The main features of GX1291 are as follows:

Data rate: 31.25SPS to 32kSPS

• Programmable gain: 1, 2, 3, 4, 6, 8, or 12

Ultra low input reference noise: 4.07 μ Vpp (0.64 μ Vrms) (BW=150Hz, G=6)

• CMRR：120dB

Flexible power consumption modes: High Speed Mode (HS), Low Power Mode (LP), Ultra Low Power Mode (ULP)

Low power mode, with a power consumption of only 410 µ W (AVDD=3V, DVDD=1.8V, ODR=500SPS, G=6)

• Built in low-temperature float benchmark; Built in clock, capable of external output, and adjustable frequency

• Built in right leg driver amplifier, lead detachment detection, temperature sensor, test signal

• Supports digital pacing detection

• Adjustable data cache depth (1/2/4/8/16/32)

Offset/Main error calibration function

• Power supply range: Analog power supply: 2.7V to 5.25V; Digital power supply: 1.8V to 5.25V

Flexible power-off and standby modes

SPI interface

• Operating temperature range: -40 ° C to+85 ° C