GX1291 Hardware and Software Replacement for ADS1291 Applied to ECG/EMG/EEG for High Precision Data Acquisition

In the modern medical field, medical instruments (ECG/EMG/EEG) are mainly used to record the electrical activity of the heart over a period of time by measuring the surface potential of living tissues, and to acquire physiological signals through bioelectrodes. In order to enhance the signal strength to remove interference and digitize the signal, a high-precision, low-power, multi-channel analog front-end chip is indispensable.

With its excellent performance, ADS1291 has been widely used in the data acquisition of medical instruments. This paper mainly introduces a24-bit GX1291, which can replace 100% of ADS1291 in hardware and software, providing an effective solution for data acquisition of these medical instruments.

The GX1291 has a built-in programmable gain amplifier (PGA), an internal low-temperature-drift reference, and a built-in frequency-adjustable oscillator. Designed for ECG and EEG application scenarios, it is equipped with functions such as right leg drive, lead off detection, digital pacing detection, etc. It can be switched to internal clock and internal reference, thus simplifying ECG/EEG peripheral circuits.

For battery application scenarios, the GX1291 provides ULP mode, which greatly improves endurance, and its data caching function, which reduces the number of interrupts of the MCU, helps to save system power consumption. Therefore, the selection of GX1291 can significantly reduce the size, power consumption and cost of ECG application products. The GX1291 is also equipped with an excitation current trap/current source based lead detection function with a current range of 6nA~399nA, which can be selected and adjusted according to product requirements.

In addition, the GX1291‘s output data rate of up to 32kSPS enables digital pacing detection. It operates with very low input reference noise, which can be as low as 0.20µVrms (1.24µVpp) at GAIN=12. The Common Mode Rejection Ratio (CMRR) is not less than 120dB in unit gain mode.In addition, the GX1291 still has an excellent performance with an SNR of 87dB at an output rate of 32kSPS. The main features of the chip are as follows:

- Data rate: 31.25SPS to 32kSPS

- Programmable Gain: 1, 2, 3, 4, 6, 8 or 12

- Ultra-low input reference noise: 4.07μVpp (0.64μVrms) (BW =150Hz, G = 6)

- CMRR: 120dB

- Flexible power modes: High-speed mode (HS), Low-power mode (LP), Ultra-low-power mode (ULP)

- Low power mode, power consumption only 410µW (AVDD=3V, DVDD=1.8V, ODR= 500SPS, G=6)

- Built-in low temperature drift reference; built-in clock with external output and adjustable frequency.

- Built-in right leg drive amplifier, lead shedding detection, temperature sensor, test signals

- Support digital pacing detection

- Data buffer depth adjustable (1/2/4/8/16/32)

- Offset/Gain error calibration function

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

- Flexible power-down and standby modes

- SPI interface

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