Application of eight channel 24 bit analog front-end software and hardware compatible with ADS1299 in portable EEG acquisition

With the development of biomedicine, electroencephalography (EEG) has become an important means of monitoring some mental illnesses. For applications that require long-term detection of EEG, EEG acquisition devices need to have a certain degree of portability. Compared to traditional non-invasive EEG acquisition devices, portable EEG acquisition devices commonly use dry electrodes, which are more comfortable to wear and have features such as low power consumption and wireless transmission.

Unlike traditional laboratory equipment, portable EEG requires capturing weak EEG signals in an unshielded environment, while meeting the requirements of long-term wearing, multi-channel synchronous recording (≥ 8 channels), and resistance to motion artifacts. The GX1299, an eight channel 24 bit analog front-end of GXSC, is designed specifically for bioelectric measurement. Its high resolution, low noise, and integrated design provide core technical support for EEG monitoring.

The GX1299 features a built-in programmable gain amplifier (PGA), internal reference, and built-in oscillator, as well as commonly used functions required for EEG and ECG applications. The extremely high integration can significantly reduce product size, power consumption, and overall cost. It can be directly powered by batteries and is suitable for portable EEG acquisition.

GX1299 operates at an output rate of 250SPS~64kSPS, and can achieve an IRN performance of 1.28 μ Vpp (0.23 μ Vrms) at an output rate of 250SPS; At 64kSPS, it has a -3dB bandwidth of 14.4kHz, with pull-up/pull-down resistors, excitation current traps/sources, and AC lead detection functions. In addition, GX1299 has a daisy chain configuration, which can solve the problem of cascading data in high channel systems. The digital cache function with a maximum depth of 16 can minimize the frequency of data retrieval, thereby reducing system power consumption. The main features of GX1299 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 driver amplifier, lead dropout detection, temperature sensor, test signal

• 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