GXSC ADC Hardware and Software Fully Replace ADS1291 in EEG Sleep Monitoring Headbands

With the growing awareness of sleep health, EEG sleep monitoring headbands—as portable sleep monitoring devices—have been widely adopted in areas such as home health monitoring and sleep disorder screening, providing users with comprehensive services including sleep stage classification, sleep quality assessment, and alerts for sleep abnormalities. Among these, EEG signals serve as the core indicator reflecting the brain’s sleep state, and their acquisition accuracy directly determines the precision of sleep monitoring.

EEG waves during sleep are faint biological signals in the microvolt range, susceptible to environmental interference and electrode contact noise. This solution utilizes the GXSC ADC chip, whose high-resolution characteristics enable precise quantification of these faint biological signals. Additionally, it employs advanced low-noise design, with an integrated programmable gain amplifier (PGA) and digital filter that effectively suppress noise interference during EEG signal acquisition.

The GXSC ADC offers an output data rate of up to 32 kSPS, enabling digital sleep stage detection. It features extremely low input reference noise during operation; at GAIN=12, the input reference noise can be as low as 0.20 µVrms (1.24 µVpp). The common-mode rejection ratio (CMRR) is no less than 120 dB in unity-gain mode. Furthermore, the chip maintains an SNR of 87 dB even at an output rate of 32 kSPS, demonstrating exceptional performance.

The main features of the GXSC ADC are as follows:

• Data rates: 31.25 SPS to 32 kSPS

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

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

• CMRR: 120 dB

• Flexible power modes: High-Speed (HS), Low-Power (LP), and Ultra-Low-Power (ULP)

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

• Built-in low-drift reference; built-in clock with adjustable frequency and external output capability

• Built-in right-lead driver, lead disconnection detection, temperature sensor, and test signal

• Supports digital pacing detection

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

• Offset/Gain error calibration

• 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

For portable battery-powered products, the GXSC ADC offers an ULP mode that significantly extends battery life. Its data buffer function reduces the number of MCU interrupts, helping to conserve system power. Therefore, selecting this chip can substantially reduce the size, power consumption, and cost of the application. It also features conduction detection based on a current sink/current source, with a current range of 6 nA to 399 nA, which can be selected and adjusted according to product requirements.