The 8-channel analog front-end chip AFE968 can replace ADS1299

An 8-channel analog front-end chip with high integration and flexible configuration,AFE 968(QFP 64 package),is becoming a cost-effective domestic choice to replace ADS1299,for scenarios such as extracranial electroencephalogram(EEG),polysomnography,electrocardiogram(ECG)and bio-impedance spectroscopy(BIS).AFE968 adopts the same level of register mapping and SPI instruction set as ADS1299,which is highly compatible in hardware pin arrangement and can greatly shorten the replacement verification cycle of the original scheme.The 24-bit no-missing-codes performance of the analog front-end chip,the common mode rejection ratio(CMRR)above 80 dB and the low input reference noise density ensure that weak electrophysiological signals can still be extracted in the 50/60 Hz power frequency interference environment.

 

The analog front-end chip AFE968 integrates eight independentδ-σanalog-to-digital converters,which supports synchronous sampling at 24-bit resolution and effectively suppresses the phase delay error between multiple channels.The front end of each channel is equipped with a programmable gain amplifier(PGA),and the gain gear can be dynamically adjusted according to the electrode impedance to adapt to the wide dynamic range input from microvolt EEG to millivolt ECG.The bias driver amplifier built in the analog front-end chip can generate common-mode signals of patients,and cooperate with AC/DC dual-mode lead drop detection to ensure real-time monitoring of electrode contact state and avoid artifact interference caused by poor contact.

 

The analog front-end chip has a built-in VDAC voltage excitation source,which supports DC bias and AC sine wave output modes,and can be flexibly used for electrode impedance measurement and skin electrical activity(EAP)monitoring.Users can configure the excitation amplitude and frequency through SPI-compatible serial interface(supporting daisy-chain topology)without external DAC chip.At the same time,high-precision reference voltage source and oscillator are integrated in the analog front-end chip,and external reference or clock input can also be selected to provide redundant design space for the system to meet the application requirements of different precision levels.

Keywords:analog front-end chip