ADS1299IPAGR

The ADS1299IPAGR is an 8-channel, low-noise, 24-bit analog front-end specifically designed for biopotential measurement applications such as EEG, ECG, EMG, and sleep monitoring. As a member of Texas Instruments ADS129x family of integrated biopotential AFEs, the ADS1299 integrates all the active components required to implement a complete 8-channel biopotential measurement system, significantly reducing board space, power consumption, and design complexity compared to discrete implementations. Each of the eight channels includes an input multiplexer (for selecting between electrode inputs, test signals, temperature sensor, and other internal signals), a low-noise programmable gain amplifier, and a 24-bit delta-sigma ADC. All channels sample simultaneously, ensuring precise time alignment across all inputs – essential for applications like EEG where phase relationships between channels carry diagnostic information. The ADS1299 achieves input-referred noise of only 1 microvolt peak-to-peak over a 70 Hz bandwidth at gain 24, which is well below the microvolt-level EEG signals it is designed to measure. The high CMRR of -110 dB effectively rejects common-mode interference such as 50/60Hz power line noise that is typically picked up by body-worn electrodes. The built-in right leg drive (RLD) amplifier further improves common-mode rejection by actively driving the patient reference electrode to cancel out common-mode voltage. Integrated lead-off detection circuitry monitors electrode impedance to detect loose or disconnected electrodes, a critical feature for reliable patient monitoring. The device also includes an internal test signal generator for self-test and verification without external stimulus. Communication is through a standard SPI interface, and daisy-chain mode allows multiple ADS1299 devices to share a single SPI bus for applications requiring more than 8 channels. The ADS1299IPAGR is the PAG-grade (commercial, 0C to +70C) 64-lead TQFP package version. An industrial temperature grade (-40C to +85C) is also available.

The ADS1299 is a highly integrated biopotential analog front end that combines multiple signal conditioning and data conversion channels on a single chip. Each of the eight independent channels begins with an input multiplexer that selects the signal source for that channel – this can be the external electrode input, an internal test signal, the temperature sensor output, or a shorted input for offset measurement. Following the MUX is a low-noise programmable gain amplifier that amplifies the biopotential signal. The gain is independently configurable per channel from 1 to 24, allowing optimization of dynamic range for different signal types (e.g., ECG uses lower gain, EEG uses higher gain). The PGA is designed for extremely low input noise (achieving 1 µVpp at gain 24) and very low input bias current (300 pA), both of which are critical for high-sensitivity biopotential measurements where electrode-tissue interface impedance can be very high. After the PGA, the amplified signal is digitized by a 24-bit second-order delta-sigma modulator per channel. All eight modulators operate in parallel and synchronously, so all eight channels sample at exactly the same time. The modulators are followed by third-order sinc digital decimation filters that convert the high-rate bitstreams from the modulators into 24-bit output words at the selected data rate. The data rate is programmable from 250 SPS to 16 kSPS. The RLD (right leg drive) amplifier is a key feature for biopotential measurement: it senses the common-mode voltage present on all the input electrodes, inverts it, and drives it back to the patient through a reference electrode. This negative feedback actively cancels common-mode interference (especially 50/60Hz power line noise), dramatically improving the effective CMRR of the system. The lead-off detection function works by sourcing or sinking small currents through each electrode input; if the electrode impedance is too high (indicating poor contact), the resulting voltage will be outside the normal range, and the device flags this condition. The device also includes an internal oscillator, internal voltage reference, and power management circuitry that allows individual channels to be powered down when not needed, reducing total power consumption. All configuration and data transfer is handled through the SPI interface, with DRDY pins indicating when new conversion data is available.

• Clinical and research EEG (electroencephalogram) recording systems
• Brain-computer interface (BCI) devices and neurofeedback systems
• ECG/EKG monitors and cardiac diagnostic equipment
• EMG (electromyography) muscle activity measurement
• Sleep study equipment and polysomnography
• Fetal monitoring and fetal ECG
• Wearable health monitoring devices
• Portable medical diagnostics and point-of-care testing
• Biomedical research and neuroscience laboratory equipment
• Evoked potential (EP) and event-related potential (ERP) measurement