High precision analog-to-digital converters are crucial in fields such as medical electronics and bioelectric potential measurement. TI's ADS1299 has long held an important position in this field. However, with the continuous development of domestic chip technology, the LHE7909 chip launched by Linghui Lixin has become a powerful substitute for ADS1299 due to its excellent performance.
1,、 Analysis of Performance Parameters of LHE7909
（1） Resolution and noise performance
LHE7909 has a high resolution of 24 bits, which means it can achieve high-precision signal conversion. In the detection of weak bioelectric signals, noise is a key interfering factor. LHE7909 performs excellently, with input reference noise as low as 0.8 μ Vpp when the gain (G) is 24 and the sampling rate is 250 sps; When G is 6 and the sampling rate is 250sps, the input reference noise is 1 μ Vpp. In contrast, ADS1299 has an input reference noise of 1 µ Vpp at a bandwidth of 70Hz. It can be seen that under specific conditions, LHE7909 has superior noise performance and can more accurately capture weak bioelectric signals, providing a more reliable data foundation for medical diagnosis.
（2） Channel configuration and sampling rate
This chip supports 4-channel, 6-channel, or 8-channel configurations, and this multi-channel synchronous sampling function is particularly suitable for multi-sensor data acquisition systems. Whether it is the synchronous acquisition of electrical activity in multiple regions of the brain in electroencephalogram (EEG) monitoring, or the simultaneous capture of electrical signals in different parts of the heart in electrocardiogram (ECG) monitoring, LHE7909 can handle it with ease. Its data rate range is 250sps to 32ksps (some data shows up to 64ksps), which can meet the sampling speed requirements of different application scenarios. In some medical monitoring scenarios that require high real-time performance, such as dynamic electrocardiogram monitoring, higher data rates can more timely reflect changes in cardiac electrical activity.
（3） Common mode rejection ratio and programmable gain
In terms of common mode rejection ratio (CMRR), LHE7909 has a high value of -120dB, which means it can effectively suppress common mode interference signals and ensure the accuracy of the collected bioelectric signals. In practical application environments, there are various electromagnetic interferences, and high CMRR can enable LHE7909 to operate stably in complex electromagnetic environments. Its programmable gain (PGA) provides a choice of 1/2/3/4/6/8/12/24 times, allowing users to flexibly adjust the gain according to the amplitude of the actual input signal, adapting to different intensities of bioelectric signals, greatly improving the applicability of the chip.
2,、 LHE7909 feature advantages display
（1） High integration design
LHE7909 is equipped with a programmable gain amplifier (PGA), a reference source, and an oscillator. This highly integrated design greatly reduces the complexity and cost of peripheral circuit design. In the past, when using ADS1299, additional peripheral devices may need to be configured to achieve similar functions. However, LHE7909 integrates these functions inside the chip, making the entire system smaller in size, lower in power consumption, and improving system stability and reliability. For example, in the design of portable medical devices, high integration means that the device can be made lighter and easier for patients to carry and use.
（2） Flexible working mode
The chip supports flexible power-saving and standby modes, which is particularly important for portable medical devices. When the device is in a non continuous working state or has low battery life, the battery life can be extended by switching to low-power mode. Meanwhile, it is compatible with the Serial Peripheral Interface (SPI) serial interface, facilitating communication with other microcontrollers or processors and facilitating system integration and development.
（3） Chrysanthemum Chain Mode Extension
LHE7909 supports daisy chain mode and can connect multiple chips in series to expand the number of channels. In some applications that require a large number of channels for data acquisition, such as multi lead electrocardiogram monitoring systems, connecting multiple LHE7909 chips through daisy chain can easily expand the number of channels without redesigning complex circuit structures, greatly improving the scalability of the system.
3、 Packaging and compatibility considerations
LHE7909 adopts LQFP-64 packaging, which is convenient for PCB layout. During the circuit board design process, engineers can more easily carry out wiring and component installation. More importantly, LHE7909 is compatible with replacing TI's ADS1299, which is undoubtedly a blessing for enterprises that have already used ADS1299 for product design. When conducting domestic substitution or product upgrading, there is no need for large-scale redesign of hardware circuits. Simply replace the chip with LHE7909 and make appropriate adjustments to the software to achieve a smooth transition of the product, greatly reducing the research and development costs and time costs of the enterprise.
In summary, Linghui Lixin's LHE7909 chip surpasses or is equivalent to TI's ADS1299 in many aspects due to its excellent performance parameters, unique characteristic advantages, and wide range of application field compatibility. It also provides convenience for users in packaging and compatibility, making it an ideal substitute for ADS1299. It is expected to play a greater role in medical electronics, bioelectric potential measurement, and industrial sensors, and promote the development of related industries.
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