Sensor interface module

Abstract

The invention discloses a sensor interface module, which comprises a closed-loop pre-amplifier and an analog to digital converter connected with the closed-loop pre-amplifier. An operational amplifier in the closed-loop pre-amplifier completely closes output current by closing a common grid tube and a matching tube in an output stage cascode structure, so that an additional large size proportion switch tube is prevented from being serially connected to an output stage current path, low power consumption is achieved, and the additional layout area is prevented from being increased; and a first capacitor array of a digital to analog conversion network in the analog to digital converter is a major decision part of a load capacitor of the pre-amplifier, and on the premise of ensuring the matching accuracy of an on-chip unit capacitor, the capacitor array is reused as the load capacitor, so that the closed-loop pre-amplifier can easily provide hundreds to thousands hertz of closed-loop bandwidth, and the sensor interface module can be applied to a biomedical instrument with different input signal bandwidth.

Description

technical field [0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a sensor interface module suitable for biomedical instruments. Background technique [0002] Sensors are widely used in implantable and portable biomedical instruments such as electroencephalogram recorder (EEG), electrocardiogram recorder (ECG), neural signal recorder (NSR); and the sensor interface module is mainly responsible for detecting the weak The analog voltage signal is converted into a high-precision digital signal output. This interface module mainly includes a pre-stage closed-loop amplifier and a high-precision successive approximation analog-to-digital converter (successive approximation ADC) connected to it, which can provide input from the above sensors The weak analog signal is amplified and filtered, and then quantized as a digital signal output. [0003] In biomedical instrument applications, the voltage amplitude of the input analog s...

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Problems solved by technology

[0007] (1) In order to ensure sufficient on-chip integrated capacitor matching accuracy for 12-bit successive approximation analog-to-digital converters, the value range of the minimum unit capacitance value of the capacitor array needs to be set to 0.5-1pF, which means 12-bit binary weighted The capacitor array will require hundreds of pF on-chip integrated capacitors, which will still occupy too much layout area and greatly increase the chip cost

[0008] (2) In the 12-bit successive approximation analog-to-digital converter architecture, the total capacitance of the entire capacitor array is reused as the load capacitance of the pre-stage operational amplifier to realize the aforementioned filtering function, but due to the total capacitance of the 12-bit binary-weighted capacitor array The capacitance value is as large as hundreds of pF, which will limit the closed-loop bandwidth used by the closed-loop amplifier for filtering to below tens of Hz, which is lower than the input signal bandwidth required by the above-mentioned biomedical instruments, and it is difficult to implement the corresponding sensor interface module

[0009] (3) In the framework of the high-precision successive approximation analog-to-digital converter, its input is connected to a 12-bit binary weighted capacitor array, so the capacitor array is an input sampling capacitor, but since the total capacitance of the capacitor array is as large as hundreds of pF, The resulting large RC time constant will prolong the sampling settling time of the analog-to-digital converter, resulting in sampling errors and affecting accuracy

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