Power-down protection circuit for chemical sensor

Abstract

The invention discloses a power-down protection circuit for a chemical sensor, which can control the formation of a power-down short-circuit state or a power-on disconnection state between the drain electrode ends of two NMOS transistors through a combination of the two NMOS transistors and a charge pump which are connected with each other through source electrodes, so that the short-circuit protection of the chemical sensor when the circuit is powered down is realized, and polarity damage of the chemical sensor due to the excessively high voltage of two poles is avoided. The power-down protection circuit is characterized by comprising an operational amplifier circuit board, wherein the operational amplifier circuit board is internally provided with a first operational amplifier, the positive input end of the first operational amplifier is connected with a grounding end, the negative input end of the first operational amplifier is an access end of the positive electrode end of the sensor, the negative input end of the first operational amplifier is connected with the drain electrode of the first NMOS transistor, the source electrode of the first NMOS transistor is connected with the source electrode of the second NMOS transistor, the drain electrode of the second NMOS transistor is an access end of the negative electrode end of the sensor, the grid electrode of the first NMOS transistor and the grid electrode of the second NMOS transistor are respectively connected with a charge pump, and the charge pump is connected with an oscillator.

Description

technical field [0001] The invention relates to a power-down protection technology for sensors, in particular to a chemical sensor power-down protection circuit, which can control the drain terminal of the two NMOS tubes through the combination of two NMOS tubes interconnected at the source and a charge pump. A power-down short-circuit state or a power-on disconnection state is formed between them, so as to realize the short-circuit protection of the chemical sensor when the circuit is powered off, so as to avoid polarization damage to the chemical sensor. Background technique [0002] At present, the two output terminals of the carbon monoxide sensor (CO sensor) should be short-circuited after the circuit is powered off, that is, the positive terminal WE of the sensor is short-circuited with the negative terminal CE of the sensor, so as to ensure that the sensor will not generate extreme voltage due to the voltage difference between the two poles exceeding the rated voltage....

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Problems solved by technology

The inventor found that the disadvantage of this solution is that the peripheral circuits must be increased, thereby increasing the circuit cost

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