Operational amplifier offset self-calibration circuit applied to voice coil motor driver chip

Abstract

The invention discloses an operational amplifier offset self-calibration circuit applied to a voice coil motor driver chip. The operational amplifier offset self-calibration circuit comprises an operational amplifier (OPAMP), a counting latch, a comparator, an oscillator and a digital analog converter for calibration (DAC), wherein the output end of the OPAMP is connected with the negative pole input end of the comparator; the output end of the comparator is connected with the input end of the oscillator and one input end of the counting latch; the output end of the oscillator is connected with another input end of the counting latch; the output end of the counting latch is connected with the input end of the DAC for calibration; the output end of the DAC for calibration is connected witha signal feedback end of the OPAMP; and the input end and the output end of the OPAMP are further respectively connected with the voice coil motor driver chip. The offset of the OPAMP can be eliminated or greatly decreased, the accuracy of output current of the motor driver chip is improved, the service time of the system battery is prolonged, and the condition that the chip development and test cost is increased due to offset calibration by using a fuse wire is avoided.

Description

technical field [0001] The invention relates to the technical field of semiconductor equipment, in particular to an operational amplifier offset self-calibration circuit applied to a voice coil motor drive chip. Background technique [0002] There are many ways to achieve camera focusing, among which voice coil motor (Voice Coil Motor, VCM) is the most widely used due to its simple structure, small size, and fast response speed. , autofocus camera modules for video monitors, scanners, etc. [0003] The circuit block diagram of the voice coil motor driver chip, such as figure 1 As shown, the modules included in voice coil motor driver chip 100 are: I2C interface, main DAC of digital-to-analog converter, output operational amplifier OPAMP, output stage power transistor NM0, current detection resistor Rsense, freewheeling diode Dio0 and reference reference source Reference, The circuit equivalent model 110 of the voice coil motor includes coil inductance L1 and coil internal ...

AI Technical Summary

Problems solved by technology

This technique is limited in continuous-time applications, and clock switching non-idealities introduce noise and degrade system performance

[0008] 3) Use the fuse trimming (Trimming) scheme, but trimming will increase the development and testing costs of the entire chip

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