Dynamic correction circuit for current source of current-steering digital-to-analog convertor

Abstract

The invention relates to a dynamic correction circuit for the current source of a current-steering digital-to-analog convertor. The current source comprises multiple groups of current source modules, each current source module comprises a first MOS (metal oxide semiconductor) tube unit and a second MOS tube unit which are connected in series; the first MOS tube unit comprises a plurality of first MOS tubes connected in parallel, and the source electrodes and drain electrodes of the first MOS tubes are respectively connected to form the source electrode and drain electrode of the first MOS tube unit; the source electrode of the first MOS tube unit is connected with an external power supply; and the correction circuit is composed of a feedback control module as well as a correction MOS tube subunit, a capacitor and a switch which are arranged in each group of current source modules. The dynamic correction circuit is used for dynamically correcting the current source to stabilize the current source basically so as to obtain a digital-to-analog convertor with better properties.

Description

technical field [0001] The invention relates to an integrated circuit, in particular to a dynamic correction circuit for a current source of a digital-to-analog converter. Background technique [0002] In analog integrated circuits or in interface circuits, the digital-to-analog conversion module is a very common functional module used to convert digital signals into analog signals, especially in integrated circuits that have developed to the GHz level and have an accuracy of 14bit and above. At present, the main structure adopted is a digital-to-analog converter in the form of a current steering to realize the above functions. [0003] In the above-mentioned digital-to-analog converter with high-speed and high-precision current steering structure (especially with a precision above 14bit), the high-level current source is a key module, especially the size or deviation of the high-level current source will directly determine the amplitude change of the output signal , that i...

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Problems solved by technology

[0003] In the above-mentioned digital-to-analog converter with high-speed and high-precision current steering structure (especially with a precision above 14bit), the high-level current source is a key module, especially the size or deviation of the high-level current source will directly determine the amplitude change of the output signal , that is to say, under any working condition, the value of the high-level current source determines the output signal characteristics. If the deviation of the current source is relatively small, the steps of the output waveform will change relatively uniformly, and there will be no missing codes, otherwise it will cause The potential of the output signal fluctuates and brings a large harmonic distortion of the output signal

[0004] Taking a 16-bit digital-to-analog converter as an example, set its high bit to 5 bits. Generally, the high bit is a thermometer code to realize the high-bit current source control. Therefore, the 5-bit high-bit current source generates a 31-bit code through coding, so that 31 identical current source modules are required to be coded to control the working status of the thermometer; for example figure 1 As shown, when the high bit of the digital-to-analog converter is 5 bits, 31 sets of current source modules are required, and the 31 sets of current source modules are respectively numbered as CSM1, CSM2...CSM30, CSM31, and each current source module consists of the first , the second MOS tube unit M1', M2' constitute; as figure 2 As shown, if the deviation between these current source modules is relatively large, the waveform of the output signal OUT of the digital-to-analog converter will have a large deviation (assuming that the ideal output waveform should be sinusoidal), resulting in output harmonic distortion. Serious, this situation will be more serious especially in high-speed circuits, which is one of the main non-ideal factors affecting the dynamic characteristics of high-speed digital-to-analog converters

[0005] Therefore, people in the industry usually use many techniques to improve the matching of high-level current sources, or use various background correction techniques to improve the accuracy of current source values, so as to improve the dynamic characteristics of digital-to-analog converters; however, these existing methods generally need a lot of money

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