Differential Amplifier Trimming Circuit With T-Network Precision Tuning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for adjusting the common-mode rejection ratio of differential amplifiers require high precision, which is difficult to achieve with general digital trimming methods, leading to increased costs and errors due to the need for laser trimming, and these errors cannot be corrected after chip packaging.
Innovation Solution
A trimming circuit with a T-shaped resistor network structure that uses an all-digital method, incorporating a k-bit resistive network with low n-bits as an R-2R network and high (k−n)-bits connected in series with trimming resistors, allowing for precise adjustment without traditional laser trimming, and utilizing MOS transistors for switches to minimize on-resistance and circuit cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser trimming method is used to achieve high precision common-mode rejection ratio adjustment, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent changes the trimming parameter from resistance value adjustment (laser trimming) to capacitance value adjustment through digital control. By using a digital-to-analog converter (DAC) to control the capacitance in the T-shaped resistor network, the system achieves high precision trimming without requiring complex laser trimming equipment, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent replaces the mechanical/optical laser trimming system with an electronic digital control system. Instead of using laser to physically modify resistor values, the invention uses digital signals to control MOS switches that adjust capacitance values in the T-shaped network, substituting a complex mechanical/optical system with a simpler electronic system while maintaining high precision
2Manufacturing precision
If laser trimming method is used to achieve high precision adjustment, then manufacturing precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the trimming parameter from resistance value adjustment (laser trimming) to capacitance value adjustment through digital control. By using a digital-to-analog converter (DAC) to control the capacitance in the T-shaped resistor network, the system achieves high precision trimming without requiring complex laser trimming equipment, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent replaces the mechanical/optical laser trimming system with an electronic digital control system. Instead of using laser to physically modify resistor values, the invention uses digital signals to control MOS switches that adjust capacitance values in the T-shaped network, substituting a complex mechanical/optical system with a simpler electronic system while maintaining high precision
3Manufacturing precision
If laser trimming is performed before chip packaging, then manufacturing precision is improved, but reliability decreases due to uncorrectable errors from packaging stress
Solution Approach 1:
The patent applies preliminary digital trimming before chip packaging to establish an initial precise resistor ratio, and then provides post-packaging digital trimming capability to correct any errors introduced by packaging stress. This two-stage preliminary action ensures both initial precision and final reliability, resolving the contradiction between manufacturing precision and reliability
Solution Approach 2:
The patent makes the trimming system dynamic by enabling trimming operations both before and after chip packaging. The digital control system allows the circuit to be re-trimmed in the field if needed, transforming a static fixed-resistor system into a dynamic adjustable system that can adapt to changes caused by packaging stress, thereby improving reliability while maintaining precision
4Device complexity
If general digital trimming methods are used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent changes the trimming parameter from resistance value adjustment (laser trimming) to capacitance value adjustment through digital control. By using a digital-to-analog converter (DAC) to control the capacitance in the T-shaped resistor network, the system achieves high precision trimming without requiring complex laser trimming equipment, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent replaces the mechanical/optical laser trimming system with an electronic digital control system. Instead of using laser to physically modify resistor values, the invention uses digital signals to control MOS switches that adjust capacitance values in the T-shaped network, substituting a complex mechanical/optical system with a simpler electronic system while maintaining high precision
Data Source
AI summary
The present application discloses a trimming circuit of differential amplifier, wherein an output end of the differential amplifier is coupled to a first input end of the differential amplifier through a first voltage-dividing resistor; a shift voltage is coupled to a second input end of the differential amplifier through a second voltage-dividing resistor; the first voltage-dividing resistor and the second voltage-dividing resistor respectively form a T-shaped resistor network structure; the T-shaped resistor network structure comprises: a k-bit resistive network coupled to a T-shaped node and a reference power supply end, wherein a low n-bits of the k-bit resistive network is an R-2R resistive network, and part of branches are connected in series with at least one trimming resistor, and each trimming resistor is connected in parallel with a switch.