On-Chip Reference Current Circuit With ZQ-Calibrated Resistor Array
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Solution Overview
Problem
Existing on-chip reference current generating circuits are sensitive to variations in temperature, voltage, and process tolerances, leading to instability in the reference current output, which affects the accuracy of oscillator frequencies in integrated circuits.
Innovation Solution
The on-chip reference current generating circuit employs a ZQ calibration circuit to calibrate a pull-down resistor unit composed of transistors in parallel, ensuring its equivalent resistance is insensitive to temperature and process variations, and includes a bypass resistor unit to maintain a current path during initialization, thereby stabilizing the reference current output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If an on-chip polycrystalline resistor is used to generate reference current, then the circuit integration is improved, but the reference current stability deteriorates due to high sensitivity to temperature and process variations
Solution Approach 1:
The pull-down resistor unit is segmented into multiple parallel transistor branches, each with independently controllable switches. This segmentation allows individual calibration of each branch to compensate for process variations, thereby maintaining stable equivalent resistance while remaining fully integrated on-chip.
Solution Approach 2:
The invention dynamically adjusts the equivalent resistance of the pull-down resistor unit by changing the conduction state of individual transistor branches through calibration. This parameter adjustment compensates for manufacturing variations and temperature effects, maintaining stable reference current without requiring off-chip resistors.
2Reliability
If off-chip resistors are used to ensure stable reference current, then the reference current stability is improved, but the component miniaturization deteriorates due to additional pin resources and space occupation
Solution Approach 1:
The invention merges the functions of the pull-down resistor and calibration circuit into a single integrated on-chip unit. The pull-down resistor unit uses transistors and switches that are fully compatible with standard CMOS fabrication, eliminating the need for separate off-chip resistor components and reducing overall device footprint.
3Volume of moving object
If on-chip transistors are used to replace off-chip resistors, then the component integration is improved, but the resistance precision deteriorates due to process tolerance variations
Solution Approach 1:
The invention performs preliminary calibration during the manufacturing process to determine the actual resistance values of each transistor branch. Calibration data is stored and used to pre-adjust the conduction states of switches, compensating for process variations before the device is put into service, thereby achieving high precision without requiring off-chip components.
Solution Approach 2:
The invention implements a feedback mechanism where the actual resistance values of transistor branches are measured during calibration, and this information is used to adjust the conduction states of switches. This closed-loop approach compensates for manufacturing variations and ensures precise equivalent resistance matching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a stable reference current that is insensitive to temperature and process variations, enhancing the accuracy of oscillator frequencies and reducing the need for off-chip components, which saves space and production costs.
Implementation Method 1
employs a ZQ calibration circuit to calibrate a pull-down resistor unit composed of transistors in parallel, ensuring its equivalent resistance is insensitive to temperature and process variations
Implementation Method 2
includes a bypass resistor unit to maintain a current path during initialization, thereby stabilizing the reference current output
Implementation Method 3
The finally obtained Vref is insensitive to variations of processes, voltages, and temperatures. As an on-chip resistor, R0 generally is a polycrystalline resistor, and its resistance may vary greatly with temperature or process tolerances
Data Source
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AI summary
An in-chip reference current generation circuit for supplying at least one reference current to at least one load. The in-chip reference current generation circuit comprises: a transistor (M1), an operational amplification unit (opamp), wherein a reference voltage (Vrefl) is input into a positive input end of the operational amplification unit, a negative input end thereof is coupled to a source electrode of the transistor (M1), and an output end thereof is coupled to a gate electrode of the transistor (M1); a first pull-down resistor unit (10) coupled between the source electrode of the transistor (M1) and the ground, wherein the first pull-down resistor unit (10) is a resistor until calibrated by a ZQ calibration circuit (100); and a current mirror unit (12) coupled between a drain electrode of the transistor (M1) and a power supply voltage and used for outputting a generated current for use by a load. The in-chip reference current generation circuit can provide a stable reference current.