I/O Driver Calibration Using Body Biasing for Temperature Noise
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Solution Overview
Problem
High-speed I/O driver circuits face noise issues due to simultaneous switching of multiple resistors during temperature changes, which existing binary weighted resistor banks fail to address effectively, increasing design complexity and chip area usage.
Innovation Solution
A calibration circuit with a voltage bias generator and temperature sensor adjusts the bias signal to match the impedance of an external resistor, changing current flow through switches without activating or deactivating them, thus compensating for temperature variations linearly and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If binary weighted resistor banks are used for calibration, then calibration precision is improved, but noise is introduced due to simultaneous switching of multiple resistors
Solution Approach 1:
The patent changes the calibration approach from binary switching (0 or 1) to analog parameter adjustment by varying the body bias voltage of switches. This allows continuous adjustment of switch resistance values to match impedance to the external resistor, achieving precise calibration without the discrete switching noise inherent in binary weighted resistor banks.
2Object-generated harmful factors
If thermometer coding is used to avoid simultaneous switching, then noise is reduced, but design complexity and chip area increase
Solution Approach 1:
Instead of using thermometer coding which requires complex switch networks and routing, the patent adjusts the resistance value of existing switches continuously by changing their body bias voltage. This parameter-based approach achieves noise reduction while maintaining simple binary switch control, avoiding the complexity and area overhead of thermometer coding.
3Object-generated harmful factors
If thermometer coding is used to avoid simultaneous switching, then noise is reduced, but chip area increases
Solution Approach 1:
The patent uses body bias voltage adjustment to change switch resistance parameters, allowing precise impedance matching with the same physical switch infrastructure. This eliminates the need for additional switches and routing required by thermometer coding, thereby reducing chip area while maintaining noise reduction benefits.
4Measurement precision
If binary weighted resistor banks are used, then calibration precision is improved, but switching noise occurs during temperature changes
Solution Approach 1:
The patent replaces discrete binary switching with continuous parameter adjustment of switch resistance through body bias voltage control. This allows the calibration circuit to adapt to temperature changes by smoothly adjusting resistance values rather than switching between discrete states, eliminating switching noise while maintaining calibration precision.
5Object-generated harmful factors
If body bias voltage adjustment is used instead of switch activation, then noise is reduced and chip area decreases, but requires temperature sensing and bias generation circuitry
Solution Approach 1:
The patent introduces a body bias voltage generator as an intermediary component that converts temperature sensor output into appropriate bias voltages for the switches. This mediator enables automatic temperature compensation through parameter adjustment without requiring complex control logic, balancing the added circuit complexity with significant reductions in switching noise and chip area.
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
This approach reduces noise in I/O driver outputs, eliminates the need for thermometer coding, and decreases pre-driver chip area and signal congestion, achieving up to 15% driver calibration change through body biasing without altering the binary code established at startup.
Implementation Method 1
a temperature sensor electrically connected to the voltage bias generator
Implementation Method 2
the voltage bias generator (in response to a temperature change output by the temperature sensor) starts a calibration procedure by sweeping the body bias voltage of the switches in the calibration circuit only
Implementation Method 3
The calibration is linear in nature to compensate for temperature variations
Implementation Method 4
a comparator device electrically connected to the switches of the calibration circuit and to a reference resistor (a fixed impedance)
Data Source
AI summary
A calibration circuit is connected to an input/output driver, a voltage bias generator is connected to the calibration circuit and the input/output driver, and a temperature sensor is connected to the voltage bias generator. The calibration circuit and input/output driver each include a bank of resistors and corresponding switches. Bodies of the switches are connected to the voltage bias generator, and the switches are biased by a bias signal output from the voltage bias generator. The calibration circuit includes a comparator device connected to the switches and to a reference resistor. Activation and deactivation of selected ones of the switches is made to match the reference resistor. Also, the voltage bias generator adjusts the bias signal when a temperature change is sensed by the temperature sensor. Thus, the switches change current flow as the bias signal changes, without changing which of the switches are activated or deactivated.