Pre-Driver Bias Switching for Tunable Output Driver Slew Control
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Solution Overview
Problem
In advanced technology nodes, such as the 12 nm fin-type field effect transistor (FinFET) technology, increasing channel lengths for generating different pre-driver signals is difficult due to process limitations, leading to costly solutions like inverter chains with remote voltage generators that consume area and power and are not tunable for process variations.
Innovation Solution
The pre-driver circuit employs multiple signal generation stages with a local switching bias circuit that provides different bias voltages to each stage, allowing for sequential and adjustable transition of pre-driver signals, reducing noise by fine-tuning delays and slew rates through a multiplexor that selectively applies bias voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If FETs with different channel lengths are used to generate different pre-driver signals, then different delays can be achieved, but in advanced technology nodes process limitations make increasing channel lengths difficult
Solution Approach 1:
The patent changes the control parameter from channel length to gate voltage. By applying different gate voltages to FETs with the same channel length, the patent achieves different signal delays without modifying the physical channel length, thus overcoming process limitations in advanced technology nodes
Solution Approach 2:
The patent introduces dynamic control of FET delays through adjustable gate voltages. The delays are no longer fixed by physical dimensions but can be dynamically tuned by changing voltage levels, enabling adaptation to process variations and precise delay control
2Loss of time
If inverter chains with remote voltage generators are used to generate pre-driver signals, then different delays can be achieved, but area consumption and power consumption increase
Solution Approach 1:
The patent merges the delay generation function into the existing pre-driver circuit structure by controlling FET gate voltages. This eliminates the need for separate inverter chains and remote voltage generators, reducing both area consumption and power consumption while achieving the same delay functionality
Solution Approach 2:
The patent extracts the delay control function from complex external circuits (inverter chains with remote voltage generators) and implements it locally within the pre-driver using simple FET gate voltage control, simplifying the overall system and reducing resource consumption
3Loss of time
If inverter chains with remote voltage generators are used to generate pre-driver signals, then different delays can be achieved, but the delay amount is not tunable for process variation
Solution Approach 1:
The patent introduces dynamic control of FET delays through adjustable gate voltages. The delays are no longer fixed by physical dimensions but can be dynamically tuned by changing voltage levels, enabling adaptation to process variations and precise delay control
Solution Approach 2:
The patent changes the control parameter from fixed physical dimensions to adjustable electrical parameters (gate voltages). This enables continuous tuning of delay amounts to compensate for process variations and optimize performance across different manufacturing conditions
Data Source
AI summary
A disclosed pre-driver circuit includes multiple signal generation stages configured to receive different bias voltages from local switching bias circuit(s). In some embodiment, pre-driver circuit has multiple switching bias circuits, each with a bias voltage node connected to a corresponding stage. In other embodiments, the pre-driver circuit has a single switching bias circuit with multiple bias voltage nodes and a multi-input/multi-output multiplexor with inputs connected to the bias voltage nodes and outputs connected to the stages. The switching bias circuit(s) and a primary inverter in each stage all receive the same input signal. When this input signal transitions, the switching bias circuit(s) supply bias voltages to the stages and the primary inverters turn on in sequence and slowly, thereby ensuring that pre-driver signals generated by the different stages transition in sequence and at a relatively slow rate. Once the last pre-driver signal transitions, the switching bias circuit(s) turn off.