Output Driver Slew-Rate Control for Impedance Matching
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Solution Overview
Problem
Low-power semiconductor devices face challenges in securing signal integrity without a termination control circuit, leading to issues with impedance matching and inter-symbol interference, which affects data eye security and output signal reliability, especially at high speeds.
Innovation Solution
A data output circuit that includes a plurality of driving units controlled by driving force control codes, a slew rate control signal generation block, and signal delay units to manage signal delay amounts, allowing for controlled slew rate and impedance matching without a separate termination control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a termination control circuit (ODT circuit) is included to suppress reflective waves and secure signal integrity, then signal integrity is improved, but constant DC current consumption increases
Solution Approach 1:
The invention extracts the essential function of the termination control circuit (impedance matching and reflective wave suppression) and implements it through a simplified driver strength control mechanism that selectively activates driving units based on control signals, eliminating the need for a separate ODT circuit and its associated DC current consumption
Solution Approach 2:
The output driver circuit performs its own impedance matching and reflective wave suppression functions through the driver strength control circuit, without requiring an external termination control circuit. The driving units self-adjust their activation state based on control signals to maintain signal integrity
2Reliability
If driving force is increased to maintain signal integrity in low-power devices, then signal reliability is improved, but inter-symbol interference increases causing gentle slopes
Solution Approach 1:
The invention dynamically adjusts the driving force by selectively activating or deactivating specific driving units based on control signals. This dynamic control allows the circuit to optimize between signal strength and inter-symbol interference, preventing gentle slopes while maintaining signal integrity through adaptive driver strength modulation
Solution Approach 2:
The invention changes the effective driving force parameter by controlling which driving units are activated. By adjusting the combination of active driving units based on control signals, the circuit modifies its output characteristics to maintain steep slopes and prevent inter-symbol interference while ensuring reliable signal transmission
Data Source
AI summary
A semiconductor device includes a plurality of driving units configured to drive an output node based on an input signal and be on/off controlled based on driving force control codes, respectively, a slew rate control signal generation block configured to generate a slew rate control signal based on the driving force control codes, and a plurality of signal delay units configured to delay the input signal by respectively different delay amounts, transfer resultant signals to the plurality of driving units, and be respectively controlled in their delay amounts based on the slew rate control signal.