Dynamic On-Die Termination for Longer Parallel Bus Packages
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Solution Overview
Problem
In multi-chip packages, existing signal termination methods such as high impedance and static on-die termination either limit package length due to signal reflections or impact direct current margins, making it difficult to implement debug tools effectively.
Innovation Solution
Dynamic on-die termination (ODT) is employed, which adjusts termination voltage based on received signals in a single-ended parallel bus configuration, using a bus holder circuit with hysteresis, a time delay circuit, and a time blanking circuit to prevent noise interference and ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high impedance or static on-die termination is used, then signal termination is achieved, but package length is limited due to signal reflections
Solution Approach 1:
The patent applies dynamic on-die termination (ODT) that automatically adjusts termination impedance based on the operational state of the device. When the device is inactive, ODT enables low impedance termination to reduce signal reflections and allow longer package lengths. When the device becomes active, ODT switches to high impedance state to maintain proper signal levels. This dynamic switching resolves the contradiction between achieving good signal termination and supporting longer package lengths.
2Reliability
If static on-die termination is used, then signal reflections are reduced, but direct current margins are impacted
Solution Approach 1:
The dynamic ODT circuit switches between low impedance state (when inactive) to reduce signal reflections and high impedance state (when active) to preserve DC margins. This dynamic behavior eliminates the need for static termination that would continuously degrade DC margins, thereby resolving the contradiction between reflection reduction and DC margin preservation.
3Reliability
If termination voltage is applied immediately, then signal termination is effective, but noise interference and ringing occur
Solution Approach 1:
The patent incorporates a time delay circuit that delays the application of termination voltage until after the signal transition has occurred. This preliminary timing arrangement ensures that termination is applied at the optimal moment, avoiding noise interference and ringing that would result from immediate termination voltage application, while still maintaining effective signal termination.
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
Dynamic ODT reduces signal reflections, allows for longer package lengths without impacting DC levels, and supports higher frequency debug signals while maintaining strict eye height margins.
Implementation Method 1
a bus holder circuit with hysteresis
Data Source
AI summary
An apparatus includes a terminal, a first device coupled to the terminal via a first node, the first device to drive a signal on the terminal via the first node, and a second device coupled to the terminal via a second node, wherein the second device comprises a dynamic on-die termination (ODT) circuit coupled to the second node. The dynamic ODT circuit includes: a bus holder circuit to receive the signal from the first device at the second node and select a termination voltage based on the signal, a response delay circuit coupled to the bus holder circuit, the response delay circuit to delay application of the termination voltage to the second node, and a time blanking delay circuit coupled to the bus holder circuit and the response delay circuit to prevent the termination voltage from changing before a threshold period of time elapses.