Inter-Die Signal Repeater Scheme for Tall Memory Stacks
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Solution Overview
Problem
Current inter-die signaling schemes in multi-die memory packages face challenges with increasing signal load, leading to higher capacitance, power consumption, and propagation delays as stack height increases, which are exacerbated by electrostatic discharge components and unidirectional signal transmission.
Innovation Solution
Implementing multiplexers within the memory stack to repeat inter-die signals, reducing the need for electrostatic discharge components and optimizing signal transmission by inserting multiplexers before transmitters on each die to manage signal load and enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmitter size is increased to counteract the increasing load on inter-die signals, then the signal transmission capability is improved, but the board space footprint increases, current consumption increases, propagation delays increase, and die-to-die variation increases
Solution Approach 1:
The patent divides the signal transmission path into multiple segments by introducing intermediate repeater elements within the package. Instead of relying on a single large transmitter to drive all the way to distant dies, the signal path is segmented into shorter hops with repeaters positioned at intermediate points (such as on interposer or substrate), thereby reducing the burden on any single transmitter and allowing smaller footprint while maintaining transmission capability.
Solution Approach 2:
The patent introduces intermediary repeater elements that act as mediators in the signal transmission path. These repeaters receive signals from transmitters and re-drive them toward destination dies, effectively distributing the transmission task across multiple intermediate components rather than requiring one oversized transmitter to handle the entire path.
2Reliability
If the transmitter size is increased to counteract the increasing load on inter-die signals, then the signal transmission capability is improved, but current consumption increases
Solution Approach 1:
By segmenting the transmission path with intermediate repeaters, each transmitter only needs to drive a shorter distance to the nearest repeater rather than to the farthest die. This segmentation allows transmitters to operate at lower current levels while the repeaters collectively handle the full transmission distance, reducing overall power consumption.
Solution Approach 2:
Intermediary repeaters act as energy-saving mediators by receiving weak signals from transmitters and re-driving them with fresh signal strength. This eliminates the need for transmitters to operate at high current levels to overcome long-distance attenuation, thereby reducing current consumption while maintaining signal integrity.
3Reliability
If the transmitter size is increased to counteract the increasing load on inter-die signals, then the signal transmission capability is improved, but propagation delays increase
Solution Approach 1:
Segmenting the transmission path into shorter segments with intermediate repeaters reduces the propagation delay for each segment. Although repeaters add some processing time, the overall delay is reduced because signals travel shorter distances at higher effective speeds through each segment, compared to a single long-distance transmission path.
4Reliability
If electrostatic discharge components are included on each die to protect against ESD, then the reliability against ESD is improved, but the capacitance load on inter-die signals increases significantly
Solution Approach 1:
The patent extracts the ESD protection function from individual dies and consolidates it into dedicated ESD protection circuits located on the interposer or substrate. This separation allows ESD protection to be provided at the package level rather than requiring capacitive ESD components on every die, thereby reducing the total capacitance load on inter-die signal lines while maintaining ESD protection capability.
5Device complexity
If unidirectional signal transmission is used to simplify the signaling scheme, then the device complexity is reduced, but the capacitance load and signal load increase
Solution Approach 1:
The patent implements bidirectional signaling capability on the same physical inter-die channels, allowing signals to transmit in both directions (from primary die to secondary dies and vice versa) without requiring separate dedicated channels for each direction. This multi-functionality reduces the total number of signal lines needed compared to fully unidirectional schemes, thereby reducing overall capacitance load while maintaining manageable complexity through standardized bidirectional protocols.
Data Source
AI summary
Systems, methods, and devices related to techniques for repeating inter-die signals within a multi-die package of a memory device are disclosed. The multi-die package includes a memory stack including a first memory die handling interfacing with a host for the package and at least one second memory die coupled to and configured to communicate with the first memory die via an inter-die connection. A technique involves incorporating the use of a multiplexer positioned in front of the transmitter of each die to facilitate repetition of inter-die signals within the memory stack as needed depending on various factors associated with the memory stack, such as, but not limited to, the type of signal, the intended recipient of the inter-die signals, and the stack height of the memory stack.