Reference Voltage Switching Circuit for Semiconductor Memory Testing
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Solution Overview
Problem
Conventional semiconductor memory apparatuses cannot test core and elevated reference voltages after the package process, limiting the efficiency of the package test and reducing yield due to the inability to input these voltages through pads.
Innovation Solution
A reference voltage supplying circuit with an internal generating unit, a pad for external voltage reception, and a switching unit that selectively supplies internal or external reference voltages to the voltage generators based on a test mode, allowing for the generation and application of internal buffer reference voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If core reference voltage and elevate reference voltage are internally generated, then the reference voltage can be provided to internal voltage generators, but it is not possible to test these voltages using conventional methods
Solution Approach 1:
The reference voltage supply system is made dynamic by introducing a switching unit that can change the voltage source based on operational mode. During normal operation, the internal reference voltage generator supplies voltage to internal voltage generators. During test mode, the switching unit redirects the externally applied reference voltage to the internal voltage generators, enabling testing without changing the fundamental architecture.
Solution Approach 2:
The system changes its operational parameters based on mode signals. The switching unit responds to test mode signals to alter the connection topology, allowing the same circuit to operate in two distinct states: normal operation with internal voltage generation and test operation with external voltage application. This parameter change enables testing capability without compromising normal functionality.
2Ease of manufacture
If core reference voltage and elevate reference voltage are not input through pads, then the internal voltage generators can operate with internally generated voltages, but it is not possible to test for failures after the package process
Solution Approach 1:
The reference voltage input pads are given multi-functionality. They serve dual purposes: during normal operation, they receive data buffer reference voltage and command/address buffer reference voltage for buffer operations; during test mode, they receive test voltages for testing internal voltage generators. This universal design eliminates the need for separate test pads while enabling comprehensive testing.
Solution Approach 2:
The system dynamically reconfigures the function of reference voltage pads based on operational mode. The switching unit, controlled by mode signals, redirects the voltage supply paths to enable test operations through the same pads used during normal operation, thereby improving package test efficiency without adding extra pads or complex test infrastructure.
3Ease of operation
If data buffer reference voltage and command/address buffer reference voltage are provided externally through pads, then buffering operations can be supported, but the reference voltage cannot be used for testing internal voltage generators
Solution Approach 1:
The externally provided reference voltage pads are designed with universal functionality. They continuously provide reference voltage for buffer operations during normal mode while also serving as entry points for test voltage application during test mode. The switching unit enables seamless transition between these functions without requiring separate dedicated pads for each purpose.
Solution Approach 2:
The switching unit acts as an intermediary between the reference voltage pads and the various voltage generators. It mediates the connection by selectively routing the externally applied reference voltage to either the internal voltage generators (during test mode) or maintaining normal buffer operations (during normal mode), thereby enabling versatile reference voltage application.
Data Source
AI summary
A reference voltage supplying circuit can include an internal reference voltage generating unit configured to generate an internal reference voltage, a pad configured to receive an external reference voltage, a switching unit selectively configured to supply the internal reference voltage or the external reference voltage to an internal voltage generator in a test mode.