LPDDR3 Input Buffer Amplifier for Reference Voltage Drift Compensation
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Solution Overview
Problem
LPDDR3 input buffers face issues with output voltage drift due to variations in reference voltage, necessitating a compensation mechanism.
Innovation Solution
An amplifier with an input stage comprising a first and second current mirror, input differential pairs, current sources, and a voltage control transmission circuit that adjusts current paths based on reference voltage levels to compensate for output voltage drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a reference voltage is used to generate output voltage in LPDDR3 input buffer, then the input buffer can operate with controlled voltage levels, but the output voltage drifts due to variation of the reference voltage
Solution Approach 1:
The patent implements a feedback mechanism where the output voltage is fed back to the input stage through a transmission gate. When voltage drift is detected, the feedback signal adjusts the input differential pair to compensate for the drift, forming a closed-loop control system that maintains output voltage stability despite reference voltage variations
Solution Approach 2:
The patent introduces a transmission gate as an intermediary element between the output stage and input stage. This transmission gate acts as a mediator that conditionally connects the output voltage to the input differential pair, enabling the feedback compensation mechanism while isolating the input buffer from direct reference voltage variations
2Reliability
If a compensation mechanism is added to address output voltage drift, then output voltage stability improves, but device complexity increases
Solution Approach 1:
The patent merges the compensation function with the existing input buffer circuitry by integrating the feedback path into the input stage. The transmission gate and feedback connection are combined with the differential pair structure, allowing compensation functionality to be achieved without adding completely separate compensation circuits
Solution Approach 2:
The transmission gate serves multiple functions: it acts as a switch for the feedback path, a voltage follower for signal transmission, and a means to conditionally connect different circuit stages. This multi-functionality reduces the need for additional dedicated components for compensation
Data Source
AI summary
An amplifier with an input stage comprising: a first current mirror; a first input differential pair; a first current source; a second current source; a second input differential pair, wherein the first input differential pair and the second input differential pair receive a reference voltage; a second current mirror; and a voltage control transmission circuit. An extra current path in the first current mirror is formed and a current flowing through the extra current path flows through the second current mirror to a ground when the reference voltage is higher than a first predetermined value. Also, an extra current path in the second current mirror is formed and a current flowing through the extra current path in the second current mirror flows to the first current mirror when the reference voltage is lower than a second predetermined value.