Analog Multiplexer Gating for Multi-Power Domain Inputs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Analog multiplexers face power sequencing constraints when handling input signals from different power supply domains, leading to errors due to forward biasing of reverse-biased junctions, which increases test program complexity and cost.
Innovation Solution
A power sequence independent analog multiplexing system is introduced, where select circuits are gated by a power-on-reset signal referenced to another power domain, ensuring that input signals are only passed through after the primary supply voltage has reached a threshold level, preventing forward biasing and allowing multiple power supply domains to be handled by a single multiplexer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an analog multiplexer handles input signals from different power supply domains, then the multiplexer can support multiple channels with different supply voltages, but power sequencing constraints arise that can cause forward biasing of reverse-biased junctions and error conditions
Solution Approach 1:
The patent introduces a level shifter circuit as an intermediary component between the input signal from the second power supply domain and the analog multiplexer operating on the first power supply domain. This level shifter translates the input signal voltage levels to be compatible with the multiplexer's supply domain, eliminating the need for strict power sequencing constraints and preventing forward biasing errors.
2Adaptability or versatility
If an analog multiplexer operates with a first supply voltage while receiving input from a second supply voltage, then multiple power domains can be integrated, but test program complexity and cost increase due to power sequencing constraints
Solution Approach 1:
The level shifter acts as a mediator that decouples the power sequencing requirements between different domains. By translating voltage levels at the interface, it allows independent power ramping of different supply domains, significantly simplifying test programs and reducing test complexity while maintaining multi-power domain integration capability.
3Ease of operation
If an input analog signal is provided to the multiplexer before the first supply voltage reaches threshold level, then the multiplexer can accept early inputs, but forward biasing of drain-to-substrate junction occurs causing error conditions
Solution Approach 1:
The level shifter is designed to enable early signal acceptance from the second power domain without waiting for the first supply voltage to reach threshold levels. It performs preliminary voltage translation on the input signal, ensuring that even when the multiplexer's supply voltage is low, the translated signal remains within safe operating ranges that prevent junction forward biasing.
Data Source
AI summary
An apparatus relating generally to an analog multiplexer is disclosed. In such an apparatus, the analog multiplexer has first select circuits and at least one second select circuit. The first select circuits have respective input nodes and output nodes. The output nodes are all coupled to one another to provide an output node of the analog multiplexer. The first select circuits are coupled to a first supply voltage of a first supply domain. The at least one second select circuit is coupled to a second supply voltage of a second supply domain different from the first supply domain. The at least one second select circuit has an input port and an output port. The output port is coupled to an input node of the input nodes.