Battery Gas Gauge External Reset Circuit
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Solution Overview
Problem
Existing battery gas gauge circuits rely on internal watchdog timers for reset, which may not provide sufficient protection against all failure modes of the microcontroller, potentially leading to incomplete recovery from software loops or other failures.
Innovation Solution
An external reset control circuit is introduced, coupled between the power supply pin and the communications signal pin of the gas gauge, allowing for a software-controlled hard reset by cycling power to the gas gauge, enabling a more comprehensive reset mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an internal watchdog timer is used for reset, then the circuit complexity is reduced, but the reliability of reset functionality is insufficient
Solution Approach 1:
The patent introduces an external reset control circuit as an intermediary component between the power supply and the gas gauge microcontroller. This external circuit includes a reset controller that receives reset commands from the host controller and controls the power supply to the gas gauge, thereby providing enhanced reset functionality without requiring modifications to the gas gauge chip itself.
Solution Approach 2:
The reset functionality is segmented into multiple components: the internal watchdog timer for basic reset functions, the external reset control circuit for enhanced control, and the host controller for initiating reset commands. This segmentation allows each component to have specialized functions while working together to provide comprehensive reset capability.
2Reliability
If an external reset control circuit is added, then the reliability of reset functionality is improved, but the device complexity increases
Solution Approach 1:
The external reset control circuit is designed to perform multiple functions: it can initiate hard resets based on watchdog timer failures, respond to reset commands from the host controller, and provide power cycling control. This multi-functionality justifies the added complexity by consolidating multiple reset mechanisms into a single external circuit rather than requiring separate dedicated circuits for each function.
3Device complexity
If the communications pin is used for reset control, then the number of pins is reduced, but the measurement precision of battery parameters may be affected
Solution Approach 1:
The system uses periodic communication protocols where the communications pin alternates between data transmission and reset control functions. During normal operation, the pin is used for battery parameter measurements; when a reset command is needed, the pin temporarily switches to control the reset sequence. This periodic switching minimizes the impact on measurement precision by ensuring that reset operations are brief and occur during designated communication windows.
Data Source
AI summary
A gas gauge circuit has a power supply pin, a power return pin, power-on reset capability, and a communications signal pin. A reset control circuit is coupled between the power supply pin and the communications signal pin, or between the power return pin and the communications signal pin. The reset control circuit removes power to the gas gauge circuit in accordance with a control signal asserted on the communications signal pin. Other embodiments are also described and claimed.