Low Side NMOS Battery Protection Level Shifter
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Solution Overview
Problem
Existing battery monitoring circuits, particularly those using low side protection topography with NMOS switching devices, face challenges in reliable communication with external control devices due to potential misreferencing of digital control signals, leading to errors and hazardous conditions.
Innovation Solution
The implementation of a monitoring circuit with two sections, each equipped with a voltage level shifter to adjust the reference voltage of incoming control signals, ensuring proper communication and reference to the negative supply rail, thereby preventing errors and hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low side NMOS protection topography is used, then cost is reduced and external components are minimized, but communication reliability deteriorates due to signal misreferencing
Solution Approach 1:
A level shifter circuit is introduced as an intermediary component between the communication interface and the NMOS protection circuit. This level shifter translates communication signals from one voltage reference (PACK-) to another (ground), enabling reliable communication without requiring costly charge pumps or external energy storage elements. The level shifter mediates the voltage reference mismatch that would otherwise cause communication failures in low side NMOS protection topography.
2Ease of manufacture
If NMOS switching devices are used instead of PMOS, then cost is reduced, but signal reference stability deteriorates when switches are open
Solution Approach 1:
The level shifter acts as a stable reference intermediary that maintains consistent voltage translation regardless of the NMOS switch state. When NMOS switches are open, the level shifter ensures that communication signals remain properly referenced to ground rather than floating or becoming misreferenced to PACK-, thereby maintaining signal reference stability while using cost-effective NMOS devices.
Solution Approach 2:
The level shifter dynamically adjusts the voltage reference parameter of communication signals based on the operational state of the NMOS protection circuit. By changing the reference voltage parameter from PACK- to ground as needed, the system maintains stable communication signals while benefiting from the cost advantages of NMOS switching devices.
Data Source
AI summary
An electric circuit comprising means for communicating with an external device coupled to means for measuring the charge condition of an external battery. In some embodiments, the circuit comprises at least one level shifter for changing the reference voltage of communication signals. In some embodiments, the circuit comprises a first driver and a second driver for driving external switching elements for the controlled charge and discharge of the battery.