Stacked PMU Test Circuit for High-Precision BMS IC Testing
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Solution Overview
Problem
Designing BMS test circuits for large battery packs is challenging due to stringent electrical specifications and increasing size, requiring high precision and granularity in voltage and current measurements, which are often expensive and have large form factors, limiting chip space.
Innovation Solution
A stacked precision parametric measurement unit (PMU) with a common-mode voltage source and precision PMU connected in series, using a demultiplexer to support multiple device-under-test terminals, and integrated or external DACs for high dynamic-range measurement and control, allowing for compact and efficient voltage and current testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high precision voltage and current measurement circuits are used, then measurement precision is improved, but device area increases and chip space is limited
Solution Approach 1:
The test circuit is divided into multiple stacked PMU modules, each handling specific measurement tasks. This segmentation allows parallel processing of multiple battery cell measurements simultaneously, reducing the area required per measurement channel while maintaining high precision through dedicated measurement circuits in each module.
Solution Approach 2:
Multiple PMU modules are stacked and integrated in a nested configuration where smaller measurement circuits are embedded within larger module structures. This nesting approach maximizes the use of available chip space by efficiently packing measurement circuits, power supply units, and control logic in hierarchical layers.
2Productivity
If multiple battery modules are tested simultaneously, then productivity is improved, but device complexity increases
Solution Approach 1:
Each PMU module is designed with universal functionality to handle multiple measurement modes (voltage, current, impedance) and can be configured to test different battery cell arrangements. The modules use standardized interfaces and reconfigurable circuitry that allows the same hardware to adapt to various testing scenarios, enabling parallel testing of multiple battery modules without proportionally increasing overall system complexity.
Solution Approach 2:
The test circuit incorporates dynamic reconfiguration capabilities through switches and multiplexers that allow real-time adjustment of measurement channels and connections. This dynamic adaptability enables the system to efficiently manage multiple battery modules by dynamically allocating measurement resources, reducing the need for dedicated complex circuitry for each module.
3Measurement precision
If high dynamic-range measurement capability is achieved, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The PMU modules employ periodic sampling and measurement techniques where measurements are taken at optimized intervals rather than continuously. This periodic action maintains high dynamic-range measurement capability by capturing critical voltage and current variations while significantly reducing average power consumption compared to continuous high-precision measurement modes.
Solution Approach 2:
The measurement circuits dynamically adjust their operating parameters (such as gain, bandwidth, and sampling rate) based on the measured signal characteristics. When signals are stable, the circuits operate in low-power mode with reduced precision requirements, while automatically switching to high-precision high-power mode only when dynamic changes are detected, thus maintaining measurement capability while minimizing overall power consumption.
Data Source
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AI summary
A test circuit (300) is disclosed. The test circuit (100) comprises a first parametric measurement unit, PMU (315), comprising: a first electrical source (335), an output terminal to connect the first electrical source to a first terminal of a device-under-test, DUT (360), and a low-sense terminal. The test circuit further comprises a second PMU (314) comprising: a second electrical source, and an output terminal to connect the second electrical source to a second terminal of the DUT. The test circuit further comprises a common-mode voltage source (325), wherein the common-mode voltage source (325) is configured to provide a larger range of voltages at lower precision steps than the first and second electrical sources. The test circuit further comprises a switch (435) with configurations comprising: a first configuration where the switch (345) connects the low-sense terminal of the first PMU (315) to the output terminal of the second PMU (314), and a second configuration where the switch connects the low-sense terminal of the first PMU (315) to the common-mode voltage source (325). Also disclosed is a system and a method of using a test circuit.