Current Mirror Monitor Circuit for Op-Amp Offset Compensation
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Solution Overview
Problem
Existing semiconductor devices face challenges in accurately monitoring load current due to input offset voltages of operational amplifiers, leading to deviations in monitor current measurements, especially when the load is absent, which can affect measurement accuracy.
Innovation Solution
A semiconductor device with a current monitor circuit that includes a mirror circuit, operational amplifier, and current adjustment circuit to adjust monitor current to zero by using switches, resistance elements, and a comparator to compensate for input offset voltages, ensuring accurate current monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current monitor circuit uses an operational amplifier to copy load current, then current monitoring function is achieved, but input offset voltage causes measurement accuracy to deteriorate
Solution Approach 1:
The patent performs preliminary adjustment of the operational amplifier's input offset voltage during device initialization or manufacturing. By pre-adjusting the offset voltage before normal operation, the measurement accuracy is improved without requiring continuous correction during current monitoring, thus resolving the contradiction between achieving accurate current monitoring and dealing with offset voltage errors.
Solution Approach 2:
The patent implements a feedback mechanism where the monitor current is continuously compared against a reference value, and the operational amplifier's offset voltage is dynamically adjusted based on the comparison result. This feedback loop compensates for offset voltage effects in real-time, maintaining high measurement accuracy while accounting for the harmful offset voltage.
2Reliability
If current monitoring is performed continuously, then load current can be monitored, but power consumption increases
Solution Approach 1:
The patent employs periodic sampling of the load current instead of continuous monitoring. The current monitor circuit activates at specific intervals to measure the load current, then enters a low-power state between measurements. This periodic action maintains sufficient monitoring reliability for most applications while dramatically reducing the average power consumption of the current monitor circuit.
Solution Approach 2:
The patent enables the current monitor circuit to automatically adjust its activity level based on system conditions. When the system is in a stable state, the monitor reduces its activity to minimize power consumption. When changes are detected or during critical operations, the monitor increases activity to maintain reliability, thus achieving self-service optimization of the power-reliability trade-off.
Data Source
AI summary
According to one embodiment, a semiconductor device includes: a first circuit configured to drive a load couplable to a first terminal by supplying a load current to the load; and a third circuit including a second circuit configured to copy the load current based on a first voltage of the first terminal and output a first current obtained by copying the load current, the third circuit being configured to monitor a second current based on the first current. The third circuit further includes a fourth circuit configured to adjust the second current in a case where the load current is not supplied to the load.