Load Current Sensing with Ton/2 Timing for Fast Transient Tracking
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Solution Overview
Problem
Existing load current sensing methods in SoCs face challenges in accurately tracking current during transients due to low bandwidth and latency issues, leading to inaccuracy and delayed response, which affects thermal management and power efficiency.
Innovation Solution
The implementation of a Ton/2 generator that accounts for the delay between HSFET ON generation and actual turn-on time, enabling a digital tracking algorithm to sample current with high accuracy and reduce latency, thereby improving current reporting precision and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensing methods are used, then the system can obtain current information, but the bandwidth is low and latency is high leading to inaccurate tracking during transients
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing current information from multiple previous sampling points in a buffer memory before a transient event occurs. When a transient is detected, the system immediately retrieves and processes the pre-stored current data along with its derivative, eliminating the need to wait for sequential sampling during the transient event. This resolves the contradiction by providing both accurate current tracking and low latency response simultaneously.
2Speed
If sampling frequency is increased to improve transient tracking, then response speed improves, but system complexity and power consumption increase
Solution Approach 1:
The patent implements dynamics by using an adaptive sampling strategy where the sampling frequency is dynamically adjusted based on system conditions. During normal steady-state operation, the system uses a lower sampling frequency to minimize power consumption and complexity. When a transient event is detected through monitoring current changes, the system automatically increases the sampling frequency to capture the transient behavior accurately. This resolves the contradiction by achieving high response speed only when necessary, while maintaining low complexity during normal operation.
3Reliability
If guard banding is increased to ensure current limits are not exceeded, then reliability improves, but average efficiency decreases
Solution Approach 1:
The patent applies feedback by implementing a real-time current monitoring system that continuously compares the measured current (and its rate of change) against predefined current limits and maximum safe operating area constraints. When the current approaches but has not yet exceeded the limit, the system provides early warning feedback to the control logic, allowing for proactive current reduction. This eliminates the need for conservative guard banding, as the system can operate right up to the actual current limits while maintaining reliability through continuous monitoring and immediate corrective action.
4Measurement precision
If conventional sampling methods are used, then the system can detect current, but the bandwidth limitations cause delayed response during load transients
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing current information from multiple previous sampling points in a buffer memory before a transient event occurs. When a transient is detected, the system immediately retrieves and processes the pre-stored current data along with its derivative, eliminating the need to wait for sequential sampling during the transient event. This resolves the contradiction by providing both accurate current tracking and low latency response simultaneously.
Solution Approach 2:
The patent applies dimensionality change by transitioning from single-point current sampling to multi-point temporal sampling. Instead of measuring current at a single instant, the system collects current data from multiple previous sampling points (I[n-1], I[n-2], etc.), stores them in a buffer, and uses them to calculate both the current value and its time derivative. This adds a temporal dimension to the measurement, enabling the system to accurately capture transient behavior that would be missed by conventional single-point sampling methods.
Data Source
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AI summary
A Ton/2 generator retrofits a digital tracking algorithm to an analog Constant-On-Time (COT) Controller to enable fast sensing. The Ton/2 generation is cognizant of the delay between high-side switch (HSFET) on generation and the actual turn-on time of the HSFET so that there is no deviation of sampling point, and current is reported with high accuracy. The digital tracking algorithm automatically takes higher steps during load transients to enable faster tracking and scales the measured current (Ipeak/2) based on a discontinuous conduction mode (DCM) period for DCM current reporting.