Bandgap Reference Circuit with Capacitor Refresh for Low Standby Power
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Solution Overview
Problem
Integrated circuits face instability due to temperature-dependent changes in reference voltage, leading to increased power consumption and circuit area when using separate bandgap reference circuits for low power operation.
Innovation Solution
A semiconductor device incorporating a bandgap reference circuit that outputs an active reference voltage, with a charging circuit and comparing circuit to monitor voltage differences across capacitors, generating a pulse signal for intermittent BGR circuit activation, reducing power consumption and circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bandgap reference circuit is used to generate stable reference voltage, then temperature sensitivity is reduced, but power consumption increases in standby mode
Solution Approach 1:
The BGR circuit is activated periodically using a sampling signal rather than continuously. A capacitor maintains the reference voltage during intervals when the BGR circuit is inactive, enabling periodic refresh operation that reduces standby power consumption while maintaining voltage stability during active periods
Solution Approach 2:
The capacitor is pre-charged to the reference voltage level before the BGR circuit is deactivated. This preliminary charging action allows the capacitor to supply the reference voltage during the interval when the BGR circuit is in standby, avoiding the need for continuous BGR operation
2Use of energy by stationary object
If a separate bandgap reference circuit is added for low power operation, then power consumption is reduced, but circuit area increases
Solution Approach 1:
The same BGR circuit serves dual purposes: it operates continuously in normal mode to provide stable reference voltage, and is activated periodically in standby mode to refresh the capacitor. This multi-functional use eliminates the need for separate low-power reference circuits, reducing overall circuit area
Solution Approach 2:
The normal mode BGR circuit and the low power reference voltage generation function are merged into a single system. The capacitor acts as an energy storage element that bridges the two operating modes, allowing one circuit to fulfill multiple functions across different operational states
3Reliability
If the BGR circuit is activated continuously, then reference voltage stability is maintained, but power consumption increases
Solution Approach 1:
The BGR circuit transitions from continuous operation to periodic operation, activated only when the sampling signal is high. This periodic activation reduces power consumption while the capacitor maintains reference voltage stability during intervals when the BGR circuit is inactive
Solution Approach 2:
The capacitor serves as an intermediary energy storage element between the BGR circuit and the rest of the system. It accumulates energy when the BGR circuit is active and releases energy when the BGR circuit is in standby, mediating the transition between continuous and periodic operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a stable low power reference voltage insensitive to PVT variations, reducing power consumption and circuit area by intermittently activating the BGR circuit and using a smaller second capacitor to detect voltage changes.
Implementation Method 1
a bandgap reference (BGR) circuit configured to output an active reference voltage at a first node according to a sample signal
Implementation Method 2
a first charging circuit configured to charge a first capacitor using the active reference voltage according to the sample signal
Implementation Method 3
a second charging circuit configured to charge a second capacitor using the active reference voltage according to the sample signal
Implementation Method 4
a comparing circuit configured to compare a voltage difference between a charge voltage of the first capacitor and a charge voltage of the second capacitor with a threshold value
Data Source
AI summary
A reference voltage generating circuit includes a bandgap reference (BGR) circuit configured to output an active reference voltage at a first node according to a sample signal; a first charging circuit configured to charge a first capacitor using the active reference voltage according to the sample signal; a second charging circuit configured to charge a second capacitor using the active reference voltage according to the sample signal; and a comparing circuit configured to compare a voltage difference between a charge voltage of the first capacitor and a charge voltage of the second capacitor with a threshold value, wherein the sample signal is a pulse signal generated using an output of the comparing circuit and the charge voltage of the first capacitor is provided as a low power reference voltage in a low power operation mode.