Bandgap Reference Shutdown Switching for Fast Wakeup
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Solution Overview
Problem
Devices in Cat NB1 low-data-rate applications face challenges in adhering to strict design requirements of ultra-low off-state current and fast wakeup times, as reducing off-state current tends to increase wakeup time, creating a trade-off that is difficult to manage.
Innovation Solution
A controller with a switching device, such as a MOSFET, is implemented to control the bandgap reference block's current path, allowing it to be in an open and non-conducting position in the off mode to limit leakage current to less than 10 nA, and switching to a closed and conducting position for fast activation, maintaining components at the rail voltage for quick transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the bandgap reference block is kept in a fully conducting state to enable fast wakeup, then the turn-on time is reduced, but the off-state current increases significantly
Solution Approach 1:
The switching device is configured to maintain the bandgap reference block in a partially conducting state during off-mode, preserving voltage levels and component states in advance. This preliminary action allows the block to transition rapidly to full conduction when activated, achieving fast wakeup times while keeping the block in a low-power state during normal off-mode operation.
2Loss of energy
If the switching device completely interrupts the current path to reduce leakage current, then off-state current is reduced to less than 10 nA, but the turn-on time increases due to the need to re-establish conductive paths
Solution Approach 1:
The switching device is positioned to selectively control the current path through the bandgap reference block, applying different conduction characteristics to different parts of the circuit. During off-mode, the switch interrupts the main current path to reduce leakage, while maintaining local voltage conditions that enable rapid re-conduction when activated, thus achieving both low leakage and fast turn-on.
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
This approach effectively reduces leakage current and minimizes transition time from the off mode to the on mode, enabling both low off-state current and fast wakeup times, thus addressing the design requirements of Cat NB1 applications.
Implementation Method 1
a switching device coupled in series between the reference node and the at least one powered component and configured to provide a conductive path through the at least one powered component from the voltage rail node to the reference node in response to the controller being in the on mode, and to interrupt the conductive path through the at least one powered component in response to the controller being in the off mode
Implementation Method 2
a bandgap reference core configured to generate a bandgap voltage signal based on a rail voltage at the voltage rail node
Implementation Method 3
an error amplifier, and a bias voltage generator... the at least one powered component is configured to generate one or more of the bandgap voltage signal, a power amplifier bias signal, and a regulator bias current signal
Data Source
AI summary
Examples of the disclosure include a controller having a mode of operation including one of an on mode and an off mode, the controller including a voltage rail node, a reference node, at least one powered component configured to generate a bandgap voltage signal based on a rail voltage at the voltage rail node, a switching device coupled in series between the reference node and the at least one powered component and configured to provide a conductive path through the at least one powered component from the voltage rail node to the reference node in response to the controller being in the on mode, and to interrupt the conductive path through the at least one powered component in response to the controller being in the off mode.