SPI Select Pin Wakeup Circuit for Reduced Power Mode
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Solution Overview
Problem
Electronic devices in reduced power modes, such as sleep mode, cannot receive commands to exit this mode via standard SPI bus interfaces due to the select signal being released, necessitating an additional pin for waking up the device, which increases device size and cost.
Innovation Solution
A circuit is configured to monitor the select signal on an SPI control interface, entering reduced power mode when the signal is released and exiting when asserted, eliminating the need for an extra pin by utilizing a D flip-flop and NAND gate to generate a Wakeup signal for transitioning between power states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional pin is added to receive wake-up signals, then the device can exit reduced power mode reliably, but the device size and cost increase
Solution Approach 1:
The select pin is made multi-functional by enabling it to serve both its traditional SPI device selection function and an additional wake-up trigger function. When the select signal transitions from released to asserted state, it doubles as a wake-up command, allowing the device to exit reduced power mode without requiring a separate dedicated wake-up pin.
Solution Approach 2:
The functionality of a separate wake-up pin is merged into the existing select pin of the SPI interface. The circuit combines the device selection signal and wake-up signal functions into a single pin, eliminating the need for an additional pin while maintaining both functionalities.
2Use of energy by moving object
If the select signal is released to enter reduced power mode, then power consumption is reduced, but the device cannot receive commands to exit the mode via SPI bus
Solution Approach 1:
The circuit monitors the select signal state in advance to determine when to transition to reduced power mode. By detecting the released state of the select signal before entering the low-power mode, the device ensures it can still respond to wake-up triggers without requiring continuous SPI bus monitoring, thus saving power while maintaining operability.
Solution Approach 2:
The select signal acts as an intermediary mechanism that bridges the gap between power management and communication functionality. It mediates between the need to reduce power consumption by releasing the select line and the need to maintain the ability to receive commands, by serving dual purposes as both a power management signal and a potential wake-up trigger.
Data Source
AI summary
Methods, systems, and apparatus, including computer programs encoded on computer storage media, for controlling power states of a device. In one aspect, a circuit is configured to perform operations comprising: receiving, on a data pin of an SPI control interface, a command to enter a reduced power mode; determining that a select signal on a select pin of the SPI control interface has been released; in response to receiving the command to enter the reduced power mode and determining that the select signal has been released, causing the circuit to enter the reduced power mode; determining that the select signal on the select pin of the SPI control interface has been asserted; and in response to determining that the select signal on the select pin has been asserted, causing the circuit to exit the reduced power mode.