Always-On LDO Switching for Coin-Cell WLAN Sleep Power
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Solution Overview
Problem
Existing wireless local area network (WLAN) devices powered by coin cell batteries face challenges in maintaining an always-on regulated voltage during sleep modes with minimal current consumption, especially during cold boot and sleep transitions.
Innovation Solution
An integrated circuit (IC) with an always-on low-dropout (AON LDO) voltage regulator that switches between battery power and switched-mode power supply (SMPS) during cold boot and sleep modes, using a switch to bypass the pass transistor and enable/disable the regulator as needed, optimizing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a linear regulator (LDO) is used to maintain always-on regulated voltage, then voltage stability is improved, but current consumption increases
Solution Approach 1:
The system dynamically switches between LDO and SMPS based on operational state. During sleep modes, the LDO is disabled and a switch bypasses it, connecting the regulated voltage node directly to the battery. During active modes, the LDO is enabled to provide stable voltage. This dynamic configuration resolves the contradiction by having voltage stability when needed and minimal current consumption when the device is idle.
Solution Approach 2:
The LDO regulator is periodically enabled and disabled based on the device's operational state. It operates during active periods to provide stable voltage, then is turned off during sleep periods to minimize current consumption. This periodic operation pattern allows the system to achieve both voltage stability and low power consumption at different times as needed.
2Reliability
If the LDO regulator is always enabled to provide stable voltage, then voltage regulation is improved, but power consumption increases
Solution Approach 1:
The system transitions the LDO between enabled and disabled states dynamically. A control mechanism monitors the operational state and switches the LDO off during sleep modes, connecting the output node directly to the battery through a switch. During active modes, the LDO is enabled to provide regulated voltage. This resolves the contradiction by providing voltage regulation only when reliability is needed.
3Use of energy by moving object
If a switch is added to bypass the pass transistor, then current consumption during sleep mode is reduced, but device complexity increases
Solution Approach 1:
A switch is introduced as an intermediary element between the battery and the regulated voltage node. This switch acts as a mediator that can connect the node directly to the battery during sleep modes, bypassing the LDO's pass transistor and eliminating its quiescent current consumption. The switch is controlled by a simple logic circuit that monitors the operational state, making the added complexity minimal while achieving significant power savings.
Data Source
AI summary
Techniques and apparatus for operating an always-on low-dropout (LDO) voltage regulator during cold boot and different sleep mode scenarios for a device including the LDO regulator. The LDO regulator may be disposed, for example, in a wireless local area network (WLAN) device powered by a coin cell battery. One example apparatus may be an integrated circuit (IC), which may be disposed in such a WLAN device and/or may be a power management unit (PMU). The IC generally includes a first port for coupling to a battery, a second port, a switched-mode power supply (SMPS) including a power supply input coupled to the second port, and an LDO regulator including a power supply input selectively coupled to the first port or to an output of the SMPS.