Sleep Current Arithmetic behind a Five Year Battery Claim
Five-year battery claims require balancing microampere sleep floors, primary cell passivation derating, and protocol airtimes across 43,800 hours.
Power Gating Load Switch
Meaning
Integrated power switches disconnect unused sub-circuits from the power rail during inactive periods to eliminate quiescent current draw. Incorporating a power gating load switch allows microcontrollers to turn off high-power peripherals like radios or sensors when they are not in use. This isolation is a standard method for extending the operating life of battery-powered systems.
Control Logic
A dedicated digital signal from the processor drives the gate of the internal pass transistor to connect or disconnect the load. In typical configurations, a power gating load switch includes a slow turn-on feature that limits the inrush current caused by the capacitance of the downstream circuit. This controlled ramp prevents voltage dips on the main supply rail that could otherwise reset the microcontroller.
Design Tradeoff
Adding switches to the board introduces a small series resistance and increases the component count. While a power gating load switch minimizes leakage, it introduces a voltage drop across the transistor and consumes board space. Engineers must balance the leakage savings during sleep against the voltage reduction during peak active currents.
Parameter Selection
Selecting the device requires matching the switch resistance and current rating to the peripheral load. This selection of power gating load switch ensures minimal voltage drop during active operation.