Primary Cell Voltage Response during Multi-Second Cellular Repetition Bursts
Continuous multi-second cellular repetition bursts pull battery voltage below brownout limits unless buffered by low-ESR capacitors.
Transient Minimum Voltage
Meaning
Instantaneous dip in output potential occurs when a load is suddenly applied to a primary battery that has been idle. Mitigation of transient minimum voltage is a main concern for engineers designing low power devices with high peak current requirements. This phenomenon is caused by the initial resistance of the passivation layer on the lithium anode.
Recovery Duration
The time it takes for the potential to climb back above the nominal level after reaching the transient minimum voltage varies with temperature and load. A warm battery recovers in milliseconds while a cold one might stay below the threshold for several seconds. If the pulse duration is shorter than the recovery time, the device remains at risk of brownout resets during the entire transmission.
Capacitor Integration
Placing a large storage capacitor in parallel with the battery can mask the effect of transient minimum voltage by providing the initial surge of current. This component prevents the system voltage from dropping below the reset point of the electronic hardware during the radio startup sequence.
Safety Margin
System designers must specify a threshold that remains above the cutoff of the voltage regulators under worst case thermal conditions. Testing this value across the entire operating temperature range ensures the reliability of the product in the field.