Meaning
Dynamic power instability refers to a brief, rapid drop in the supply voltage of a circuit when a heavy electrical load is suddenly connected or switched on. A transient voltage sag occurs before the power supply’s feedback loop or local decoupling capacitors can respond to the sudden increase in current demand. This temporary dip can cause digital processors to reset or experience logic errors if the voltage falls below the minimum operating threshold.
Supply Recovery
The duration and depth of the voltage drop depend on the impedance of the power distribution network. A high-impedance path prevents the power source from delivering current quickly, which prolongs the transient voltage sag and delays the return to a stable supply level. This recovery phase is governed by the response time of the voltage regulator module and the equivalent series resistance of the output capacitors.
System Instability
Microcontrollers are sensitive to these sudden drops, which can trigger internal brownout reset circuits. This reset interrupts normal operations and can cause data corruption in non-volatile memory.
Mitigation Design
Placing bulk ceramic and tantalum capacitors close to the load reduces the sag depth. This design is verified through transient load step testing during board bring-up.
