Power-Good (PG) signal in an eFuse IC serves as a monitoring mechanism that provides an indication of whether the output voltage of a power supply has stabilized within a predefined range. When a power supply is initially turned on or undergoes a sudden change, there is a brief period during which the output voltage may not be at its nominal value due to the internal dynamics of the power supply. If this unregulated voltage is fed directly to sensitive electronic components, it could lead to malfunctions or even permanent damage.

The PG signal acts as a gatekeeper, holding off the power supply from energizing the rest of the circuit until the output voltage has reached a predetermined threshold and is stable. When the voltage meets the specified requirements, the PG signal transitions to an active state, signaling that the power supply is safe to power the rest of the system.

Benefits of Power-Good Signal

• Reliable Power Sequencing: In systems with multiple power supplies or voltage domains, the PG signal ensures proper sequencing of power supplies, preventing potential latch-up or damage caused by incorrect power-up sequences.
• Enhanced System Protection: By preventing sensitive components from being powered until the output voltage is stable, the PG signal helps protect against power-related damage and increases the lifespan of electronic devices.
• Reduced Downtime: With the PG signal actively monitoring the power supply, potential faults can be detected early, leading to quicker fault isolation and reduced downtime during maintenance or troubleshooting.
• Improved System Stability: The PG signal helps maintain a consistent power supply, reducing the risk of voltage fluctuations that could destabilize sensitive components or lead to data corruption.

Measures to implement Power-Good Signal in eFuse IC

• Voltage Comparator: The heart of the PG signal circuitry is a voltage comparator. This comparator continuously monitors the output voltage of the power supply and compares it to a reference voltage. The reference voltage is set slightly below the nominal output voltage and represents the threshold at which the power supply is considered stable.
• Hysteresis: To prevent chattering or rapid toggling of the PG signal when the output voltage hovers around the threshold voltage, hysteresis is introduced in the voltage comparator. Hysteresis creates a dead band, ensuring that the output voltage must cross a higher threshold before transitioning from active to inactive or vice versa.
• Delay Circuit: To avoid false triggering of the PG signal due to temporary voltage fluctuations during power-up or power-down, a delay circuit is often incorporated. This circuit ensures that the PG signal remains inactive for a short period after the power supply is turned on, allowing the output voltage to stabilize before the comparison process begins.
• Open-Drain Output: The PG signal is typically implemented as an open-drain output. This means that the eFuse IC can pull the PG signal low when the voltage is outside the acceptable range, but it does not actively drive it high when the voltage is within the acceptable range. Instead, an external pull-up resistor is used to pull the signal high when the PG signal is inactive.

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