Key components and types of power-on reset circuits

Infineon / Mitsubishi / Fuji / Semikron / Eupec / IXYS

Key components and types of power-on reset circuits

Posted Date: 2024-01-17

Power-on reset refers to restoring various parts of the system to a known initialization state through specific circuit designs or electronic components when power is applied to a circuit or system to ensure that the system can start working in a reliable and expected manner.

When a circuit or system is powered off for a period of time and then powered back on, it may face some unknown states or abnormal situations, such as internal registers not being cleared correctly, logic levels not being initialized, external devices not being initialized, etc. These unknown states or abnormal conditions may cause the system to operate abnormally or generate errors.

In order to solve this problem, the power-on reset circuit generates a reset signal when the power supply is turned on and passes it to various parts of the system to trigger the initialization process of the system. The reset signal can reset the logic levels to a known state, clear register contents, initialize external devices, etc., ensuring that the entire system starts in a controllable state.

Through power-on reset, unknown system states can be avoided and the system can be ensured to start running from a stable and controllable state. Power-on reset is commonly used in various electronic devices and systems, including microprocessors, microcontrollers, embedded systems, integrated circuits, etc. It is an important part of ensuring system reliability and normal operation.

Key components of power-on reset circuit

The key devices are: MC34064.

Figure internal structure block diagram

Input and output characteristic curve

Key electrical parameters of power-on reset circuit

The output of output pin 1 of MC34064 (the output after stabilization) is as shown in the figure below:

What are the classifications of power-on reset circuits?

Power-on reset circuits can be classified according to implementation methods and functional characteristics. The following are some common power-on reset circuit classifications:

1. Reset circuit based on power monitoring chip: This reset circuit uses a specialized power monitoring chip to generate a reset signal by monitoring the power supply voltage. Power monitoring chips usually have adjustable threshold and delay functions to adapt to different application needs.

2. Gate-based reset circuit: This reset circuit uses logic gates to generate a reset signal by inputting supply voltage and other control power lines into the logic gates. The gate power-on reset circuit can be a simple combinational logic circuit, or a more complex gate array or programmable logic device (such as FPGA).

3. Based on the internal reset circuit of the microcontroller: Many microcontrollers and microcontrollers have built-in reset circuits, which can automatically generate a reset signal when the chip is powered on. These reset circuits can usually be set and adjusted based on the configuration bits inside the chip.

4. External manual reset circuit: This reset circuit consists of buttons, switches or other manual input components, and the user can achieve the reset operation through manual triggering. This manual reset circuit is commonly used during troubleshooting, system debugging, and development.

5. Reset delay circuit: Some power-on reset circuits may also include a delay circuit to provide a delay for the reset signal. The delay time can be configured according to system requirements, and the delay function can be implemented through capacitor charge and discharge and/or resistor control.

These classifications are just one of the common power-on reset circuit classifications, and the specific reset circuit design may be customized based on application requirements and system characteristics.

Review Editor: Huang Fei

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