IR3621MTR

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The IR3621MTR is a high-performance, synchronous, step-down, DC-to-DC converter controller designed for synchronous step-down buck power supply applications. It is designed to operate from a wide input voltage range from 4.5 V to 24 V and to provide an adjustable output voltage up to 10.5 V with up to 3 A output current capability. The IR3621MTR has a wide selection of control features and protection features to help ensure proper system operation.

Operation Principle

The IR3621MTR regulates the output voltage through a valley-fill topology. The basic operation of the controller is as follows: When the voltage of Output sense pin exceeds the internal 8-bit PWM reference voltage, the controller initiates the “Power On” cycle and begins switching the low-side external MOSFET. Then the current is driven from the output capacitors to the load and the output voltage will follow the reference voltage. Once the voltage of Output sense pin falls below the reference voltage, the controller shuts the switching off, and the output voltage will be regulated until the next cycle is initiated.

The duty cycle of the PWM can be adjusted through the “auto-skip” function, and the hysteretic function of the PWM operation is implemented to reduce the total ripple of the output voltage. The valley-fill topology used in the IR3621MTR also helps to reduce switching loss by reducing the on-time of the switching. The output voltage can be adjusted with the external resistive voltage divider connected to the voltage adjust pin. The IR3621MTR also provides a 2X mode and a CP mode, which can be used to further reduce the output ripple.

Protection Features

The IR3621MTR offers a variety of protection features to protect the system from short- and/or open-circuit faults, over-current faults and thermal conditions. The protection features are as follows:

• Thermal Shutdown (TSD): This protection feature prevents the IC from overheating due to an external fault or overload condition, and will automatically re-engage after the fault is removed.
• Under-Voltage Lockout (UVLO): This protection keeps the converter from operating in a low-input voltage environment.
• Output Over-Voltage Protection (OVP): This protection is intended to avert any potential damage to the load due to excessive output voltage or current.
• Output Short-Circuit Protection (SCP): This protection feature keeps the output voltage from falling too low when there is an external short.
• Output Open-Circuit Protection (OCP): This protection feature prevents the output from exceeding its maximum rating, resulting in instability and/or permanent damage.
• Output Over-Current Protection (OCP): This protection feature limits the output current and prevents the IC from over-stressing its resources.

Applications

The IR3621MTR is suitable for a variety of DC-to-DC converter applications such as 5V, 15V, and 24V step-down converters, automotive applications, and distributed power systems. The IC is also suitable for solutions that require wide range input and/or output regulation, synchronous operation, high efficiency and/or transient response, and/or low thermal performance, such as LED lighting, point-of-load, telecom, server, and automotive systems.

Conclusion

The IR3621MTR is a versatile, high performance DC-to-DC converter controller designed to provide adjustable output voltages up to 10.5 V with a maximum load current of 3 A. This controller supports a variety of features such as auto-skip, hysteretic PWM, 2X mode, and CP mode to ensure optimal operation for synchronous step-down buck power supply applications. The device also offers several protection features, such as thermal shutdown, UVLO, OVP, SCP, OCP and OCP to protect the system from short- and/or open-circuit faults, over-current faults and thermal conditions. The IR3621MTR is suitable for a variety of applications, especially those requiring wide input and/or output voltage range, synchronous operation, and high efficiency.

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