RT8861GWQ

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Part Status:	Active

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RT8861GWQ application field and working principle

Introduction

The RT8861GWQ is a dual-system high-efficiency synchronous step-down switching converter. RT8861GWQ integrates two identical synchronous step-down buck currents into a unit. The output voltage can be adjustable from 0.5V to 4.5V, and the output current can reach 1.5A in one channel and 3A in total. RT8861GWQ has good thermal performance, wide Vin (7V-22V), accurate output voltage, adjustable soft-start, low noise and high EMI, and allows multiple chips to work in parallel.

Application Field

RT8861GWQ can be preferably used in a variety of electronic products, such as tablet PC, smart phone, wireless communication base station, automotive electronics and industrial control system to give power supply, such as core processor, power amplifier, LCD display and peripheral circuits.

Working Principle

The RT8861GWQ includes an internal high-side power MOSFET, a low-side MOSFET, an oscillator, a PWM control block, a compensation block, and a power-good signal driver. The operating principle is as follows.The RT8861GWQ is driven by the oscillator and runs according to the preset frequency. The oscillator control signal is the triangular wave signal, and the frequency is set according to the external resistor Rt and the internal capacitor Cs. The Oscillator waveform is used to control the HSFET and LS FET through a PWM controller made up of operational amplifiers and voltage comparators, and the waveform is also used to sample output voltage through voltage comparator and error amplifier, to perform closed loop control in regulation.The output voltage is adjusted through the resistors R1 and R2, where the resistors R1 and R2 form a voltage divider. When the reference voltage is higher than the feedback voltage, the output voltage of the error amplifier is high and the PWM controller is off, then the high side and low side MOSFETs are off and the output voltage is regulated.The external soft start capacitor is used to control the current flowing into the soft start circuit and the current flowing into the low-side MOSFET is controlled. The soft start time is adjustable by soft start capacitor or voltage reference voltage.Theoretically, RT8861GWQ is suitable for systems with an input voltage range of 7V~22V and an output voltage range of 0.5V~4.5V. Multi-channel support allows simultaneous hot-plugging and multiple channel load sharing.

Conclusion

RT8861GWQ is a dual-system high-efficiency synchronous step-down switching converter, which is applied in a variety of electronic products, such as tablet PC, smart phone, wireless communication base station, automotive electronics and industrial control system. It has a wide Vin (7V-22V), accurate output voltage, adjustable soft-start, low noise and high EMI, and allows multiple chips to work in parallel. It is driven by the oscillator, where the oscillator control signal is the triangular wave signal and the frequency is set according to the external resistor Rt and the internal capacitor Cs. The output voltage is controlled through voltage comparator and error amplifier, to perform closed loop control in regulation. It is suitable for systems with an input voltage range of 7V~22V and an output voltage range of 0.5V~4.5V.

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