NCP81239MNTXG Integrated Circuits (ICs)

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NCP81239MNTXG Application Field and Working Principle

The NCP81239MNTXG is a Pulse Width Modulated (PWM) Synchronous Buck Synchronous Rectified DC-to-DC controller from ON Semiconductor's NexFET Family. This device is a member of the Phase-Locked-Loop (PLL) enabled voltage regulator family. It provides a regulated output voltage by entering both input voltage and output voltage parameters.

The NCP81239MNTXG is designed for use in DC/DC buck converters with a wide input voltage range from 3.7V to 80V and an output voltage range from 0.8V to 32V. This device features an ultra-high frequency error amplifier and a low jitter PLL boost design, providing high frequency synchronization performance and fully featured programmability controlling all key parameters of the converter.

The NCP81239MNTXG is a high performance switched mode power supply controller specially designed for synchronous buck applications with current mode control and fast transient response. It provides adjustable output voltage, output current and over-temperature protection. It also offers both current and voltage mode control techniques, allowing it to achieve fast line, load and transient response.

Details and Features

The NCP81239MNTXG have an input supply voltage range of 3.7 – 80V, making them suitable for a wide range of applications. There is also a regulated output voltage range of 0.8V-32V. This device is capable of up to 5A of output current and is protected against over-temperature and short circuit conditions. This device utilizes PLL enabled voltage regulators, error amplifiers and low-jitter PWM boost design, providing high frequency synchronization performance and full programmability, controlling all the key parameters of the converter.

The NCP81239MNTXG includes an integrated voltage regulator feedback input and delivers output voltage accuracy as low as ±2%. The feedback control also provides programmable current and temperature protection. The device also offers both current and voltage mode control techniques, allowing it to achieve fast line, load and transient response.

The NCP81239MNTXG also features an internal PLL synchronization circuit, allowing it to synchronize to an external signal source. This circuit provides low jitter, allowing for fast response to output voltage and current changes. In addition, the PLL can be switched off for the cost efficiency of a non-synchronous converter. The device also offers a selectable 250kHz/500kHz/1MHz switching frequency, allowing customers to optimize the power supply design for their application.

Applications

The NCP81239MNTXG is suitable for a wide range of applications across many end-markets. These include: smartphones and tablets, automotive, industrial, medical, PC and many more. Due to its wide input voltage range and programmable parameters it is ideal for synchronous buck DC-DC systems.

The NCP81239MNTXG is capable of powering processor cores, FPGAs, ASICs, DSPs, microcontrollers, memory and other system components, providing reliable power in space constrained applications.

Working Principle

The NCP81239MNTXG is an ultra-fast buck converter consisting of a PWM controller, a synchronous rectifier, a bootstrap-capacitor, a synchronization clock controller, a voltage feedback loop and an adjustable current limit circuit. The device uses a pulse width modulation (PWM) technique to generate power efficiency, lowered output ripple voltage and low operational noise. It also features a digital error amplifier which is used to compare the setpoint voltage to the actual output voltage and then adjust the converter duty cycle accordingly.

The synchronous rectifier is used to convert the high voltage pulse width modulation (PWM)signal into a near DC voltage. It switches off when the peak value of the PWM signal is lower than the DC voltage of the output power source, and turns on when the reverse is true. This allows the device to deliver high power efficiency from the input voltage to the output voltage.

The bootstrap capacitor is used to charge up when the NCP81239MNTXG is switching the load at high frequencies, providing the necessary gate voltage to the MOSFETs of the synchronous rectifier. It also regulates the gate voltage to maintain accurate current control.

The synchronization clock controller generates internal oscillator operating frequency which is used to control the output current and voltage of the NCP81239MNTXG circuit. The internal oscillator frequency can be synchronized externally to either 250kHz, 500kHz or 1MHz by connecting an external clock reference signal to the NCP81239MNTXG’s CLK pin.

The voltage feedback loop consists of an external voltage divider connected to the V_FB pin that is used to compare the external setpoint voltage divider voltage to the output power source voltage. The resulting error signal is used as an input to the internal error amplifier and is used to adjust the current limit circuit and modulate the PWM duty cycle accordingly.

Finally, the adjustable current limit circuit utilizes an external resistor connected to the CURRENT_LIMIT pin to set the maximum output current of the NCP81239MNTXG circuit. This current limit circuit allows the circuit to operate in both the continuous conduction and discontinuous conduction modes of operation, protecting the NCP81239MNTXG in case of overload.

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