ISL78268ARZ-T7A

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The ISL78268ARZ-T7A is a high-performance synchronous buck regulator secondary-side controller designed to achieve low power dissipation, high efficiency and high power density. The controller features a 3MHz fixed frequency with two independent PWM/PFM switching and a soft-start ramp-up. It uses a voltage and current mode loop compensation architecture to provide fast transient performance and excellent noise filtering. This integrated circuit is suitable for regulating primary and secondary side voltages of multiple output power supplies. Its on-chip clock allows the user to use this device in fixed frequency and spread spectrum mode.

Application Field

The ISL78268ARZ-T7A is suitable for use in mobile and desktop applications, as well as in wide range of dc-dc switching controllers. It can be used in applications such as memory DRAM, USB and SOIC8 interfaces, power supply controllers, power management, and microcontrollers. Its highly efficient synchronous buck regulator design makes it suitable for high current, high speed, low power consumption and fast transient response. It helps reduce switching losses and associated EMI noise. Moreover, it helps achieve a high power density.

Working Principle

The ISL78268ARZ-T7A is an analog synchronous buck DC-DC switching controller based on voltage and current mode loop compensation. It implements a 3MHz fixed frequency with two independent PWM/PFM switching. The synchronous buck regulator is made up of two switches, an inductor, and two capacitors. One switch is driven by an internal high-side MOSFET, and the other is driven by a low-side external MOSFET. The current mode loop compensation reduces the output capacitance and the gate drive of the large external MOSFET without compromising transient response. The high-side MOSFET switch is driven by four levels of adaptive adaptive gate drive to turn-on. Also, the soft-start ramp-up is used to reduce inrush current and minimize system start-up time.

The external PWM/PFM input and the current mode loop compensation allow fast transient response and full cycle-by-cycle current sensing. The connection between the high-side and low-side drivers is done through an adjustable current sense resistor. The high-side MOSFET gate voltage is regulated to an adjustable maximum switch on voltage in order to minimize energy consumption. The primary-side and the secondary-side are synchronized to minimize the turn-on transients of the low-side MOSFET, thus reducing the output capacitance.

The internal clock signal allows the user to use this device in fixed frequency and spread spectrum mode. This can further reduce electromagnetic interference in the switching environment. The external PWM input allows the user to control the pulse width modulation frequency. The internal slow start circuit is responsible for gradually increasing the output voltage. Moreover, the internal power-on reset prevents inrush current and ensures accurate start.

Conclusion

The ISL78268ARZ-T7A is an ideal DC-DC switching controller for energy-efficient applications. It is a high-performance synchronous buck regulator controller suitable for mobile and desktop applications. It integrates a 3MHz fixed frequency with two independent PWM/PFM switching and a soft-start ramp-up. Moreover, its primary-side and the secondary-side are synchronized to minimize the turn-on transients of the low-side MOSFET and reduce output capacitance. Its adjustable current sense resistor provides fast transient response and full cycle-by-cycle current sensing. The external PWM input allows the user to control the pulse width modulation frequency. The ISL78268ARZ-T7A can provide excellent noise filtering and high power density making it a great choice for DC-DC switching controllers.

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