ISL6551ARZ-T

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ISL6551ARZ-T is a DC-DC switching controller designed to control two external P-channel MOSFETs to generate either a positive or negative voltage in the range from -8 V to +100 V. It can be used in a variety of applications that require very low quiescent current and excellent accuracy, such as LCD bias voltage generators, Solid State Drives (SSDs) and battery chargers. This article will cover the application field and working principle of the ISL6551ARZ-T.

Applications

The ISL6551ARZ-T is ideally suited for applications requiring high efficiency and fast transient response. Some of the common applications include LCD bias voltage generators, Solid State Drives (SSDs) and battery chargers. In addition, the ISL6551ARZ-T can be used in active power factor correction, dc/dc stepping down, up-conversion and multi-phase regulators.

The ISL6551ARZ-T can be used for step-down and step-up converters, such as boost, flyback, buck, SEPIC, Ξ compensation and double-ended forward, providing very fast response time to changes in input voltage and load. The high switching frequencies, with the integrated spread spectrum, make it possible to easily achieve the stringent EMI requirements. The Power Good output provides a signal to the system when the output voltage is within the accuracy of the power supply. The power-fail handler allows the system to be switched off instantly in the event of a power failure.

Working Principle

The ISL6551ARZ-T is a current mode switching controller that uses a fixed frequency oscillator, combined with a current sense comparator, to control the current in an external MOSFET transistor. It relies on an external resistor and diode to provide the necessary feedback to ensure regulated output voltage. When the output voltage reaches the set point, the duty cycle of the switching transistor is set to sustain the output voltage. The duty cycle varies with the load current and is determined by the sense resistor and the output voltage.

The operating frequency of the ISL6551ARZ-T is selected either by an internal clock or by an external clock source. The frequency is also adjustable, allowing for improved noise performance or lower output noise. The current sense amplifier of the ISL6551ARZ-T can detect peak currents up to 6 A, and the power-good handler provides an output when the output voltage falls outside the specified range. The over-temperature protection shuts down the output when the internal temperature of the device is too high.

The ISL6551ARZ-T provides several features to improve system performance, such as integrated spread spectrum, a low-voltage lockout and soft-start/hiccup circuitry to prevent inrush current. The ISL6551ARZ-T also includes programmable output voltage and current limit, cycle-by-cycle current limit and overtemperature protection.

Conclusion

The ISL6551ARZ-T is a current mode switching controller designed to control two external P-channel MOSFETs to generate either a positive or negative voltage in the range from -8 V to +100 V. The switch is programmable, allowing for adjustable frequency and voltage. The ISL6551ARZ-T can be used in a variety of applications that require very low quiescent current and excellent accuracy, such as LCD bias voltage generators, Solid State Drives (SSDs) and battery chargers. It can be used for step-down and step-up converters and includes features such as integrated spread spectrum, a low-voltage lockout and soft-start/hiccup circuitry. The Power Good output provides a signal to the system when the output voltage is within the accuracy of the power supply. This article covered the application field and working principle of the ISL6551ARZ-T.

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