MAX857CSA+T

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The MAX857CSA+T is a unique DC-DC switching regulator, which is capable of creating a highly efficient voltage conversion without producing much noise. It is an integrated for single-ended low noise, step-up/ step-down regulator with an internal high-side switch. The switch regulator is designed to provide more than 3A of output current in the specified input voltage range of 2.7V to 5.5V. The efficiency is improved by up to 97%, while total external components are reduced, making it suitable for powering point-of-load applications. MAX857CSA+T is an ideal choice for battery operated systems which require high efficiency, low thermal stress, and a wide input voltage range.

Application Field

The MAX857CSA+T switch regulator is designed for use in a variety of applications. From low energy wearable and portable battery powered devices, to test and measurement, automotive and industrial applications, this IC has wide application areas.

• Mobile communication: Laptop computer charger applications, cellular telephone charger applications, handsets.
• Portable devices: Handheld PCs, portable games, mini disc players, digital cameras.
• Personal computer peripherals: Internal modems, CD-ROM drives, external tape back- up systems.
• FTL/Joystick based systems: Battery backup control system, hand held test and measurement systems.
• Consumer electronics: remote controls, electronic toys, cable TV modems, low power solutions.
• Industrial control: audio/video systems, modems, power supply in industrial control and remote sensing.
• Automotive: Lighting systems, charging circuits.

Working Principle

The MAX857CSA+T provides a high frequency topology that incorporates a power MOSFET switch and an integrated inductor. This topology can operate as either a step-up or a step-down converter. The power MOSFET switch is activated by a 5V logic input signal and is able to handle load currents up to 3A. As the logic signal transitions from low-to-high, the switch turns on, connecting the input voltage to the inductor. The inductor then rapidly charges up and sets the inductor current.

When the signal transitions from high-to-low, the MOSFET switch turns off, interrupting the input voltage. The magnetic force created by the inductor opposes the change of current flow and forces the inductor current to continue flowing. The current now flows through the diode and is connected to the output voltage. The input voltage has been converted to the output voltage and the cycle repeats itself.

The MAX857CSA+T use an internal error amplifier for controlling the output voltage. The amplifier provides a regulated voltage across an external output voltage divider network. If the output voltage is too low, the voltage across the divide network increases, which drives the error amplifier\'s output high. This turn on the MOSFET switch and the inductor begins a new cycle.

By monitoring the output voltage and automatically adjusts the duty cycle to maintain the output voltage. The duty cycle can be easily adjusted by changing the value of the external resistor as desired. This allows the user to set the required voltage output.

The MAX857CSA+T also features a soft-start feature that helps limit the inrush current during start-up and helps prevent output capacitor flooding. The MAX857CSA+T\'s light load capability and the ability to maintain operation in a very light load environment makes it ideal for a variety of point of load applications.

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