High-Speed, Adjustable, Synchronous Step-Down Controllers with Integrated Voltage Positioning

The MAX1716/MAX1854/MAX1855 step-down controllers are intended for core CPU DC-DC converters in notebook computers. They feature a dynamically adjustable output (5-bit DAC), ultra-fast transient response, high DC accuracy, and high efficiency needed for leading-edge CPU core power supplies. Maxim's proprietary Quick-PWM™ quick-response, constant-on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns "instant-on" response to load transients while maintaining a relatively constant switching frequency.

The MAX1716/MAX1854/MAX1855 are designed specifically for CPU core applications requiring a voltage-positioned supply. The voltage-positioning input (VPS), combined with a high DC accuracy control loop, is used to implement a power supply that modifies its output set point in response to the load current. This arrangement decreases full-load power dissipation and reduces the required number of output capacitors.

The 28V input range of the MAX1716/MAX1854/MAX1855 enables single-stage buck conversion from high-voltage batteries for the maximum possible efficiency. Alternatively, the devices' high-frequency capability combined with two-stage conversion (stepping down the +5V system supply instead of the battery) allows the smallest possible physical size. The output voltage can be dynamically adjusted through the 5-bit digital-to-analog converter (DAC) inputs.

The MAX1716/MAX1854/MAX1855 are available in a 24-pin QSOP package. For applications requiring SpeedStep® power control (see the MAX1717).

Applications

* Computers: Desktop, Workstation, Server * Notebook Computers * Servers * Workstations

* High-Efficiency Voltage Positioning

* Quick-PWM Architecture

* ±1% VOUT Line-Regulation Accuracy

* Adjustable Output Range (5-Bit DAC)

* MAX1716: 0.925V to 1.6V

* MAX1854: 0.925V to 2.0V

* MAX1855: 0.600V to 1.75V

* 2V to 28V Input Range

* 200/300/400/550kHz Switching Frequency

* Output Undervoltage Protection

* Overvoltage Protection (MAX1716/MAX1855)

* Drive Large Synchronous-Rectifier MOSFETs

* 1.7ms Digital Soft-Start

* 700µA ICC Supply Current

* 1µA Shutdown Supply Current

* 2V ±1% Reference Output

* VGATE Transition-Complete Indicator

* Small 24-Pin QSOP Package