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High-Speed Step-Down Controller with Accurate Current Limit for Notebook Computers

Product Details

Key Features

Simplified Block Diagram

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Key Features

  • Ultra-High Efficiency
  • Accurate Current-Limit Option
  • Quick-PWM with 100ns Load-Step Response
  • 1% VOUT Accuracy Over Line and Load
  • 1.8V/2.5V Fixed or 1V to 5.5V Adjustable Output Range
  • 2V to 28V Battery Input Range
  • 200/300/450/600kHz Switching Frequency
  • Adjustable Overvoltage Protection
  • Adjustable Undervoltage Protection
  • 1.7ms Digital Soft-Start
  • Drives Large Synchronous-Rectifier FETs
  • 2V ±1% Reference Output
  • Power-Good Window Comparator

Applications/Uses

  • 1.8V and 2.5V Supplies
  • Chipset/RAM Supplies as Low as 1V
  • CPU Core Supplies
  • Notebook Computers

Description

The MAX1844 pulse-width modulation (PWM) controller provides high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high-voltage batteries to generate low-voltage CPU core or chipset/RAM supplies in notebook computers.

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. Efficiency is enhanced by an ability to drive very large synchronous-rectifier MOSFETs. Accurate current sensing to ensure reliable overload protection is available using an external current-sense resistor in series with the synchronous rectifier. Alternatively, the synchronous rectifier itself can be used for less accurate current sensing at the lowest possible power dissipation.

Single-stage buck conversion allows the MAX1844 to directly step down high-voltage batteries for the highest possible efficiency. Alternatively, two-stage conversion (stepping down the 5V system supply instead of the battery) at a higher switching frequency allows the minimum possible physical size.

The MAX1844 is intended for CPU core, chipset, DRAM, or other low-voltage supplies as low as 1V. It is available in 20-pin QSOP, and QFN packages and includes both adjustable overvoltage and undervoltage protection.

For a dual step-down PWM controller with accurate current limit, refer to the MAX1845. The MAX1714/ MAX1715 single/dual PWM controllers are similar to the MAX1844/MAX1845 but do not use current-sense resistors.

Simplified Block Diagram

MAX1844: Functional Diagram MAX1844: Functional Diagram Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .