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Quick-PWM Slave Controllers for Multiphase, Step-Down Supplies

Product Details

Key Features

Applications/Uses

Simplified Block Diagram

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Key Features

  • Quick-PWM Slave Controller
  • Precise, Active Current Balance (±1.25mV)
  • Accurate, Adjustable Current-Limit Threshold
  • Optimized for Low-Output Voltages (≤ 2V)
  • 4V to 28V Battery Input Range
  • Fixed 300kHz (MAX1887) or Selectable 200kHz/300kHz/550kHz (MAX1897) Switching Frequency
  • Drive Large Synchronous-Rectifier MOSFETs
  • 525µA (typ) ICC Supply Current
  • 20µA Standby Supply Current
  • < 1µA Shutdown (MAX1897) Supply Current
  • Small 16-Pin QSOP (MAX1887), Compact 20-Pin 5mm x 5mm QFN (MAX1897), or 20-Pin 5mm x 5mm Thin QFN (MAX1897)

Applications/Uses

  • CPU Core Supplies
  • Notebook Computers
  • Servers/Desktop Computers
  • Single-Stage (BATT to VCORE) Converters
  • Telecom
  • Two-Stage (+5V to VCORE) Converters

Description

The MAX1887/MAX1897 step-down slave controllers are intended for low-voltage, high-current, multiphase DC-to-DC applications. The MAX1887/MAX1897 slave controllers can be combined with any of Maxim's Quick-PWM™ step-down controllers to form a multiphase DC-to-DC converter. Existing Quick-PWM controllers, such as the MAX1718, function as the master controller, providing accurate output voltage regulation, fast transient response, and fault protection features. Synchronized to the master's low-side gate driver, the MAX1887/MAX1897 include the Quick-PWM constant on-time controller, gate drivers for a synchronous rectifier, active current balancing, and precision current-limit circuitry.

The MAX1887/MAX1897 provide the same high efficiency, ultra-low duty factor capability, and excellent transient response as other Quick-PWM controllers. The MAX1887/MAX1897 differentially sense the inductor currents of both the master and the slave across current-sense resistors. These differential inputs and the adjustable current-limit threshold derived from an external reference allow the slave controller to accurately balance the inductor currents and provide precise current-limit protection. The MAX1887/MAX1897's dual-purpose current-limit input also allows the slave controller to automatically enter a low-power standby mode when the master controller shuts down.

The MAX1887 triggers on the rising edge of the master's low-side gate driver, which staggers the on-times of both master and slave, providing out-of-phase operation that can reduce the input ripple current and consequently the number of input capacitors. The MAX1897 features a selectable trigger polarity, allowing out-of-phase or simultaneous in-phase operation.

Simplified Block Diagram

MAX1887, MAX1897: Typical Operating Circuit MAX1887, MAX1897: Typical Operating Circuit 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 .