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MAX1887, MAX1897
Quick-PWM Slave Controllers for Multiphase, Step-Down Supplies


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Data Sheet
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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.

Key Features   Applications/Uses
  • 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)

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

    Key Specifications:   Step-Down Switching Regulators
    Part Number VIN (min) (V) VIN (max) (V) IOUT (A) Operating Current, ICC (max) (mA) Number of DC-DC Outputs Operating Freq. (kHz) Features EV-Kit Package RoHS Available Operating Temp. Range (°C) Price**
    MAX1887  4 28 20 0.8 1 300
    Adjustable Frequency
    Current Limit
    Fixed Frequency/ PWM Operation
    Shutdown
    Synchronous Rectifier
    Yes QSOP/16 No -40 to +85  
    MAX1897  550 QFN/20
    THIN QFN/20
    Yes $2.24 @ 1k
    See All Step-Down Switching Regulators (223)

    Key Specifications:   Switch-Mode DC-DC Power Supplies
    Part Number Topology VIN (min) (V) VIN (max) (V) Number of DC-DC Outputs Digital/VID Programmed Output IOUT (A) Operating Current, ICC (max) (mA) Operating Freq. (kHz) Internal Power Switch(es) Package Price**
    MAX1887  Step-Down 4 28 1 No 20 0.8 300 No QSOP/16  
    MAX1897  550 QFN/20
    THIN QFN/20
    $2.24 @ 1k
    See All Switch-Mode DC-DC Power Supplies (429)
    Notes:
    **This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

    Diagram
    MAX1887, MAX1897: Typical Operating Circuit
    Typical Operating Circuit

    Application Notes
  • Application Note 1832: Power Supply Engineer's Guide to Calculate Dissipation for MOSFETs in High-Power Supplies - MAX1897

    Evaluation Kits
    none

    Reliability Reports
  • Show FIT data for:
  • Reliability Report: MAX1887EEE.pdf
  • Request Reliability Report for:

    Software/Models
    none

    Ordering Information
    Notes:

    1. Other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales.
    2. Didn't Find What You Need? Ask our applications engineers. Expert assistance in finding parts, usually within one business day.
    3. Part number suffixes: T or T&R = tape and reel; + = RoHS/lead-free; # = RoHS/lead-exempt. More: SeeFull Data Sheet or Part Naming Conventions.
    4. * Some packages have variations, listed on the drawing. "PkgCode/Variation" tells which variation the product uses. Note that "+", "#", "-" in the part number suffix describes RoHS status. Package drawings may show a different suffix character.


    Devices: 1-8 of 8

    MAX1887 Free
    Sample
    Buy
    Package: TYPE PINS FOOTPRINT
      DRAWING CODE/VAR *
    Temp RoHS/Lead-Free?
    Materials Analysis
    MAX1887EEE  
    QSOP;13 pin;
    Dwg: 21-0055H (PDF)
    Use pkgcode/variation: E16-1*
    -40°C to +85°C See data sheet
    MAX1887EEE-T  
    QSOP;13 pin;
    Dwg: 21-0055H (PDF)
    Use pkgcode/variation: E16-1*
    -40°C to +85°C See data sheet
    MAX1897 Free
    Sample
    Buy
    Package: TYPE PINS FOOTPRINT
      DRAWING CODE/VAR *
    Temp RoHS/Lead-Free?
    Materials Analysis
    MAX1897EGP  
    QFN;20 pin;
    Dwg: 21-0091J (PDF)
    Use pkgcode/variation: G2055-2*
    -40°C to +85°C RoHS/Lead-Free: No
    Materials Analysis
    MAX1897EGP-T  
    QFN;20 pin;
    Dwg: 21-0091J (PDF)
    Use pkgcode/variation: G2055-2*
    -40°C to +85°C RoHS/Lead-Free: No
    Materials Analysis
    MAX1897ETP  
    THIN QFN;20 pin;
    Dwg: 21-0140L (PDF)
    Use pkgcode/variation: T2055-4*
    -40°C to +85°C RoHS/Lead-Free: No
    Materials Analysis
    MAX1897ETP-T  
    THIN QFN;20 pin;
    Dwg: 21-0140L (PDF)
    Use pkgcode/variation: T2055-4*
    -40°C to +85°C RoHS/Lead-Free: No
    Materials Analysis
    MAX1897ETP+  
    THIN QFN;20 pin;
    Dwg: 21-0140L (PDF)
    Use pkgcode/variation: T2055+4*
    -40°C to +85°C RoHS/Lead-Free: Lead Free
    Materials Analysis
    MAX1897ETP+T  
    THIN QFN;20 pin;
    Dwg: 21-0140L (PDF)
    Use pkgcode/variation: T2055+4*
    -40°C to +85°C RoHS/Lead-Free: Lead Free
    Materials Analysis

    More Information
  • New Product Press Release 2001-11-29 

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    Document Ref.: 19-2188; Rev 1; 2002-09-27
    This page last modified: 2007-07-18



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