MAX1774:Dual, High-Efficiency, Step-Down Converter with Backup Battery Switchover

Dual-Output Step-Down DC-DC Converter Supplies PDA/Palmtop Computers with Automatic Battery Switchover

The MAX1774 is a complete power-supply solution for PDAs and other hand-held devices. It integrates two high-efficiency step-down converters, a boost converter for backup battery regulation, and four voltage detectors in a small 32-pin QFN or 28-pin QSOP package. The MAX1774 accepts inputs from +2.7V to +28V and provides an adjustable main output from 1.25V to 5.5V atover 2A. The secondary core converter delivers an adjustable voltage from 1V to 5V and can deliver up to 1.5A. Both the main and core regulators have separate shutdown inputs. When the AC adapter power is removed, an external P-channel MOSFET switches input to the main battery. When the main battery is low, the backup step-up converter sustains the main output voltage. When the backup battery can no longer deliver the required load, the system shuts down safely to prevent damage. Four on-board voltage detectors monitor the status of the AC adapter power, main battery, and backup battery. The MAX1774 evaluation kit is available to help reduce design time.

Key Features
  • Dual, High-Efficiency, Synchronous-Rectified Step-Down Converters
  • Thin, Small (1mm High) QFN Package
  • Step-Up Converter for Backup Battery
  • Main Power
    • Adjustable from +1.25V to +5.5V
    • Over 2A Load Current
    • Up to 95% Efficiency
  • Core Power
    • Adjustable from 1V to 5V
    • Internal Switches
    • Up to 1.5A Load Current
    • Up to 91% Efficiency
  • Automatic Main Battery Switchover
  • 100% (max) Duty Cycle
  • Up to 1.25MHz Switching Frequency
  • Input Voltage Range from +2.7V to +28V
  • Four Low-Voltage Detectors
  • 170µA Quiescent Current
  • 8µA Shutdown Current
  • Digital Soft-Start
  • Independent Shutdown Inputs
MAX1774: Functional Diagram
MAX1774: Functional Diagram
  • Handheld Computers
  • Internet Access Tablets
  • PDAs
  • POS Terminals
  • Subnotebooks
titleDownload file
MAX1774 Data SheetMAX1774.pdf
Part NumberPrimary TopologyMonitor/Control FeaturesDC-DC/Power FeaturesBattery Charger FeaturesVIN
Oper. Freq.
minmaxminmaxSee Notes
MAX1774Step-DownShutdownCurrent Limit
Fixed Freq./PWM
Soft Start
Sync. Rectifier
Battery Backup2.72815.522600QSOP/28$4.03 @1k
Design kits & evaluation modules
Related Products
  • MAX1775:Dual-Output Step-Down DC-DC Converter for PDA/Palmtop Computers
Ordering Information
Part NumberStatusRecommended ReplacementPackageTempRoHS
MAX1774EEINo Longer AvailableMAX1774EEI+QSOP,;28 pin;61.9 mm²-40°C to +85°CNo
MAX1774EEI+ActiveQSOP,;28 pin;61.9 mm²-40°C to +85°CLead Free
MAX1774EEI+TActiveQSOP,;28 pin;61.9 mm²-40°C to +85°CLead Free
MAX1774EEI-TNo Longer AvailableMAX1774EEI+TQSOP;28 pin-40°C to +85°CSee data sheet
MAX1774EMJNo Longer AvailableMAX1774EEI+-40°C to +85°CSee data sheet
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