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Power-Source Selector for Dual-Battery Systems

Selector Provides Power-Source Control for Dual-Battery Systems, Minimizes System Cost

Product Details

Key Features

Parametric specs for Battery Fuel Gauges, Protectors, and Monitors
Functions Selector
Battery Type 2-4 Cell Li-Ion
5-10 Cell NiMH
Parameters Measured Voltage
End Equipment Host
VSUPPLY (V) (min) 4.75
VSUPPLY (V) (max) 28
Package/Pins TQFN/28
Oper. Temp. (°C) -40 to +85
Budgetary
Price (See Notes)
3.36
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Simplified Block Diagram

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Parameters

Parametric specs for Battery Fuel Gauges, Protectors, and Monitors
Functions Selector
Battery Type 2-4 Cell Li-Ion
5-10 Cell NiMH
Parameters Measured Voltage
End Equipment Host
VSUPPLY (V) (min) 4.75
VSUPPLY (V) (max) 28
Package/Pins TQFN/28
Oper. Temp. (°C) -40 to +85
Budgetary
Price (See Notes)
3.36

Key Features

  • Automatically Detects and Responds to:
    • Low-Battery Voltage Condition
    • Battery Insertion and Removal
    • AC-Adapter Presence
    • Airline-Adapter Presence
  • Step-Down and Step-Up Charger Compatibility
  • Fast Break-Before-Make Selection
    • Allows Hot Swapping of Power Sources
    • No External Schottky Diodes Needed
  • 50µA Maximum Battery Quiescent Current
  • Implements Battery Capacity Relearning
  • Allows Usage of Aircraft Supply
  • Direct Drive of P-Channel MOSFETs
  • Simplifies Power-Management µP Firmware
  • 4.75V to 28V AC-Adapter Input Voltage Range
  • Small 28-Pin Thin QFN Package (5mm x 5mm)

Applications/Uses

  • Dual-Battery Portable Equipment
  • Internet Tablets
  • Notebook and Subnotebook Computers

Description

The MAX1538 selector provides power-source control for dual-battery systems. The device selects between an AC adapter and dual batteries based on the presence of the three power sources and the state of charge of each battery. The MAX1538 includes analog comparators to detect AC/airline-adapter presence and determine battery undervoltage. Fast analog circuitry allows the device to switch between power sources to implement a break-before-make time, which allows hot swapping of battery packs. The MAX1538 independently performs power-source monitoring and selection, freeing the system power-management µP for other tasks. This simplifies the development of µP power-management firmware and allows the µP to enter standby, reducing system power consumption.

The MAX1538 supports “relearn mode,” which allows the system to measure and fully utilize battery capacity. In this state, the part allows the selected battery to be discharged even when an AC adapter is present. The MAX1538 can also be used to power the system in an aircraft. On detecting an airline adapter, the MAX1538 automatically disables charging or discharging of battery packs and only allows the system to be powered from the adapter.

The MAX1538 is available in a space-saving 28-pin thin QFN package with a maximum footprint of 5mm x 5mm.

Simplified Block Diagram

MAX1538: Typical Operating Circuit MAX1538: 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 .