MAX8819 - A Complete Power Solution for Handheld Applications

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Introduction of a complete power solution chip for handheld applications

Introduction of a complete power solution chip for handheld applications

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  • 1. MAX8819: A Complete Power Solution for Handheld Applications
    • Source: MAXIM
  • 2. Introduction
    • Purpose
      • This training module introduces a complete power solution chip for handheld applications.
    • Outline
      • Overview of the MAX8819
      • Battery charger
      • Smart Power selector
      • 3 step-down converters and 1 step-up converter.
    • Content
      • 14 pages
  • 3. Overview of the MAX8819
    • The MAX8819A is a complete power-management IC that integrates
      • a Li+ charger
      • Smart Power Selector™ circuitry
      • four DC-DC regulators
    • This highly integrated, efficient device offers the most savings in not only BOM cost, but also in space
    • Proprietary Smart Power Selector circuitry makes the best use of AC-to-DC adapter power or limited USB power, enabling a highly energy-efficient solution.
    • The MAX8819A is ideal for use in portable media players, MP3 players, GPS devices, and other handheld devices
  • 4. Typical Operating Circuit Travel light: advanced USB charger eliminates bulky adapter, meets USB 2.0 specifications Dimming control: high-efficiency step-up regulator drives 2 to 6 WLEDs “ Instant-on” response: Smart Power Selector shares system and battery power, enabling operation with dead or no battery Maximizes battery life: three 95% efficient, 2MHz step-down regulators
  • 5. Battery Charger
    • It first detects the battery voltage.
      • If the battery voltage is less than 3.0V, the charger enters prequalification mode and charges the battery at 10% of the maximum fast-charge current while deeply discharged.
      • Once the battery voltage rises to 3.0V, the charger transitions to fast-charge mode and applies the maximum charge current.
    • The battery voltage rises until it approaches the battery regulation voltage.
    • When charge current decreases to 10% of the maximum fast charge current, the charger enters a 33min top-off state and then charging stops.
    Prequalification Fast-Charge (Constant Voltage) Fast-Charge (Constant Voltage) TOP-OFF Done V BATREG V BATPRQ Battery Voltage
  • 6. Battery Charger cont’d
    • Charge Status Output (CHG)
      • CHG indicates charger status.
        • CHG is low when the charger is in its prequalification or fast charge states.
        • When a timer count is exceeded in either state, CHG indicates the fault by blinking at a 2Hz rate and remains in that state.
      • When the MAX8819 is used with a MPU, connect a pull up resistor between CHG and the system logic voltage to indicate charge status to the MPU.
    • Charge Timer
      • A fault timer prevents the battery from charging indefinitely.
          • tPREQUAL = 33min
          • tFSTCHG = 660min
          • tTOP-OFF = 33min
  • 7. Smart Power Selector™
    • When external power is connected, the Smart Power Selector allows the system to operate with no battery or a deeply discharged battery.
    • It automatically switches the system load from the battery and makes the best use of limited USB or adapter power, while charging the battery from input power not used by the system.
    • The Smart Power Selector also provides thermal-limiting circuitry that reduces the battery-charge rate to prevent the charger from overheating.
  • 8. Three Step-Down Converters
  • 9. Step-Down Control Scheme
    • At light load, the step-down converter switches only as needed to supply the load.
    • At higher load currents (~80mA), the step-down converter transitions to fixed 2MHz switching.
    • All of the step-down regulators are capable of operating in 100% duty-cycle dropout.
    • The minimum duty cycle for all step-down regulators is 12.5%, allowing a regulation voltage as low as 1V over the full SYS operating range.
    • REG1 is optimized for 100% duty-cycle operation, and REG3 is optimized for low duty-cycle operation
  • 10. Dynamic Output Voltage Adjustment for Step-Down Converters
  • 11. Short-Circuit Protection for Step-Down Converters
  • 12. Ste-up Converter (REG4)
    • The step-up converter operates by regulating the voltage at FB4 to 0.5V.
    • The step-up converter can be configured as a white light emitting diodes (WLED) driver.
    WLEDs drivers configuration
  • 13. Thermal-Overload Protection
    • The IC reduces the DC current limit by 5%/ º C when the die temperature exceeds +100 º C.
    • The IC disables all regulator outputs and the battery charger when the junction temperature rises above +165 º C.
    • When the junction temperature cools by approximately 15 º C, the regulators and charger resume the state indicated by the enable input by repeating their soft-start sequence.
    • The thermal-overload shutdown is a fail-safe mechanism.
    • Proper thermal design should ensure that the junction temperature of the MAX8819 never exceeds the absolute maximum rating of +150 º C.
  • 14. Additional Resource
    • For ordering MAX8819, please click the part list or
    • Call our sales hotline
    • For additional inquires contact our technical service hotline
    • For more product information go to
      • http://www.maxim-ic.com/quick_view2.cfm/qv_pk/5843