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New Generation Switching Power Manager with USB On-the-Go
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New Generation Switching Power Manager with USB On-the-Go


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Introduction of the key features of the LTC3576, its basic operation and typical applications

Introduction of the key features of the LTC3576, its basic operation and typical applications

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  • 1. New Generation Switching Power Manager with USB On-the-Go
  • 2. Introduction
    • Purpose
      • This training module introduces the key features of the LTC3576, its basic operation and typical applications.
    • Outline
      • Key features of the LTC3576
      • Internal functional circuits
      • Typical applications
    • Content
      • 17 pages
  • 3. Design Challenges for USB-capable Charger
    • USB-capable battery charging in many cases means more convenience to the user.
    • However, there are some limitations when the USB is used for charging the device’s batteries.
    • The main challenges for the system designer include:
      • Maximizing current delivered from the USB port
      • Managing power flow between multiple input voltage sources, the battery and load
      • Minimizing heat
      • Maximizing charging efficiency
      • Minimizing solution footprint and profile
  • 4. A Solution for the Challenges - LTC3576
    • The LTC3576 is a member in a family of multifunction power management IC. It consists of:
      • A bidirectional switching power manager with input overvoltage protection and USB On-The-Go (OTG) functionality
      • A stand-alone battery charger
      • Three high efficiency synchronous buck regulators
      • An ideal diode
      • I 2 C control
      • An always-on LDO
    • The LTC3576 is available in a low profile 38-pin (4mm x 6mm x 0.75mm) QFN package.
    • The LTC3576 is designed to make optimal use of the power available from a variety of sources, while minimizing power dissipation and easing thermal budgeting constraints.
  • 5. PowerPath Control
    • Benefits:
      • Bat-Track adaptive output control capability with an external high-voltage buck regulator
      • Improved thermal performance with power flowing to the system load
      • Improving power delivery efficiency to the system load and to the battery
    USB Power in Power Out Step down regulator USB Current Limit Program & Monitor
  • 6. USB On-the-Go (OTG)
    • The bidirectional PowerPath switching regulator acts as a step-up converter to deliver power from V OUT to V BUS .
  • 7. Input Current Limit Program
    • The current limit value has 5 settings ranging from 500 µA to 1A.
    • The input current limit is programmed by
      • I LIM0 & I LIM1 pins
      • I 2 C serial port
    High Power Suspend (USB 2.5mA Limit) 0 1 1 X 0 X X D6 5x Mode (USB 100mA Limit) 1 1 Low Power Suspend (USB 500 µ A Limit) 0 1 10x Mode (Wall 1A Limit) 1 0 1x Mode (USB 100mA Limit) 0 0 USB Setting I LIM0 / C0 I LIM1 / C1
  • 8. Bat-Track Control
    • ACPR: indicates the external switching regulator is suitable for used by LT3576.
    • Wall: determine when power is applied to the external regulator.
    • V C : Bat-Track external switching regulator control output.
    When external power is detected, the USB input is automatically disabled.
  • 9. Ideal Diode
    • The ideal diode is always on and will respond quickly whenever V OUT drops below BAT.
    • The diode consists of a precision amplifier that controls the gate of an optional external ideal diode P-channel MOSFET.
  • 10. Suspend LDO & Always-On LDO
    • Suspend LDO
    • If the LTC3576 are configured for USB suspend mode, the bidirectional switching regulator is disabled and the suspend LDO provides power to the VOUT pin.
    • The suspend LDO will prevent the battery from running down when the portable product has access to a suspended USB port.
    • 3.3V LDO Always-On LDO
    • This LDO is used to provide power to a system pushbutton controller, standby microcontroller or real time clock.
    • If the LDO3V3 output pin is not used, it should be disabled by connecting it to VOUT.
  • 11. Battery Charge Control
    • The constant-current/constant-voltage battery charger features:
      • Automatic recharge
      • Automatic termination by safety timer
      • Low voltage trickle charging
      • Bad cell detection
      • Over-temperature charge pausing
    • Depending on available input power and external load conditions, the battery charger may or may not be able to charge at the full programmed rate.
    • The CHRG pin indicates the status of the battery charger.
  • 12. I 2 C Interface
    • The LTC3576 may receive commands from a master device using 2-wire I 2 C interface.
    • The I 2 C port is designed to be operated at speeds of up to 400kHz.
    • The I 2 C serial port can be disabled by grounding the DVCC pin.
    Timing Diagram
  • 13. General Purpose Step-down Regulators
    • Three operating modes to meet the different noise / power needs.
      • Pulse skip mode for moderate to heavy loads
      • Burst mode for light loads
      • LDO mode for light loads
  • 14. USB On-the-Go Application
    • The LTC3576 as the host
    • The LTC3576 as the slave
    Fig 1 Fig 2
  • 15. Typical Application 1
  • 16. Typical Application 2 Same circuits to connect with the MCU, please refer to Application 1
  • 17. Typical Application 3 Same circuits to connect with the MCU, please refer to Application 1
  • 18. Additional Resource
    • For ordering the LTC357 switching power manager, please click the part list or
    • Call our sales hotline
    • For additional inquires contact our technical service hotline
    • For more product information go to