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MAX77859 Buck-Boost Converter

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ADI's MAX77859 is a high-efficiency, high-performance buck-boost converter targeted for systems requiring a wide input voltage range (2.5 V to 22 V). The IC can supply up to 6 A of output current in buck mode and 4 A in boost mode (VIN = 3.7 V, VOUT = 5 V). The IC allows systems to change the output voltage dynamically through the I2C serial interface. MAX77859A features an I2C-adjustable output current limit with resolutions of 50 mA/step (with 10 mΩ sense resistance) to support USB-C® PPS requirements. MAX77859B is a non-PPS version and is optimized for low quiescent current. Systems equipped with MAX77859 can provide fast-charging peripheral devices with higher output voltage, minimizing power loss across cable/connector and reducing charging time.

Depending on the operating conditions, the IC operates either in SKIP mode or forced-PWM (FPWM) mode to optimize efficiency. The default output voltage is 5 V when using internal feedback resistors. The IC can also be configured to any default output voltages between 3 V and 20 V when using external feedback resistors. The output voltage is adjustable dynamically (DVS) between 3.2 V and 16 V in 20 mV steps when using internal feedback resistors or between 3 V to 20 V when using external feedback resistors (with step size dependent on the external feedback resistor ratio) by programming the internal reference voltage through I2C serial interface.

MAX77859A features output current limit. Using a 10 mΩ sense resistor, the output current limit threshold is adjustable dynamically between 1 A and 5 A in 50 mA steps through an I2C serial interface with a 3 A default value.

The SEL pin allows a single external resistor, RSEL, to connect to AGND to program the following:

  • I2C interface target address (4 options)
  • Switching current limit threshold (4 options)
  • Feedback resistor selection (internal or external)

The MAX77859WEVKIT# evaluation kit (EV kit) is a fully assembled and tested printed circuit board (PCB) that demonstrates the high-efficiency, high-performance buck-boost MAX77859 regulator. The EV kit is factory-configured as internal feedback with a default startup output voltage of 5 V. Other startup voltages can be achieved with external feedback resistors.

Features and Benefits
  • Wide input voltage range: 2.5 V to 22 V
  • Programmable output voltage
    • 3.2 V to 16 V with internal feedback resistors
    • 3.0 V to 20 V with external feedback resistors
  • USB-C Power Delivery (PD)/Programmable Power Supply (PPS)
    • 20 mV output voltage step size
    • 50 mA output current limit step size
  • Max. output current
    • Buck mode: 6 A
    • Boost mode: 4 A (VIN = 3.7 V, VOUT = 5 V)
  • 7.8 A typical switching current
  • Automatic SKIP mode and forced-PWM mode
  • Output active discharge
  • RSEL configuration
    • I2C interface target address
    • Switching current limit threshold
    • Internal/external feedback resistors
  • I2C programming
    • DVS
    • Slew rate of output voltage change
    • Output current limit threshold
    • Switching current limit threshold
    • Switching frequency
    • FPWM operation
    • Loop compensation
    • Power OK (POK) and fault status/interrupts
  • Open-drain status/interrupts in
  • Available in a 3.01 mm x 2.78 mm 42 wafer-level packaging (WLP) or 4.0 mm x 4.0 mm 19 FC2QFN
  • USB PD 3.0 (PPS) Dynamically Reconfigurable Processor (DRP) applications
  • Space-constrained applications