1. Overview and Function

️· Type: Monolithic, constant-frequency, current-mode step-down DC-DC converter.
️· Purpose: To convert an input voltage to a lower output voltage.
️· Key Feature: Current-mode operation for better transient response and stability.
️· Packages: FE/UF and BD packages, with an exposed pad (important for signal ground connection).

2. Pin Functions (Highlights)

️· SYNC/MODE (Pin 1/4): Selects operating mode (Forced Continuous or Burst Mode) and can be used for external clock synchronization.
️· PGOOD (Pin 2/5): Indicates the output voltage is within regulation (+/-10%). Pulled low when the output is out of spec.
️· RT (Pin 3/6): Sets the switching frequency with an external resistor.
️· ITH (Pin 4/7): Error amplifier compensation point. Critical for control loop stability.
️· FB (Pin 5/8): Feedback pin, compares output voltage to a reference.
️· RUN (Pin 6/10): Enables/disables the converter. Can be tied to PVIN for always-on operation.
️· TRACK/SS (Pin 7/11): Allows output voltage to "track" an external voltage or use an external soft-start capacitor. Important: Don't tie to INTVCC or PVIN.
️· SGND (Pins 17/9, 21): Signal ground – a critical reference point.
️· PGND (Pins 8, 9, 10/12, 13, 14, 15): Power ground.
️· SW (Pins 11, 12, 13/16, 17, 18, 19): Switch node connection to the inductor.
️· BOOST (Pin 14/20): Bootstrapped supply to the top-side floating gate driver.
️· PVIN (Pin 15/1, 2): Power input supply - must be decoupled with a capacitor.
️· INTVCC (Pin 16/3): Internal 5V LDO output.
️· Exposed Pad (Pin 17/21): Signal ground - MUST be soldered to the PCB.

3. Operating Modes

️· Forced Continuous Mode:
- Enabled by connecting SYNC/MODE to INTVCC.
- Minimizes switching harmonics but less efficient at light loads.
- Keeps ripple low
️· Burst Mode Operation:
- Enabled by connecting SYNC/MODE to a voltage between 0.42V and 1V.
- Increases efficiency at light loads by operating the MOSFETs intermittently.
- Quiescent current drops to 75µA in sleep mode.
- Pulse-skipping can be implemented with SYNC/MODE tied to ground.
️· Synchronization: The oscillator can be synced to an external clock (300kHz – 1.3MHz).

4. Control Loop and Features

️· Current-Mode Control: Inductor current is monitored to regulate output voltage.
️· Overvoltage/Undervoltage Protection: PGOOD output goes low if voltage is out of tolerance. Converter enters a shutdown mode.
️· Frequency Range: 300kHz to 3MHz (set by RT resistor).

5. Key Considerations

️· Exposed Pad: The exposed pad *must* be soldered to the PCB for proper signal grounding.
️· SYNC/MODE Pin: Carefully consider the voltage applied to this pin to select the desired operating mode.
️· TRACK/SS Pin: Avoid improper connections to INTVCC or PVIN.