The FR9855B is a synchronous step-down DC/DC converter with fast constant on time (FCOT) mode control. The device provides 4.5V to 18V input voltage range and 5.5A continuous load current capability. Operation frequency depends on input and output voltage condition. At light load condition, the FR9855B can operate at power saving mode to support high efficiency and reduce power loss.

The FR9855B fault protection includes cycle-by-cycle current limit, short circuit protection, UVLO and thermal shutdown. The soft-start function prevents inrush current at turn-on. The FR9855B use fast constant on time control that provides fast transient response, the noise immunity and all kinds of very low ESR output capacitor for ensuring performance stabilization.

The FR9855B is offered in SOP-8 (Exposed Pad) and TDFN-10 (3mmx3mm) packages, which provides good thermal conductance.

• Low RDS(ON) Integrated Power MOSFET (70mΩ/38mΩ)
• Wide Input Voltage Range: 4.5V to 18V
• Output Voltage Range: 0.6V to 8V
• 5.5A Output Current
• FCOT Mode Enables Fast Transient Response
• Pseudo 630kHz Frequency
• Power Good Function
• Input Under Voltage Lockout
• Internal 1ms Soft-Start
• Cycle-by-Cycle Current Limit
• Hiccup Short Circuit Protection
• Over Temperature Protection with Auto Recovery
• SOP-8 (Exposed Pad) and TDFN-10 (3mmx3mm) Packages