The RAA211651 is an integrated 60V, 5A synchronous buck regulator with the Constant On-Time (COT) control scheme. It supports a wide range of input voltage from 4.5V to 60V and adjustable output voltage (0.8V to maximum duty cycle * VIN). It also features a very low quiescent current, typically 10μA at 24V input. The modulation scheme used allows for high efficiency at all output load levels, especially at light-load conditions.

The RAA211651 is based on the COT modulator, where the on-time is determined by the input voltage level and the resistor connected to the SET pin. The switching frequency varies with the load. At light load, switching frequency drops reducing the switching losses. Also, with internal compensation, the regulator works in Diode Emulation mode reducing the losses at light-load conditions.

To limit inrush current during startup the RAA211651 has 2ms fixed internal soft-start time. It can also be programmed by an external capacitor. The RAA211651 also provides programmable startup delay time for sequencing purposes.

The RAA211651 provides comprehensive protections including undervoltage lockout, overcurrent (positive and negative), overvoltage, and over-temperature protections.


  • 4.5V to 60V input supply range
  • 0.8V reference voltage with 1% accuracy
  • Adjustable output voltage (0.8V to Dmax*VIN)
  • Modulator: Constant On-Time (COT)
  • Low quiescent current
  • Excellent line and load regulation
  • Selectable internal or external control loop compensation
  • Variable load dependent switching frequency
  • Output Power-Good (PG) indicator
  • Programmable and optional fixed 2ms soft-start and soft-stop feature
  • Programmable startup and shutdown delay
  • Integrated LDO with bypass capability allowing for high-efficiency operation
  • Full protection: High-Side Overcurrent (HSOC) and low-side current protections in both directions, output Overvoltage Protection (OVP) and Output Undervoltage Protection (OUVP), input Undervoltage Lockout (UVLO), and Over-Temperature Protection (OTP)
  • Optional 3.3V default VOUT using internal feedback
  • 28 Ld 4mmx5mm QFN package




  • Industrial power supplies
  • 48V industrial and computing PoL
  • Battery powered applications
  • ATM, vending, and gaming machines
  • Robotics
  • Programmable logic controllers
  • After-market automotive


Type Title Date
Datasheet PDF 3.06 MB
Manual - Hardware PDF 11.83 MB
Brochure PDF 8.73 MB
Brochure PDF 5.49 MB 日本語
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