This reference design is a four-switch, buck-boost DC/DC converter used for battery backup unit (BBU) applications, targeting Open Compute Project® (OCP) Open Rack V3 Power BBU specifications. This design has a 1.4kW power capability. The converter works in either buck, buck-boost, or boost mode depending on the V_in and V_out voltage. The converter transients smoothly between each mode. Peak current mode control is employed in this design, providing a fast load transient response. Relying on the LM51770 features, no extra driver is needed for field-effect transistors.

• 1.4kW power capability per phase then N number of phases can be connected in parallel for higher power battery discharge operation
• Bidirectional conversion under varying V_in–V_out
• Multimode operation: seamless transitions between buck to buck-boost and buck-boost to boost
• Integrated average input and output current monitor or limiter either in input or output
• Peak efficiency > 98.5%. Exceptional high load efficiency for V_in ≅ V_out over the full range of the output current
• Meets OCP-V3, 50V BBU power conversion function