Buck-boost controller handles redundant battery systems in autonomous vehicles

By Gina Roos, editor-in-chief

Analog Devices Inc. has launched the Power by Linear LT8708/-1 bidirectional buck-boost switching regulator controller that operates between two batteries that have the same voltage, making it well-suited for redundancy in autonomous vehicles. The 98% efficient LT8708/-1, which operates from an input voltage that can be above, below, or equal to the output voltage, can also be used in electric and hybrid vehicles, where redundant 12-V, 24-V, or 48-V batteries are commonly found. The LT8708/-1 can also be used in 48-V/12-V and 48-V/24-V dual-battery systems.

Operating between the two batteries, the LT8708/-1 prevents system shutdown if one of the batteries fails. The LT8708-1 is used in parallel with the LT8708 to add power and phases. “The LT8708-1 always operates as a slave to the master LT8708, can be clocked out of phase, and has the capability to deliver as much power as the master,” said ADI. In addition, one or more LT8708-1s can be connected to a single master, which will proportionally increase power and current capability of the system.

The LT8708/-1 operates with a single inductor over a 2.8-V to 80-V input voltage range and can produce an output voltage from 1.3 V to 80 V. This can deliver up to several kilowatts of power depending on the choice of external components and number of phases, said ADI. It also simplifies bidirectional power conversion in battery/capacitor backup systems that need regulation of V_OUT , V_IN , and/or I_OUT /I_IN in the forward or reverse direction.

ADI said that the device’s six independent forms of regulation allow it to be used in numerous applications, including automotive, solar, telecom, and battery-powered systems.

Key features:

• Operates with two batteries with the same or different voltages
• Synchronous rectification: up to 98% efficiency
• Delivers up to several kilowatts with multiphase operation
• Single inductor allows V_IN above, below, or equal to V_OUT
• Six independent forms of regulation:
  o   V_IN current (forward and reverse)
  o   V_OUT current (forward and reverse)
  o   V_IN and V_OUT voltage
• Forward and reverse discontinuous conduction mode supported
• Supports MODE and DIR pin changes while switching
• V_IN range: 2.8 V (Need EXTV_CC > 6.4 V) to 80 V
• V_OUT range: 1.3 V to 80 V
• Available in 40-lead 5 × 8-mm QFN with high-voltage pin spacing

The LT8708 is available in three temperature grades, with operation from –40°C to 125°C for the extended and industrial grades and a high-temp automotive range of –40°C to 150°C.

Available now, pricing for the LT8708/-1 (5 × 8-mm QFN-40) starts at $6.60.