L6986ITR [STMicroelectronics]

The L6986I is a device specifically designed for the isolated buck topology. Due to the P-Channel MOSFET as high-side power switch the device features 100% duty cycle operation. The primary output voltage can be accurately adjusted, whereas the isolated secondary output is derived by using a given transformer ratio. No optocoupler is required. The primary sink capability up to 1.9 A (even during soft-start) allows a proper energy transfer to the secondary side as well as enables a tracked soft-start of the secondary output. The control loop is based on a peak current mode architecture and the device operates in forced PWM. The 300 ns blanking time filters oscillations, generated by the transformer leakage inductance, making the solution more robust. Pulse by pulse current sensing on both power elements implements an effective constant current protection in the primary side. Due to the primary reverse current limit, the secondary output is protected against short circuit events. A primary output voltage supervisor, which notifies primary output voltage regulation through the RST open collector output, overvoltage protection, adjustable switching frequency, synchronization and a programmable soft-start are also available.

• Designed for iso-buck topology
• 4 V to 38 V operating input voltage
• Primary output voltage regulation / no optocoupler required
• 1.9 A typical sink peak primary current capability
• Peak current mode architecture in forced PWM operation
• 300 ns blanking time
• 8 µA I_Q-SHTDWN
• Adjustable f_SW and synchronization
• Embedded primary output voltage supervisor
• Adjustable soft-start time
• Internal primary current limiting
• Overvoltage protection
• R_{DS(on) HS} = 180 mΩ, R_{DS(on) LS} = 150 mΩ
• Thermal shutdown