Features

Designed for iso-buck topology

3.5 V to 38 V operating input voltage

Primary output voltage regulation / no optocoupler required

4.5 A source / sink peak primary current capability

Peak current mode architecture in forced PWM operation

390 ns blanking time

200 kHz to 1 MHz programmable switching frequency. Stable with low ESR

capacitor: min 2 μF

Internal compensation network

2 μA shutdown current

Internal soft-start

Enable

Overvoltage protection

Output voltage sequencing

Thermal protection

Optional spread spectrum for improved EMC

Power Good

Synchronization to external clock

QFN16 (3x3 mm) package

Applications

Isolated IGBT/SiC MOSFET gate drive supply

OBC (On-board charger) for HEV/EV

Electric traction systems

Description

The L6983I is a device specifically designed for isolated buck topology. 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 -4.5 A (even during soft-start) allows a proper energy transfer

to the secondary side as well as enabling 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 390 ns blanking time filters oscillations, generated by

the transformer leakage inductance, making the solution more robust.

The compact QFN16 3x3 mm package and the internal compensation of the L6983I

help minimize design complexity and size.

The switching frequency can be programmed in the 200 kHz - 1 MHz range with

optional spread spectrum for improved EMC. The EN pin provides enable/disable

functionality.

The typical shutdown current is 2 μA when disabled. As soon as the EN pin is pulled

up the device is enabled and the internal 1.3 ms soft-start takes place. The L6983I

features Power Good open collector that monitors the FB voltage. Pulse by pulse

current sensing on both power elements implements an effective constant current

protection and thermal shutdown prevents thermal run-away.