STMicroelectronics A6983I

The A6983I 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 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 390 ns blanking time filters oscillations, generated by the transformer leakage inductance, makes the solution more robust. Both the compact QFN-16 (3x3 mm) package and the internal compensation of the A6983I help minimizing the design complexity and size. The switching frequency can be programmed in the 200 kHz to 1 MHz range with an optional spread spectrum for improved EMC. The EN pin provides a 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 A6983I features a 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 runaway.

Key features

• AEC-Q100 qualified, designed for iso-buck topology
• Operating input voltage range from 3.5V to 38V, load dump tolerant up to 40V
• Primary output voltage regulation, no optocoupler required
• Peak current mode architecture in forced PWM operation
• Internal compensation network, internal soft-start, enable pin
• Overvoltage protection, output voltage sequencing, thermal protection
• Optional spread spectrum for improved EMC, power good, synchronization to external clock
• Minimum on-time is 390ns typical at (T_J = -40 to 150°C, V_IN = 12V)
• Shutdown current from VIN is 2?A typical at (V_EN = G_ND, T_J = -40 to 150°C, V_IN = 12V)
• Operating temperature range from -40°C to 150°C, QFN16 package

Applications

• Automotive isolated IGBT/SiC MOSFET gate drive supply
• OBC (on-board charger) for HEV/EV
• Electric traction systems