A6983IQTR [STMicroelectronics]

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.

• AEC-Q100 qualified
• Operating temperature range: -40 °C to +150 °C for T_j
• Designed for iso-buck topology
• 3.5 V to 38 V operating input voltage
• Load dump tolerant up to 40 V
• 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
• 25 μA operating quiescent current
• 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 pin
• Overvoltage protection
• Output voltage sequencing
• Thermal protection
• Optional spread spectrum for improved EMC
• Power Good
• Synchronization to external clock
• QFN16 (3x3 mm) package