Asynchronous buck converters deliver high efficiency in automotive 48V PoL applications

Diodes Incorporated has introduced four new automotive-compliant asynchronous buck converters for 48V low-voltage rail (PoL applications. The AP68255Q/AP68355Q and AP6A255Q/AP6A355Q include 500mΩ power MOSFETs to deliver high-efficiency step-down DC-DC conversion with up to 3.5A of continuous output current. These converters cover the full automotive battery range from 5.5V to 80V/100V, including load dump scenarios. They can be employed in various applications, including 48V motor control, ADAS, telematics, infotainment, body control, instrument clusters, and lighting systems.

The new buck converters employ COT control to maintain a nearly constant switching frequency (300kHz). This technique results in fast load/line transient response, easy loop stabilisation, and low output voltage ripple, making the devices more straightforward to include by needing fewer external components. The proprietary gate-driver arrangement in these devices decreases switch node ringing effects without sacrificing the turn-on and turn-off times of the N-channel MOSFET switch. This method helps lower the high-frequency radiated EMI noise normally associated with MOSFET switching.

The built-in overcurrent protection with frequency foldback mode ensures high load-current support while decreasing junction temperature under fault conditions. The overtemperature protection circuit immediately shuts down the controller’s output voltage at 160C. When the temperature drops below the 140C safety threshold, the converter automatically restarts. These protection features prevent controller damage or malfunction, maximising system reliability.

The AP68255Q/355Q and AP6A255Q/355Q asynchronous buck converters are available in the thermally enhanced SO-8EP package with an operating temperature range of -40C to +125C.