Automotive synchronous buck regulator

July 03, 2013 // By Graham Prophet
An AEC Q100 qualified PWM IC for power-supply applications features “power OK” capability, excellent loop stability and fast transient response.

The A8650 from Allegro MicroSystems Europe is a robust synchronous buck regulator IC designed for automotive power-supply applications in areas such as instrument clusters, HVAC, navigation, and audio systems. The AEC Q100 qualified device is an adjustable-frequency, high output current, PWM regulator that integrates a high-side P-channel MOSFET and a low-side N-channel MOSFET. It incorporates current-mode control to provide simple compensation, excellent loop stability, and fast transient response.

Key features of the A8650 include a switching frequency that is externally adjustable from 250 kHz to 2.4 MHz, an externally set soft-start time to minimise inrush currents, an enable/synchronisation input to either turn the output voltage on or off and/or synchronise the PWM switching frequency, and a “power OK” output to indicate when the output voltage is within its regulated limits. The sleep mode current of the A8650’s control circuitry is less than 3 µA.

Protection features include input undervoltage lockout, cycle-by-cycle overcurrent protection, “hiccup” mode short-circuit protection, overvoltage protection, and thermal shutdown. In addition, the A8650 provides open-circuit, adjacent pin short-circuit, and short-to-ground protection at every pin to satisfy the most demanding automotive applications.

The A8650 uses external compensation to accommodate a wide range of power components to optimise transient response without sacrificing stability. It regulates input voltages from 2.5V to 5.5V down to output voltages as low as 0.8V, and is able to supply at least 2A of load current. The A8650 is available in a 10-pin eMSOP package (suffix LY) with exposed pad for enhanced thermal dissipation.

Allegro Microsystems;