Automotive Multiple Output Buck-Boost Regulator

Allegro MicroSystems, LLC announces a new power management IC that uses a buck or buck-boost pre-regulator to efficiently convert automotive battery voltages into a tightly-regulated intermediate voltage, complete with control, diagnostics, and protections. The unique buck-boost design of Allegro’s A4409, allows sub 5V input voltage operation to accommodate the latest automotive idle-stop requirements. The output of the main switching regulator supplies two 5V LDOs, one at 300mA and the other at 200mA. Designed to supply power to microprocessor/DSP plus sensors, transceivers, and other loads, the A4409 is designed for automotive control units.

The Enable Input to the A4409 is compatible to a high-voltage battery level (ENBAT). Diagnostic outputs from the device include a power-on-reset output (NPOR). Long-term system reliability is increased by the use of dual internal bandgap voltage references, one for regulation and one for fault-checking.

The A4409 also contains a window watchdog timer that can be programmed to accept a wide range of clock frequencies (WDADJ). The watchdog timer has a fixed 30ms activation delay to accommodate processor startup, and has an enable/disable pin (active low, WDENn) to facilitate initial factory programming or field re-flash programming.

Additional protection features include foldback overcurrent protection for the LDO outputs. Also the main he switching regulator includes pulse-by-pulse current limit, hiccup mode short-circuit protection, LX short-circuit protection, and missing asynchronous diode protection, and the IC has an over-temperature thermal shutdown. The A4409 is supplied in a low profile (1.2 mm maximum height), 20-lead eTSSOP package (suffix “LP”) with exposed thermal pad. It is priced at $2.13 in quantities of 1,000.