Multiple-output automotive regulator IC with buck/boost capability

November 23, 2015 // By Graham Prophet
A4409 from Allegro MicroSystems Europe is a power management IC that uses a buck or buck/boost pre-regulator to convert automotive battery voltages into a tightly regulated intermediate voltage, complete with control, diagnostics and protection features.

This AEC-Q100 qualified device features two LDO regulators, window watchdog timer and power-on-reset output. The buck/boost design of the A4409 allows operation at input voltages below 5V to accommodate the latest automotive idle-stop requirements. The output of the main switching regulator supplies two low-dropout (LDO) 5V regulators, one at 300 mA and the other at 200 mA.

This combination of features makes the A4409 suited to supplying power to systems incorporating combinations of microprocessors, digital signal processors, sensors, transceivers and other loads in applications such as automotive control units.

The 'enable' input to the A4409 is compatible with a high battery voltage level, and 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. The watchdog timer has a fixed 30 msec activation delay to accommodate processor startup, and has an enable/disable pin to facilitate initial factory programming or field re-flash programming.

Additional protection features include foldback overcurrent protection for the LDO outputs. The main switching regulator also includes pulse-by-pulse current limiting, '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. Data sheet here.

Allegro MicroSystems; www.allegromicro.com