A4408 automotive power management IC has buck-boost pre-regulator

Allegro MicroSystems Europe has designed a multi-output automotive power management IC (PMIC) with buck-boost pre-regulator to convert battery voltages. The A4408 has a synchronous buck, three internal LDOs (low drop out regulators), watchdog timer, a power-on-reset output (NPOR), and fault flags.

The PMIC 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 output of Allegro’s A4408 supplies a 5.0V/115mA tracking/protected LDO, a 3.3V/165mA LDO, a 5.0V/325mA LDO, and an adjustable output synchronous buck regulator (1.25V/700mA).

The A4408 is intended for under-the-hood applications, with automotive applications such as electronic power steering (EPS), transmission control units (TCUs), advanced braking systems (ABS), advanced driver assistance systems (ADAS), emissions control modules.

The A4408 contains a watchdog timer that can be programmed to accept a wide range of clock frequencies. The timer has a fixed activation delay to accommodate processor start-up and an enable/disable pin (active low, WDENn) to facilitate initial factory programming or field re-flash programming.

Diagnostic outputs from the A4408 include a power-on-reset output (NPOR). POK5V indicates the status of the 5.0V and 5.0V protected LDOs. Fault Flag 0 (FF0) and Fault Flag 1 (FF1) retain the last fault to reset the microcontroller. Dual bandgaps, one for regulation and one for fault checking, improve long-term reliability of the A4408, says Allegro.

Enable inputs to the A4408 include a logic-level (ENB) and two high-voltage (ENBAT1 and ENBAT2) inputs. The A4408 provides flexibility by including a Track pin to set the reference of the tracking regulator to either the 5.0 or the 3.3V output, so the A4408 can be adapted across multiple platforms with different sensor types. The Mode pin selects the NPOR under-voltage threshold for the V5 and V5P outputs.

Protection features include under- and over-voltage lock-out on all four central processor units (CPU) supply rails. In case of a shorted output, all linear regulators feature fold-back over-current protection. The V5P output is protected from a short-to-battery event. Both switching regulators include pulse-by-pulse current limit, hiccup mode short-circuit protection, LX short-circuit protection, missing asynchronous diode protection (VREG), and thermal shutdown.

The A4408 is supplied in a low profile (1.2 mm maximum height) 38-lead eTSSOP with exposed thermal pad.



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