Automotive power management IC designed with a synchronous buck
A new power management IC has been introduced by Allegro MicroSystems Europe, 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 output of Allegro’s A4408 supplies a 5V/115mA tracking/protected LDO, a 3.3V/165mA LDO, a 5V/325mA LDO, and an adjustable output synchronous buck regulator (1.25V/700mA).
The A4408 is suitable for under-hood applications, with key automotive applications including: Electronic Power Steering (EPS), Transmission Control Units (TCU), Advanced Braking Systems (ABS), Advanced Driver Assistance Systems (ADAS), Emissions Control Modules, and other automotive applications.
The A4408 contains a watchdog timer that can be programmed to accept a wide range of clock frequencies (WDADJ). The watchdog timer has a fixed activation delay to accommodate processor start-up. The watchdog timer has an enable/disable pin (active low, WDENn) to facilitate initial factory programming or field reflash programming.
Diagnostic outputs from the A4408 include a power-on-reset output (NPOR). POK5V indicates the status of the 5V and 5V 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.
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 5V or the 3.3V output, so the A4408 can be adapted across multiple platforms with different sensor types. The MODE pin selects the NPOR undervoltage threshold for the V5 and V5P outputs.
Protection features include under- and overvoltage lockout on all four CPU supply rails. In case of a shorted output, all linear regulators feature foldback overcurrent protection. In addition, 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 (1.2mm maximum height) 38-lead eTSSOP package (suffix ‘LV’) with exposed thermal pad.