Automotive PMIC uses buck-boost pre-regulator with diagnostics

PCIM Europe 2017 Stand 7-441 Allegro MicroSystems Europe introduces a multi-output, automotive PMIC with buck-boost pre-regulator. The A4408 is designed with a synchronous buck, three internal LDOs (low drop-out linear regulators), watchdog timer, power on reset (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 protection. The output 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 PMIC can be used for engine applications including, electronic power steering (EPS), transmission control units (TCU), advanced braking systems (ABS), advanced driver assistance systems (ADAS) and emissions control modules.

A watchdog timer can be programmed to accept a range of clock frequencies. The timer has a fixed activation delay to accommodate processor start-up. An enable/disable pin facilitates initial factory programming or field reflash programming.

Diagnostic outputs include a 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, are claimed to improve long-term reliability.

Enable inputs include a logic-level (ENB) and two high-voltage (ENBAT1 and ENBAT2) inputs. A Track pin sets the reference of the tracking regulator to either the 5.0V or the 3.3V output, so the PMIC 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 CPU supply rails. In case of a shorted output, all linear regulators feature foldback 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 PMIC is supplied in a low profile (1.2mm maximum) 38-lead eTSSOP with exposed thermal pad.