A4408: Adjustable Frequency Buck or Buck-Boost Pre-Regulator with a Synchronous Buck, 3 Internal LDOs, Watchdog Timer, NPOR, and FF0/FF1

The A4408 is 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 output of the pre-regulator supplies a 5 V / 115 mA_MAXtracking/protected LDO, a 3.3 V / 165 mA_MAXLDO, a 5 V / 325 mA_MAXLDO, and an adjustable output synchronous buck regulator (1.25 V_TYP/ 700 mA_DC). Designed to supply CAN or microprocessor power supplies in high-temperature environments, the A4408 is ideal for underhood applications.

使输入A4408包括逻辑电平(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 V or the 3.3 V output, so the A4408 can be adapted across multiple platforms with different sensors and supply rails. The MODE pin selects the NPOR undervoltage threshold for the V5 and V5P outputs.

Diagnostic outputs from the A4408 include a power-on-reset output (NPOR). POK5V indicates the status of the 5 V and 5 V 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 longterm reliability of the A4408.

The A4408 contains a watchdog timer that can be programmed to accept a wide range of clock frequencies (WD_ADJ). The watchdog timer has a fixed activation delay to accommodate processor startup. The watchdog timer has an enable/disable pin (active low, WD_ENn) to facilitate initial factory programming or field reflash programming.

保护功能包括下和过电压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 (1.2 mm maximum height) 38-lead eTSSOP package (suffix “LV”) with exposed thermal pad.

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• Electronic Power Steering (EPS)
• Transmission Control Units (TCU)
• Advanced Braking Systems (ABS)
• Emissions Control Modules
• Other automotive applications

• Automotive AEC-Q100 qualified
• 2.8 to 36 V_INoperating range, 40 V_INmaximum
• Buck or buck-boost pre-regulator (VREG)
• Adjustable PWM switching frequency: 250 kHz to 2.4 MHz
• PWM frequency can be synchronized to external clock
• Adjustable synchronous buck regulator (1.25 V_NOM)
• 3.3V (3V3) and 5V (V5) internal LDO regulators with foldback short-circuit protections
• 5V (V5P) internal tracking LDO regulator with foldback short-circuit and short-to-battery protections
• TRACK sets either 3V3 or V5 as the reference for V5P
• Power-on reset (NPOR) with fixed delay of 15 ms
• Programmable watchdog timer with activation delay
• Active-low watchdog timer enable pin (WDENn)
• Dual bandgaps for increased reliability: BG_VREF, BG_FAULT
• MODE pin sets the NPOR undervoltage threshold for V5 and V5P
• Fixed POK5V undervoltage threshold for V5 and V5P
• Logic enable input (ENB) for microprocessor control
• Two ignition enable inputs (ENBAT1 and ENBAT2)
• FF0, FF1 Fault Flags—last microcontroller RESET indicators
• Slew rate control pin helps reduce EMI/EMC
• Frequency dithering helps reduce EMI/EMC
• Overvoltage and undervoltage protection for all four CPU supply rails
• Pin-to-pin and pin-to-ground tolerant at every pin
• Thermal shutdown protection
• −40°C to 150°C junction temperature range