A4409: Adjustable Frequency Buck or Buck-Boost Pre-Regulator with 2 LDOs, Window Watchdog Timer, and NPOR


The A4409 is a 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, 300 mAMIN LDO and a 5 V, 200 mAMIN LDO. Designed to supply CAN or microprocessor power supplies in high-temperature environments, the A4409 is ideal for underhood applications.

Enable-input to the A4409 is compatible to a high-voltage battery level (ENBAT).

Diagnostic outputs from the A4409 include a power-on-reset output (NPOR) with a fixed 22.5 ms typical delay. Dual bandgaps, one for regulation and one for fault checking, improve long-term reliability of a system designed around the A4409.

The A4409 contains a window watchdog timer that can be programmed to accept a wide range of clock frequencies (WDADJ). The watchdog timer has a fixed 30 ms activation delay to accommodate processor startup. The watchdog timer has an enable/disable pin (active low, WDENn) to facilitate initial factory programming or field reflash programming.

Protection features include dual control loop for pre-regulator rail. In case of a shorted output, all linear regulators feature foldback overcurrent protection. The switching regulator includes pulse-by-pulse current limit, hiccup mode short-circuit protection, LX short-circuit protection, missing asynchronous diode protection, and 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.



Provides System Power for (μC/DSP, CAN, sensors, etc.)
in Automototive Control Modules, such as:

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

Top Features

  • Automotive AEC-Q100 qualified
  • VIN operating range from 3 to 36 V, with 40 V maximum
  • Buck or buck-boost pre-regulator (VREG)
  • Adjustable PWM switching frequency: 250 kHz-2.4 MHz
  • PWM frequency can be synchronized to external clock
  • Two 5 V internal LDO regulators with foldback short-circuit protection
  • Power-on reset (NPOR) with fixed delay of 22.5 ms
  • Programmable window watchdog timer with a fixed activation delay of 30 ms
  • Active low, watchdog timer enable/disable pin (WDENn)
  • Dual bandgaps for increased reliability:
    • BG1 for VREG, 5V0, and VCP reference
    • BG2 for V5 reference, and VREG, 5V0, and VCP fault detection
  • Ignition-enable input (ENBAT)
  • Frequency dithering helps reduce EMI/EMC
  • Undervoltage protection for all output rails
  • Pin-to-pin and pin-to-ground tolerant at every pin
  • Thermal shutdown protection
  • −40°C to 150°C junction temperature range

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
APEK4409KLP-01-MH DEMO BOARD -20°C to 85°C No -- Contact your
local sales rep
Distributor Stock
A4409KLPTR-T 20-lead TSSOP -40°C to 150°C Yes View Data Contact your
local sales rep
Distributor Stock

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.