Pololu 12V 4.5A Step-Down Voltage Regulator D42V55F12 (Up to 60V Input)

Need a clean, efficient 12V rail from a higher-voltage DC source? The D42V55F12 is a compact synchronous buck (step-down) regulator that converts up to 60V input down to a stable 12V output. It’s ideal for 24V/36V/48V systems powering 12V loads where you want high efficiency, low heat, and extra control features like Enable (for low-power / load disconnect) and Power Good (for sequencing and monitoring).

Input voltage: up to 60V (minimum input depends on dropout vs load).
Output: 12V with 3% accuracy. :contentReference[oaicite:2]{index=2}
Typical efficiency: 85%–95% depending on VIN and load.
Current capability: typical max is 4.5A at 42V in, with a typical continuous range of ~3.5A to 6.5A depending on input voltage and thermal conditions.

Why/Benefits

Efficient 12V from high-voltage rails

Synchronous buck design for high efficiency and lower heat than linear regulators.
Switching frequency around 400kHz under heavy loads.
Soft-start ramps output gradually to reduce inrush current on startup.

More control + safer operation

EN (Enable): put the regulator in a low-power state and disconnect the load (great for battery systems).
Power Good: useful for sequencing, fault detection, and voltage monitoring.
Built-in protections: reverse-voltage, over-current, and over-temperature shutoff.

Technical specifications

Pololu item	D42V55F12
Topology	Synchronous buck (step-down) switching regulator
Input voltage (VIN)	12V to 60V (minimum input depends on dropout vs load)
Output voltage (VOUT)	12V (3% accuracy)
Typical max output current	4.5A (typical at 42V in; thermals/ VIN affect continuous current)
Typical continuous current range	~3.5A to 6.5A (see Pololu current graph)
Efficiency	Typically 85% to 95% (VIN/load dependent)
Switching frequency	~400kHz under heavy loads
Quiescent current	<0.2mA typical no-load; EN low-power ~50µA + 1µA per volt on VIN
Size / Weight	1.0" × 1.0" × 0.355" (25.4 × 25.4 × 9mm), 6.5g
Mounting	Three 0.086" mounting holes for #2 or M2 screws
Extra I/O	Enable (EN) + Power Good output

Pinout & power notes

Important:

Minimum VIN is load-dependent: in practice, VIN must be about VOUT + dropout, and dropout increases with output current.
EN low-power draw: EN can reduce consumption, but at very high VIN the EN low-power current can exceed the regulator’s normal quiescent current (see Pololu quiescent notes).
Like any high-power DC-DC, keep power leads short/thick and ensure airflow if you’re running near the current limit.

Core connections: VIN, GND, VOUT
Control/monitoring: EN (Enable) and PG (Power Good) for sequencing/fault detection.
Some connections are duplicated across multiple pins for easier wiring and lower resistance.

FAQ

Is it okay for 48V to 12V conversion?

Yes—this regulator is designed for high-voltage inputs up to 60V and is commonly used in 24V/36V/48V systems stepping down to 12V.
Will it always output 4.5A?

4.5A is the typical max rating at 42V in; real continuous current depends on VIN, airflow, ambient temperature, and thermal dissipation (Pololu provides a continuous current graph).
What is Power Good used for?

Power Good can help with sequencing (turning on other rails in order), fault detection, and voltage monitoring.
Do I need to consider dropout voltage?

Yes. Like all buck regulators, VIN must be higher than VOUT by at least the dropout voltage, which increases with load current.