Pololu 3.3V 1.5A Step-Up/Step-Down Voltage Regulator S8V9F3

PololuSKU: POL-4964
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The Pololu S8V9Fx family of efficient switching regulators (also called switched-mode power supplies (SMPS) or DC-to-DC converters) convert both higher and lower input voltages to a regulated output voltage. They take input voltages from 1.4V to 16V and increase or decrease them as necessary, offering typical efficiencies of 80% to 90% and typical continuous output currents over 1 A for input voltages close to the output voltage. (Note: The minimum start-up voltage is 2.7V; see the connections section for details.)

This particular model (S8V9F3) takes an input voltage of 1.4V to 16V (2.7 V startup) and offers a fixed 3.3V output with a typical maximum output current of 1.5A.

The flexibility in input voltage offered by this family of regulators is especially well-suited for battery-powered applications in which the battery voltage begins above the regulated voltage and drops below as the battery discharges. Without the typical restriction on the battery voltage staying above the required voltage throughout its life, new battery packs and form factors can be considered.

The S8V9Fx regulators have under-voltage lockout and over-current protection. A thermal shutdown feature also helps prevent damage from overheating and a soft-start feature limits the inrush current and gradually ramps the output voltage on startup.

Warning: During normal operation, this product can get hot enough to burn you. Take care when handling this product or other components connected to it.


  • Input voltage: 1.4V to 16V (Note: minimum start-up voltage is 2.7V)
  • Output voltage: 3.3V with 4% accuracy
  • Typical maximum continuous output current: 1A to 1.5A when the input voltage is close to the output voltage (see the maximum continuous output current graph below for current capabilities across the full input voltage range)
  • Typical efficiency of 80% to 90%, depending on input voltage and load (see the efficiency graph below)
  • Under 3 mA typical no-load quiescent current (see the quiescent current graph below); can be reduced to 10 µA to 15 µA per volt on VIN by disabling the board
  • Soft-start feature limits inrush current and gradually ramps output voltage
  • Over-current protection and over-temperature shutoff
  • Input under-voltage lockout
  • Power-saving feature maintains high efficiency at low currents
  • Compact size: 0.4″ × 0.65″ × 0.1″ (10.2 mm × 16.5 mm × 2.6 mm); see the dimension diagram for more information


Minimum operating voltage 1.4V
Maximum operating voltage 16V
Continuous output current 1.5A
Output voltage 3.3V
Reverse voltage protection? N
Maximum quiescent current 3mA
Output type fixed 3.3V
Size 0.4″ × 0.65″ × 0.1"
Weight 0.8 g
PCB dev codes reg31a
Other PCB markings 0J14112

Using the Regulator


The step-up/step-down regulator has four main connections: the output voltage (VOUT), ground (GND), the input voltage (VIN), and an enable input (EN).

VOUT is the regulated output voltage. The regulator’s soft-start feature gradually ramps up the VOUT voltage on start-up to limit in-rush current draw.

The input voltage, VIN, should be between 2.7 V and 16 V when the regulator is first powered. After the regulator is running, it can continue operating down to 1.4 V. Lower inputs can shut down the voltage regulator; higher inputs can destroy the regulator, so you should ensure that noise on your input is not excessive, and you should be wary of destructive LC spikes (see the LC voltage spike section below for more information).

The regulator, which is enabled by default, can be put into a low-power sleep state by bringing the EN pin low (under 1 V). Leaving the pin disconnected or bringing the pin above 1.3 V will enable the regulator. The quiescent current draw in sleep mode is dominated by the current in the 100 kΩ pull-up resistor from ENABLE to VIN, which altogether will be between 10 µA and 15 µA per volt on VIN.

Typical efficiency

The efficiency of a voltage regulator, defined as (Power out)/(Power in), is an important measure of its performance, especially when battery life or heat are concerns.

Maximum continuous output current

The maximum achievable output current of the regulator varies with the input voltage but also depends on other factors, including the ambient temperature, airflow, and heat sinking. The graph below shows the maximum output currents that the regulators in the S8V9Fx family can deliver continuously at room temperature in still air and without additional heat sinking.

Warning: During normal operation, this product can get hot enough to burn you. Take care when handling this product or other components connected to it.

Quiescent current

The quiescent current is the current the regulator uses just to power itself, and the graph below shows this as a function of the input voltage. The module’s EN input can be driven low to put the board into a low-power state where it typically draws between 10 µA and 15 µA per volt on VIN.

LC Voltage Spikes

When connecting voltage to electronic circuits, the initial rush of current can cause voltage spikes that are much higher than the input voltage. If these spikes exceed a regulator’s maximum voltage, the regulator can be destroyed. If you are connecting more than about 9 V, using power leads more than a few inches long, or using a power supply with high inductance, we recommend soldering a 33 μF or larger electrolytic capacitor close to the regulator between VIN and GND. The capacitor should be rated for at least 20 V.

More information about LC spikes can be found in our application note, Understanding Destructive LC Voltage Spikes.


Package Contents

The regulator is supplied with a 4×1 straight male header strip and a 4×1 right-angle male header strip.

The through-holes are arranged with a 0.1″ spacing along the edge of the board for compatibility with standard solderless breadboard, perfboards and connectors that use a 0.1″ grid. You can solder wires directly to the board or solder in the included breakaway 4×1 straight male header strip or the 4×1 right-angle male header strip as desired.

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