The S9V11F5 switching step-up/step-down regulator efficiently produces 5 V from input voltages between 2 V and 16 V. (Note: it requires an input voltage of at least 3 V to start, but it can operate down to 2 V after startup.) Its ability to convert both higher and lower input voltages makes it useful for applications where the power supply voltage can vary greatly, as with batteries that start above but discharge below 5 V. The very compact (0.3″ × 0.45″) module has a typical efficiency of over 90% and can supply a typical output current of up to 1.5 A when the input voltage is around 5 V.

The Pololu step-up/step-down voltage regulator S9V11F5 is a switching regulator (also called a switched-mode power supply (SMPS) or DC-to-DC converter) that uses a buck-boost topology. It takes an input voltage from 2 V to 16 V and increases or decreases the voltage to a fixed 5 V output with a typical efficiency of over 90%. Note that this regulator requires an input voltage of at least 3 V to start, but it can operate down to 2 V after startup. Additionally, note that the startup current is limited to approximately 700 mA until the output voltage reaches 5 V; after startup, the available current is a function of the input voltage (see the Typical Efficiency and Output Current section below).

The flexibility in input voltage offered by this regulator is especially well-suited for battery-powered applications in which the battery voltage begins above 5 V 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. For instance, a 4-cell battery holder, which might have a 6 V output with fresh alkalines but a 4.8 V nominal voltage with NiMH cells and a 4.0 V output with partially discharged cells, can now be used for a 5 V circuit. In another typical scenario, a disposable 9V battery powering a 5 V circuit can be discharged to under 3 V instead of cutting out at 6 V, as with typical linear or step-down regulators.

The regulator has short-circuit protection, and thermal shutdown prevents damage from overheating; the board does not have reverse-voltage protection.

Features

• Input voltage: 2 V to 16 V (note: this regulator requires 3 V to start, but it can operate down to 2 V after startup)
• Fixed 5 V output with +5/-3% accuracy
• Typical maximum continuous output current: 1.5 A (when input voltage is around 5 V; the Typical Efficiency and Output Current section below shows how the achievable continuous output current depends on the input voltage)
• Power-saving feature maintains high efficiency at low currents (quiescent current is less than 0.2 mA)
• Integrated over-temperature and short-circuit protection
• Small size: 0.3″ × 0.45″ × 0.15″ (7.6 × 11.4 × 3.8 mm)

Using the Regulator

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

Connections

The step-up/step-down regulator has just three connections: the input voltage (VIN), ground (GND), and the output voltage (VOUT). These through-holes are arranged with a 0.1″ spacing along the edge of the board for compatibility with standard solderless breadboards and perfboards and connectors that use a 0.1″ grid. You can solder wires directly to the board or solder in either the 3×1 straight male header strip or the 3×1 right-angle male header strip that is included. VOUT is labeled on the silkscreen on one side of the board, and GND is in the middle and can be identified by its square pad.

The input voltage, VIN, should be between 3 V and 16 V when the regulator is first powered. After it is running, it can continue operating down to 2 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 below for more information).

The output voltage, VOUT, is regulated to a fixed 5 V, but it can be as high as 5.2 V when there is little or no load on the regulator.

Typical Efficiency and Output Current

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. As shown in the graph below, this switching regulator typically has an efficiency of 85% to 95%. A power-saving feature maintains these high efficiencies even when the regulator current is very low.

The maximum achievable output current of the board varies with the input voltage but also depends on other factors, including the ambient temperature, air flow, and heat sinking. The graph below shows maximum output currents that the regulator can deliver continuously at room temperature in still air and without additional heat sinking. The regulator can temporarily deliver up to around 2 A, though it will typically quickly overheat under such conditions and go into thermal shutdown.

Note that the startup current is limited to approximately 700 mA, and currents in excess of this are only available after the output has finished rising to 5 V. Large capacitive loads will generally not pose a problem because they will gradually charge up even with the current limit active, so while they may increase the time it takes the regulator to start up, the regulator should still eventually get to 5 V. A purely resistive load, however, could prevent the regulator from ever reaching 5 V. For example, if you put a 5 Ω resistor between VOUT and GND and then apply power to the regulator, the output voltage will never rise past 3.5 V, the voltage at which the current draw reaches the 700 mA limit. As such, this regulator is intended for applications like robotics, where any large loads are controllable and can be applied only after the regulator has finished starting up.

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 the regulator’s maximum voltage, the regulator can be destroyed. If you are connecting more than about 12 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.