The S9V11x family of efficient switching regulators (also called switched-mode power supplies (SMPS) or DC-to-DC converters) use a buck-boost topology to convert both higher and lower input voltages to a regulated output voltage. They take input voltages from 2 V to 16 V and increase or decrease them as necessary, offering typical efficiencies of 85% to 95% and typical continuous output currents over 1.5 A for input voltages close to or greater than the output voltage. (Note: The minimum start-up voltage is 3 V, but the regulator will operate down to 2 V after startup.)

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.

These regulators have short-circuit protection, and thermal shutdown prevents damage from overheating. The boards do not have built-in protection against reverse voltage, but reverse-voltage protection modules are available for adding that functionality. Note that the startup current is limited to approximately 700 mA until the output voltage reaches the nominal voltage; after startup, the available current is a function of the input voltage (see the maximum continuous output current graph below).

The different members of this family offer different output voltage options, from fixed voltages (some with selectable alternatives) to adjustable voltages that can be set anywhere between 2.5 V and 9 V. Some versions also have an adjustable low-voltage cutoff that can be set anywhere in the 2 V to 16 V output voltage range and used to prevent your battery from over-discharging. This is particularly useful for battery chemistries that can be damaged when over-discharged, including Li-ion and LiPo. The chart below lists all the regulators in the S9V11x family along with the key features of each version:

Step-Up/Step-Down Voltage Regulator               Pololu 5V Step-Up/Step-Down Voltage                2.5-9V Fine-Adjust Step-Up/Step-Down  Voltage 

S9V11E2x, bottom view with dimensions          Regulator S9V11F5 next to a US quarter             Regulator w/ Adjustable Low-Voltage Cutoff 

and a US quarter for size reference.                         dollar for size reference.                                 S9V11MACMA next to US quarter dollar for size reference.

Details for item #5719:

This item is the S9V11E2A, which outputs a user-adjustable voltage between 2.5 V and 9 V. This version of the S9V11E2x can be distinguished from the fixed-output versions by the presence of the voltage adjustment trim pot.

2.5-9V Adjustable Step-Up/Step-Down     2.5-9V Adjustable Step-Up/Step-Down       Step-Up/Step-Down Voltage Regulator

Voltage Regulator S9V11E2A.                       Voltage Regulator S9V11E2A                           S9V11E2x, bottom view.           

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)
• Output voltage: 2.5 V to 9 V (adjustable)
• Max continuous output current when input voltage ≥ output voltage: 1.7 A (note: startup current is limited to 700 mA until output voltage reaches the nominal voltage; see the maximum continuous output current graph below for current capabilities across the full input voltage range)
• Low quiescent current: < 0.2 mA for most combinations of input and output voltages (see the quiescent current graph below)
• Enable input can be used to put the board into a low-power state where it typically draws 10 µA per volt on VIN
• Soft-start feature limits inrush current and gradually ramps output voltage
• Integrated over-temperature and short-circuit protection
• Power-saving feature maintains high efficiency at low currents
• Compact size: 0.43″ × 0.65″ × 0.16″ (10.9 × 16.5 × 4.0 mm); see the dimension diagram (305k pdf) for more information

Using the Regulator:

Connections

The S9V11E2x step-up/step-down regulator has four main connections: the output voltage (VOUT), ground (GND), the input voltage (VIN), and an enable input (EN).

The input voltage, VIN, should be between 3 V and 16 V when the regulator is first powered. After the regulator 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 the LC voltage spike section below for more information).

VOUT is the regulated output voltage, which is determined by the trimmer potentiometer position (see the setting the output voltage section below for details). The regulator’s soft-start feature gradually ramps up the VOUT voltage on start-up to limit in-rush current draw.

The regulator, which is enabled by default, can be put into a low-power sleep state by reducing the voltage on the EN below 0.7 V, and it can be brought out of this state again by increasing the voltage on EN past 0.8 V. The quiescent current draw in this sleep mode is dominated by the current in the 100 kΩ pull-up resistor from EN to VIN, which is approximately 10 µA per volt on VIN (e.g. approximately 30 µA with 3 V in). The tight tolerance of the enable input allows a precise low-VIN cutoff to be set, such as with the output of an external voltage divider powered by VIN, which is useful for battery powered applications where draining the battery below a particular voltage threshold could permanently damage it.

The four connections are labeled on the back side of the PCB and are arranged with a 0.1″ spacing along the edge of the board for compatibility with solderless breadboards, connectors, and other prototyping arrangements that use a 0.1″ grid. You can solder wires or 0.1″ header pins directly to the board. Note: header pins are not included with this product, but 1×4 straight male headers and 1×4 right-angle male headers are available separately.

S9V11E2x step-up/step-down voltage regulators, soldered with straight and right-angle headers (not included), on a breadboard.

Setting the output voltage

The output voltage of the regulator is controlled with a trimmer potentiometer. Turning the potentiometer clockwise increases the output voltage.

Output voltage settings for the 2.5-9V Adjustable Step-Up/Step-Down Voltage Regulator S9V11E2A.

Please note that the output voltage can be set below 2.5 V at the low end of the potentiometer’s range and above 9 V at the high end. While this is not likely to damage the regulator, it might not work reliably or its output could become unstable when the output voltage is not within the recommended 2.5 V to 9 V range.

The output voltage can be up to 3% higher than normal when there is little or no load on the regulator. The output voltage can also drop depending on the current draw, especially when the regulator is boosting a lower voltage to a higher one (stepping up), although it should remain within 5% of the set voltage.

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, air flow, and heat sinking. The graph below shows maximum output currents that the regulators in the S9V11x family can deliver continuously at room temperature in still air and without additional heat sinking (note: this graph does not apply to the smaller S9V11F5, which has lower output current capabilities due to its more compact PCB; see the graphs on its product page for more information).

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.

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 10 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 the regulator’s maximum voltage (16 V), the regulator can be destroyed. In our tests with typical power leads (~30″ test clips), we observed spikes approaching 16 V at input voltages approaching 9 V. Power supplies or leads with high inductance will make these spikes worse. An electrolytic capacitor (33 μF is a good starting point) can be added close to the regulator between VIN and GND to help suppress these spikes.