The Pololu step-up/step-down voltage regulator S7V7F5 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 2.7 V to 11.8 V and increases or decreases the voltage to a fixed 5 V output with a typical efficiency of over 90%.
This flexibility in input voltage 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.
In typical applications, this regulator can deliver about 1 A continuous when the input voltage is higher than 5 V (stepping down) and 500 mA continuous when the input is lower than 5 V (stepping up); please see the graphs at the bottom of this page for a more detailed characterization. The regulator has short-circuit protection, and thermal shutdown prevents damage from overheating; the board does not have reverse-voltage protection.
For an adjustable-output version of this regulator, consider Pololu's step-up/step-down voltage regulator S7V8A.
- input voltage: 2.7 V to 11.8 V
- fixed 5V output with +5/-3% accuracy
- typical continuous output current: 1 A when stepping down; 500 mA when stepping up (Actual continuous output current depends on input voltage. See Typical Efficiency and Output Current section below for details.)
- power-saving feature maintains high efficiency at low currents (quiescent current is less than 0.1 mA)
- integrated over-temperature and short-circuit protection
- small size: 0.35″ × 0.475″ × 0.1″ (9 × 12 × 3 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.
The step-up/step-down regulator has just three connections: the input voltage (VIN), ground (GND), and the output voltage (VOUT). These three connections are labeled on the back side of the PCB, and they 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.
The input voltage, VIN, should be between 2.7 V and 11.8 V. Lower inputs can shut down the voltage 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 output currents at which this voltage regulator’s over-temperature protection typically kicks in after a few seconds. These currents represent the limit of the regulator’s capability and cannot be sustained for long periods, so the continuous currents that the regulator can provide are typically several hundred milliamps lower, and Pololu recommend trying to draw no more than about 1 A from this regulator throughout its input voltage range.
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 9 V, using power leads more than a few inches long, or using a power supply with high inductance, Pololu 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 16 V.
More information about LC spikes can be found in Pololu's application note, Understanding Destructive LC Voltage Spikes.
This product is listed in:
Documentation and Resources:
- The Maker Revolution
The Maker Revolution celebrates the creation of new devices and the modification of existing ones - the transition from a consumer buying goods to eventually having a major part in their creation. The Maker Revolution places strong emphasis on free (...
- How to Use DC Regulators/Converters
So, you might have the best project in the world, an amazing idea and design, but no matter how clever your circuitry or how advanced your prototype is, unless you can power your project correctly, it all counts for nothing. Often you will need diffe...
- Powering Portable Projects: Batteries
Want to make your project portable? We've put together a quick guide to get you up to speed on battery options and help you decide which batteries might be best for your project. Batteries are a whole different game to plug packs and benchtop power s...
- Our recommendation on Breadboard Power Supplies
So, you’re looking for the right way to power your breadboard? You’ve found that your Arduino Uno just doesn’t quite have the juice to power up your circuit. It's likely that the microcontroller can output around 400mA when using th...
Exact shipping can be calculated on the view cart page (no login required).
We deliver Australia-wide with these options:
- $3 for Small Items (3-7 days, not tracked, only available on selected small items)
- $6.95 for Standard Post (2-4 days, tracked)
- $8.95 for Express Post (Overnight for Australia Post Next Day Network, tracked)
- Pickup - Free! Only available to customers who live in the Newcastle region (only after we email you to notify your order is ready)
International Orders - the following rates are for New Zealand and will vary for other countries:
- $11.49 for Pack and Track (3+ days, tracked)
- $16.50 for Express International (2-5 days, tracked)
If you order lots of gear, the postage amount might increment based on the weight of your order.
Our physical address (here's a PDF which includes other key business details):
Unit 18, 132 Garden Grove Parade
Take a look at our customer service page if you have other questions such as "do we do purchase orders" (yes!) or "are prices GST inclusive" (yes they are!). We're here to help - get in touch with us to talk shop.