5V Step-Up/Step-Down Voltage Regulator S9V11F5

Overview

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 S9V11E2x, bottom view with dimensions and a US quarter for size reference.

Pololu 5V Step-Up/Step-Down Voltage Regulator S9V11F5 next to a US quarter dollar for size reference.

2.5-9V Fine-Adjust Step-Up/Step-Down Voltage Regulator w/ Adjustable Low-Voltage Cutoff S9V11MACMA next to US quarter dollar for size reference.

Details for item #2836

This item is the S9V11F5, which outputs a fixed 5 V.

Pololu 5V Step-Up/Step-Down Voltage Regulator S9V11F5 (silkscreen side).

Pololu 5V Step-Up/Step-Down Voltage Regulator S9V11F5 (silkscreen side).

Pololu 5V Step-Up/Step-Down Voltage Regulator S9V11F5 (non-silkscreen side).

Pololu 5V Step-Up/Step-Down Voltage Regulator S9V11F5 (non-silkscreen side).

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
• Max continuous output current when input voltage ≥ output voltage: 1.5 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 of the operating range (see the quiescent current graph below)
• 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
• Small size: 0.3″ × 0.45″ × 0.15″ (7.6 × 11.4 × 3.8 mm)

Using the Regulator

Connections

The S9V11F5 step-up/step-down regulator has three connections: the input voltage (VIN), ground (GND), and the output voltage (VOUT).

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 5 V output voltage. 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 three connections 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 directly to the board or solder in either of the included 0.1″ 3×1 straight male or 3×1 right-angle male header strips.

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.

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 current that this S9V11F5 regulator can deliver continuously at room temperature in still air and without additional heat

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 12 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.

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