3.3V Step-Up/Step-Down Voltage Regulator w/ Fixed 3V Low-Voltage Cutoff S9V11F3S5C3

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.

We manufacture these boards in-house at our Las Vegas facility, so we can make these regulators with customized components to better meet the needs of your project If you are interested in customization, please contact us for a quote.

Details for item #2873

This item is the S9V11F3S5C3, which outputs a fixed 3.3 V that can be changed to 5 V using a selection input and features a fixed 3 V low-voltage cutoff.

3.3V Step-Up/Step-Down Voltage Regulator S9V11F3S5 (silkscreen side).

3.3V Step-Up/Step-Down Voltage Regulator S9V11F3S5 (silkscreen side).

3.3V Step-Up/Step-Down Voltage Regulator S9V11F3S5 (non-silkscreen side).

3.3V Step-Up/Step-Down Voltage Regulator S9V11F3S5 (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 3.3 V output with +5/-3% accuracy (can be changed to 5 V using the SEL pin)
• 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)
• Fixed 3 V low-voltage cutoff with hysteresis protects batteries from over-discharging
• Enable input can be used to put the board into a low-power state where it typically draws 7 µA per volt on VIN
• Low quiescent current: < 0.2 mA for most of the operating range (see the quiescent current graph below)
• Power-good output can be used for sequencing, fault detection, and voltage monitoring
• Integrated over-temperature and short-circuit protection
• Power-saving feature maintains high efficiency at low currents
• Compact size: 0.5″ × 0.6″ × 0.17″ (12.7 × 15.3 × 4.3 mm)

Using the Regulator

Connections

The step-up/step-down regulator has five main connections all located along the same edge of the board: the output voltage (VOUT), ground (GND), the input voltage (VIN), an enable input (EN), and a power good indicator (PG). A sixth pin, SEL, can optionally be used to change the output voltage from 3.3 V to 5 V.

The output voltage, VOUT, defaults to 3.3 V but can be changed to 5 V with output voltage selection pin whose operation is described below.

The input voltage, VIN, should be between 3 V and 16 V. Lower inputs will 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 regulator is put in a low-power sleep state when voltage on the EN pin falls below 0.7 V, and the regulator is brought out of its low-power state when the voltage on EN rises back above 0.8 V. On this regulator version, the EN pin is tied to VIN through a voltage divider that sets the low-voltage cutoff threshold to 3 V (specifically, there is a 154 kΩ resistor to VIN and a 47 kΩ resistor to ground). Once the input falls below this 3 V threshold, the regulator will stay disabled until the input rises above 3.4 V (which causes the voltage on EN to rise past its hysteresis threshold of 0.8 V). This low-VIN cutoff is useful for battery powered applications where over-discharging the battery could permanently damage it. The quiescent current draw in this sleep mode is dominated by the current in the voltage divider, which is approximately 7 µA per volt on VIN (e.g. approximately 20 µA with 3 V in).

The “power good” indicator, PG, is an open-drain output that goes low when the regulator’s output falls below around 90% of the nominal voltage, including when the enable pin is held low. The power good indicator is held low until the output reaches 95% of the nominal voltage when it is powering up or coming out of low-power mode. Otherwise, the PG pin is high-impedance, so an external pull-up resistor is required to use this pin.

The select input, SEL, can be driven above 1.1 V (up to 16 V) to change the output voltage of the regulator to 5 V. Driving the pin low or leaving it disconnected sets the output to 3.3 V. To permanently set the output to 5 V, you can solder a piece of wire between SEL and the unpopulated pad next to it, which is pulled up to VIN; the following picture shows an example of this:

Included hardware

The five main 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 pieces of the included breakaway 6×1 straight male header strip or the 5×1 right-angle male header strip as desired. The additional straight male header pin can be soldered into the SEL input, though this could prevent the regulator from being used in a breadboard.

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.

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