The Pololu adjustable boost regulator is a very flexible switching
regulator (also called a switched-mode power supply, SMPS, or DC-to-DC
converter) that can generate voltages higher than its input voltage. We
offer two adjustable ranges: approximately 2.5 V to 9.5 V and 4 V to 25 V.
The output voltage can be set using the trimmer potentiometer in the
upper-right corner of the board. The input voltage range is 1.5 V to
16 V (the input voltage should be kept below the output voltage). The
integrated 2 A switch allows for output currents high enough to drive
small motors, as in our 3pi robot, and allows large voltage gains, such as obtaining 24 V from two NiMH or NiCd cells.
Some example applications include:
- Powering 5 V or 3.3 V systems from lower-voltage batteries.
- Powering 5 V subsystems (e.g. sensors) in lower-voltage (e.g. 3.3 V) systems.
- Achieving consistent actuator operation when powered by fluctuating batteries
- Powering high-brightness LEDs or a large number of LEDs in series
- input voltage: 1.5 V to 16 V
- output adjustable from 2.5 V to 9.5 V or 4 V to 25 V
- 750 kHz switching frequency
- 2 A switch (and input) limit
- integrated over-temperature and over-current shutoff
- typical efficiency of 80-90% when doubling voltage and with 100-500 mA output
- small size: 10.7 x 22.4 x 5.8 mm (0.42" x 0.88" x 0.23")
- weight without header pins: 1.6 g (0.06 oz)
The boost regulator has just three connections: the input voltage,
ground, and the output voltage. 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.
Setting the output voltage
The output voltage can be adjusted using a meter and a light load
(e.g. a 1k resistor). Turning the potentiometer clockwise increases the
output voltage. The output voltage can be affected by a screwdriver
touching the potentiometer, so the output measurement should be done
with nothing touching the potentiometer. The potentiometer has no
physical end stops, which means that the wiper can be turned 360 degrees
and into an invalid region in which the output voltage is set to
approximately 2.5 V (for both the 2.5 V to 9.5 V and 4 V to 25 V
versions). The input voltage should not exceed the output voltage, so
we recommend setting the output voltage with the input voltage set to
around 2.5 V.
The absolute limit for the input voltage is double the output set
voltage. For example, if the output is set to 6 V, the input must not
exceed 12 V. Once the input exceeds the output set point, the output
voltage will rise with the input voltage since the input is connected to
the output through an inductor and a diode.
Note: The trimmer
potentiometer is not rated for continual adjustment back and forth; the
intended application is to set the output voltage a few times in its
Efficiency and available output current
The available output current depends on the input and output
voltages. The input current is limited to approximately 2 A, and, as
shown in the graphs below, the efficiency is typically 80% to 90%.
Therefore, the maximum available current will be approximately 800 mA
when doubling the input voltage and approximately 400 mA when
quadrupling the input voltage. At high output powers, the 20% lost in
the regulator will cause substantial heating, which can limit the
available output power (the regulator will automatically shut off if its
internal temperature gets too high). At low output currents and high
input and output voltages, the efficiency drops closer to 50%, though
the lower power involved prevents heating from being an issue.