Pololu 2.5V, 500mA Step-Down Voltage Regulator D24V5F2

Pololu 2.5V, 500mA Step-Down Voltage Regulator D24V5F2
Overview
Pololu 2.5V, 500mA Step-Down Voltage Regulator D24V5F2
Pololu step-down voltage regulator
D24V5Fx next to a 7805 voltage regulator
in TO-220 package.
The D24V5Fx family of buck (step-down) voltage regulators generates lower output voltages from
input voltages as high as 36 V. They are switching regulators (also called switched-mode power
supplies (SMPS) or DC-to-DC converters) and have a typical efficiency between 80% to 93%,
which is much more efficient than linear voltage regulators, especially when the difference
between the input and output voltage is large. These regulators have a power-save mode that
activates at light loads and a low quiescent (no load) current draw, which make them well suited for
low-power applications that are run from a battery. These regulators are available in eight different
fixed output voltages:
The different versions of this regulator all look very similar, so the bottom silkscreen includes a
blank space where you can add your own distinguishing marks or labels. This product page
applies to all four versions of the D24V5Fx family.
The regulators feature short-circuit/over-current protection, and thermal shutdown helps prevent
damage from overheating. The boards do not have reverse-voltage protection.
If you need more output current, consider our D15V35F5S3 and D15V70F5S3 3.3V/5V step-down
voltage regulators, which can typically deliver a continuous 3.5 A and 7 A, respectively.
Features
Input voltage:
3 V to 36 V for output voltages of 1.8 V and 2.5 V
[output voltage + dropout voltage] to 36 V for output voltages of 3.3 V and higher
(see below for more information on dropout voltage)
Fixed 1.8 V, 2.5 V, 3.3 V, 5 V, 6 V, 9 V, 12 V, or 15 V output (depending on regulator
version) with 4% accuracy
Maximum output current: 500 mA
Typical efficiency of 80% to 93%
500 kHz switching frequency (when not in power-save mode)
200 µA typical no-load quiescent current
Integrated over-temperature and over-current shutoff
Small size: 0.5″ × 0.4″ × 0.1″ (13 mm × 10 mm × 3 mm)
Using the regulator Connections
The buck regulator has four connections: shutdown (SHDN), input voltage (VIN), ground (GND),
and output voltage (VOUT).
The SHDN pin can be driven low (under 0.4 V) to turn off the output and put the board into a lowpower state. There is a 100 kΩ pull-up resistor between the SHDN pin and VIN, so if you want to
leave the board permanently enabled, the SHDN pin can be left disconnected. While the SHDN pin
is being driven low, the current draw of the regulator is dominated by the current through the pullup resistor and will be proportional to the input voltage. (At 36 V in it will draw about 360 µA.)
The input voltage, VIN, powers the regulator. Voltages between 3 V and 36 V can be applied to
VIN, but for versions of the regulator that have an output voltage higher than 3 V, the effective
lower limit of VIN is VOUT plus the regulator’s dropout voltage, which varies approximately linearly
with the load (see below for graphs of dropout voltages as a function of the load). Additionally,
please be wary of destructive LC spikes (see below for more information).
The output voltage, VOUT, is fixed and depends on the regulator version: the D24V5F1 version
outputs 1.5 V, D24V5F2 version outputs 2.5 V, the D24V5F3 version outputs 3.3 V, the D24V5F5
version outputs 5 V, the D24V5F6 version outputs 6 V, the D24V5F9 version outputs 9 V, the
D24V5F12 version outputs 12 V, and the D24V5F15 version outputs 15 V
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 directly to the board or
solder in either the 4×1 straight male header strip or the 4×1 right-angle male header strip that is
included.
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. This family of switching
regulators typically has an efficiency of 80% to 95%, though the actual efficiency in a given system
depends on input voltage, output voltage, and output current. See the efficiency graph near the
bottom of this page for more information.
In order to achieve a high efficiency at low loads, this regulator automatically goes into a powersave mode where the switching frequency is reduced. In power-save mode, the switching
frequency of the regulator changes as necessary to minimize power loss. This could make it harder
to filter out noise on the output caused by switching.
Typical dropout voltage
The dropout voltage of a step-down regulator is the minimum amount by which the input voltage
must exceed the regulator’s target output voltage in order to ensure the target output can be
achieved. For example, if a 5 V regulator has a 1 V dropout voltage, the input must be at least 6 V
to ensure the output is the full 5 V. Generally speaking, the dropout voltage increases as the output
current increases. See the “Details” section below for more information on the dropout voltage for
this specific regulator version.
Details for item #2841
The graphs below show the typical efficiency and dropout voltage of the 2.5 V D24V5F2 regulator
as a function of the output current:
Note that since this regulator has a minimum input voltage of 3 V, the dropout voltage cannot go
below 0.5V.
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 (36 V), the regulator can be destroyed. In our tests with typical power leads (~30″ test
clips), input voltages above 20 V caused spikes over 36 V.
If you are connecting more than 20 V or your power leads or supply has high inductance,
we 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 50 V.
More information about LC spikes can be found in our application note, Understanding Destructive
LC Voltage Spikes.
Documentation on producer website.
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