Pololu 5V, 1A Step-Down Voltage Regulator D24V10F5
The compact (0.5? × 0.7?) D24V10F5 synchronous buck voltage regulator
takes an input voltage of up to 36 V and efficiently reduces it to
5 V while allowing for a maximum output current of
1 A.
This regulator offers typical efficiencies between 85% and 90% and has a
very low dropout, so it can be used with input voltages as low as a few
hundred millivolts above 5 V. The pins have a 0.1? spacing, making this
board compatible with standard solderless breadboards and perfboards.
Overview
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| Pololu step-down voltage regulators D24V10Fx and D24V5Fx next to a 7805 voltage regulator in TO-220 package. |
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The D24V10Fx family of step-down voltage regulators features the
Intersil ISL85410 1A synchronous buck regulator and 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) with typical efficiencies between 80% and 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
applications that are run from a battery. These regulators are
available in five 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 five
versions of the D24V10Fx family.
The SHDN pin can be used to put the board in a low-power state that
reduces the quiescent current to approximately 10 µA to 20 µA per volt
on VIN, and a PG (power good) output can be used to monitor the state of
the regulator’s output voltage.
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 do not need quite as much current, consider the very similar
D24V5Fx family of step-down voltage regulators, which can deliver up to
500 mA in a wide range of output voltages:
The picture on the right shows a 1 A D24V10Fx regulator next to a
0.5 A D24V5Fx regulator and a common 7805 linear regulator in a TO-220
package.
Features
- Input voltage: [output voltage + dropout voltage] to 36 V (see below for more information on dropout voltage)
- Fixed 3.3 V, 5 V, 6 V, 9 V, or 12 V output (depending on regulator version) with 4% accuracy
- Maximum output current: 1 A
- Typical efficiency of 80% to 93%
- 500 kHz switching frequency (when not in power-save mode)
- 2 ms soft-start reduces in-rush current on power-up
- 200 µA typical no-load quiescent current
- Integrated over-temperature and over-current shutoff
- Small size: 0.7? × 0.5? × 0.14? (18 mm × 13 mm × 3.5 mm)
Using the regulator
Connections
The buck regulator has five connections: power good (PG). shutdown (SHDN), input voltage (VIN), ground (GND), and output voltage (VOUT).
The “power good” indicator, PG, is an open-drain
output that drives low when the regulator’s output voltage falls below
80% or rises above 120% of its target output voltage. This output is
also actively held low for the duration of the regulator’s 2 ms
soft-start period and while the regulator is being disabled by the SHDN
input or by over-temperature or over-current fault conditions. An
external pull-up resistor is generally required to use this pin.
The SHDN
pin can be driven low (under 0.4 V) to turn off the output and put the
board into a low-power state. There is a 100 kO 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 pull-up 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 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 D24V10F3 version outputs 3.3 V, the D24V10F5
version outputs 5 V, the D24V10F6 version outputs 6 V, the D24V10F9
version outputs 9 V, and the D24V10F12 version outputs 12 V.
The five 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 5×1 straight male header strip or the 5×1 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 93%, 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 power-save 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 #2831
The graphs below show the typical efficiency and dropout voltage of
the 5 V D24V10F5 regulator as a function of the output current:
Schematic diagram
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| Schematic diagram for the Pololu D24V10Fx family of 1 A step-down voltage regulators. |
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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.
