Pololu 5V, 500mA Step-Down Voltage Regulator D24V5F5

This 5 V boost (step-up) voltage regulator generates higher output voltages from input voltages as low as 0.5 V, and it also automatically switches to a linear down-regulation mode when the input voltage exceeds the output. This makes it great for powering 5 V electronics projects from 1 to 3 NiMH, NiCd, or alkaline cells or from a single lithium-ion cell.

When boosting, this module acts as a switching regulator (also called switched-mode power supplies (SMPS) or DC-to-DC converters) and has a typical efficiency between 70% to 90%. The available output current is a function of the input voltage, output voltage, and efficiency (see Typical Efficiency and Output Current section below), but the input current can typically be as high as 1.2 A.

The regulator’s thermal shutdown engages at around 140°C and helps prevent damage from overheating, but it does not have short-circuit or reverse-voltage protection.

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 boost regulator has three connections: input voltage (VIN), ground (GND), and output voltage (VOUT).

The input voltage, VIN, must be at least 0.5 V for the regulator to turn on. However, once the regulator is on, the input voltage can drop as low as 0.3 V and the 5 V output voltage will be maintained on VOUT. Unlike standard boost regulators, this regulator has an additional linear down-regulation mode that allows it to convert input voltages as high as 5.5 V down to 5 V for small to moderate sized loads. When the input voltage exceeds 5 V, the regulator automatically switches to this down-regulation mode. The input voltage should not exceed 5.5 V. Please be wary of destructive LC spikes that might cause the input voltage to surpass 5.5 V (see below for more information).

The 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 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 3×1 straight male header strip or the 3×1 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. As shown in the graphs below, this switching regulator typically has an efficiency of 70 to 90%.

The maximum achievable output current is approximately proportional to the ratio of the input voltage to the output voltage. If the input current exceeds the switch current limit (typically somewhere between 1.2 and 1.5 A), the output voltage will begin to drop. Additionally, the maximum output current can depend on other factors, including the ambient temperature, air flow, and heat sinking.

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.

Dimensions

Size:	0.35? × 0.45? × 0.1?
Weight:	0.4 g

General specifications

Minimum operating voltage:	0.5 V
Maximum operating voltage:	5.5 V
Maximum input current:	1.2 A2
Output voltage:	5 V
Reverse voltage protection?:	N
Maximum quiescent current:	1 mA3

Identifying markings

PCB dev codes:	reg12b
Other PCB markings:	0J7517

Details for item #2843

The graphs below show the typical efficiency and dropout voltage of the 5 V D24V5F5 regulator as a function of the output current:

Notes:

Without included optional headers.

Regulator may overheat at lower input currents when VIN is much lower than VOUT. Available output current is a function of VIN, VOUT, and the regulator efficiency.

The highest quiescent currents occur at very low input voltages; for most of the input voltage range, the quiescent current is well below 1 mA.