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 a typical efficiency of over 85% and a typical output current of up to 1.5 A. 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.

The different members of this family offer different output voltage options, from fixed voltages with selectable alternatives to adjustable voltages that can be set anywhere between 2.5 V and 9 V using a precision 11-turn potentiometer. 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:

Regulator		Output voltage	Typical max current output*	Input voltage range	Low-voltage cutoff	Size	Price
	#2868 S9V11MACMA	2.5 V – 9 V (fine-adjust)	1.5 A	2 V – 16 V (3 V startup)	fine-adjust	0.50″ × 0.60″ × 0.25″	$13.95
	#2869 S9V11MA	2.5 V – 9 V (fine-adjust)					$10.95
	#2870 S9V11F5S6CMA	5 V (6 V selectable)			fine-adjust		$10.95
	#2871 S9V11F3S5CMA	3.3 V (5 V selectable)			fine-adjust		$10.95
	#2872 S9V11F3S5	3.3 V (5 V selectable)				0.50″ × 0.60″ × 0.17″	$7.95
	#2873 S9V11F3S5C3	3.3 V (5 V selectable)			3 V (fixed)		$7.95
	#2836 S9V11F5	5 V				0.30″ × 0.45″ × 0.17″	$8.95
*For input voltages close to the output. Actual achievable maximum continuous current is a function of input and output voltage and is limited by thermal dissipation. See the output current graphs on the product pages for more information.

These regulators have short-circuit protection, and thermal shutdown prevents damage from overheating; they do not have reverse-voltage protection. 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 Typical efficiency and output current section below).

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 5 V output with +5/-3% accuracy
• Typical maximum continuous output current: 1.5 A (when input voltage is around 5 V; the Typical Efficiency and Output Current section below shows how the achievable continuous output current depends on the input voltage)
• Power-saving feature maintains high efficiency at low currents (quiescent current is less than 0.2 mA)
• Integrated over-temperature and short-circuit protection
• Small size: 0.3″ × 0.45″ × 0.15″ (7.6 × 11.4 × 3.8 mm)

Using the Regulator

During normal operation, this product can get hot enough to burn you. Take care when handling this product or other components connected to it.

Connections

The step-up/step-down regulator has just three connections: the input voltage (VIN), ground (GND), and the output voltage (VOUT). These 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 either the 3×1 straight male header strip or the 3×1 right-angle male header strip that is included. VOUT is labeled on the silkscreen on one side of the board, and GND is in the middle and can be identified by its square pad.

The input voltage, VIN, should be between 3 V and 16 V when the regulator is first powered. After it is running, it can continue operating down to 2 V. Lower inputs can 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 output voltage, VOUT, is regulated to a fixed 5 V, but it can be as high as 5.2 V when there is little or no load on the regulator.

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 graph below, this switching regulator typically has an efficiency of 85% to 95%. A power-saving feature maintains these high efficiencies even when the regulator current is very low.

The maximum achievable output current of the board 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 regulator can deliver continuously at room temperature in still air and without additional heat sinking. The regulator can temporarily deliver up to around 2 A, though it will typically quickly overheat under such conditions and go into thermal shutdown.

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.

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, the regulator can be destroyed. If you are connecting more than about 12 V, using power leads more than a few inches long, or using a power supply with 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 20 V.

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