Pololu 9Volt, Step-Up/Step-Down

This switching regulator uses the SEPIC topology to produce 9 V from input voltages between 2.5 V and 18 V. The wide input range coupled with its ability to convert both higher and lower input voltages makes it useful for applications where the power supply voltage can vary greatly, as with batteries that start above but discharge below 9 V. The compact (0.4″ — 0.575″) module can supply over 300 mA in typical applications.

Overview

The Pololu step-up/step-down voltage regulator S10V3F9 is a switching regulator (also called a switched-mode power supply (SMPS) or DC-to-DC converter) with a single-ended primary-inductor converter (SEPIC) topology. It takes an input voltage from 2.5 V to 18 V and increases or decreases the voltage to a fixed 9 V output with a typical efficiency of 70% to 80%.

This flexibility in input voltage is especially well-suited for battery-powered applications in which the battery voltage begins above 9 V and drops below as the battery discharges. Since it lacks the typical restriction that the battery voltage stay above the required voltage throughout its life, new battery packs and form factors can be considered. For instance, a 7-cell battery holder, which might have an 11 V output with fresh alkalines but an 8.4 V nominal voltage with NiMH cells and a 7 V output with partially discharged cells, can now be used to produce a steady 9 V output.

In typical applications, this regulator can deliver over 300 mA continuous; please see the graphs at the bottom of this page for a more detailed characterization. The regulator’s thermal shutdown prevents damage from overheating, but it does not have short-circuit or reverse-voltage protection.

Features
•Input voltage: 2.5 V to 18 V (can be higher than, the same as, or lower than the 9 V output)
•Fixed 9 V output with 4% accuracy
•Typical continuous output current: 300 mA (actual continuous output current depends on input voltage; see Typical Efficiency and Output Current section below for details)
•<2 mA typical no-load quiescent current
•Integrated over-temperature shutoff
•Small size: 0.40″ — 0.575″ — 0.1″ (10 mm — 15 mm — 3 mm)

Connections

This step-up/step-down 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 power down the regulator. The quiescent current in this shutdown mode is dominated by the current in the 10 kΩ pull-up resistor from SHDN to VIN. With SHDN held low, this resistor will draw 0.1 mA per volt on VIN (for example, the shutdown current with a 5 V input will be 0.5 mA). This pin should only ever be driven low or left floating; this can be accomplished with a physical switch that toggles it between ground and disconnected, or electrically with something like a transistor controlled by an I/O line.

The input voltage should be between 2.5 V and 18 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 be wary of destructive LC spikes (see below for more information).